Instytut Łączności

Germán Arévalo
Migration of a 40-channel WDM optical ring, from 400Gb/s-OOK to a 2Tb/s-DSP-assited-PAM4 solution: A real case study in Ecuador
G. V. Arévalo, R. Tenesaca, and M. Tipán
Telecommunications Research Group, Universidad Politécnica Salesiana, Ecuador
The evolution of data transport services demands a continuous upgrade of the bandwidth for communication systems. This upgrade must be efficient, low cost, and maximize transmission capabilities. This study analyzes the feasibility of migrating a DWDM optical fiber ring deployed by the Ecuador National Electricity Company to increase its bandwidth from 400 Gb/s to 2 Tb/s, using four-level amplitude modulation, predistortion, and digital signal processing techniques. With the implementation of analogic predistortion in the transmitter, combined with a one-pole one-zero filter for pre-emphasis, the system can increase its bandwidth keeping an optimal performance and low bit error rate. The results show an improvement in the bit error rate/received power ratio when predistortion is applied. The bit error rate further improves using digital filtering on the transmitter side.

Yossef Ben-Ezra
Superoscillating signal transmission over dispersive media
Y. Ben-Ezra and B. I. Lembrikov, Faculty of Electrical Engineering, Holon Institute of Technology, Israel
Superoscillating signals are band-limited signals that oscillate in some regions faster than their largest Fourier component [1], [2]. Superoscillatory functions have a variety of interesting applications in quantum mechanics, signal processing, subwavelength imaging, optics, etc.  (see, for instance, [3] and references therein). However, the superoscillation amplitude is usually small compared to the typical values of the amplitude in non-super oscillating regions. Such small values are constructed by the near-perfect coherent destructive interference among the function’s spectral components. For large superoscillations, persisting over an extended region requires an exact relationship of phases. Such interference is sensitive to noise, especially in the form of random phases in the Fourier components [4]. Due to the chromatic dispersion in the single-mode fibers different spectral components of the signal travel at slightly different group velocities. This phenomenon is referred to as group-velocity dispersion (GVD) [5]. GVD can significantly change the phase relations of the Fourier components of the superoscillating signal and even lead to its complete deconstruction. Superoscillations have been investigated by using the wavelet transforms [6]. In this work, we studied theoretically the influence of the chromatic dispersion in a single mode fiber on the transmission of the superoscillating signals. We have carried out numerical simulations demonstrating the influence of the dispersion on variety of superoscillating signals. We have demonstrated perfect reconstruction of a superoscillating signal transmitted over dispersive media using the digital signal processing and machine learning algorithms.
Keywords: superoscillation, optical communication, digital signal processing.
[1] E. Katsav, M. Schwartz, Yield-optimized superoscillations, IEEE Transactions on Signal Processing, 61:3113-3118 (2013).
[2] P. J. S. G. Ferreira, A. Kempf, Superoscillations: Faster than the Nyquist rate, IEEE Transactions on Signal Processing, 54:3732-3740 (2006).
[3] M. Berry, N. Zheludev, Y. Aharonov, F. Colombo, I. Sabadini, D. C. Struppa, J. Tollaksen, E. T. F. Rogers, Fei Qin, Minghui Hong, Roadmap on superoscillations, Journal of Optics, vol. 21, no. 5, (2019).
[4] M. V. Berry, Suppression of superoscillations by noise, J. Phys. A: Math. Theor., 50:025003 (2017).
[5] G. P. Agrawal, Fiber-Optic Communication Systems, John Willey & Sons, Fifth edition, (2021).
[6] Y. Ben Ezra, B. I. Lembrikov, M. Schwartz, S. Zarkovsky, Applications of wavelet transforms to the analysis of superoscillations, in: Wavelet Theory and its Applications. Edited by S. Radhakrishnan, IntechOpen, London, UK, pp. 195-214 (2018).

Steinar Bjørnstad
A scalable data collection system for continuous state of polarisation monitoring
S. Bjørnstad^1,2, T. Dreibholz², and J. Ali^2
1Tampnet AS, Stavanger, Norway
²SimulaMet, Oslo, Norway
The society dependency on the telecommunication infrastructure is continuously increasing as different infrastructures, such as energy and telecommunication, now have mutual dependencies. This calls for increased monitoring of the fibre network, which is a highly critical part of the infrastructure. State of Polarisation (SoP) of light propagating through fibre transmission systems is impacted by any vibrations and mechanical impacts on the fibre. By continuously monitoring SoP, any unexpected movements of a fibre along a fibre-path may be traced. Movements may be caused by e.g. work in node rooms impacting patch-cords, trawlers or other types of sub-sea equipment touching or hooking into sub-sea fibre cables, digging close to a fibre-cable or geophysical phenomena like earthquakes. In this paper, we describe a low-cost scalable system for SoP monitoring and give examples of patterns monitored in different types of fibre infrastructures. The monitoring system consists of single-unit rack mount instruments connected to taps from live optical transmission signals. Each instrument has local storage for 1-2 years of data and is periodically automatically uploading data to a server for backup and data-access purposes. Examples of patterns observed are movements of a fibre-patch cord in a node-room, thunderstorm impact on a Fibre-To-The-Home (FTTH) cable and 50 Hz pattern on a fibre-cable spun around a high-voltage power air-cable.

Sonia Boscolo
Digital signal processing for optical phase conjugation assisted coherent systems
L. H. Nguyen, T. T. Nguyen, A. Ellis, S. Sygletos, and S. Boscolo
Aston Institute of Photonic Technologies, Aston University, Birmingham, UK

Ivan Djordjevic
Entanglement assisted MIMO quantum radars
I. B. Djordjevic, University of Arizona, Tucson, USA
In this invited paper, we will describe our entanglement assisted (EA) MIMO quantum radar technique with multiple entangled transmitters and coherent detection-based receivers. This scheme exploits the phase sensitive quantum correlation on the receivers’ sides to improve the receiver sensitivity. To increase overall signal-to-noise ratio, we use the spatial MIMO concept. To reduce the system cost and complexity, the optical phase conjugation (OPC) on signal photons is performed on a transmitter side, so that commercially available classical, balanced coherent detectors can be used on receiver side instead of traditional OPC-based EA receivers.

Roberto Gaudino
TDEC metric for 50G-PON using optical amplification
M. Casasco¹, G. Caruso^1,2, I. Cano², A. Pagano³, R. Mercinelli³, M. Valvo³, V. Ferrero¹, and R. Gaudino^1
1Dipartimento di Elettronica e Telecomunicazioni, Politecnico di Torino, Italy
²Huawei Technologies, Munich Research Center, Germany
³Access Innovation, TIM - Telecom Italia, Torino, Italy
The Transmitter and Dispersion Eye Closure (TDEC) is a metric originally introduced by IEEE 802.3 for short reach optical transmission in datacenters and later adopted for 50G-PON in ITU-T Recommendation G.9804.3. TDEC evaluates the performance of a transmission system as a penalty due to eye-diagram closure, comparing it to a reference ideal transmitter. To this end, the standard defines a procedure to be followed involving filtering, equalization and the definition of time windows inside the eye diagram. The purpose of this article is to show the correlation between TDEC and the Optical Modulation Amplitude receiver sensitivity in 50G-PON scenario using optical amplifiers either as booster at transmitter side (for the downstream direction) or as pre-amplifiers at receiver (in the upstream direction).
Keywords: passive optical networks, 50G-PON, TDEC, FTTH.

Miguel Gonzalez-Herraez
Time-expanded in distributed optical fiber sensing
M. Soriano-Amat¹, H. F. Martins², V. Durán³, S. Martin-Lopez¹, M. Gonzalez-Herraez¹, and M. R. Fernández-Ruiz^1
1Universidad de Alcalá, Grupo de Ingeniería Fotónica, Madrid, Spain
²Instituto de Óptica “Daza de Valdés” IO-CSIC, Madrid, Spain
³GROC-UJI, Institute of New Imaging Technologies, University Jaume I, Castellón, Spain
Phase-sensitive optical time-domain reflectometry (φOTDR) is a well-known distributed optical fiber sensing technique widely employed in applications that require thousands of measuring points, such as structural health monitoring, seismology or perimeter surveillance. Time-domain interrogators typically offer longer sensing ranges and faster dynamics but significantly worse spatial resolution than their optical frequency domain counterparts. Recently, a new φOTDR scheme exploits the dual-frequency comb technology to cover the performance gap between that typically offered by conventional φOTDR and OFDR interrogators. In this novel sensing technique, called time-expanded (TE-)φOTDR, one optical frequency comb (OFC) probes the fiber to produce a series of backscatter traces. A second comb with almost identical specifications than the previous one but slightly different line spacing serves as a reference. The beating between both OFCs leads to a frequency down conversion of the backscatter traces upon photodetection, allowing obtaining spatial resolution in the cm scale with MHz bandwidth detectors. Thanks to the use of a pair of OFCs under quasi-integer ratio mode and an atomic rubidium clock, we achieve the dynamic interrogation of up to 100,000 sensing points in a fiber with centimeter spatial resolution and in real time.
Keywords: OTDR, dual-frequency comb, quasi-integer-ratio dual combs, distributed acoustic sensing, Rayleigh scattering.

Norbert Hanik
The nonlinear Fourier transform and its extension to the strong coupling multi-mode case
B. Leible and N. Hanik, Technical University of Munich, Germany
Searching for ways to overcome the impending "capacity crunch" in fiber-optic data-transmission networks, the interest in communication systems utilizing the nonlinear Fourier transform (NFT) for signal generation/detection has been rekindled in recent years. The NFT provides a domain for signal modulation, in which, for a specific underlying channel, all modulated components are independent from each other during propagation. While there are still some open problems, especially concerning perturbations that are not part of the NFT's underlying channel model and issues linked to the complexity of potential implementations, the topic has been studied in a plethora of publications, even dealing with adjacent topics like NFT-aided measurement methods for fiber parameters. Another topic, that has been studied with increased vigor in recent years, is the field of space division multiplexing (SDM), including multi-mode fiber channels. The NFT, mostly studied for the case of single-mode fiber channels, can also be utilized in the context of the strong-coupling multi-mode channel, leading to potential synergies with SDM. In this paper, we present the basics of the NFT for the strong coupling multi-mode channel, show that several properties of the single-mode case can be extended to the multi-mode channel and present some modified algorithms to implement the necessary transformations.

Carmen Mas Machuca
Cost-efficient capacity scaling using multi-wavelength transponders and adaptive modulation
J. Müller^1,2, G. Di Rosa¹, A. Autenrieth¹, J.-P. Elbers¹, and C. Mas-Machuca^3
1Adtran, Munich, Germany
²Chair of Communication Networks, Technical University of Munich, Germany
³Chair of Communication Networks, Universität der Bundeswehr München, Germany
Scaling the capacity of optical networks to meet increasing traffic demands while keeping costs and power usage low is crucial. Multi-wavelength transponders have potential as cost-efficient options, but they make network planning more complex. Additionally, the improved symbol and modulation rate adaptivity further increases the network throughput. We extend our previous network planning study for multi-wavelength transponders by considering an increased modulation rate adaptivity using probabilistic shaping. Additionally, we take reduced requirements for guard-bands of multi-wavelength transponders into account, thereby improving the spectral efficiency. We report results for planning studies on a continental as well as a national optical backbone network topology, showing the potential of multi-wavelength transponders for cost-efficient capacity scaling.

Francesco Prudenzano
Optical combining in medium infrared wavelength range and its applications
A. Annunziato, F. Anelli, A. M. Loconsole, M. C. Falconi, V. Portosi, V. V. Francione, and F. Prudenzano
Department of Electrical and Information Engineering, Politecnico di Bari, Italy
A review on the optical combining in medium infrared wavelength range is illustrated. Moreover, details on the design, fabrication and characterization of combiners based on multimode step-index fluoroindate optical fibers (InF₃) are given. The electromagnetic design of the combiner is carried out through modal investigation and the beam propagation method is exploited to evaluate the transmission efficiency. In the fabrication process, including the normalization procedure, the low melting temperature and the mechanical properties of fluoroindates are taken into account. The repeatability and absence of crystallization are verified. The experimental results agree with the simulation and pave the way for a number of applications in the mid-infrared spectral range.

Ben Puttnam
High data-rate and wideband transmission in single and multi-core fibers
B. Puttnam, R. Luis, G. Rademacher, Y. Awaji, and H. Furukawa
National Institute of Information and Communications Technology, Tokyo, Japan
We explore S, C + L-band transmission in low-core count multi-core fibers (MCFs). After reviewing progress in wideband transmission demonstrations in both single-mode and multi-core fibers we focus on two experiments demonstrating 57 km, 1 Pb/s transmission with 20 THz transmission bandwidth and 342 Tb/s transmitted over 3000 km in a 4-core MCF with standard cladding diameter. Finally, we briefly explore the potential benefit of increased spectral efficiency in MCF transmission by exploiting reduced (IC-XT) at lower wavelengths.
Keywords: space-division multiplexing, multi-core fibers wideband transmission, multi-band transmission.

Carla Raffaelli
Towards 6G AI-enabled service orchestration in the cloud continuum
G. F. Pittalà, D. Borsatti, G. Davoli, W. Cerroni, D. Tarchi, and Carla Raffaelli
DEI – University of Bologna, Bologna, Italy
End-to-end service orchestration leveraging computing and communication resources in the cloud continuum is addressed. A modular architecture is proposed to facilitate data-driven/AI adoption, while achieving enhanced energy efficient automation in 6G service provisioning. A selection of available enabling technologies to deploy the architecture is presented.
Keywords: 6G, service orchestration, cloud continuum, artificial intelligence, energy efficiency.

Anastasiia Sheveleva
Experimental investigation of phase-space portraits of ideal four-wave mixing
A. Sheveleva¹, A. Ermolaev², P. Colman¹, J. M. Dudley², and C. Finot^1
1Laboratoire Interdisciplinaire CARNOT de Bourgogne, Université de Bourgogne, Dijon, France
²Université de Franche-Comté, Institut FEMTO-ST, Besançon, France
Due to the growth of higher-order sidebands and to optical losses which restrict the potential interaction distance, it is notoriously challenging to experimentally observe the idealized four-wave mixing dynamics. In order to address this issue, we propose to iteratively change the phase and amplitude conditions of a signal made of three equally spaced spectral lines that is then injected into a short segment of optical fiber. Such segmented approach enables us to mimic an effective propagation over tens of kilometers - a distance that greatly exceeds the 500 m fiber in use. Our experimental study reveals the complete phase-space topology exhibiting several Fermi-Pasta-Ulam-Tsingou recurrence cycles, the existence of a stationary wave as well as the presence of a system separatrix, which marks the transition between two distinct spatiotemporal evolution regimes. When plotted on a phase portrait, the wave dynamics follows close orbits that are uniquely defined by initial conditions, hence do not intersect. By changing abruptly during propagation the control parameters, such as the average power, we demonstrate both theoretically and experimentally that it is possible to connect two states that are not initially located on the same closed trajectory. Finally, we also investigate the benefits of supervised machine learning techniques in two different ways. Firstly, we combine non-iterated measurements with a feed-forward neural network. Results demonstrate that the network can extract the key characteristics of the phase-space topology and can accurately forecast the nonlinear dynamics. Secondly, we have implemented the technics of sparse identification of nonlinear dynamics. Starting from a set of several trajectories that can be potentially affected by noise, we are able to retrieve quantitatively the governing terms in the differential equations systems.

Marco Tacca
Experimental demonstration and results of cross layer monitoring using open source network observability platform
N. Ellsworth¹, S. Troia², Tianliang Zhang¹, M. Tacca¹, G. Maier², and A. Fumagalli^1
1University of Texas at Dallas, USA
²Politecnico di Milano, Italy
Continuous monitoring of key network elements plays a crucial role in ensuring the smooth operation and optimal performance of communication networks. By monitoring various network parameters in real-time, network administrators can detect and prevent potential issues before they lead to significant disruptions. In this paper, we propose and demonstrate results from the implementation of a cross-layer monitoring in optical transport networks using an open source network observability platform (open-NOP). We exploit open source tools as cost-effective and efficient solutions for network monitoring and management. The experiment involves using different network devices and collecting and analyzing data from various network layers, including physical, data link, network and transport layers. The results demonstrate that open-NOP provides comprehensive network visibility and enables effective cross-layer monitoring.

Emanuele Virgillito
Detection, localization end emulation of environmental activities using SOP monitoring of IM-DD optical data channels
E. Virgillito¹, S. Straullu², F. Aquilino², R. Bratovich³, H. Awad¹, R. Proietti¹, R. Pastorelli³, and V. Curri^1
1DET, Politecnico di Torino, Italy
²Links Foundation, Torino, Italy
³SM-Optics, Vimercate, Italy
Optical telecommunications networks have become pervasive to satisfy the continuously growing internet traffic demand. At the same time, there's a huge interest in deploying a wide sensor network for in order to offer enhanced network services for environmental monitoring, such as early detection of earthquakes. In this context, there's a large interest in using the large infrastructure deployed for telecommunications also for environmental sensing. In this paper we employ the state of polarization (SOP) monitoring of intensity modulated channels, still widely deployed in metro and access network. We show experimental demonstration of environmental events' detection and localization and propose a waveplate model-based simulative tool aimed at emulating the SOP variation induced by seismic waves propagated along fiber network segments, to test their detection and localization in presence of further SOP noise induced by anthropic activities.

Tianhua Xu
Physics-informed neural network for fibre channel modelling in optical communication systems
J. Uduagbomen¹, S. Lakshminarayana¹, Zheng Liu², M. S. Leeson¹, and Tianhua Xu^1,2
1School of Engineering University of Warwick, Coventry, UK
²School of Precision Instruments and Opto-Electronics Engineering, Tianjin University, China
Over 95% of the data traffic is carried over optical fibre communication links. The split-step Fourier method (SSFM) has been widely employed to model the evolution of optical signals along the fibre channels in optical communication systems. However, the split-step Fourier method requires very high computational resources, especially for ultra-long-haul and wideband communication systems. Meanwhile, deep learning techniques can be applied to investigate the evolution of optical signals along the fibre links, where the nonlinear Schrödinger equation (NLSE) can be solved directly using neural networks to avoid the huge complexity of the split-step Fourier simulations. In this work, we will discuss the application of neural networks in modelling the evolution of different types of optical pulses along fibre transmission channels.

Xuelin Yang
High-speed random number generation and key distribution in fiber networks using amplified spontaneous emission
Xinran Huang, Zhi Chai, Mingye Li, Liuming Zhang, Zanwei Shen, Weiqiang Sun, and Xuelin Yang
State Key Laboratory of Advanced Optical Communication Systems and Networks, Shanghai Jiao Tong University, China
Amplified spontaneous emission (ASE) noise with inherent quantum nature is promising for true random number generator (TRNG) and secure key generation and distribution (SKGD). A high-speed TRNG and a physical-layer SKGD scheme are proposed and demonstrated using the polarization dynamics of an ASE source. The ASE-based randomness is enhanced in TRNG using digital signal processing on the two orthogonal polarization modes, while the fluctuation of the state of polarization (SOP) in ASE is applied as the random source in SKGD. A 16.8 Tb/s TRNG is successfully demonstrated with spectrum slicing of ASE. An error-free SKGD with a key generation rate (KGR) of 10.1 Gb/s is demonstrated over a 10-km standard single-mode fiber channel.
Keywords: Amplified spontaneous emission, state of polarization, True random number generator, Secure key generation and distribution.

Mario Zitelli
Characterization of the modal distribution from linear and nonlinear mode coupling in multimode fibers
M. Zitelli, M. Ferraro, F. Mangini, and S. Wabnitz, Department of Information Engineering, Electronics and Telecommunications, Università degli Studi di Roma Sapienza, Italy
Beam mode power content is experimentally investigated in long spans of multimode graded-index fiber; two different power distribution laws are found in the weakly nonlinear regime affected by linear disorder, and in the strong nonlinear regime.

Domenico Di Mola
Enabling customer self-driving networking experience via cloud delivered Metro cloud solution
D. Di Mola and G. Grammel, Juniper Networks
Network sustainability and scalability are key challenges for network operators while they are ramping up 5G services and cloud delivered applications. Automation and AIOps represent key enabler for self-driving network, helping with network TCO reductions and time to market. Cloud solutions must provide a robust architecture to security concerns.

Mirosław Klinkowski
Application of linear regression in latency estimation in packet-switched 5G xHaul networks
M. Klinkowski¹, J. Perelló², and D. Careglio^2
1National Institute of Telecommunications, Wrocław, Poland
²Universitat Politècnica de Catalunya, Barcelona, Spain
In this work, we aim at investigating the applicability of machine learning (ML), namely, a linear regression (LR) model for estimation of flows latencies in packet-switched 5G xHaul networks. The analysis is performed in a network scenario in which the switches are connected using high-capacity fiber links.
Keywords: 5G, xHaul, packet-switched network, latency modeling, machine learning, linear regression.

Antonio Napoli
Point-to-multi-point coherent optics on data processing units (DPUs) for beyond-5G low-latency applications
F. Cugini, C. Castro, and A. Napoli, Infinera, Munich, Germany
Coherent pluggable transceivers supporting both point-to-point and point-to-multi-point optical transmissions are proposed to be encompassed within Data Processing Units (DPUs) for cost-effective converged infrastructures including packet, optical, and edge computing resources.

Marc Ruiz
Comparison of statistical and machine learning-based approaches for telemetry data size reduction
A. El Sayed¹, M. Ruiz¹, H. Harb², and L. Velasco^1
1Advanced Broadband Communications Center, Universitat Politècnica de Catalunya, Spain
²College of Engineering and Technology, American University of the Middle East, Kuwait
The implementation of next generation beyond 5G use cases such as the Digital Twin (DT) requires the transportation of increasingly large amounts of sensor telemetry data. The reduction of the size of these time series shaped data through compression has many benefits, ranging from energy savings in systems where sensors have limited power to transport network bandwidth reduction. Both statistical analysis-based and machine learning (ML)-based approaches have been employed to tackle this task with varying degrees of success. In this paper, we compare two methods for time series data compression: a statistical similarity-based one, and an autoencoder (AE)-based one.
Keywords: telemetry data, B5G, compression, statistical similarity, auto-encoders.

Yaping Zhang
Evaluations of 10Gbps/25Gbps narrow band DBR EMLs for 5G smart applications
Mengxiao Li^1,2, Kun Shang², Jianfei Gu^1,2, Yuchao Zhang^1,2, Haikun Zhang¹, and Yaping Zhang^2,3
1University of Jinan, Jinan, Shandong, China
²Shandong Institute of Industrial Technology, Innovation Park, Jinan, Shandong, China
³OptoChip Optoelectronics Ltd, Jinan, China
For the European green and digital twin transition the fixed network are paramount as the foundational infrastructure. Optical communication is a cornerstone in that transition and therefore the 6th generation fixed network is the target for research and innovation in ICT. The vision of that roadmap towards F6G has various dimensions to be advanced. Since the digital

Marcus Brunner
The 6th generation fixed network (F6G): Vision and directions
M. Brunner, Huawei Technologies Switzerland AG, Zurich, Switzerland
For the European green and digital twin transition the fixed network are paramount as the foundational infrastructure. Optical communication is a cornerstone in that transition and therefore the 6th generation fixed network is the target for research and innovation in ICT. The vision of that roadmap towards F6G has various dimensions to be advanced. Since the digital transformation is touching all areas, the F6G networks need to be able to fulfil a broad set of application demands. The growth of photonics communication from the core networks towards the end-points including the edges of the network, fibre to the room, fibre to the machine, optics to the things is expected.

Nicola Calabretta
SOA-based optical networks with sub-microsecond control plane for low-latency applications
H. Santana¹, A. Mefleh², and N. Calabretta^1
1Eindhoven University of Technology, The Netherlands
²KPN, CTO, Technology Roadmap and Architecture, The Hague, The Netherlands
We propose and demonstrate a network of photonically connected edge data centres. The nodes utilize SOA-based optical add/drop multiplexers and the fast control plane is implemented with an FPGA-based supervisory channel. Results show microsecond-time control, time-slotted operation and deterministic latency with nanosecond jitter and error-free communication for up to 5 nodes. Keywords: transparent networks, edge data centres, fast control plane.

Ivan Cano
FDMA in point-to-multipoint fibre access systems for non-residential applications
I. N. Cano¹, G. Caruso^1,2, Jinlong Wei^1,3, G. Talli¹, C. Bluemm¹, S. Calabro¹, H. von Kirchbauer¹, U. Wuensche¹, P. Leyva⁴, H. Rongfang¹, Kuo Zhang⁵, and Zhicheng Ye^5
1Huawei Technologies Munich Research Center, Germany
²Politecnico di Torino, Italy
³Huawei Technologies, Munich Research Center, now with Pengcheng Laboratory, Shenzhen, China
⁴Citrobits GmbH, Munich, Germany
⁵Huawei Technologies, Optical Research Department, Dongguan, China
Optical access networks are seeing growing applications for use cases beyond residential, for example in campuses and as Industry 4.0 intra-factory networks, which introduce different requirements in terms of bandwidth delivery and latency. We present an uplink access system with simultaneous transmission and detection of several users by means of frequency division multiplexing (FDM). We demonstrate a multiple uplink access system with DBPSK signals and coherent detection that targets a low and deterministic latency. We achieve Rx sensitivities of -43.5dBm, -40dBm, and -34dBm at BER of 10-3 at 2.5GBaud, 5GBaud, and 8GBaud respectively after 20km of fibre. Furthermore, we show the possibility of employing time-division multiplexing (TDM) within the frequency bands. We also present real-time services showing that the system can allow latency-sensitive and best-effort applications to share the network.

Roberto Gaudino
Experimental demonstration of a 400 Gb/s full coherent transmission in an in-field metro-access scenario
M. Casasco¹, G. Rizzelli², A. Pagano³, R. Mercinelli³, M. Valvo³, V. Ferrero¹, and R. Gaudino^1
1Dipartimento di Elettronica e Telecomunicazioni, Politecnico di Torino, Italy
²Links Foundation, Torino, Italy
³Telecom Italia, Torino, Italy
The current challenge for the physical layer of next generation optical access network based on PON architectures is to increase the capacity above 100 Gbps per wavelength. This target may require a revolution for PON, moving from direct detection (DD) to optical advanced modulation formats and coherent detection. In fact, the performances of full-coherent systems for ultra-high bit rates are, in terms of receiver sensitivity, significantly better than standard DD receivers, obtaining power budget of more than 30 dB. In this scenario of large available power budget, it will even be possible to envision a convergence of the access with the metro segment, also considering that wavelength routing functionalities based on Reconfigurable Optical Add Drop Multiplexers (ROADM) can be inserted at the boundary between the two network domains. In this future possible scenario, it becomes thus fundamental to study the resulting power budget for both the metro and the access network, in order to optimize the overall optical performance.  To this end, we show in this paper experimental results obtained on a 33-km deployed metropolitan fiber link on a PM-16QAM full-coherent transmission at 50 Gbaud (400 Gbps) in terms of BER curves as a function of received optical power in a practical emulation of downstream metro-access transmission. A Reconfigurable Optical Add-Drop Multiplexer is introduced in the middle of the link to implement a wavelength routed metro-access scenario.
Keywords: passive optical networks, metro-access convergence, coherent transmission systems, FTTH.

Maria Medeiros
ML-based optimization of geometric constellation shaping for unamplified coherent optical systems
B. M. Oliveira¹, M. S. Neves¹, F. P. Guiomar¹, M. C. R. Medeiros², and P. P. Monteiro^1
1Instituto de Telecomunicações and University of Aveiro, Portugal
²Department of Electrical and Computer Engineering, Univ Coimbra, Portugal
With increasingly higher data rate requirements imposed on short-reach links, coherent optical systems are expanding to shorter distances. To achieve a cost-efficient and low-complexity solution, optical amplifiers can be removed, enabling the deployment of the already standardized use of unamplified coherent links. However, the system performance is now governed by a peak power constraint, and therefore the conventional constellations become sub-optimal.  We will present how an end-to-end machine learning algorithm can optimize the constellation geometry. We also show the importance of a well-suited model for the channel, by experimentally comparing the performance achieved with geometries optimized for both amplified and unamplified links.
Keywords: coherent optical communications, machine learning, unamplified links.

Antonio Napoli
Digital subcarrier based point-to-multipoint coherent transceivers for bidirectional transmission
A. Napoli, Infinera, Munich, Germany
Coherent P2MP technology can enable high-capacity bidirectional transmission for x-Haul networks. In this contribution, we review the technology, requirements, and potentiality to support next generation mobile transport networks.

Moshe Nazarathy
Optical DACs for ultra-high-speed green photonic interconnects
M. Nazarathy¹ and I. Tomkos^2
1Faculty of Electrical and Computer Engineering, Technion, Israel Institute of Technology, Haifa, Israel
²Electrical and Computer Engineering Department, University of Patras, Greece
We review the principles of operation and latest conceptual advances in optical DACs for next-gen Ultra-High-Speed (UHS) photonic interconnects. Optical DACs ‘done right’ enable UHS optical transmitters at high-resolution, high photonic-efficiency and high energy-efficiency. An oDAC is defined as a Transmit-Optical-Sub-Assembly (TOSA) unit generating a constellation of C=2B levels, comprising a collection of B modulators with static or slowly-adjustable ‘glue optics’; the admissible drives of the B modulators are specified as either two-level (NRZ, OOK) or 4-level (unipolar or bipolar PAM4); neither higher-order electrical driving-DACs, nor power-hungry digital encoders at baud rate are allowed.  We model and compare serial (segmented-MZM) vs. multi-parallel oDAC architectures and their win-win combination. We develop analytical models of serial and multi-parallel oDACs based on the code matrix concept. We introduce suitable metrics for oDACs characterisation. A ‘perfect’ oDAC features a max-full-scale (inherently optical-loss-free) uniform constellation (having equispaced levels), minimizing BER. We prove that for coherent (COH) detection links it is possible to design ‘perfect’ oDACs in the optical-field domain, but for a direct-detection link there exists no ‘perfect’ oDAC in the optical-power domain. We show how oDACs are assembled as building blocks in complete IQXY optical transmitters for Lite-COH transmission links, at unprecedented performance, energy-efficiencies, reconfigurability.

Francisco Rodrigues
PIC-based transceiver for access networks: Package and functionalities verification towards a commercial solution
F. Rodrigues^1,2,3, J. Santos^1,2,3, C. Rodrigues¹, H. Neto¹, and A. Teixeira^1,2,3
1PICadvanced, S.A., Ílhavo, Portugal
²Instituto de Telecomunicações (IT), University of Aveiro, Portugal
³Department of Electronics, Telecommunications, and Informatics (DETI), University of Aveiro, Portugal
InP monolithic PIC design packaged towards a standard form factor transceiver level is presented, showcasing the packaging options taken and presenting the overall transceiver performance against key specifications for access networks demonstrating the commercial feasibility of PIC based transceivers for these applications.

Josep Segarra
Band evaluation of coherent udWDM-PON with paired lasers
J. Segarra, V. Sales, and J. Prat, Universitat Politècnica de Catalunya, Barcelona Spain
The development of coherent high density WDM-PONs with hundreds of channels is a promising technology to increase the spectral efficiency and to reduce the consumption per user. Nevertheless the employment of low cost lasers with limited tunability can reduce the ability to assign the channels. In this work we consider the use of non-preselected transmitter and receiver paired lasers, with a fixed distance between their wavelengths, which facilitates the bidirectional channel assignment and alignment. However, a discontinuous bandwidth configuration in neighbor up/down segments is mandatory, decreasing the laser tunability capability when it is compared to two different separated up/down bandwidths. We evaluate the channel assignment in a dynamic wavelength allocation (DWA) procedure for this case of paired lasers with bandwidth organization in up/down segmented bandwidth.

Behnam Shariati
F5G OpenLab: Enabling twin transition through ubiquitous fiber connectivity
B. Shariati, M. Balanici, P. Safari, J. Fischer, and R. Freund, Fraunhofer Heinrich Hertz Institute, Berlin, Germany
The paper introduces a new open laboratory, the F5G OpenLab, which aims at fostering the advancement of fiber-based solutions for everything. F5G OpenLab intends to aid in creating a sustainable and eco-friendly ICT industry and accelerate the digital transformation through autonomous networking solutions that are secure and trustworthy. In particular, the purpose of the F5G OpenLab is to establish an ecosystem for the validation of optical networking solutions that facilitate twin transition, provide a vendor-neutral platform for the assessment of vertical use cases, and enable the development of fiber-based solutions. It provides a platform to verify and unify next-gen networking solutions, access to early hardware and software releases, and unique testing and measurement facilities. Finally, the F5G OpenLab supports the development of blueprints for a green and digital transformation, capitalizing on the benefits of fiber technology for all industry sectors. We present its architecture as well as key features and capabilities. Moreover, we report several proof-of-concept demonstrations focused on industry 4.0 vertical use-cases.

Chris Vagionas
Multi-RAT fiber-wireless technologies towards 6G networks
C. Vagionas¹, R. Maximidis¹, K. Kanta², P. Toumasis², G. Giannoulis², D. Apostolopoulos², G. Kalfas¹, M. Gatzianas¹, A. Mesodiakaki¹, H. Avramopoulos², A. Miliou¹, and N. Pleros^1
1Dep. of Informatics, CIRI, Aristotle University of Thessaloniki, Greece
²School of Electrical and Computer Engineering, National Technical University of Athens, Greece
At the dawning of the beyond 5G era, broadband last mile connectivity is stimulating rapid developments in optical and wireless technologies that will efficiently handle the traffic generated by mobile users and demanding network applications. To this end, multiple Radio Access (multi-RAT) technologies operating at various millimeter wave (mmWave) frequencies, e.g. V-/E-/D-band are being actively pursued, in parallel with the investigation of efficient fiber wireless fronthaul schemes, e.g. Analog Radio over Fiber (ARoF) or Intermediate Frequency over Fiber (IFoF), to deliver low-complexity, broadband, last-mile connectivity. However, integrating such novel technologies in an actual mobile network infrastructure remains a challenge, as it needs to support compatibility with the network operators' equipment. The current talk aims to present a holistic Fiber Wireless (FiWi) connectivity, demonstrating the co-existence of Analog and Digital RoF traffic along with flexible, reconfigurable point-to-multipoint connectivity to multi-RAT antenna units. Experimental results on high capacity FiWi fronthaul links operating in the V- (60 GHz) and D- (145 GHz) will be presented. Moreover, end-to-end, integrated real-time traffic and network operation will also be discussed and experimentally presented, indicating a possible technology roadmap towards multi-RAT 6G networks.

Carmen Vázquez Garcia
Performance evaluation of high data rate transmission and optically powered IoT ecosystem over SI-POF for smart home applications
F. M. A. Al-Zubaidi , D. S. Montero , P. J. Pinzón, and C. Vázquez , The Carlos III University, Madrid, Spain
In this work, we present a real time multi-Gbit/s data transmission based on SI-POF for in-home and short-range networks. Power over Fiber (PoF) solutions are also integrated with the SI-POF communication link to feed Internet of Things (IoT) nodes for smart home applications. The work presents different powering architecture, examples of low power consumption IoT nodes, power budget analysis, scalability analysis of PoF systems and its impact on data signal quality.

Morteza Ahmadian
ML-aided SOP compensation to increase key exchange rate in QKD systems
M. Ahmadian, M. Ruiz, J. Comellas, and L. Velasco, Universitat Politècnica de Catalunya, Barcelona, Spain
Secure communications have become a requirement for virtually all kind of applications. Currently, two distant parties can generate shared random secret keys by using public key cryptography. However, quantum computing represents one of the greatest threats for the finite complexity of the mathematics behind public key cryptography. In contrast, Quantum Key Distribution (QKD) relies on properties of quantum mechanics, which enables eavesdropping detection and guarantees the security of the key. Among QKD systems, polarization encoded QKD has been successfully tested in laboratory experiments and recently demonstrated in closed environments. In this paper, we propose a Machine Learning (ML) -based polarization tracking and compensation that is able to keep shared secret key exchange to high rates even under large fiber stressing events. Exhaustive results using both synthetic and experimental data show remarkable performance, which can simplify the design of both quantum transmitter and receiver, as well as enable the use of aerial optical cables, thus reducing total QKD system cost.

Sima Barzegar
Reinforcement learning for autonomous traffic flow capacity management
S. Barzegar, M. Ruiz, and L. Velasco, Optical Communications Group, Universitat Politècnica de Catalunya, Barcelona, Spain
As the dynamicity of the traffic increases, the need for self-network operation becomes more evident. One of the solutions that might bring cost savings to network operators, is that of the dynamic capacity management of large packet flows, especially in the context of packet over optical networks. Machine Learning, and particularly Reinforcement Learning (RL), seem to be an enabler for autonomicity, as a result of its inherent capacity to learn from experience. In this tutorial, we introduce RL and review its application for autonomous capacity management of traffic flows.

Davide Careglio
Disaggregated delay modeling in multidomain networks
D. Careglio, M. Ruiz, and L. Velasco, CCABA, Universitat Politècnica de Catalunya, Barcelona, Spain
Accurate delay estimation is one of the enablers of future network connectivity services. If such connectivity services require isolation (slicing), such delay estimation should not be limited to a maximum value defined in the Service Level Agreement, but to a finer-grained description of the expected delay in the form of, e.g., a continuous function of the load. Obtaining accurate end-to-end (e2e) delay modeling is even more challenging in a multi-operator (Multi-AS) scenario, where the provisioning of e2e connectivity services is provided across heterogeneous multi-operator (Multi-AS or just domains) networks. In this work, we propose a collaborative environment, where each domain models intra-domain delay components of inter-domain paths and share those models with a broker system providing the e2e connectivity services. The broker, in turn, models the delay of inter-domain links based on e2e monitoring and the received intra-domain models.

Alberto Castro
Predicting loss in optical transport segments: A GNN-GRU approach for a nationwide optical network
F. Donnangelo¹, I. Bianchi¹, A. Rodríguez², and A. Castro^1
1School of Engineering, Universidad de la República, Uruguay
²ANTEL, Uruguay
Optical networks play a crucial role in providing high-speed Internet and communication services. The performance and reliability of these networks are critical to ensuring the quality of the services provided to customers. Hence, predicting and preventing potential downtime in optical networks is of utmost importance. In this paper, we present a novel approach for predicting loss in optical networks. Our strategy combines Graph Neural Networks (GNNs) and Gated Recurrent Units (GRUs) to capture both spatial and temporal features of the optical network. By utilizing the GNN to capture spatial data and the GRU to detect temporal relationships, this methodology can predict the location of future problematic links and simulate the effects of traffic redistribution. We gathered and analyzed real data from a nationwide Internet Service Provider optical network to train and test the proposed algorithm. By exploiting the satisfactory results obtained from our methodology, network operators can proactively take measures to improve the network's performance and avoid potential downtime.

Daniel Chaves
Multipath provisioning for survivable elastic optical networks with optimized RSA ordering selection
H. A. Dinarte^1,2, G. W. Teixeira², R. C. Almeida Jr.¹, K. D. R. Assis³, H. Waldman⁴, and D. A. R. Chaves^2
1Federal University of Pernambuco, Recife, Pernambuco, Brazil
²University of Pernambuco, Recife, Pernambuco, Brazil
³Federal University of Bahia, Salvador, Bahia, Brazil
⁴State University of Campinas, Campinas, Sao Paulo, Brazil
To ensure protection in elastic optical networks, survivability strategies are usually implemented during routing and spectrum assignment  (RSA). The order in which the RSA is performed may affect the network performance. Therefore, finding an efficient RSA policy can provide a considerable increase in network resilience by providing protection, as well as increasing the number of served connections. RSA problem is usually solved by dividing it into two sub problems, routing (R) and spectrum assignment (SA). RSA can prioritize either shortest routes over contiguous slots groups of lower indexes by solving R first and then solving SA (R-SA order), or the opposite (SA-R order). Another form to improve the network performance is by utilizing the multipath strategy during the RSA. The multipath strategy allows traffic from a single user to be split into several independent flows and then be routed across the network via different paths. In this paper, we propose a new protection RSA scheme by applying a genetic algorithm, which defines the most suitable policy between R-SA and SA-R for each source-destination node pair, and that uses multipath protection in order to provide resource optimization.
Keywords: elastic optical networks, RSA ordering, genetic algorithm, multipath protection, bandwidth squeezing.

Jaume Comellas
PILOT: A methodology for modeling the performance of packet connections
J. Comellas, M. Ruiz, and J. Velasco, Optical Communications Group, Universitat Politècnica de Catalunya, Barcelona, Spain
Network Services automation requires predictable Quality of Service (QoS) performance, measured in terms of throughput, delay and jitter, to allow making proactive decisions. QoS is typically guaranteed by overprovisioning capacity dedicated to the packet connection, which increases costs for customers and network operators, especially when the traffic generated by the users and/or the virtual functions highly varies over the time. This paper presents the PILOT methodology for modeling the performance of packet connections during commissioning testing in terms of throughput, delay and jitter. PILOT runs in a sandbox domain and constructs a scenario where an efficient traffic flow simulation environment, based on the CURSA-SQ model, is used to generate large amounts of data for Machine Learning (ML) model training and validation. The simulation scenario is tuned using real measurements of the connection obtained from a set of active probes.
Keywords: sandbox domain, performance modeling and prediction.

Mariano Devigili
Extending the OCATA digital twin to the frequency domain
M. Devigili¹, M. Ruiz¹, N. Costa², C. Castro³, A. Napoli³, J. Pedro^2,4, and L. Velasco^1
1Optical Communications Group (GCO), Universitat Politècnica de Catalunya, Barcelona, Spain
²Infinera Unipessoal Lda., Carnaxide, Portugal
³Infinera, Munich, Germany
⁴Instituto de Telecomunicações, IST, Lisboa, Portugal
We extend the OCATA time domain digital twin to the frequency domain. It is shown that deep learning-based models enable to predict the linear and nonlinear impairments affecting the optical constellations, whereas analytical models are suitable to estimate the filter penalties affecting the optical spectrums. Illustrative results show the benefits of the proposed approach for failure detection and identification.
Keywords: digital twin, failure management, optical networks.

Pol González
A distributed telemetry architecture for optical networks
P. González, L. Velasco, and M. Ruiz, Optical Communications Group, Universitat Politècnica de Catalunya, Barcelona, Spain
A distributed telemetry system is proposed with agents receiving and analyzing data before sending it to a centralized manager. Intelligent data aggregation on optical constellations telemetry largely reduces data rate without introducing significant error.    

Masab Iqbal
Reliable quantum communication
M. Iqbal, L. Velasco, and M. Ruiz, Optical Communications Group , Universitat Politècnica de Catalunya, Barcelona, Spain
The quantum Internet is expected to provide information-theoretic security for data transmission by combining quantum and classical communication. Classical networks have well-established protocols for reliable end-to-end transmission that implicitly duplicate classical bits. However, due to the no-cloning theorem, quantum bits (qubits) cannot be copied. In this paper, we summarize our previous work on the use of a Universal Quantum Copying Machine (UQCM) to create imperfect clones. In this way, the Quantum Automatic Repeat Request (QARQ) protocol, inspired by its classical counterpart, can be developed. To investigate the viability of QARQ, a simulation platform is created that implements QARQ for quantum communication. The results explore whether its application is suitable, while maintaining enough quality of the qubit state.
Keywords: reliable quantum communication, qubit retransmission, universal quantum cloning machine.

Prasunika Khare
SSMS: A split step multiband simulation software
P. Khare¹, N. Costa², J. Pedro^2,3, A. Napoli⁴, F. Arpanaei⁵, J. Comellas¹, M. Ruiz¹, and L. Velasco^1
1Optical Communications Group, Universitat Politècnica de Catalunya, Barcelona, Spain
²Infinera Unipessoal Lda., Carnaxide, Portugal
³Instituto de Telecomunicações, Instituto Superior Técnico, Lisboa, Portugal
⁴Infinera, Munich, Germany
⁵Universidad Carlos III de Madrid, Spain
We introduce SSMS, a multiband optical fiber simulator entirely developed in MATLAB. SSMS solves the Generalised nonlinear Schrödinger equation (GNLSE) – the single-mode fiber wave equation – relying on the 4th order Runge Kutta method in Interaction Picture and adaptive step size approach and compared with well-known split-step Fourier method (SSFM). The simulator exploits the S+C+L band frequency range.
Keywords: multiband optical transmission, split-step Fourier method.

Marc Ruiz
CURSA-SQ models for time-sensitive networking
M. Ruiz, D. Careglio, and L. Velasco, Universitat Politècnica de Catalunya, Barcelona, Spain
Considerable research and standardization efforts are being made to support time-sensitive traffic, e.g., generated by applications like Industry 4.0 and 5G fronthaul, on packet networks. This paper focuses on analyzing the impact of conveying time-sensitive traffic in operators’ networks when such traffic is mixed with best-effort traffic. In particular, extensions to a continuous G/G/1/k queue model are proposed to evaluate two different Ethernet technologies, synchronous and asynchronous, supporting time-sensitive flows in terms of their influence on the performance of best-effort traffic.

Luis Velasco
Secure optical communications based on fast cryptography
L. Velasco, M. Iqbal, and M. Ruiz, Optical Communications Group, Universitat Politècnica de Catalunya, Barcelona, Spain
Although security solutions, like Advanced Encryption Standard (AES) and ChaCha, are common at the packet layer, secure transmission at the optical layer is still not implemented. The reason is that such cryptographic methods are not fast enough to support high-speed optical transmission and might introduce significant delay. Moreover, methods for key exchange, key generation and key expansion need to be implemented on standard coherent transponders. In this paper, we summarize a secure cryptographic solution for optical connections named Light Path SECurity (LPsec), which involves fast data encryption using stream ciphers and key exchange using Diffie-Hellman (DH) protocol through the optical channel. To support encryption of high-speed data streams, a fast, general purpose Pseudo-Random Number Generator (PRNG) is used. Moreover, to make the scheme more secure against exhaustive search attacks, an additional substitution cipher is proposed. In contrast to the limited encryption speeds that standard stream ciphers can support, LPsec can support high-speed rates.

Luis Velasco
Using a SNR digital twin for failure management
L. Velasco, S. Barzegar, and M. Ruiz, Optical Communications Group, Universitat Politècnica de Catalunya, Barcelona, Spain
The development of Digital Twins to represent the optical transport network might enable multiple applications for network operation, including automation and fault management. In this work, we use GNPy as a Signal to Noise Ratio (SNR) digital twin of the optical network for failure management applications. The methodology proposed for failure management consists in comparing the QoT measured in the transponders with the one estimated using the digital twin and try to explain detected deviations as changes in the value of input parameters of the Quality of Transmission (QoT) model representing the optical devices, like noise figure (NF) in optical amplifiers (OA) and reduced Optical SNR in the Wavelength Selective Switches (WSS). By applying reverse engineering, the value of those modeling parameters can be estimated as a function of the observed QoT of the lightpaths. Experiments reveal high accuracy estimation of modeling parameters, and results obtained by simulation show large anticipation of soft-failure detection and localization, as well as accurate identification of degradations before they have a major impact on the network.

Shaoxuan Wang
Optical network traffic analysis under B5G/6G RAN operation
Shaoxuan Wang, M. Ruiz, and L. Velasco, Optical Communications Group, Universitat Politècnica de Catalunya, Barcelona, Spain
The advent of 6G will revolutionize the way Radio Access Networks (RAN) will be operated. Expected massive small cell deployments and features, such as flexible and adaptive functional splitting, are expected to change not only the volume, but also the requirements of the traffic to be supported by the fixed transport network. This paper presents an insight into 6G RAN operation, focusing on how such operation will impact the autonomous operation of the fixed network.

Jordi Casademont
Awareness information dissemination using aggregation into collective perception messages for connected vehicles
J. Marias I Parella¹, J. Casademont^1,2, F. Vázquez-Gallego¹, and E. Lopez-Aguilera^1,2
1i2CAT Foundation, Barcelona, Spain
²Universitat Politècnica de Catalunya, Barcelona, Spain
In the last few years, two critical situations have arisen in the ecosystem of Intelligent Transportation Systems (ITS) related to the Vehicle-to-Everything (V2X) radio technologies, that are delaying their commercial development. One is the unclear standard to use for this radio access layer, and the other is the limited coverage range of the used frequencies in the presence of obstacles, like buildings in an urban scenario. In this paper we present an infrastructure architecture, which utilizes edge computing that receives V2X messages in varying radio technologies and optimally forwards awareness information, using CPM messages, to all vehicles regardless of their radio technology, increasing at the same time the area where these messages are received.
Keywords: C-ITS, V2X, CAM, CPM, MEC, LDM.

Kira Kastell
Radio Jamming in vehicle-to-everything communication systems: Threats and countermeasures
A. S. da Silva^1,2,3,4, J. P. J. da Costa^1,2, G. A. Santos⁵, Z. Miri¹, M. I. B. M. Fauzi¹, A. Vinel³, E. P. de Freitas⁴, and K. Kastell^1
1Hamm-Lippstadt University of Applied Sciences, Hamm, Germany
²Graduate School for Applied Research in North Rhine-Westphalia, Bochum, Germany
³Karlsruhe Institute of Technology, Karlsruhe, Germany
⁴Federal University of Rio Grande do Sul, Porto Alegre, Brazil
⁵Faculty UnB Gama, University of Brasılia, Brazil
More than 1.35 million lives are lost due to traffic accidents, with 94% of these accidents caused by human error. In order to significantly improve the traffic safety and efficiency, automated driving systems, including Advanced Driver Assistance Systems (ADAS) and autonomous driving, exchanges sensor and perception data between the automated vehicle and its surrounding objects via Vehicle to Everything (V2X) communication. Although V2X technologies, such as dedicated short-range communication (DSRC) and cellular vehicle-to-everything (C-V2X), are essential for the safety in certain driving use cases, they may completely fail in the presence of radio interference. Therefore, the development of robust V2X systems to deal with radio jamming in automated driving applications is crucial. In this paper, we present scenarios of the radio jamming attacks considering traditional driving use cases of V2X systems and we propose countermeasures against these attacks. Using a simulation environment, we validate the proposed countermeasures mitigating the effects of radio jamming.

Kira Kastell
Path planning algorithm for a hybrid wireless sensor network and UAV as mobile sink considering energy constraints
L. C. Moro¹, A. S. da Silva^1,2,3,4, O. A. R. da Cruz¹, J. A. da Silva¹, J. P. J. da Costa^2,3, C. E. Pereira¹, A. Vinel⁴, E. P. de Freitas¹, and K. Kastell^2
1Federal University of Rio Grande do Sul, Porto Alegre, Brazil
²Hamm-Lippstadt University of Applied Sciences, Hamm, Germany
³Graduate School for Applied Research in North Rhine-Westphalia, Bochum, Germany
⁴Karlsruhe Institute of Technology, Karlsruhe, Germany
Wireless sensor networks (WSNs) are essential in today's state-of-the-art applications. This network has been used in different domains, from precision agriculture to body area networks in e-health systems. However, the main issue regarding using WSNs is energy consumption. To tackle this problem, one of the broadest used techniques is the clustering technique. To improve energy usage in the network even more, some studies demonstrate the efficiency of employing a mobile sink, which can be an Unmanned Aerial Vehicle (UAV), depending on the application, to collect data from the static network nodes. This article approaches this problem by proposing a path planning algorithm based on A* search for a UAV considering wind field constraints. It is also considered the position of the cluster heads to reduce the energy consumption of the static network nodes and the flying data collector vehicle. The results demonstrate that the developed modified A* algorithm and the deployed clustering technique are efficient in finding an optimal path and reducing the network's energy consumption.

Matthias Koepp
An automotive communication bus using OFDMA
M. Koepp, K. Habel, and V. Jungnickel, Fraunhofer Heinrich Hertz Institute, Berlin, Germany
Today’s automotive communication systems use baseband pulse modulation and time division or carrier sense multiple access (TDMA/CSMA). In future in-vehicle networks (IVNs), more devices need to be connected in a multipoint-to-multipoint topology. We have developed a new automotive bus system based on orthogonal frequency division multiple access (OFDMA) enabling better channel adaptation and fine-granular multi-user access. We highlight the advantages of OFDMA in automotive and industrial applications, introduce our system concept and demonstrate its feasibility by means of an FPGA-based prototype. Finally, we discuss the use of electrical and optical media.

Chun-Nien Liu
Fabrication of a Cr⁴⁺: YAG crystal fiber and its use in a mode-locked all-fiber laser source
Kai-Chieh Chang¹, Chun-Nien Liu², Sheng-Lung Huang¹, and Wood-Hi Cheng^3
1Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei, Taiwan
²Department of Electronic Engineering, National Chung Hsing University, Taichung, Taiwan
³Graduate Institute of Optoelectronic Engineering, National Chung Hsing University, Taichung, Taiwan
An all-fiber Cr⁴⁺: YAG doped mode-locked laser is successfully developed at the first time. The results indicate a lasing threshold of 150 mW, maximum output power of 300mW, a signal-to-noise ratio of 70-dB and a repetition frequency of 15.9 MHz. This is an important achievement because it shows that the Cr⁴⁺: YAG mode-locked laser has the potential to be used in spectral domain optical coherence tomography applications.
Keywords: fiber design and fabrication, Cr⁴⁺: YAG material, mode-locked laser, fiber amplifiers and oscillators, optical coherence tomography.

Oskars Ozolins
High-baudrate silicon photonics ring resonator and Mach-Zehnder modulators for short-reach applications
O. Ozolins^1,6,7‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬, A. Ostrovskis^1,2, M. Koenigsmann³, T. Salgals^1,2, B. Krüger³, F. Pittalà³,‪ R. P. Scott⁴, H. Haisch³, H. Louchet³, A. Marinins¹, S. Spolitis^1,2, J. Porins¹, Lu Zhang⁵, R.Schatz⁶, Xianbin Yu⁵, V. Bobrovs¹, M. Gruen³, Xiaodan Pang^{1‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬,6,7
1}Institute of Telecommunications, Riga Technical University, Latvia
²Communication Technologies Research Center, Riga Technical University, Latvia
³Keysight Technologies Deutschland GmbH, Böblingen, Germany
⁴Keysight Technologies, Inc., Santa Clara, USA
⁵College of Information Science and Electronic Engineering, Zhejiang University, and Zhejiang Lab, Hangzhou, China
⁶Department of Applied Physics, KTH Royal Institute of Technology, Stockholm, Sweden
⁷RISE Research Institutes of Sweden, Kista, Sweden
Silicon photonics (SiP) is a key enabling technology for high-baudrate communication. It is a key technology for future 800 Gbps and 1.6 Tbps solutions to meet the ever-increasing demands. The 800G pluggable multi-source agreement (MSA) suggests that intensity-modulated direct-detection (IM/DD) is the most sustainable way forward [1]. The high operational bandwidth of each transceiver component is essential. An ultra-compact SiP slow light modulator with record-high bandwidth of 110 GHz shows the potential [2]. Therefore, both multilevel pulse amplitude modulation (PAM) and on-off keying (OOK) should be considered. SiP offers excellent production yield and has a substantial role in optical interconnects. SiP ring resonator modulators (RRM) have unique advantages like a small footprint, simple driver configuration, low power consumption, and suitability for multichannel applications. On the other hand, the SiP Mach-Zehnder modulator (MZM) offers differential drive benefits.  In this paper, we demonstrate SiP MZM/RRM-based transmitters to achieve highest-baudrate OOK and PAM4 signals below 6.7% overhead (OH) hard-decision forward error correction (HD-FEC) threshold of 4.5×10-3. These are characterized with [3]. We also managed to achieve high baudrate OOK, PAM4, and PAM6 signal transmission with SiP MZM and RRM over 100 meters single mode fiber (SMF).
[1] M. Spyropoulou, et al., The future of multi-terabit datacenter interconnects based on tight co-integration of photonics and electronics technologies, OFC’23, p. Tu3I.3.
[2] C. Han, et al., Ultra-compact silicon modulator with 110 GHz bandwidth, OFC’22, p. Th4C.5.
[3] Keysight Integrated Photonics Test Setup, https://www.keysight.com/us/en/products/software/pathwave-test-software/integrated-photonics-test-products.html‬‬‬

Liam Barry
Enabling high capacity WDM transmission systems for data centre and access networking applications
M. Troncoso Costas, L. N. Venkatasubramani, A. G. Reza, M. McCarthy, C. Browning, and L. Barry
The Rince Institute, Dublin City University, Ireland
With the ever-increasing popularity of online services, such as streaming platforms, online storage and gaming, the bandwidth requirements in optical transmission systems continue to grow. This increase in transmission capacity requirements is driving the need for low-power, cost-effective and more spectrally efficient solutions in data centre (DC) interconnects and passive optical network (PON) based optical access systems. With coherent technology not expected to be introduced in DC and PONs in the short to medium term, the transition to more advanced intensity modulation with direct detection (IM/DD) modulation formats such as PAM can enable capacity increases without requiring an increase in bandwidth/sampling rate from the electronic components. However, the power budget in both DC and PON systems becomes more challenging as the baud rate and modulation format cardinality increase. To overcome power budget issues the use of integrated semiconductor optical amplifiers (SOA) in the transmission systems can provide required gain at low cost, low power consumption and small footprint. The use of an SOA to increase the power budget however introduces additional penalties coming from excess noise and nonlinear distortions including amplified spontaneous emission (ASE) and power saturation in single channel systems, in addition to four-wave mixing (FWM) and cross-gain modulation (XGM) in WDM systems. This work outlines key technologies that can enable optically amplified high capacity WDM Transmission Systems for Data Centre and Access Networking Applications, including the use of optical frequency combs, advanced DSP and probabilistic shaping.

Alberto Castro
Optical datacenter network performance prediction
F. Donnangelo and A. Castro, School of Engineering, Universidad de la República, Uruguay
With the exponential growth of data and the increasing demand for data storage and processing, optimizing the performance of datacenter networks has become a critical challenge. In this paper, we present a novel approach to tackle this challenge by focusing on predicting ToR-to-ToR communication latency in an optical datacenter network using XGBoost, a powerful and efficient machine learning algorithm. By leveraging XGBoost and utilizing tabular data describing the datacenter network configuration, our methodology offers a cutting-edge solution for improving network reconfiguration in data centers, enabling proactive network optimization and performance improvement. In our experiments, XGBoost was trained and tested on a dataset comprising network configurations and corresponding latency measurements. The results of our experiments are encouraging, showing that XGBoost can accurately predict network latency. By forecasting network latency, datacenter network operators can make informed decisions about network reconfiguration, significantly improving network performance.

Yun Chung
High-speed IM/DD system based on OTDM technique for next-generation datacenter network
M. S. Kim, S. H. Bae, J. W. Park, K. Yu, and Y. C. Chung
Korea Advanced Institute of Science and Technology, School of Electrical Engineering, Daejeon, Korea
We report on the novel optical-time-division-multiplexing (OTDM) technique which can double the per-wavelength data rate of the intensity-modulation/direct-detection (IM/DD) system.  By using this technique, we demonstrate the transmission of a 300-Gb/s PAM8 signal with LiNbO₃ Mach-Zehnder modulators having a 3-dB bandwidth of only 17.2 GHz.  We also fabricate the proposed OTDM transmitter in a silicon-photonics chip and utilize it in the same transmission experiment.

Jaume Comellas
Optical interconnection for datacenters: To switch or not to switch
J. Comellas and G. Junyent, Optical Communications Group, Universitat Politècnica de Catalunya, Barcelona, Spain
Optical interconnection is seen as a promising solution to alleviate the congestion problems inside datacenters. Previously reported studies focus solely on optical circuit switching to establish connections. In this work we compare performance of these previous schemes with a model where static optical channels are deployed. A switch architecture using only demultiplexers and couplers, is proposed for datacenter optical interconnection, and its performance is compared with that of a WSS based switch. Results obtained by simulation show that the performance of the proposed simpler interconnect approaches that of the WSS-based one when datacenter traffic profile follow normal random distributions.
Keywords: optical routing, datacenter architecture, optical interconnection.

Stephan Pachnicke
Comparison of passive photonic reservoir computing architectures for signal equalization of future generation intra-DCN and mobile fronthaul systems
S. Kühl, L. E. Kruse, and S. Pachnicke, Christian-Albrechts-University of Kiel, Germany
Fiber-optic transmission systems must be evolving continuously to meet the increasing demand for bandwidth. This directly leads to more complex modulation formats and higher symbol rates being used in the future. The latter, in particular, poses a challenge for Digital Signal Processing (DSP) algorithms necessary for equalization and non-linearity mitigation of the transmitted signals, since implementations based on electric components will inevitably reach their fundamental physical limits with exponentially increasing baud rates. As an alternative, the concept of Neuromorphic Signal Processing (NSP) is being investigated. It is inspired by the information processing methods that have naturally developed in biological systems, which often operate highly parallel and energy efficient. Derived from Artificial Recurrent Neural Networks (RNNs), Reservoir Computing (RC) implements the NSP paradigm by passing the signal through a non-linear reservoir, transforming it into a higher dimensional computational space. It has been shown, that it is sufficient to classify the behavior of the reservoir with linear algorithms to recover the information carried by the signal. By implementing the reservoir itself with passive photonic components, most of the computational complexity can be shifted into the optical domain. This reduces the complexity of the required electronic DSP considerably, enabling higher data rates and lower power consumption. The architecture of the reservoir itself remains an open research topic with a variety of factors at play such as their equalization performance, physical size, power consumption, and fabrication cost. In this paper we provide a comprehensive comparison of the equalization performance of various passive photonic RC architectures operating under the same conditions for realistic optical transmission system architectures to be used in future short reach intra-Data Center Network (DCN) or mobile fronthaul systems.

Weiqiang Sun
Challenges and opportunities of a vastly distributed cloud computing infrastructure – In the context of the Dong Shu Xi Suan (DSXS) Project of China
Ruiyun Liu, Shengnan Yue, Junyi Shao, Shuai Zhang Jiawen Zhu, Baojun Chen, Weiqiang Sun, and Weisheng Hu, Shanghai Jiao Tong University, China
It has been widely recognized that placing cloud data centers near clean energy sources or in cooler environments may reduce the operational cost and carbon footprint. But when the scale of the system, in terms of the overall computing power and territorial coverage, is large, such benefits may be offset by the additional cost of moving data around and the complexity of efficiently utilizing the network and computational resources. In this short paper, we discuss the benefits and challenges of a vastly distributed cloud computing infrastructure, in the particular context of the east-west synergized cloud computing project in China, i.e., the Dong Shu Xi Suan Project (DSXS). We discuss the state of art research that are relevant to this topic, and explore the potential technological advances such a project may bring.

Romuald Houdré
Design and optimization of doubly resonant second harmonic generation in photonic crystal cavities based on a bound state in the continuum
Jun Wang¹, M. Clementi², J.-F. Carlin¹, A. Barone², M. Galli², D. Gerace², N. Grandjean¹, and R. Houdré^1
1Institut de Physique, Faculté des Sciences de Base, EPFL, Lausanne, Switzerland
²Dipartimento di Fisica, Università degli Studi di Pavia, Italy
We will report on the design and optimization of the generation, in gallium nitride photonic crystal cavities, of second harmonic in the visible range achieved with a doubly resonant structure between a heterostructure cavity mode and a bound state in the continuum. We will discuss on the possibility of the reversed frequency down-conversion process.

Igor Lyubchanskii
Optical heterostructures based on one-dimensional four-component photonic crystals
A. Biswal¹, D.-J. Jwo¹, H. Behera², G. V. Morozov³, and I. L. Lyubchanskii^4,5
1Department of Communications, Navigation and Control Engineering, National Taiwan Ocean University, Keelung, Taiwan
²Department of Mathematics, SRM Institute of Science and Technology, Kattankulathur, India
³Scottish Universities Physics Alliance, University of the West of Scotland, Paisley, UK
⁴Donetsk Institute for Physics and Engineering (branch of Kharkiv) of the National Academy of Sciences of Ukraine, Kyiv, Ukraine
⁵Faculty of Physics, Karazin Kharkiv National University, Ukraine
We consider light propagation through a system of either two or three one-dimensional photonic crystals, made of alternating layers of four different dielectric materials. In particular, the transmittance and bandgap structure of such a compound are investigated, both analytically and numerically. Symmetric and asymmetric arrangements of the constituent crystals are discussed.

Anna Tasolamprou
Surface states in topologically trivial and non-trivial photonic crystals
A. C. Tasolamprou^1,2, M. Kafesaki^1,2, C. M. Soukoulis^1,4, E. N. Economou^1,5, and T.Koschny^5
1Institute of Electronic Structure and Laser, Foundation for Research and Technology Hellas, Heraklion, Greece
²Section of Electronic Physics and Systems, Department of Physics, National and Kapodistrian University of Athens, Greece
³Department of Materials Science and Technology, University of Crete, Heraklion, Greece
⁴Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, USA
⁵Department of Physics, University of Crete, Heraklion, Greece
Topological insulators exhibit topologically non-trivial electronic band structure, which features an electronic band gap that causes insulating behavior in the bulk while simultaneously supporting protected, unidirectional transport of electrons along their surface without any back-scattering, mostly unperturbed by local defects and impurities. In 2005 this unique electronic feature was transferred to the realm of photonics with the discovery of the quantum Hall effect analogue in photonic crystals. Topological photonics attracts such great scientific attention mainly due to the fundamental feature coming from the topological protection the unidirectional, back-scattering-free propagation of electromagnetic energy, immune to any perturbations. Here we discuss and compare the cases of topologically non-trivial and trivial surface states found at the interfaces of a photonic crystal and the free space.

Mario Falconi
Recent advances in mid-infrared fluoroindate fiber lasers
M. C. Falconi, Department of Electrical and Information Engineering, Politecnico di Bari, Italy
Fluoroindate glasses have been the subject of considerable research efforts in recent years due to their interesting properties for mid-infrared laser emission at wavelengths above 3 μm. Compared to other glasses, e.g. ZBLAN glasses, they offer a lower phonon energy and a better thermal stability and they can host dopant concentrations as high as 10 mol%. The purpose of this review is to illustrate some of the latest examples of rare-earth-doped fluoroindate fiber lasers, operating in both continuous-wave and pulsed regimes. Details about the theoretical models, the pumping schemes, the experimental setups, and the performance in terms of output power and slope efficiency are extensively discussed.

Jan Mrázek
Transparent ceramic fibers for short- and mid-infrared lasers
J. Mrázek, O. Podrazký, J. Aubrecht, I. Bartoň, Y. Baravets, and J. Proboštová
Institute of Photonics and Electronics of the Czech Academy of Sciences, Prague, Czech Republic
Fiber laser power has increased significantly over the past two decades, reaching hundreds of kilowatts. However, the traditional glass materials do not longer meet the demanding requirements that must be fulfilled to prepare high-power lasers operating in short- and mid- infrared for their limited thermal stability or high phonon energy. Transparent ceramic materials represent a promising alternative to the glass. In this contribution we demonstrate laser-assisted processing of transparent ceramic bulks and fibers emitting within the spectral range 2.0 – 2.9 μm. The samples of rare earth-doped (Er3+, Eu3+, and Ho3+) yttrium titanates Y2Ti2O7 and yttrium dioxide Y2O3 transparent ceramics were prepared by selective laser sintering of nanocrystalline powders. We studied the laser-processing conditions on the structure of the transparent ceramic samples and we evaluated the optical properties with special attention to the luminescence in the spectral range 2.0 – 2.9 μm. We tested the selective samples as active laser media in Fabry-Perrot laser set-up and we evaluated the basic laser characteristics.  The further tailoring of chemical composition and processing conditions can further contribute to the preparation of novel ceramic luminophores emitting in short- and mid- infrared as a high-thermally and chemically stable alternative to conventional glass fibers allowing to extend the properties of fiber lasers.

Pavel Peterka
Thulium cross sections temperature dependence and its effect on fiber laser operation
P. Peterka¹, B. Jiříčková^1,2, O. Schreiber³, and M. Grábner^1
1Institute of Photonics and Electronics of the Czech Academy of Sciences, Prague, Czechia
²Faculty of Nuclear Science and Physical Engineering, Czech Technical University in Prague, Czechia
³Narran s.r.o., Brno, Czechia
Thulium fiber lasers operating at wavelengths at around 2 micrometers have many unique applications in medicine, material processing, nonlinear frequency conversion, defense etc., but their output power significantly lags behind its potential, looking for laser technology breakthroughs that would eventually enable further increase of their output power. The main power limiting factors are associated with thermal and temperature effects. In this paper, recently reported temperature-dependent thulium cross sections are reviewed as well as application of these cross-section spectra for prediction of thulium fiber laser operation using two models. Firstly, closed-form expressions for the laser threshold and slope efficiency of thulium fiber lasers pumped at 790 nm by an ideal and realistic two-for-one process are derived. Secondly, comprehensive spatially and spectrally resolved numerical model is used.
Keywords: thulium, fiber lasers, temperature effect, cross sections, fluorescence lifetime, heating, cooling.

Sławomir Sujecki
Pulsed fluoride glass fiber lasers operating near 3 µm
S. Sujecki¹, Ł. Sójka¹, Ł. Pajewski¹, S. Phang², M. Farries², D. Furniss², E. Barney², T. Benson², A. Seddon², and S. Lamrini^3
1Wroclaw University of Science and Technology, Poland
²The University of Nottingham, UK
³LISA laser products GMBH, Katlenburg-Lindau, Germany
Pulsed fluoride glass fiber based lasers have many potential important applications in materials processing, medicine and defense. At present a number of continuous wave fluoride glass fiber lasers are offered commercially. However, there is still a large scope for the development of pulsed lasers. Therefore, in this contribution we give an up-to-date review of the recent progress in the development of gain switched and Q-switched fluoride glass fiber lasers. Also we present modelling methods for the design of lanthanide ion doped fluoride glass fiber lasers and experimental results on dysprosium and erbium ion doped gain switched and Q-switched fluoride glass fiber lasers.

Sergey Sergeyev
Harnessing vector multi-pulsing soliton dynamics
S. V. Sergeyev¹, H. Kbashi¹, and C. Mou^2
1Aston Institute of Photonic Technologies, College of Engineering and Physical Sciences, Aston University, Birmingham, UK
²Key Lab of Specialty Fiber Optics and Optical Access Network, Shanghai Institute for Advanced Communication and Data Science, Joint International Research Laboratory of Specialty Fiber Optics and Advanced Communication, Shanghai University,  China
We demonstrate that mode-locked fiber laser polarization dynamics is characterized by switching between orthogonal states of polarization. In this way, soliton structures such as breathers and rogue waves appear. We use injecting optical signal with a slowly evolving state of polarization to control the dwelling time nearby each state of polarization and support regular rather than random switching between the quasi-equilibrium states.

Filip Todorov
Rare-earth-doped silica optical fibers and all-fiber lasers operating in the 2-μm spectral range
F. Todorov, M. Kamrádek, and I. Kašík
Institute of Photonics and Electronics, Czech Academy of Sciences, Prague, Czech Republic
Laser sources operating in the infrared range around 2 μm are attractive for industrial applications such as processing of transparent thermoplastic polymers, as well as for spectroscopy, gas sensing, medical applications, nonlinear frequency conversion to mid-infrared, etc. Fiber lasers benefit from their all-fiber design compared to other types of lasers and give the opportunity to build a well thermally controllable device with robust and compact design. Thulium- and holmium-doped optical fibers are usually used for the design of a 2-μm fiber laser nowadays. In this paper, an overview of our selected results in the research on thulium- and holmium-doped optical fibers, fiber lasers, and related research topics in the 2-μm spectral range are given.
Keywords: rare-earth (RE) doped optical fibers, nanoparticle doping, preform shaping, fiber lasers.

Joan Gené
Practical spectral efficiency estimation for optical networking
J. M. Gené¹, J. Perelló¹, J. Cho², and S. Spadaro^1
1Universitat Politècnica de Catalunya, Barcelona, Spain
²Infinera Corporation, Holmdel, USA
Assigning the right spectral resources is the key to flex-grid optical networking. Finding the optimal spectral allocation is a daunting task, as there are many variables at play that make accurate network models very complex. From a fiber transmission perspective, several impairments such as amplified spontaneous emission (ASE) noise from amplifiers or nonlinear interference noise (NLIN) and crosstalk (XT) generated through transmission set a limit on spectral efficiency. From a modem or router perspective, modulation format, signal intensity, and spectral allocation affect the achievable capacity. On top of that, the network conditions are dynamic, causing the channel capacity to change over time. If one is willing to sacrifice a small fraction in efficiency, some bounds can be found to guarantee a static level of service. In this work, we present a simplified strategy that provides a good tradeoff between performance and complexity.

Eiji Oki
Performance of defragmentation approach based on route partitioning in 1+1 protected elastic optical networks
E. Oki¹ and B. C. Chatterjee^2
1Kyoto University, Japan
²South Asian University, New Delhi, India
Spectrum fragmentation suppresses spectrum usage in survivable elastic optical networks (EONs). Survivable EONs with full and quasi-1+1 protected services require an effective spectrum defragmentation approach. Full-1+1 path protection ensures dependability without disrupting traffic when the backup route cannot be reallocated. If a working path fails while its backup route is being moved, the reliability of a service that provides full-1+1 protection goes down. To defragment them, network operators must carefully study EONs with full-1+1 and quasi-1+1 protected lightpaths. In 1+1 protected EONs with full and quasi-1+1 protected services, route partitioning-based defragmentation reduces spectrum fragmentation and blocking probability. Retuning interference arises when a full-1+1 protected lightpath cannot be returned to fill up a gap created by a terminated lightpath owing to interfering from another lightpath that stops it from retuning farther. The introduced defragmentation approach minimizes this interference. A simulation study demonstrates the efficacy of the presented defragmentation approach with route partitioning.

Jordi Perelló
Evaluating the impact of the guard band width on the benefits of probabilistic constellation shaping in future flex-grid over multicore fibre optical backbone networks
J. Perelló¹, J. M. Gené¹, J. Cho2, and S. Spadaro^1
1Universitat Politècnica de Catalunya – BarcelonaTech, Spain
²Infinera Corporation, Holmdel, USA
Probabilistic constellation shaping (PCS) has emerged as an advanced modulation technique that provides a fine-grained software-defined trade-off between achievable spectral efficiency (SE) and transmission reach to deliver optimal channel capacity at any distance. This paper quantifies the network throughput benefits resulting from adopting PCS in future Flex-Grid over multicore fibre optical backbone networks, compared to using traditional uniform modulation formats. In particular, different inter-channel guard band width configurations are accounted in our study, aiming to set guidelines on the filtering requirements at network spectrum selective switches (SSS) to take full PCS advantage in future optical backbone networks.
Keywords: optical networks, flex-grid, SDM, guard bands, probabilistic constellation shaping.

Nicola Sambo
Energy efficiency in next-generation optical networks
N. Sambo¹, C. Castro², N. Costa³, P. Castoldi¹, and A. Napoli^2
1Scuola Superiore Sant’Anna, Pisa, Italy
²Infinera, Munich, Germany
³Infinera Unipessoal Lda., Carnaxide, Portugal
Energy consumption in optical network infrastructures is investigated identifying energy-hungry key components and network functionalities. Solutions based on smart pluggables are presented to increase energy efficiency at the edge of the metro segment.
Keywords: energy consumption, energy efficiency, CO2, smart pluggables, digital sub-carrier multiplexing.

Antonio Tartaglia
Perspectives for co-packaged optics in radio access networks
A. Tartaglia, F. Cavaliere, M. Lostedt, A. Bigongiari, A. Palagi, U. Parkholm, A. Tavemark, S. Stracca, A. D’Errico, S. Lessard, and M. Johansson
BNEW DNEW TP OS&FH Optical Systems, Ericsson, Genova, Italy
Co-packaged optics (CPO) is an emerging technology for providing optical interconnections with a bandwidth density of the order of Terabit/s per millimeter square. All current development and standardization efforts focus on data centers, for example to connect very high-capacity switches improving energy efficiency and footprint compared to designs based on pluggable optics. We think CPO will have an important role also in 6G networks, to meet the demand for high capacity at low energy consumption. This paper illustrates use cases and requirements for CPO natively designed for radio applications and outlines standardization and industrialization paths. HIGH-LEVEL DESCRIPTION OF THE TALK: Moore’s law cannot longer sustain the demand for higher compute bandwidth without radical innovation in the integrated circuits process, packaging and architectures.  With the increase of the baud rate, traditional copper interconnects are posing increasing challenges to meet targets in energy efficiency, bandwidth, link loss and  transmission distance at acceptable cost points. Solving these issues requires a new approach embracing a wide assortment of expertise such as integrated circuits design, digital signal processing, optical communications, switching and packaging.  CPO captures this trend proposing an advanced integration of optics and silicon on a single packaged substrate. The cloud infrastructure is today the main market driver for CPO, first introduced in multi-terabit switches and high-performance computing units in data centers.  But the exponential traffic growth expected with the introduction of the 6G mobile generation will create a similar need for high interconnect bandwidth at low energy also in the radio access network (RAN); not only in the transport network connecting radio units (RU), distributed units (DU) and central units (CU) but also for chip-to-chip interconnects in hardware-dense boards, like massive Multi-Input Multi-Output (MIMO) antenna systems, especially when moving to higher frequencies, up sub-Terahertz. Today, there is no common understanding in the industry on which are the use cases and the requirements for the use of CPO in the RAN. This holds for both silicon manufacturers and suppliers of optical transceivers: all current development and standardization efforts focus on data centers. Part of that work is also applicable to radio systems, but there are significant differences mainly related to the different deployment environment  (operation at high temperature, eye-safety issues with external lasers, cabling issues over long distances, stringent synchronization and timing requirements, etc.). We will illustrate the new requirements of “CPO for RAN applications” and the technical advances made in that direction. We will also highlight the work which remains to be done to secure the creation of an open, standard-based ecosystem. We believe 6G poses the opportunity for this to happen, and for all the relevant industries to gather around one same table.

Carmen Vázquez Garcia
Reconfigurable MCF-SDM designs for 5/6G RAN and PON with optical feeding capability
F. M. A. Al-Zubaidi, R. Altuna , J. D. López-Cardona, D. S. Montero, and C. Vázquez, The Carlos III University, Madrid, Spain
We explore the use of MCF to implement an SDM optical network capable of addressing future challenges of 5/6G fronthaul architecture. The work proposes different designs that can support RAN and PON in parallel with the integration Power over Fiber (PoF) technology. Different scenarios will be presented that will be analyzed theoretically with simulation and some experiments. The analysis will show the data transmission capacity, PoF feeding capability and its impact on data signal quality.

Kentaro Nishida
Super-resolution imaging of plasmonic and dielectric nanostructures by using photothermal scattering nonlinearity
K. Nishida1 and Shi-Wei Chu^1,2,3
1Department of Physics, National Taiwan University, Taipei, Taiwan
²Molecular Imaging Center, National Taiwan University, Taipei, Taiwan
³Brain Research Center, National Tsing Hua University, Hsinchu, Taiwan
Optical scattering microscopy allows us to visualize the material structure with the advantages of label-free and contactless. Conventionally, the spatial resolution of optical microscopy was restricted to about half of the light wavelength, and the application to nanomaterial observation was challenging. In our research, we developed the techniques for super-resolution scattering imaging of plasmonic and dielectric nanostructures by efficiently utilizing their photothermal scattering nonlinearity. We discovered that plasmonic scatterings from metallic nanoparticles exhibit strong saturation at the center of the illumination focal spot, where excitation intensity is specifically high, due to the thermal increase of imaginary permittivity. By reconstructing the image with the saturated scattering signal, we obtained the high spatial resolution scattering image, reaching about λ/8 of the excitation wavelength. In addition, we recently discovered the giant nonlinearity of Mie scattering from a single silicon nanoparticle based on the thermal shift of resonant spectrum, and demonstrated the application to super-resolution imaging of silicon nanostructure.

Constantin Simovski
Accurate estimation of non-resonant far-field superresolution by a glass microparticle
C. Simovski and R. Heydarian, Aalto University, Helsinki, Finland
It has been known since 2011 that metamaterial superlenses and hyperlenses are not necessary for far-field superresolution without fluorescent labels. Optical engineers built practical imaging devices based on simple glass microspheres which grant much better spatial resolution and much higher magnification than the best known hyperlenses. However, this phenomenon was explained theoretically only in some resonant cases. We theoretically revealed a non-resonant mechanism of this imaging and have shown that the diffraction limit is beaten, because the location of a virtual image (shaped by a microsphere from the radiation of a real subwavelength dipole) is determined not by the intensity maximum of this radiation but by its intensity zero. This is so because the virtual image of the point dipole is created by the dipole moment component directed to the image center. Further, via extensive numerical simulations we revealed a new scenario of nanoimaging in which the virtual source of the imaging beam arises not in front of the sphere (as in all reported experiments) but behind it -- in the space between it and the objective lens. However, in these works our estimates of the ultimate spatial resolution were heuristic (not reliable enough). In this presentation we accurately obtain optimistic and pessimistic bounds for the spatial resolution achievable in a realistic nanoimaging system (an object, a glass microparticle and a microscope). Since the point-spread function method is not applicable to hollow wave beams (and our imaging beam is namely hollow) the maximal and minimal bounds for the ultimate spatial resolution were obtained combining the back-propagation method and the COMSOL Multiphysics solver. Using the same solver, we also convincingly explain the role of the substrate in obtaining the needed radial polarization of the object. As we assumed earlier, it results from the cross-polarization effect that arises for a tiny scatterer located in a crevice between the microsphere and the substrate.

Sima Barzegar
Intent-based networking for zero-touch optical networking
S. Barzegar, M. Ruiz, and L. Velasco, Universitat Politècnica de Catalunya, Barcelona, Spain
The Intent-Based Networking (IBN) paradigm targets at defining high-level abstractions, so network operators can define what are their desired outcomes without specifying how they would be achieved. The latter can be achieved by leveraging network programmability, monitoring and data analytics, as well as the key assurance component. In this paper, we introduce the IBN paradigm and its application to optical networking, highlighting the benefits that Machine Learning (ML) algorithms can provide to IBN. Illustrative examples of intent-based operation are presented for proactive self-configuration and cooperative intent operation.
Keywords: Intent-based networking, network automation.

Andrea Bianco
Using SHAP values to validate model’s uncertain decision for ML-based lightpath quality-of-transmission estimation
H. Houssiany¹, O. Ayoub², C. Rottondi³, and A. Bianco^3
1Lebanese University, Beirut, Lebanon
²University of Applied Sciences and Arts of Southern Switzerland, Lugano, Switzerland
³Politecnico di Torino, Italy
We apply Quantile Regression (QR) for lightpath quality-of-transmission (QoT) estimation with the aim of identifying uncertain decisions and then exploit Shapley Additive Explanations (SHAP) to quantify lightpath features’ importance by means of SHAP values and validate the model’s decisions in a post-processing phase. Numerical results show that our approach can eliminate more than 98% of false predictions and that SHAP values can validate up to 90% of the model's uncertain decisions.
Keywords: lightpath QoT estimation, uncertainty quantification, explainable artificial intelligence.

Stefano Biasi
Microresonator-based photonic neural network
S. Biasi and L. Pavesi, Nanoscience Laboratory, Department of Physics, University of Trento, Italy
Over the past decade, artificial intelligence has improved computing capabilities by playing an important role in applications ranging from object recognition [1,2] to playing board games [3]. The implementation of machine learning technology finds fertile ground in the field of photonics [4]. Thus, many demonstrations based on optoelectronic structures have reported state-of-the-art performance in various tasks. Integrated optics, especially silicon photonics, may be the disruptive technology [5]. Indeed, it can meet the demand for scalability of neural networks in space and time by mitigating problems related to control complexity, physical size, and power consumption. Here, we show how a silicon microresonator coupled to a bus waveguide can be used as a CMOS-compatible neuron for large-scale integration. To this end, we discuss the use of a single microresonator as a reservoir computing through the virtual node approach [6]. In addition, we show the limitations of using three microresonators as active nodes within an all-on-chip feed-forward neural network [7] and finally we demonstrate an implementation of the extreme learning machine algorithm using an array of coupled microresonators.
[1] C. Zhang and Y. Lu, Study on artificial intelligence: The state of the art and future prospects, Journal of Industrial Information Integration, vol. 23, p. 100 224, (2021).
[2] O. Russakovsky et al., ImageNet large scale visual recognition challenge, Int. J. Comput. Vis 115, 211–252 (2015).
[3] D.Silver et al. Mastering the game of go with deep neural networks and tree search, Nature 529, 484–489 (2016).
[4] N. L. Kazanskiy, M. A. Butt, and S. N. Khonina, Optical computing: Status and perspectives, Nanomaterials, vol. 12, no. 13, p. 2171, (2022).
[5] P. Xu and Z. Zhou, Silicon-based optoelectronics for general-purpose matrix computation: A review, Advanced Photonics, vol. 4, no. 4, p. 044 001, (2022).
[6] M. Borghi, S. Biasi, and L. Pavesi, Reservoir computing based on a silicon microring and time multiplexing for binary and analog operations, Scientific Reports, vol. 11, no. 1, pp. 1–12, (2021).
[7] S. Biasi, R. Franchi, D. Bazzanella, and L. Pavesi, On the effect of the thermal cross-talk in a photonic feed-forward neural network based on silicon microresonators, Frontiers in Physics, vol. 10, p. 1 093 191, (2022).

Octavia Dobre
A machine learning-based approach for nonlinearity compensation in subcarrier multiplexing system
W. S. Saif¹, S. K. Orappanpara Soman²,  and O. A. Dobre^1
1Faculty of Engineering and Applied Science, Memorial University, St. John's,  Canada
²School of Engineering, Ulster University, Belfast, UK
In this paper, for the first time in the literature, we investigate the potential of applying machine learning (ML) techniques for nonlinearity compensation in high-speed subcarrier multiplexing (SCM) systems. Our proposed method aims to effectively deal with the effects of both self-subcarrier and cross-subcarrier nonlinearities in a 64-quadrature amplitude modulation dual-polarization system with 120 Gbaud transmission. The performance of the proposed approach is evaluated and discussed in comparison with non-ML approaches in the literature. The results of this study demonstrate the potential of using ML techniques to improve the performance of SCM systems and to make them suitable for real-world implementation. We envisage that our results will initiate further research on applying ML techniques in SCM systems for high baud rate systems.

Georgios Ellinas
ML-aided traffic-driven service provisioning in elastic optical networks
H. Maryam, T. Panayiotou, and G. Ellinas
Department of Electrical and Computer Engineering School of Engineering, University of Cyprus, Nicosia, Cyprus
In this work, the capabilities of an encoder-decoder learning framework are leveraged to accurate predict multi-step ahead traffic over a long future horizon (i.e., for several planning intervals ahead). To effectively exploit this information, a traffic-driven service (re)provisioning algorithm is developed aiming at minimizing undesired service disruptions while maintaining service overprovisioning at desired levels.

Carlos Natalino
Machine-Learning-as-a-Service for optical networks: Use cases and benefits
C. Natalino¹, N. Mohammadiha^2,3, A. Panahi², and P. Monti^1
1Department of Electrical Engineering, Chalmers University of Technology, Gothenburg, Sweden
²Department of Computer Science and Engineering, Chalmers University of Technology, Gothenburg, Sweden
³Ericsson Research, Gothenburg, Sweden
Machine Learning (ML) models have been a valuable tool to assist on the design and operation of optical networks. Several use cases have benefited from ML models, such as Quality-of-Transmission (QoT) estimation, device modeling, constellation shaping, and attack/anomaly prediction/detection. ML models are expected to be ubiquitous in optical network management and operations thereof. However, the amount of human intervention and empirical decisions needed to select the exact ML model, train and evaluate its performance, and ultimately deploy and use the model, may become a bottleneck for widespread ML use in optical networks. Machine-Learning-as-a-Service (MLaaS) has the potential to greatly reduce human intervention and empirical decisions during the creation, evaluation, and deployment of ML models. In this talk, we will firstly discuss optical network use cases that can benefit from MLaaS. Then, we detail our proposed architecture for MLaaS. Finally, performance results for two use cases will be presented.

Mariana Ramos
Machine learning-based polarization drift compensation for high speed DV-QKD homodyne receiver
M. F. Ramos, E. Gutmann, and H. Hübel, Austrian Institute of Technology, Wien, Austria
Discrete variables quantum key distribution (DV-QKD), with its well-studied and scrutinized BB84 protocol, benefits from being very attractive for highly secure communications. However, current detection schemes rely on the use of InGaAs SPDAs, which limits not only its use in high temperature environments, but also high secure communication rates. A possible approach is the use of coherent homodyne detection schemes for polarization encoding based DV-QKD combined. To deploy polarization encoding DV-QKD over standard optical fiber high speed networks, the polarization drift suffered due to birefringence over the channel must be compensated.  In this work, we use a machine learning (ML) polarization tracking and compensation algorithm combined with a coherent homodyne receiver, thus allowing the deployment of high-speed polarization encoding based DV-QKD in standard optical fibers. The ML-algorithm predicts the SOP evolution keeping the error rate below 1%. In this way, the overhead to polarization monitoring is reduced leading to a secure key exchange rate (SKR) of 79 Mbps for a communication over 40 km optical fiber.
Keywords: quantum key distribution, coherent-detection, machine-learning, SOP drift compensation.

Abraham Sotomayor
A comparison of machine learning techniques for fiber non-linearity compensation: Multilayer perceptron vs. learned digital backpropagation
A. Sotomayor¹, E. Pincemin¹, V. Choqueuse², and M. Morvan^3
1Orange Labs, Lannion, France
²ENIB, Brest, France
³IMT Atlantique, France
In this paper, we analyze the performances of a Multilayer Perceptron (MLP) and the physics-based model called Learned Digital Backpropagation (LDBP) for compensating for fiber non-linear impairments in coherent transmission systems. We applied both methods numerically to a single-channel single polarization 200Gb/s 16QAM system along 5x100km and 10x100km of standard single-mode fiber. We evaluated both techniques in terms of bit error rate (BER) and computational complexity (CC). Furthermore, we identified three study cases for the MLP depending on its position in the receiver. In our setup, the results showed that the LDBP improves BER much better than the MLP, even at 1 step/span. We also showed that the CC of the LDBP is lower than the MLP one concerning real multiplications per symbol. However, in the real life, the LDBP, being a sequential technique, might take more processing time than the MLP which is easily parallelizable.
Keywords: nonlinear equalizer, neural networks, multilayer perceptron, learned digital backpropagation.

Huy Quang Tran
Integration of ML pipeline in transport network management as code for RMSA optimization in EONs
H. Q. Tran, J. Errea, V.-Q. Pham, D. Verchere, and D. Zeghlache
NSSR Lab, Bell Labs Core Research, Paris-Saclay, France
The emerge of 5G and upcoming 6G traffic requires advanced mechanisms to control optical network infrastructure and manage spectrum resource. We applied the Optical Transport Network Management as Code (OTNMaC) approach to automate the cloud-native control functions deployment for infrastructure management. Additionally, ML-aided Routing, Modulation and Spectrum Allocation (RMSA) algorithms are important to optimize spectrum resource given the dynamicity of service requests in Elastic Optical Networks (EONs). Thus, a ML pipeline is introduced to facilitate the creation of ML-aided RMSA models. Moreover, the requested bandwidth distribution of the traffic matrix may vary at a certain time which leads to a data drift. This effect degrades the accuracy of the ML model. For that reason, we propose the integration of ML pipeline in OTNMaC to provide an adaptation mechanism to automate RMSA models deployment in network infrastructure control and resource management for EONs.

Xu Wang
Machine learning assisted underwater wireless optical communication
Xu Wang, Heriot Watt University, Edinburgh, UK
Underwater wireless optical communication (UWOC) provides high transmission data rate, high security, and low latency communication to link the nodes in underwater sensing network. The main change for an UWOC system is the large absorption and scattering losses in the water that reduces the received optical signal-to-noise ratio (OSNR), thus limits the transmission distance. Advanced signal processing technologies are hereby essential in UWOC systems to improve the transmission distance. In this work, we have applied the Deep Echo State Network (DeepESN) in high-speed UWOC system to assist signal processing for both PAM and QAM-OFDM signals. We have experimentally verified the effectiveness of DeepESN in UWOC systems and demonstrated over 40.5 meters error-free underwater transmission with 100-167 Mbps data-rate.

Tijmen Euser
Hollow-core-fibre microreactors for photocatalysis
T. Lawson^1,2, A.S. Gentleman^1,2, E. Miele¹, M. H. Frosz³, E. Reisner², and T. G. Euser^1
1NanoPhotonics Centre, Cavendish Laboratory, Department of Physics, University of Cambridge, UK
²Department of Chemistry, University of Cambridge, UK
³Max Planck Institute for the Science of Light, Erlangen, Germany
We use optofluidic hollow-core fibres (HCFs), connected to microfluidic coupling cells, to monitor photocatalytic reactions in systems that combine molecular catalysts with particulate light absorbers. Our recent work focuses on molecular catalysts combined with carbon nanodots. Carbon nanodots (CNDs) are one of the most promising light-absorber materials due to their unique scalability, biocompatibility, water solubility, and stable optical properties. Key to improving their performance in solar catalysis are charge-transfer processes. This talk will review how these processes can be investigated through fibre-enhanced absorption-, fluorescence-, and Raman spectroscopy.
Keywords: fibre-optic sensors, photonic crystal fibre, fluorescence, photocatalysis.

Peter Mosley
Quantum frequency conversion in photonic crystal fibre for universal wavelength interfaces
P. J. Mosley, Centre for Photonics and Photonic Materials, Department of Physics, University of Bath, UK
In order to scale up quantum networks it is essential to ensure wavelength compatibility between photons emitted by information-processing nodes. Bragg-scattering four-wave mixing in photonic crystal fibre (PCF) provides a means to convert single photons between pairs of wavelength bands separated by a frequency shift controlled by the detuning of two pump fields. However, typically a different PCF is required for phase matched conversion of each particular pair of source and target wavelength, and the conversion efficiency drops rapidly if another source wavelength differs by only a few nanometres. In this talk, we discuss how careful design of the PCF dispersion enables frequency conversion to the telecoms C-band of photons from anywhere within an ultra-broad range of source wavelengths spanning hundreds of nanometres. We present recent experimental results demonstrating the implementation of this type of universal quantum frequency conversion interface [1]. We show that our device can convert heralded single photons at 1551 nm to any wavelength between 1226 - 1408 nm and we discuss ongoing efforts to extend this span even further by reducing noise generated during the conversion process.
[1] Bonsma-Fisher et al., Phys. Rev. Lett. 129, 203603 (2022).

Radan Slavik
Stable latency (hollow core) optical fibres
R. Slavík, Zitong Feng, F. Poletti, and D. J. Richardson, Optoelectronics Research Centre, University of Southampton, UK
Light propagating through an optical fibre changes its group delay due to ambient temperature variations. This is detrimental in applications that are time-sensitive, including modern and next-generation telecom networks and infrastructures such as data centres. We review strategies how to reduce this effect and in particular how the emerging hollow core optical fibres can address this impairment.

Vittorio Curri
Is the digital twin of the optical transport the enabler for multi-band open and disaggregated optical networks?
V. Curri, DET, Politecnico di Torino, Italy
The largest portion of the installed optical fibers is the ITU-T G.652D that may enable a low loss transmission bandwidth exceeding 50 THz, so multi-band transmission is a solid cost-effective option to enable pay-as-you-grow network capacity growth. Moreover, the open and disaggregated network management is currently proposed by several consortia as an option for multi-vendor interoperability and infrastructure sharing and slicing. We comment on the need of a vendor agnostic digital twin of the physical layer to enable the openness, focusing on the peculiarities of the multi-band transmission scenario.

Andrea Fumagalli
Accurate representation of signal spectra in the optical network emulation (ONE) engine
A. Gomathinayakam Latha¹, M. R. Rahim¹, Tianliang Zhang¹, R. Hui², and A. Fumagalli^1
1OpNeAR Lab, The University of Texas at Dallas, Richardson, USA
²University of Kansas, Lawrence, USA
The Optical Network Emulation (ONE) engine is a software tool that offers students the opportunity to learn how to control and operate open optical (wavelength division multiplexing) networks, such as those based on the Open ROADM MSA standards. This paper describes multiple modeling techniques that are implemented in ONE to represent the signal spectra at any link/fiber section of the emulated transport network. These techniques make use of various polynomial fitting and deconvolution computation methods.

Tibor Berceli
Optical modulation methods for transmission of OFDM wireless signals
T. Berceli and M. L. Iványi
Budapest University of Technology and Economics, Hungary
The next generation mobile communication systems require new modulation methods to achieve high transmission capacity with low distortion. The signal transmission in the mobile network is strongly affected by frequency selective fading. The OFDM modulation can counterbalance that problem. However, the OFDM modulation method is sensitive to the nonlinearity of the transmission channel. In this paper several optical modulators are investigated transmitting OFDM wireless signals with high bit rate. By evaluating our investigation results optimum modulator types with optimum operation points can be determined for specific applications.

Robert Minasian
Integrated microwave photonic signal processing and sensing
R. Minasian and Xiaoke Yi, The University of Sydney, Australia
Integrated microwave photonic signal processing offers a new powerful paradigm due to its inherent advantages including wide bandwidth and immunity to electromagnetic interference. Microwave photonics, which merges the worlds of RF and photonics, shows strong potential as a key enabling technology to provide new signal processing systems and sensors that can overcome inherent electronic limitations. Currently there is a significant global drive to achieve integration of photonic signal processors on silicon platforms, especially since this leverages the CMOS fabrication technology to enable boosting the performance of future systems performing communications and sensing with the potential for implementing high bandwidth, fast and complex functionalities. Advances in silicon photonics integrated signal processing are presented. These include dense optical integration techniques for LIDAR on-a-chip systems, widely tunable microwave photonic filters, compact nanophotonic signal processors and high-resolution integrated sensors. These photonic processors herald new capabilities for achieving high-performance signal processing.

Claudio Porzi
Silicon photonics for millimeter-wave band signal generation
C. Porzi¹, A. Malacarne², F. Scotti², M. Scaffardi², P. Ghelfi², and A. Bogoni^1,2
1TeCIP Institute, Scuola Superiore Sant’Anna, Pisa, Italy
²Photonic Networks and Technologies National Laboratory, CNIT, Pisa, Italy
By providing large bandwidth and supporting efficient frequency re-use, the millimeter (mm-) wave band enables low-latency high-capacity wireless communications in 5G and 6G radio access/backhaul networks. Optical heterodyning of two laser carriers in a high-speed photodiode is a convenient approach for generating radio waveforms up to the (sub)THz range. However, in order to increase the stability of the operation, reduce the dimensions and power consumption, and simultaneously breaking down the fabrication costs of the subsystem, photonic integration represents a promising viable solution. We report of recent advancements in our approach for realizing ultra-compact and broadband photonics-based RF processors in silicon on insulator (SOI) technology for mm-wave clock signal distribution, high data rate transceivers, opto-electronic oscillators, and microwave photonics filters. Developments of fully packaged solutions matching the requirements for field trials and practical application scenarios are also discussed.

Chris Roeloffzen
Integrated microwave photonics: A chip platform by hybrid integration of InP and SiN TriPleX
C. Roeloffzen, P. Maat, I. Visscher, M. Hoekman, L. Wevers, E. Klein, P. van Dijk, R. B. Timens, R. Grootjans, F. Şahin, R. Heuvink, R. Dekker
LioniX International BV, Enschede, The Netherlands
Integrated microwave photonics (IMWP) is a novel field in which the fast-paced progress in integrated optics is harnessed to provide breakthrough performances in well-established microwave photonic processing functions, which are traditionally realized using discrete optoelectronic components. A field where IMWP is expected to have a strong impact is the one of phased array antennas. Such arrays offer a number of attractive characteristics, including a conformal array profile, broadband beamforming (beam shaping and beam steering) and interference nulling. This, however, is very challenging to achieve using only electronics processing. For this reason, the last few years, an increasing amount of effort has been directed to the development of our hybrid chip platform where Si₃N₄-based-TriPleX and InP optical waveguides are combined to enable broadband and high frequency radio signal processing in the optical domain including conversion.

Zeev Zalevsky
Microwave-based remote bio-sensing behind walls
O. Meshulam¹, N. Ozana¹, D. Scheffer², S. Zach³, and Z. Zalevsky^1
1Bar-Ilan University, Ramat-Gan, Israel
²IARD – Sensing Solutions Ltd., Kibbutz Yagur, Israel
³10 Nachum st., Kfar Saba, Israel
In this paper a novel method for microwave based remote sensing of vital signs behind walls is presented. The method is based on temporal spatial analysis of back scattered microwave signals. The use of non-optical electromagnetic radiation enables monitoring from larger distances and behind objects in contrast to similar concepts in optics. Further, such use of non-optical radiation omits the need for direct line of sight between the monitoring system and the target and enables monitoring through walls or other barriers.  Micro-vibrations due to breathing and heart pulsation affect the reflection of microwaves and cause the self-interference random patterns (i.e. speckle patterns) to vary in time and space. By using this approach, the temporal change of the speckle patterns due to changes in vital signs can be tracked behind walls.  In this paper we present a system in WiFi frequencies band consisting of two radio-frequency (RF) transmitters and either one or three RF receivers to detect single or multiple breathing or non-breathing human subjects, behind different type of walls. The results showed that the system was able to distinguish between breathing states, to determine the vibration frequency of heartbeats, and to distinguish between subjects’ vital signs in few cases. In low SNR cases statistical analysis was applied to extract breathing and heartbeats frequencies, by a sweep of 20 different transmitted signals in sequence. This is the first step towards real time remote detection of human vital signs using RF speckle patterns.
Keywords: speckle, antenna, optical scattering, spectrum analyzer network.

Hovik Baghdasaryan
The Poynting vector in light-emitting multilayer micro/nanostructures: Wavelength-scale analysis by the method of single expression
H. V. Baghdasaryan¹, T. M. Knyazyan¹, T. T. Hovhannisyan¹, M. Marciniak², and T. Baghdasaryan^3
1National Polytechnic University of Armenia, Yerevan, Armenia
²National Institute of Telecommunications, Warsaw, Poland
³Brussels Photonics(B-PHOT), Vrije Universiteit Brussel (VUB), Brussels, Belgium
The Poynting vector is a unique mathematical expression that describes electromagnetic energy flow. It allows monitoring and observing specific features of electromagnetic waves’ interaction with confined structures. Calculation of the Poynting vector outside of any confined structure is feasible without difficulty. However, with the advent of modern photonics, there is a necessity to have information about energy flow within micro/nanostructures, consisting of dielectric, semiconductor or metallic nano-layers. Apparently, this information is attainable only numerically. Application of widely accepted approach of counter-propagating waves within confined multilayer structures is cumbersome for this type of analysis. An advantage of the method of single expression (MSE) is its high suitability in monitoring distributions of the Poynting vector and electric field within any multilayer structure. In the current work we make use of this advantage of the MSE to identify optimal configuration of 1D reflective type light-emitting microstructures. The RCLED with metallic back mirror is analysed numerically by the MSE.
Keywords: Poynting vector, amplifying multilayer micro/nanostructure, light-emitting micro/nanostructure, method of single expression, numerical modelling.

Sylwester Latkowski
Next-generation InP technology for high-demand communication networks and emerging applications
Y. Wang, S. Latkowski, E. Panina, J. van der Tol, K. Williams, and Y. Jiao
Institute for Photonic Integration, Eindhoven University of Technology, The Netherlands
Optical and terrestrial networks are subject to everlasting strive for reduced cost, size, weight, and power consumption along with continuous demand to increase data bandwidth. For all of these to be fulfilled high degree of parallelism at extreme line rates is necessary. Such can be achieved with the use of integrated photonics. Current advances in next-generation photonic integration developed at the Eindhoven University of Technology provide an unprecedented density of integration. This no-compromise monolithic integration technology offers a fully comprehensive set of active and passive functions including detection, amplification,  and lasers that can be combined with nanophotonics on a chip level. This next-generation technology is supported with an open-access PDK, and is currently accessible via JePPIX.

Radu Malureanu
Investigation of material properties for use in UV metasurfaces
L. Yu. Beliaev¹, M. Hagen Jakobsen¹, E. Shkondin², P. Voss Larsen², A. Lavrinenko¹, and R. Malureanu^1
1Technical University of Denmark, Dept. of Electronics and Photonics Engineering, Lyngby, Denmark
²Technical University of Denmark, DTU Nanolab, Lyngby, Denmark
The conventional use of UV light – light between the wavelengths 200 and 400nm – is limited due to difficulties in controlling its properties, but it has huge potential for applications, particularly in medicine (pharmacology, phototherapy and sanitation) and nanotechnology (high-resolution lithography). Metasurfaces (MSs) are structured surfaces with a wide range of specific functionalities, from standard ones like lenses and polarisers to more complex ones, including beam shaping, beam splitting and light modulation. They are used in a broad wavelength range, starting from visible and ending in the radio range, where they are generally known as frequency-selective surfaces. The main bottleneck in developing dielectric MSs for UV light is that there are limited materials available. The situation is similar to the one in plasmonics research several years ago when a massive effort was aimed at finding alternative plasmonic materials. Most conventional dielectrics for visible and near-infrared optics are extremely lossy in the UV range, making them unsuitable for the purpose.  In this paper, we will present an initial investigation of the properties of several materials we have identified that have the potential to be used in fabricating UV MSs. We will discuss the various optical properties but also asses their feasibility from a nanofabrication point of view.

Ana Quirce
Experimental study of quantum random number generation using polarization switching in gain-switched VCSELs
I. Rivero, M. Valle-Miñón, A. Quirce, and A. Valle
Instituto de Física de Cantabria, Universidad de Cantabria-CSIC, Santander, Spain
We have experimentally demonstrated that the random excitation of the linear orthogonal polarization modes of a gain-switched vertical-cavity surface-emitting laser (VCSEL) can be used for quantum random number generation. Our VCSEL presents polarization switching under continuous wave operation. Adjusting the modulation conditions and sampling times, both polarization modes of the VCSEL can be excited with equal probability. Random bits are obtained comparing the two orthogonal polarized signals at a sampling time. The random bits obtained pass some of the National Institute of Standards and Technology (NIST) statistical tests. Keywords: VCSELs, gain switching, polarization switching, quantum random number generation.

Anna Sitek
Low-energy electronic states in tubular wires
A. Sitek¹ and A. Manolescu^2
1Institute of Theoretical Physics, Wroclaw University of Science and Technology, Poland
²Department of Engineering, Reykjavik University, Iceland
We study theoretically the electron energies and localization in a hexagonal nanotube which is the outer part of a core-shell nanowire. We show that the lowest transverse states are localized in the corner areas of the cross section leading to conductive channels along the edges. We study the impact of spin-orbit interaction on the edge states in uniform and inhomogeneous structures and we show that the bands of homogeneous system are hardly affected by spin-orbit interaction but the effect considerably increases in the disordered wire.
Keywords: core-shell nanowires, nanotubes, spin-orbit interaction, polygonal cross section.

Vincenzo Eramo
Neural graphs: An effective solution for the resource allocation in NFV sites interconnected by elastic optical networks
V. Eramo, F.G. Lavacca, F. Valente, V. Filippetti, A. Rosato, A. Verdone, and M. Panella
DIET, Sapienza University of Rome, Italy
The paper proposes and investigates neural graph-based solution for the prediction of the processing capacities needed by the Virtual Network Function Instances in a Network Function Virtualization environment. The proposed solution is centralized and performed by the Orchestrator which: i) acquires the processing capacity values measured by the Virtual Network Function Manager; ii) builds neural graphs each one relative to a measure period and where each node of a graph represents a VNFI and it is labelled with the measured processing capacity of that VNFI; iii) evaluates the prediction of the processing capacities needed by each VNFI node by means of spatial and temporal convolution operations that allow for a capture of spatial and temporal correlations of the processing capacities required by the VNFIs. Instead of applying regular convolutional and recurrent units, we formulate the problem on graphs and build the model with complete convolutional structures, which enable much faster training speed with fewer parameters.

Salvatore Spadaro
Control and orchestration solutions for end-to-end time sensitive services in future 6G networks
S. Spadaro, F. Agraz, and A. Pagès Cruz,  Universitat Politècnica de Catalunya, Barcelona, Spain
The provisioning of time sensitive end-to-end services in future 6G networks imposes multiple technical challenges, spanning from the data plane to the control and orchestration planes. In particular, the automation of the provisioning and maintenance of connectivity services with deterministic constraints over multiple technology/administrative domains requires Control and Orchestration solutions able to assure the strict time service requirements. In line with that, the paper investigates the main requirements imposed to the Control and Orchestration planes and it also shows potential enabling architectures for end-to-end guarantees.
Keywords: time sensitive networks, SDN, control and orchestration.

Helene Carrere
Supporting data traffic growth with low cost amplification solutions
C. Cruz^1,2, Q. Hochart^1,2, A. Wilk², O. Delorme², R. S. Joshya¹, A. Balocchi¹, N. Vaissière², J. Decobert², C. Calo², and H. Carrere^1
1Laboratoire de Physique et Chmie des Nano-Objets, Université de Toulouse, France
²III-V Lab, Palaiseau, France
Global telecommunication networks based on optical fiber technology are evolving constantly. The near-exponential traffic growth of intra- and inter-data center interconnects and metropolitan networks, in particular, brings increasing challenges for the development of new low-cost and energy-efficient solutions to support bandwidth demand. Dense Wavelength Division Multiplexing solutions, capable of leveraging already existing infrastructures and potentially upscaling the existing networks by exploiting multiple optical fiber bandwidths, are being considered by network operators as an attractive way to extend the optical bandwidth of systems at a lower cost. In this work, we present the versatility of InP semiconductor optical amplifiers in the low-loss window of optical fibers. We review solutions for broadband amplification in the O, C and L bands of optical fiber transmission, and extend the study to the S band. Finally, we investigate the impact of the choices of materials and of the device geometries on their performances.

Juan Diego Ania-Castañon
Pulsed ultra-long ultrafast ring fiber oscillators
J. D. Ania-Castañón¹, I. Cáceres Pablo¹, F. Gallazzi², and P. Corredera^1
1Instituto de Óptica "Daza de Valdés", IO-CSIC, Madrid, Spain
²Tampere University, Finland
In this talk we will review the state of the art on the topic of ultra-long passively mode-locked femtosecond pulse fiber oscillators. This new fiber laser architecture relies on the use of polarization-insensitive InN-based semiconductor saturable absorber mirrors (SESAMs) and the careful management of nonlinearities in multi-kilometric fibre rings with Erbium Doped Fiber Amplifier (EDFA)-based amplification. These new sources are capable of supporting the stable generation of soliton-like pulses with durations below 200 fs, overcoming previously assumed limitations to pulse duration in ultra-long lasers, and reach ultra-low repetition rates as low as a few tens of kHz with the assistance of Raman amplification. The unique characteristics of this new family of ultrafast fiber oscillators make them suitable for a broad range of potential

Vladimir Gordienko
Fibre optic parametric amplifiers for communications
V. Gordienko, C. Gaur, F. Bessin, and N. J. Doran, Aston Institute of Photonic Technologies, Aston University, Birmingham, UK
We present our recent achievements with polarisation-insensitive fibre optical parametric amplifiers (PI-FOPAs) for optical communications. We have demonstrated a robust fully automated (black-box) PI-FOPA operation in the C and L bands simultaneously with gain of ~20dB and output power over 23dBm when amplifying polarisation-multiplexed WDM QAM signals and a bursty traffic. Additionally, we have demonstrated a PI-FOPA to amplify WDM signals in the S band and across a continuous bandwidth of 40nm. Finally, we have demonstrated a power budget improvement of a transient-sensitive link by up to 8 dB when employing a PI-FOPA with noise figure of ~6 dB as a drop-in replacement of an EDFA.

Rongqing Hui
Pump RIN to carrier phase noise transfer in distributed fiber Raman system evaluated through carrier FM noise spectrum
R. Hui¹, A. Dutta¹, and Y. Akasaka^2
1Electrical Engineering and Computer Science, University of Kansas, Lawrence, USA
²Fujitsu Network Communications, Inc., Dallas, USA
Relative intensity noise (RIN) of pump lasers can be transferred to both RIN and phase noise of the optical signal in fiber systems with distributed Raman amplification (DRA). In coherent optical systems based on complex optical field modulation, transmission quality is most susceptible to the increase of carrier phase introduced by the pump RIN. In this paper we show that carrier FM-noise spectrum can be used to evaluate the impact of pump RIN to signal phase noise transfer. The FM-noise power spectral density (PSD) depends on the spectral shape of pump RIN, as well as the frequency dependency of pump RIN to signal phase noise transfer function. Carrier FM-noise PSD in DRA systems with FBG-stabilized pump laser and FP pump laser are compared.  We also show that signal FM-noise can be increased by electrostriction nonlinearity in the fiber with the magnitude comparable to the pump RIN transfer.
Keywords: distributed Raman amplification, fiber nonlinearity, pump RIN transfer, coherent optical fiber communication, optical frequency noise, optical phase noise.

Boris Lembrikov
Optical phase conjugation (OPC) in a Silicon-Smectic A liquid Crystal (SALC) optical waveguide
B. I. Lembrikov, D. Ianetz, and Y. Ben-Ezra, Department of Electrical Engineering, Holon Institute of Technology, Israel
Phase conjugation is the process in which the phase of the output wave  is complex conjugate to the phase of an input wave [1]. The phase conjugation may occur in such nonlinear optical processes as difference-frequency generation, parametric amplification, and four-wave mixing (FWM) [1]. Optical phase conjugation (OPC) can be used in order to correct aberrations caused by the phase  distortion of the input wave and to compensate for nonlinear phase noise [1], [2]. Silicon based waveguide (WG) devices  are used in ultrahigh-speed optical signal processing up to 1.28 Tb/s [3]. FWM takes place in such WG structures utilizing the materials with the third-order optical nonlinearity [3]. In particular, optical WGs based on liquid crystals (LCs) can be implemented on a Si platform [4]-[6]. LCs are characterized by large birefringence, easy susceptibility to external field perturbation, and large optical nonlinearity [4]. Nematic LCs (NLCs) with the orientational long-range order have been mainly used and investigated theoretically and experimentally [4]-[6]. Smectic A LCs (SALCs) characterized by a layered structure and a positional long-range order can be also used in nonlinear optical signal processing due to the low scattering losses [4], [7]. Nonlinear optical two-wave mixing in a Silicon-SALC optical waveguide had been investigated theoretically in detail [8], [9]. OPC caused by FWM in the bulk SALC  has been studied theoretically [10], [11]. In this work, we studied theoretically OPC caused by FWM in Si-SALC optical WG. We solved simultaneously the Maxwell equations for the optical modes propagating in the Si-SALC WG and the hydrodynamic equations for smectic layer displacement. It is shown that the optical phase conjugation of the WG modes is possible when the input WG mode interacts with the smectic layer displacement dynamic grating created by two coupled pumping WG modes. We evaluated the smectic layer displacement dynamic grating caused by the interference of four coupled WG modes, the nonlinear polarization in the Si-SALC optical WG created by the WG interaction with the smectic layer displacement dynamic grating, and the slowly varying amplitude (SVA) of the phase-conjugate WG mode.
Keywords: optical phase conjugation (OPC), four-wave mixing (FWM), nonlinear optics, optical waveguide, smectic A liquid crystal (SALC), dynamic grating.
[1] Y. R Shen, The Principles of Nonlinear Optics,  Wiley, Hoboken, New Jersey, USA, 2003.
[2] S. L. Jansen, D. van den Borne, B. Spinnler, S. Calabrò, H. Suche, P.M. Krummrich, W. Sohler, G-D. Khoe, and H. de Waardt, Optical phase conjugation for ultra-long-haul phase-shift-keyed transmission, Journal of Lightwave Technology, vol. 24, no. 1, Jan. 2006, pp. 54-64.
[3] A. E. Willner, O. F. Yilmaz, Jian Wang, Xiaoxia Wu, A. Bogoni, Lin Zhang, S. R. Nuccio. Optically efficient nonlinear signal processing. IEEE Journal of Selected Topics in Quantum Electronics, Vol. 17, No.2, March-April 2011, pp. 320-332.
[4] I.-C. Khoo, Liquid Crystals,. 2nd ed. Wiley, Hoboken, New Jersey, USA, 2007.
[5] D. C. Zografopoulos, R. Asquini, E.E. Kriezis, A. d’Alessandro, R. Beccherelli, Guided-wave liquid crystal photonics, Lab on a Chip, vol. 12, 3598-3610, 2012.
[6] S. Obayya, M. F. O. Hamid, N. F. F. Areed, Computational Liquid Crystal Photonics, Wiley, UK, 2016.
[7] T. G. Giallorenzi, J.A. Weiss, J.P. Sheridan. Light scattering from smectic liquid-crystal waveguides. Journal of Applied Physics, Vol. 47, No. 5, May 1976, pp. 1820-1826.
[8] B. I. Lembrikov, D. Ianetz, Y. Ben-Ezra, Nonlinear optical phenomena in Silicon-Smectic A Liquid Crystal (SALC) waveguiding structures, 20th Int'l. Conf. on Transparent Optical Networks (ICTON 2018), Bucharest, Romania, 1-5 July 2018, p. Mo.D4.1.
[9] B. I. Lembrikov, D. Ianetz, Y. Ben-Ezra, Nonlinear optical phenomena in a Silicon-Smectic A Liquid Crystal (SALC) waveguide, Materials, 12, 2086, June 2019, pp. 1-17.
[10] G. F. Kventsel and B. I. Lembrikov, The four-wave mixing and the hydrodynamic excitations in Smectic A Liquid Crystals, Molecular Crystals and Liquid Crystals, 262, pp. 591-627, 1995.
[11] B. I. Lembrikov, D. Ianetz, Y. Ben-Ezra, Nonlinear optical phenomena in Smectic A Liquid Crystals, in: Liquid Crystals – Recent Advancements in Fundamental and Device Technologies, Ed. P. K. Choudhury, IntechOpen, Croatia, 2018, pp. 131-157.

Ioannis Konidakis
Post-melting encapsulation for the development of advanced composite glasses
I. Konidakis and E. Stratakis, IESL-FORTH, Heraklion, Greece
Inorganic oxide glasses offer an outstanding platform for the development of transparent materials, architectures, and coatings with unique optoelectronic, optical, and photonic features. A recent approach in this field towards advancing applications potential consists of the incorporation of functional materials like perovskite nanocrystals (PNCs), two-dimensional (2D) materials, and metallic nanoparticles (NPs), within various types of glasses. In this work, we present three examples of composite glasses upon incorporating PNCs, 2D materials, and NPs within phosphate glass by means of a recently developed post-glass melting encapsulation approach. The low-temperature synthesis protocol is simple, fast, and allows the controlled positioning of the incorporated material within the glass. Namely, the developed perovskite glasses (PV-Glasses) exhibit remarkable photoluminescence (PL) stability, and thus, resolving the main issue when it comes to the employment of perovskites for optoelectronic applications. Moreover, the encapsulation of 2D MoS2 was found to enhance the PL properties of the 2D-Glasses, upon inducing B-exciton emission. Finally, the incorporation of silver chloride crystals within phosphate glasses, induces photochromic features with remarkable response times. Based on the above, the post-melting encapsulation route paves a promising way beyond the state-of-the-art, towards the development of advanced composite glasses for a wide range of next-generation applications.
Keywords: composite glasses, post-melting encapsulation, perovskites, two-dimensional materials, photoluminescence, photochromic.

Petr Nemec
Ga-Sb-Te thin films deposited by magnetron co-sputtering
M. Kotrla, J. Gutwirth, P. Janíček, J. Přikryl, T. Halenkovič, F. Cheviré, V. Nazabal, and P. Němec, University of Pardubice, Czech Republic
More than 50 years ago, reversible electrical switching phenomenon in amorphous chalcogenides was first time reported by Ovshinsky [1]. In the end of 1980s and beginning of 1990s, phase change materials based on Ge-Sb-Te and/or Ag-In-Sb-Te systems have been discovered. The main scientific as well as technological interest of these inorganic materials is their ability to transform quickly and reversibly between amorphous and crystalline phases. Fast phase transformation can be induced reversibly through varying the electric field or temperature by heating via a laser pulse in optical recording applications. The extraordinary properties of phase change materials based on Ge-Sb-Te ternary system are connected with changes of optical reflectivity (up to 30%) and/or electrical resistivity (several orders of magnitude) taking place upon phase transition [2]. Radio-frequency (RF) sputtering is widely used for thin films fabrication due to its relative simplicity, easy control, and often stoichiometric material transfer. Specifically, rf co-sputtering technique brings advantage of adjustable electrical power ratio applied on individual cathodes which enables to obtain thin films with various compositions making this method cost-effective for compositional dependencies’ studies of materials’ properties. Magnetron sputtering is widely used for the growth of chalcogenide phase change thin films. However, co-sputtering method is less frequent and mainly used for the doping of Ge-Sb-Te materials with other elements such as C, Al, Ti, Ni, Cu, Se, Zr, Sn or Bi. Contrary, RF co-sputtering is used in this work to explore fabrication of thin Ga-Sb-Te films within broad region of chemical composition varying only the electrical power ratio applied to GaSb, GaTe or Te sputtering targets without necessity of exploiting many different compositions of the targets from Ga-Sb-Te system when simple RF sputtering is employed. The characterization of thin films in as-deposited state (amorphous phase) as well as in crystalline state (induced by thermal annealing) was performed exploiting atomic force microscopy, scanning electron microscopy with energy-dispersive X-ray analysis, classical as well as grazing incidence temperature dependent X-ray diffraction, electrical resistivity, and variable angle spectroscopic ellipsometry data. The results are discussed in relation with the chemical composition of the fabricated thin films. The financial support of the Czech Science Foundation under the project No. 22-07635S is greatly acknowledged.
[1] S. R. Ovshinsky, Phys. Rev. Lett. 21, 1450-1453 (1968).
[2] M. Bouska, S. Pechev, Q. Simon, R. Boidin, V. Nazabal, J. Gutwirth, E. Baudet, P. Nemec, Scientific Reports 6, 26552 (2016).

Krzysztof Wiśniewski
Spectroscopic properties of lead-silicate glasses with MoO₃ admixture and rare earth dopants
K. Wisniewski¹, M. Środa², K. Naveenkumar³, and P. S. Prasad^3
1Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Torun, Poland
²Faculty of Material Science and Ceramics, AGH University of Science and Technology, Krakow, Poland
³Department of Physics, National Institute of Technology, Warangal, India
Lead-silicate glass with 2 mol% of MoO₃ and rear earth dopants was studied due to the spectroscopic properties. The content of Pr, Nd and Er was varied from 0.5 to 1.5 mol% in three glass series. The addition of MoO₃ affects optical properties of glass, i.e., increasing the refractive index and decreasing the dispersion of the glass. The effect of coexisting molybdenum ion with rear earths was studied based on absorption spectra, excitation and luminescence spectra. The decay time of luminescence was measured at ambient temperature and in the temperature range from 10 K to 350 K. For the Pr³⁺ ion, with increasing concentration, an increase in luminescence is observed for the ³P₀-³F₂ transition. The increase in the concentration of ion Nd³⁺ from 0.5% to 1% is accompanied by an increase in the luminescence of the ⁴F_5/2-⁴I_9/2 transition, while a further increase in the concentration to 1.5% caused its decrease. The same effect was observed for the ⁴S_3/2-⁴I_15/2 transition in the series with Er³⁺ ion.
Keywords: lead-silicate glass, MoO₃, rare earth ions, luminescence.

Georges Boudebs
Photothermal efficiency of gold nanoparticles using cw Z-scan technique in the visible range
G. Boudebs¹, J.-B. Zinoune^1,4, C. Cassagne¹, M. Loumaigne³, M. Chis⁴, and M. H. V. Werts^2
1Univ Angers, LPHIA, SFR MATRIX, Angers, France
²Univ Rennes, CNRS, SATIE – UMR8029, Rennes, France
³Univ Angers, MOLTECH-ANJOU, SFR MATRIX, Angers, France
⁴ESAIP, St-Barthélemy d’Anjou Cedex, France
The photothermal effect may be used in a variety of applications such as biological microscopy. Light scattering from plasmonic NPs can be sufficiently strong to enable single-particle observations in dark-field microscopy. The relative contributions of light scattering and light absorption are of paramount importance in the characterization of nanoparticles and their selection and optimization for a specific application. Cw single beam Z-scan technique is applied to determine the absorption and scattering efficiencies on different size of spherical gold nanoparticles. Experimental tests are carried out at three different wavelengths in the blue, the green and the red. The quantum yields are determined through Thermal Lens (TL) effect. Details of the measurement method characteristics are given for relatively high absorption Gaussian procedure using top-hat beams. The validity of our approach is confirmed by comparing the obtained scattering data with that of the theoretical values given by the Mie theory. Very good agreement is found within the experimental errors.

Juan Bueno
Second harmonic generation microscopy of the living human eye: Limitations, performance and image improvement
J. M. Bueno¹, R. M. Martínez-Ojeda¹, F. J. Ávila², and P. Artal^1
1Laboratorio de Óptica, Universidad de Murcia, Spain
²Departamento Física Aplicada, Universidad de Zaragoza, Spain
Second Harmonic Generation (SHG) microscopy provides high resolution images of collagen-based structures, in particular ocular tissues. However, the implementation into in vivo conditions has been challenging. Here, we present a compact SHG microscope specifically developed to image the living human eye (cornea and sclera). The instrument was successfully employed to obtain non-contact and non-invasive SHG images within well-established light safety limits. Since SHG image quality is often limited by different physical factors (mainly at deeper locations), we also present some alternative methods to enhance the acquired images. These include a blind deconvolution approach and the use of incident radially polarized light. The effectiveness of a sub-10fs used as illumination source is also analyzed.

Adrian Enache
Highlighting cerebral metastases using two-photon microscopy
A. Enache^1,2,4, L. Eftimie^1,2,3, R. Hristu¹, A.-M. Graur^4,5, R. R. Glogojeanu³, M. Sajin⁴, and G. A. Stanciu^1
1Center for Microscopy-Microanalysis and Information Processing, University Politehnica of Bucharest, Romania
²Central University Emergency Military Hospital, Pathology Department, Bucharest, Romania
³Department of Special Motricity and Medical Recovery, The National University of Physical Education and Sports, Bucharest, Romania
⁴University of Medicine and Pharmacy ‚Carol Davila’, Pathology Department, Bucharest, Romania
⁵Central University Emergency Military Hospital, Radiology Department, Bucharest, Romania
The research issue examines the establishment of a pathological diagnostic that is as detailed as practicable for cerebral metastases utilizing a new technique that is used in connection with optical microscopy to accurately detect cerebral malignancies. Two-photon microscopy is a further refinement of precision fluorescence microscopy. This approach can improve the accuracy of the cerebral metastases’ diagnosis and possibly other neoplasms. In this work, we propose an additional use for TPM imaging of fixed tissues stained for conventional histopathology. Through the identification of the nucleus, cytoplasm, and individual cells, TPM can clearly differentiate a single neuron in the brain tissue and the individual malignant cell in the human tumor specimen.  We demonstrated that TPM could detect cerebral metastases, by acquiring high-quality images. Because excitation is restricted to a focal point, it also causes less photobleaching and phototoxicity, making TPM particularly useful for extended observation of cells. A key benefit of two-photon microscopy is its ability to restrict excitation to a tiny focal volume in thick samples. In fact, the application of TPM imaging in cerebral tumors has attracted increasing amounts of attention.

Engang Fu
Surface roughness and optical characterization of nanoporous silver films synthesized by one-step dealloying
S. R. Anton¹, Engang Fu², D. E. Tranca¹, S. G. Stanciu¹, A. Toma³, C. V. Sammut⁴, Zhaoyi Hu², and G. A. Stanciu^1
1Center for Microscopy-Microanalysis and Information Processing, University Politehnica of Bucharest, Romania
²State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, P.R. China
³Center for Research and Training in Innovative Techniques of Applied Mathematics in Engineering “Traian Lalescu”, University Politehnica of Bucharest, Romania
⁴Department of Physics, Faculty of Science, Msida, University of Malta, Msida, Malta
The nano-topography, surface roughness and optical properties of nanoporous silver (NPS) films are investigated as a function of the dealloying agent using atomic force microscopy and near-field optical microscopy. Detailed metrological analysis is performed to measure the effect of the dealloying agent at the nano scale. It was found that the nano-roughness formed on the surface of the films greatly affects the optical properties of the NPS film. Keywords: nanoporous silver, atomic force microscopy, scattering-type scanning near-field optical microscopy.

Sorin Hermon
Multi-sensor scanners and machine-learning data processing: A novel instrumentation and data analysis method in heritage science
R. Moreau^1,2,3, T. Calligaro^2,3,4, and Sorin Hermon^1
1APAC Labs, STARC, The Cyprus Institute, Aglantzia, Cyprus
²Fédération de Recherche CNRS, New AGLAE, Paris, France
³Chimie ParisTech, PSL University, CNRS, Institut de Recherche de Chimie de Paris, Paris, France
⁴Centre de Recherche et de Restauration des Musées de France, Paris, France
Over the past two decades, scanning X-ray fluorescence or macro X-ray fluorescence (MA-XRF) along with Reflectance Imaging Spectroscopy (RIS) and Luminescence Imaging Spectroscopy (LIS) has proven to be a revolution within the field of Cultural Heritage (CH) scientific investigation for painted artwork, with its ability to map elemental distribution over the scanned area and thus investigate the pigment composition. Two scanners combining MA-XRF, RIS and LIS for analysis of CH painted artworks were developed, as implementation of such imaging techniques acquisition set up on a MA-XRF scanner is made possible thanks to the use of optical fibre. The data generated with these instrument, consisting on a combined MA-XRF, RIS and LIS cubes, is of great interest as each point of these data-cube has an X-ray fluorescence, Reflectance and Luminescence spectroscopic signature, allowing for extensive characterization and deep understanding of the studied CH materials. The operation of such instruments is exemplified on a painted wall of Agios Ioannis Lambadistis monastery in Cyprus.
Keywords: cultural heritage science, scanning X-ray fluorescence, reflectance imaging spectroscopy, luminescence imaging spectroscopy, data fusion.

Radu Hristu
Collagen organization in second harmonic generation images for the assessment of thyroid nodule capsular invasion
R. Hristu¹, S. G. Stanciu¹, D. E. Tranca¹, L. G. Eftimie², A. Enache², and G. A. Stanciu^1
1Center for Microscopy-Microanalysis and Information Processing, University Politehnica of Bucharest, Romania
²Department of Pathology, Central University Emergency Military Hospital, Bucharest, Romania
Second harmonic generation (SHG) microscopy is an imaging technique which enables the visualization of collagen architecture within tissue samples. Going beyond simple intensity, an extension of SHG microscopy involves the acquisition of polarization dependent image stacks which are further processed with theoretical collagen models to provide quantitative information for the collagen structure and architecture. We use SHG microscopy images for the visualization of the collagen distribution in thyroid nodule capsules. More precisely, we are interested in capsular invasion, a hallmark of follicular carcinoma and a method for evaluating possible lymph node metastasis in the case of papillary thyroid carcinoma. Different image processing methods are used to assess the collagen organization which is further related to possible invasion sites in the thyroid nodule capsule.

Avi Karsenty
Overcoming silicon limitations short review: How geometrical innovation can revolutionize nanophotonics and  nanoelectronics
A. Karsenty, Jerusalem College of Technology, Israel
Despite technological advancement having pushed silicon-based computing to its speed limit, new innovations are still based on this cheap, widely available material, which makes up almost 28% of the planet's volume. Pushing silicon beyond its current boundaries will require replacing electronic communication with photonic communication. However, silicon is a priori limited by its indirect band gap, and researchers in this area are forced to look for alternative materials in addition to silicon components. Perhaps there is another path besides that of replacing silicon with other elements (Ge, GaAs, In), if their properties can be replicated by those of carefully designed silicon nanophotonics based on special structures and adapted shapes. Today, nanoelectronics and nanophotonics are at the forefront of the nano revolution. As microelectronics are based on silicon, advancements in the field of silicon photonics and photonics integrated circuits (PICs) will allow for the realization of integrated optical signaling and electronic data processing.  As can be expected, development of these devices for use in the next generation of ultrafast computers is proceeding in concert with more general efforts to develop the next generation of optoelectronic communication systems. As part of these efforts, there is a need to create a full family of new silicon nanoscale electro-optical components that can be smoothly integrated into the microelectronics industry in the future. A series of such devices (light-emitting transistors, nano-amplifiers, capacitors embedded with nano-crystals, photo- and thermo-activated modulators, sensors, waveguides, Y-junctions and more), coupling both electrical and optical properties, are currently being developed by the research team at ALEO (Advanced Laboratory of Electro-Optics), under the leadership of Dr. Avi Karsenty, and in collaboration with other institutes in USA, Europe and Israel, such as Massachusetts Institute of Technology (MIT), University Politehnica Bucharest (UPB), and Bar-Ilan University (BIU). The ALEO team, comprised of both professional engineers as well as PhD, MSc and BSc students, is engaged in advanced research on multiple fronts in collaboration with world-famous institutions in the United States, Europe, and Israel. The benefits of these devices will be experienced by a wide range of application domains: Optical communication in computers, near-field and super-resolution nanoscopy, space and airborne sensors, smart autonomous vehicle (SAV) technology, quantum computing, and of course the field of nanophotonics and nanoelectronics itself. This talk will present several examples of smart nanoscale silicon-based devices (MOSQWELL, HAND, SOIPAM, EOTEC and Au-NP tips) whose special geometrical structure enables them to overcome the well-known limitations of silicon (indirect band gap limiting photon emission), and to reinforce physical phenomena (absorption and emission spectra).

Aude Lereu
Resonant multi-dielectric coverslip for enhanced total internal reflection fluorescence microscopy
Y. Toumi¹, A. Mouttou^1,2, F. Lemarchand¹, G. Demesy¹, C. Koc¹, D. Muriaux², A. Moreau¹, J. Lumeau¹, C. Favard², and A. L. Lereu^1
1Aix Marseille Univ, CNRS, Centrale Marseille, Institut Fresnel, France
²Institut de Recherche en Infectiologie de Montpellier, CNRS, Univ of Montpellier France
Multi-dielectric coated coverslip can be designed to reach large optical field enhancement when working under proper illumination conditions and in total internal reflection. As objective-based total internal reflection fluorescence microscopy (TIRF-M) is also based on total internal reflection illumination, we propose to use the resulting large field enhancement supported in such coverslip to improve TIRF-M sensitivity by amplifying the collected fluorescence signal. We present here the optimization, realization and testing in TIRF-M of resonant coverslips designed to take into account the experimental constraints. The latter’s are due to the inverted configuration of TIRF-M together with the use of a high numerical aperture objective. The challenge is therefore to find the best coating design compromising between the angular tolerance and the field enhancement. We will report here enhanced-TIRF-M imaging over model samples but the ultimate goal here is to be able to monitor and quantify dynamics of pathogens at the membrane of living cells. The authors acknowledge the CNRS for financial supports through the 80|PRIME interdisciplinary program and the French research agency through the ANR NIS.

Ferruccio Pisanello
Fiber photometry with tapered optical fibers: Exploiting mode-division to gain depth-resolution in brain tissue
M. Bianco¹, M. Pisanello², A. Balena¹, F. Pisano¹, M. S. Andriani^1,3, C. Montinaro¹, L. Sileo², B. Spagnolo¹, M. De Vittorio^1,3, and F. Pisanello^1
1Istituto Italiano di Tecnologia (IIT), Center for Biomolecular Nanotechnologies, Lecce, Italy
‎²OptogeniX, Lecce, Italy
³Università del Salento, Dipartimento di Ingegneria dell’Innovazione, Lecce, Italy
Fiber photometry is an emerging technique enabling the monitoring of neural activity in vivo by employing optical fibers to detect functional fluorescence variations from specific genetically-encoded indicators expressed in neurons. It benefits from an ever-growing number of fluorescent indicators and it is considered a valuable tool in the field of neuroscience for investigating neural circuits underlying behavior and disease. Fiber photometry is typically performed by implanting an optical fiber or a fiber bundle in the region of interest, allowing the propagation on the same optical channel of both the excitation light and the functional fluorescence signal. However, conventional cylindrical fibers lack spatial resolution and can cause brain damage upon insertion. An alternative solution employed in fiber photometry are Tapered Optical Fibers (TFs), which allow for a smooth insertion and reconfigurable light delivery and collection for a depth which can easily reach subcortical structures of the mouse brain. In this manuscript we review the latest applications of TFs in the context of fiber photometry, discussing their light delivery and collection capabilities, the advantages offered by the microstructuring of the taper edge, and the unique possibility to detect fluorescent signals from multiple brain depths simultaneously with a single implant.
Keywords: optogenetics, fiber photometry, tapered optical fibers, fiber optics, microfabrication, neurosciences.

Adrian Podoleanu
Advances in optical coherence tomography
A. Podoleanu, Applied Optics Group, School of Physical Sciences, University of Kent, Canterbury, UK
Optical Coherence Tomography (OCT) has been initially developed as a non-invasive high resolution optical imaging modality for ophthalmology, followed by rolling the technology to other medical fields. OCT has however considerable potential in biosciences as well as in non-destructive testing. The review will present such recent applications in a variety of fields. A method and systems for direct delivery of en-face OCT images will also be presented. The signal conventionally provided by a Fourier Transform or equivalent is replaced by delivery of multiple signals, using an electrical processor for each optical path difference (OPD) in the sample investigated. The principle of operation is termed as master slave (MS) interferometry, where signal from a depth in the sample for a certain OPD in a slave interferometer is selected by setting the same OPD value in a master interferometer. The MS principle enables real time display of several en-face OCT images using ultrafast tunable lasers in downconversion configurations. To this end, I will also present our research on two technologies for ultra-fast tuning lasers for fast acquisition of OCT data: dispersive cavity with dual resonance and time stretch configurations.
Keywords: optical coherence tomography, swept sources, broadband sources, 3D imaging, depth resolved imaging.
[1] A. Gh. Podoleanu, Optical coherence tomography, Journal of Microscopy, 247(3) 209-219, (2012).
[2] A. Gh. Podoleanu, A. Bradu, Master-slave interferometry for parallel spectral domain interferometry sensing and versatile 3D optical coherence tomography, Opt. Express 21, 19324-19338 (2013).
[3] A. M. Jiménez, S. Grelet, V. Tsatourian, P.B. Montague, A. Bradu, A. Podoleanu, 400 Hz volume rate swept-source optical coherence tomography at 1060 nm using a KTN deflector, IEEE Photonics Technology Letters, vol. 34, no. 23, 1277-1280 (2021).
[4] R. Riha, A. Bradu, A. Podoleanu, Dual resonance akinetic dispersive cavity swept source at 900 kHz using a cFBG and an intensity modulator, Optics Letters, vol. 47, no. 16, 4032-4035 (2022).

Bertrand Simon
Advances and overcoming challenges in tomographic diffractive microscopy
B. Simon¹, N. Verrier², M. Debailleul², and O. Haeberlé^2
1LP2N, Institut d’Optique Graduate School, CNRS UMR 5298, Université de Bordeaux, Talence, France
²IRIMAS UR UHA 7499, Université de Haute-Alsace, Mulhouse, France
The optical microscope has been an essential tool, particularly in biology, since its invention in the 16th century. However, despite considerable efforts and numerous studies aimed at improving its imaging quality, contrast, and resolution, its use, outside of nonlinear effects (such as fluorescence, SHG, THG, CARS/RAMAN), is limited to mostly morphological studies or detection of specific elements with limited resolution. In this context, label-free, high-resolution quantitative microscopy techniques such as Tomographic diffractive Microscopy (TDM)  have become increasingly promising over the last decade thanks to their ability to map the 3D distribution of complex optical indices within specimens. These techniques are now even available through commercial devices.  However, numerous challenges remain in improving the capabilities of TDM. Achieving isotropic resolution is often overlooked, and the effect of the missing cone can be problematic for quantitative aspects. Also, additional modalities, such as polarization or multispectral approaches, should be explored to provide more specific characterization. Similarly, achieving high-speed imaging capabilities in real-time still represents a significant challenge, and further efforts are needed to accelerate the 3D image reconstruction phase. Additionally, imaging specimens with dimensions comparable to organoids or small organisms presents a genuine need, requiring addressing the problem of multiple diffraction, which increases the complexity of treatments. Finally, to date, there is no method for achieving super-resolution in quantitative phase imaging, as there is in fluorescence microscopy. To achieve this goal, it would be necessary to manipulate nonlinearities, as can be done with the on/off effect of fluorescent molecules. All of these developments constitute promising avenues that have started to be explored and that we will present.

Luigi Sirleto
Noise investigation in femtosecond stimulated Raman scattering microscopy
R. Ranjan^1,2, G. Costa^1,3, M. A. Ferrara¹, M. Sansone³, and L. Sirleto1
¹National Research Council, Institute of Applied Sciences and Intelligent Systems Napoli, Italy
²Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, USA
³Department of Electrical Engineering and Information Technologies, University “Federico II” of Naples, Italy
Stimulated Raman Scattering (SRS) microscopy enables imaging systems, performing label-free imaging with high sensitivity, high spatial and spectral resolution, 3D sectioning, and fast image acquisition. Nevertheless, due to the weak Raman cross-section of biomolecules, SRS images often suffer from low SNR, so SRS applications in biological/biomedical imaging can be compromised. In this paper, noise measurements in detection system of our in-house built Stimulated Raman Scattering microscope are carried out, demonstrating that it is shot noise limited.
Keywords: nonlinear microscopy, label-free imaging, stimulated Raman scattering, noise.

Stefan Stanciu
Super-resolved non-linear optical microscopy: Architectures, advantages and perspectives
S. G. Stanciu¹, R. Hristu¹, G. A. Stanciu¹, D. E. Tranca¹, L. Eftimie², A. Dumitru³, M. Costache³, H. A. Stenmark⁴, Juan M. Bueno⁵, P. Bianchini⁶, and E. M. M. Manders^6
1Center for Microscopy-Microanalysis and Information Processing, University Politehnica of Bucharest, Bucharest, Romania
²Pathology Department, Emergency Military Hospital, Bucharest, Romania
³Department of Pathology, Carol Davila University of Medicine and Pharmacy, Bucharest, Romania
⁴Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Norway
⁵Laboratory of Optics, Center for Research in Optics and Nanophysics, University of Murcia, Spain
⁶Nanoscopy and NIC@IIT, Italian Institute of Technology, Genoa, Italy
⁷Confocal.nl BV,  Amsterdam, The Netherlands
Non-linear optical microscopy techniques (NLO), which exploit processes upon which a sample emits light in the visible when excited with infrared photons [1], have attracted important attention to date. Among these, Second Harmonic Generation Microscopy (SHG) and Two-Photon Excited Fluorescence Microscopy (TPEF) have been demonstrated as powerful tools for the 3D visualization of tissues and advanced materials. Here we discuss two architectures for super-resolved non-linear optical microscopy. First, we present how the contrast mechanisms of SHG and TPEF imaging can be harnessed to provide resolutions beyond the diffraction barrier, when combined with the re-scan concept, previously introduced in the context of re-scan confocal microscopy [2]. Considering the current high need for techniques capable to characterize non-fluorescent samples at sub-diffraction resolution, we place special focus on showcasing the resolution advantage of Re-Scan Second Harmonic Generation Microscopy (rSHG) [3]. Second, we turn our attention to super-resolved non-linear optical microscopy based on image scanning microscopy concepts [4,5]. In the final part we discuss perspectives on combining super-resolved NLO imaging with trending artificial intelligence methods. In this context, we first discuss avenues that we are exploring for virtual super-resolved NLO based on Generative Adversarial Networks, and then switch focus towards automated diagnostics perspectives building on the combined use of complementary Deep Learning models [6].
Keywords: non-linear optical microscopy, second harmonic generation, two-photon excited fluorescence, super-resolved optical imaging.
[1] N. Mazumder, N. K. Balla, G. Y. Zhuo, Y. V. Kistenev, R. Kumar, F. J. Kao, S. Brasselet, V. V. Nikolaev, N. A. Krivova, Label-free non-linear multimodal optical microscopy—basics, development, and applications, Front. Phys. 7, 170 (2019).
[2] G. M. De Luca, R. M. Breedijk, R. A. Brandt, C. H. Zeelenberg, B. E. de Jong, W. Timmermans, L. N. Azar, R. A. Hoebe, S. Stallinga, E. M., Manders, Re-scan confocal microscopy: Scanning twice for better resolution, Biomedical Optics Express, 4(11), pp.2644-2656 (2013).
[3] S. G. Stanciu, R. Hristu, G. A. Stanciu, D. E. Tranca, L. Eftimie, A. Dumitru, M. Costache, H. A. Stenmark, H. Manders, A. Cherian, M. Tark-Dame, E. M. M. Manders, Super-resolution re-scan second harmonic generation microscopy, Proc. Natl. Acad. Sci. U.S.A., 119(47), p. e2214662119 (2022)
[4] I. Gregor, M. Spiecker, R. Petrovsky, J. Großhans, R. Ros, J. Enderlein, Rapid nonlinear image scanning microscopy, Nat. Meth., 14(11), pp.1087-1089 (2017).
[5] M. Castello, G. Tortarolo, M. Buttafava, T. Deguchi, F. Villa, S. Koho, L. Pesce, M. Oneto, S. Pelicci, L. Lanzanó, P. Bianchini, C. J. R. Sheppard, A. Diaspro, A. Tosi, G. Vicidomini, A robust and versatile platform for image scanning microscopy enabling super-resolution, FLIM. Nat Methods. 16(2):175–8 (2019).
[6] S.R. Anton et al.: Automated detection of corneal edema with deep learning-assisted second harmonic generation microscopy, IEEE J. Sel. Top. Quantum Electron., vol. 29(6), pp.1-10 (2023).

Denis Tranca
Applications of phasor data analysis on scattering scanning near-field optical microscopy investigations
D. E. Tranca¹, A. Sobetkii², R. Hristu¹, S. G. Stanciu¹, C. Stoichita¹, and G. A. Stanciu^1
1Center for Microscopy-Microanalysis and Information Processing, University Politehnica of Bucharest, Romania
²MGM Star Construct SRL, Bucharest, Romania
Investigations by using scattering scanning near-field optical microscopy (s-SNOM) usually result in acquisition of a pair of two images: amplitude and phase, which hold complementary information about the optical properties of the investigated samples. Phasor diagrams are graphical ways of complex data display and represent an alternative to classical amplitude-phase images for displaying the data contained in the s-SNOM images. In this work we propose some applications and directions for rapid analysis of s-SNOM data displayed by means of phasor diagrams based on investigations performed on different sample types: biological, organic, and inorganic materials. Our analysis demonstrates practical uses for phasor diagrams to extract valuable qualitative information from s-SNOM images.

Denis Tranca
Mechanical and optical investigations of Cr thin films deposited on Si substrate
D. E. Tranca¹, A. Sobetkii², R. Hristu¹, S. R. Anton¹, S. G. Stanciu¹, E. Vasile³, and G. A. Stanciu^1
1Center for Microscopy-Microanalysis and Information Processing, University Politehnica of Bucharest, Romania
²MGM Star Construct SRL, Bucharest, Romania
³Department of Science and Engineering of Oxide Materials and Nanomaterials, Faculty of Chemical Engineering and Biotechnologies, University Politehnica of Bucharest, Romania
Chromium thin films were prepared by high-power impulse magnetron sputtering and investigated by both mechanical and optical techniques to extract, characterize, and correlate their corresponding properties. Cr thin films have a wide palette of applications in optics, and their optical properties may differ from the bulk material. In this work we prepared Cr thin films with different thickness deposited on Si substrate and characterize their mechanical and optical properties with nanoscale resolution. We found that the thickness of the films has a high influence upon both mechanical and optical properties of the films, resulting different Young’s modulus, refractive index and extinction coefficient.

Zeev Zalevsky
Super-resolved imaging behind scattering medium
E. Israeli, A. Sanjeev, R. Salahudeen Rafeeka, G. Chen, and Z. Zalevsky
Bar-Ilan University, Ramat-Gan, Israel
Time multiplexing is a super-resolution technique that sacrifices time to overcome the resolution reduction obtained because of diffraction. There are many super resolution methods based on time multiplexing, but all of them require a-priori knowledge of the time changing encoding mask, which is projected on the object and used to encode and decode the high-resolution information. In this paper, we present a time multiplexing technique that does not require the a priori knowledge on the projected encoding mask. The concept includes illuminating the object positioned behind scattering medium, through the scattering medium. This generates illumination of the object with speckle patterns. The patterns themselves are not a-priori known but the same projected pattern can be preserved and shifted by using the memory effect of the scattering medium. By properly capturing larger number of low-resolution images encoded with the projected time-shifting speckle patterns, a high-resolution image can be reconstructed after applying proper decoding algorithm. The paper includes both numerical as well as experimental validation of the proposed novel imaging concept.
Keywords: time multiplexing, super-resolution, scattering medium, speckle patterns projection.

Hamzeh Khalili
Dynamic traffic prediction model retraining for autonomous network operation
F. Tabatabaeimehr¹, L. Velasco², M. Ruiz², H. Khalili¹, and R. Aparicio-Pardo^3
1Centre Tecnològic de Telecomunicacions de Catalunya, Castelldefels, Spain
²Optical Communications Group (GCO), Universitat Politècnica de Catalunya, Barcelona, Spain
³Université Côte d’Azur, CNRS, Inria, France
In general, the availability of an accurate machine learning (ML) model plays a particularly important role in the development of new networking solutions and is one of the main drivers for the development of 5G and beyond networking. Although an option is to update the model once inaccurate data is detected, such approach requires high computational effort, specially once the data history is large. In this paper, we propose an approach that combines a traffic prediction model based on Long Short-Term Memory (LSTM) with an analysis module for dynamic connection capacity allocation. Once the model is generated, re-training can be triggered after inaccuracies are detected by the analysis module. Illustrative numerical results show the benefits from the proposed decision-based re-training approach to reduce the number of re-training rounds while maintaining model accuracy.
Keywords: autonomous operation, metro network, traffic prediction, model retraining, LSTM.

Hovik Baghdasaryan
Reflective type multi-nanolayer electro-optical modulator for free space chip-to-chip optical interconnection: Electromagnetic modelling by the method of single expression
H. V. Baghdasaryan¹, T. M. Knyazyan¹, T. T. Hovhannisyan¹, G. R. Mardoyan², T. Baghdasaryan³, E. Leitgeb⁴, and M. Marciniak^5
1Fiber Optics Communication Laboratory, National Polytechnic University of Armenia, Yerevan, Armenia
²YEA Engineering, Engineering City, Yerevan, Armenia
³Brussels Photonics(B-PHOT), Department of Applied Physics and Photonics, Vrije Universiteit Brussel, Belgium
⁴Institute of Microwave and Photonic Engineering, Graz University of Technology, Austria
⁵National Institute of Telecommunications, Warsaw, Poland
Free space chip-to-chip optical interconnection is an emerging technology solving the problem of performance bottleneck of electrical interconnects and offering possibilities for integrated circuits in increased bandwidth of chip to chip data transfer, high density, low optical losses, low cross talk and high data rate signal processing. Chip-to-chip optical interconnection provides implementation of VCSELs, electro-optical modulators (EOMs) and photodetectors on the same or nearby silicon chip with the help of collimating microlens and micromirrors. EOMs play an essential role of modulating light for free space chip-to-chip optical interconnection. Optical properties of reflective-type multi-nanolayer EOM for free space chip-to-chip optical interconnection are modelled by the method of single expression. Reflective properties of Fabry-Perot resonant type EOM consisting of electro-optical spacer of LiNbO₃ covered by thin conducting nano-layers of ITO material embedded between asymmetric Si/SiO₂ distributed Bragg reflectors (DBRs) are analysed. Two semi-transparent ITO nano-layers of the EOM operate as electrodes for supplying electrical signal to the electro-optical material. The layers adjacent to the spacer are of higher permittivity and DBRs are asymmetric regarding the spacer to provide the necessary reflectance of the EOM structure. As an external light source, a conventional laser diode at 1.55 μm wavelength is considered. Distributions of amplitude of optical wave and power flow within the EOM structure are obtained, which are important for optimization of reflective properties of the structure. The optimal structure of the EOM providing the highest reflectance is suggested. An essential shift of the reflection peak of the EOM structure is observed at the change of permittivity of electro-optical material of optimal thickness under applied voltage. The suggested reflective type multi-nanolayer EOM can be used for free space chip-to-chip optical interconnection.
Keywords: reflective type multi-nanolayer electro-optical modulator, free space chip-to-chip optical interconnection, electromagnetic modelling, method of single expression.

Ernesto Ciaramella
Intra-satellite optical wireless communications in relevant environments
L. Gilli¹, G. Cossu¹, N. Vincenti¹, F. Bresciani², E. Pifferi², V. Schena², and E. Ciaramella^1
1Scuola Superiore Sant'Anna, Pisa, Italy
²Thales Alenia Space, Roma, Italy
We present approach, design and preliminary tests of the TOWS study, which successfully demonstrated an innovative approach to optical wireless communication in spacecrafts. The developed hardware can realize optical wireless connections among different units by means of MIL-STD 1553 signals, which is the most common type of intra-satellite data bus. The same optical transceivers are flexible and can be used in quite different relevant application scenarios.

Jian Chen
Modelling of optical communication over lighting infrastructure with ultra-wide spectral carrier clusters
Jian Chen¹, Jun Wang¹, Wenjing Sun¹, Anliang Cai¹, and Changyuan Yu^2
1School of Telecommunications and Information Engineering, Nanjing University of Posts and Telecommunications, China
²Department of Electronic and Information Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong
The flourishing lighting industry has taken the full visible light spectra upon which the communication services will be only provided as value-added. On the basis of better satisfying human visual system, high-efficiency and energy-saving, such auxiliary communication is simultaneously carried by prerequisite ultra-wide optical spectral cluster in lighting process. Novel modelling of optical communication over lighting are thus established for the purpose of analyzing simultaneous modulation and wideband detection of the signal. The model is far beyond the assumption of single wavelength or multiplexed wave as the carrier. It avoids too simple and unrealistic extension of fiber optics or wireless communication theories for characterizing optical communication over lighting. It is expected to provide theoretical and technical basis on mobile VLC which perfectly comparable with the evolved lighting infrastructure.

Giulio Cossu
Design challenges in high throughput WDM-FSO systems for satellite communications
G. Cossu, V. Spirito, M. Ninos, and E. Ciaramella, Scuola Superiore Sant’Anna, Istituto TeCIP, Pisa, Italy
The key technology to provide Terabit/s links in space is the Free Space Optics (FSO) with Wavelength Division Multiplexing (WDM). This work reports and explains how to elaborate a link budget for WDM-FSO  feeder links, i.e., links that connect an Optical Ground Station to a satellite. Designing these links is a challenging task, since the optical beams travel also through the turbulent atmosphere adding several penalties. The effects along the propagation are addressed and discussed, estimating all the impairments based on analytic and stochastic models. Then, we determined the system parameters that can provide the expected performance.

Ivan Djordjevic
Covert optical communication over turbulent terrestrial free-space optical link
V. Nafria and I. B. Djordjevic, University of Arizona, Tucson USA
Unlike traditional secure communication methods, denying unauthorized access to the content of the transmitted message, the covert communication prevents detection of the transmission attempt in the first place. In this invited paper, we review our recent activities on covert free-space optical (FSO) communication activities at the University of Arizona (UA). At UA we have established a 1.5 km-long FSO communication link between Optical Sciences (OSC) Meinel and ECE Department buildings. We use an EDFA as an ASE noise source for covert communication and perform the BPSK signaling over the FSO link at multi-Gb/s data rates. To deal with the atmospheric turbulence effects we use the adaptive optics. Different strategies to enable covert communication operating in strong turbulence regime will be presented at the conference.

Véronique Georlette
Li-Fi and Visible Light Communication for Smart Cities and Industry 4.0: Challenges, research and market status in 2023 (Tutorial)
V. Georlette and V Moeyaert, Electromagnetism and Telecommunications Dept., University of Mons, Belgium
The development of technologies that use cellular Radio Frequency (RF) networks to transmit information wirelessly has increased dramatically over the last decade. These technologies include mobile phones, tablets, connected gadgets and the Internet of Things (IoT). The simultaneous use of all these devices quickly saturates the available network. As the RF spectrum resource is limited and regulated, it is important to find alternative connectivity. To reply to this shortage of wireless connectivity, Li-Fi (Light Fidelity) and Visible Light Communication (VLC) are good candidates. Li-Fi is the high data rate bidirectional application of VLC. VLC uses visible and infrared light to transmit data wirelessly. Over the last decade, interest in VLC grew in the scientific community and on the market. However, most scientific works and products are focused on the indoor environment. The external environment for VLC applications, which would be very relevant for smart cities as well as some industrial applications, is very little covered in the literature. This tutorial aims to present the advances of these technologies and their relevance in these two environments.  As opposed to the indoors, the quantity of particles in the air in outdoor and some industrial environments is more important. Depending on the environment in which the system is deployed, the optical signal may be more or less impacted. Indeed, whether it is indoor or outdoor, the attenuation and the disturbance applied to the signal are different. The primary impactors on outdoor VLC equipment, which increase the medium's total attenuation, are mainly weather variability and the interactions between the light wave and particles in the atmosphere. These particles include dust, fog, and the possible presence of smoke due to fire or pollutants which cause phenomena such as scattering and absorption. A third effect to consider is the reflection of the optical signal on certain surfaces and their interference on the receiver’s end.  After a general state of the art of VLC and Li-Fi, this tutorial provides an overview of these phenomena and how they can be studied and mitigated. Afterward, the latest technological innovations are presented. Then, a market review will present the main challenges that Li-Fi and VLC technologies face for their massive deployment for private consumers and private companies. For instance, there is no single standard for Li-Fi and VLC. This makes it hard for manufacturers of end devices and light manufacturers to comply with just one norm. Furthermore, this technology has not reached its maturity level yet. As VLC requires the use of LEDs as its emitter’s front-end and since they were adopted a relatively short time ago, it makes this technology relevant but still needs some time for the light market to stabilize itself. Nevertheless, VLC and Li-Fi have a bright future ahead and this tutorial will conclude with practical examples of their use in smart cities and smart industries.

Erich Leitgeb
Using regular semiconductor illumination arrays (connected via power line communications) for visible light sensing
E. Leitgeb, P. Bekhrad, and K. Madane
Institute of Microwave and Photonic Engineering, Graz University of Technology, Austria
The need for technological devices to interact with one another is becoming more important in today's world, particularly with the rise in automated control systems. As data transfer speeds increase, more cables are required, leading to infrastructures overloaded with cables. To address this issue, the current paper reports on development of a Power Line Communication (PLC) system that uses an AC power distribution network to reduce the number of wires needed for connecting the illumination modules for Visible Light Sensing (VLS) or Visible Light Communications (VLC). To achieve this, the operation and capabilities of PLC chips are considered in detail and mainly used for indoor applications.  In addition, combining those developments in PLC technological domain with a state-of-the-art occupancy detection system, provide the potential to significantly decrease energy consumption in buildings up to 30%. Although a person can be detected by disturbance of Line-of-Sight between the sender and the receiver, the most sophisticated systems use LIDAR-based scanning (Light Detection and Ranging). In the latter configuration that is considered in the current work, the sender and the receiver are co-located in the same place. This is accomplished by development of a regular semiconductor illumination array that LED (Light-emitting diode) elements serve both functions (i.e., receiver and transmitter) by setting them into forward or reverse bias mode. Having combined those developments with the existing building resources by means of PLC allows the estimated building occupancy based on that visible light sensing technology to be transmitted in a highly reliable and cost-effective way with a special focus on environmental sustainability. This also requires an emphasis on the PLC network architecture, necessary for establishing communication between the LIDAR-enabled lights, each controlled with highly integrated system-on-chips that include PLC baseband modem and analogue front-end integrated circuits.  Connecting VLS via PLC is not limited to installations within buildings. To implement regular semiconductor illumination (arrays) for Visible Light Sensing could also be used for increasing the safety of people for future outdoor applications, like for monitoring different doors, gates and entrances (like for busses, trains or other public transports) and also for street crossings and underground paths. Of course the network connection can also be realised by Bluetooth Low Energy (BLE) or other Wireless LAN technologies instead of PLC.

Yiming Li
Advanced digital signal processing for high-capacity mode-division multiplexed free-space optical communications
Zhouyi Hu¹, Zhaozhong Chen², Yiming Li¹, D. M. Benton¹, A. A. I. Ali¹, 3, M. Patel¹, M. P. J. Lavery², and A. D. Ellis^1
1Aston Institute of Photonic Technology, Aston University, Birmingham, UK
²James Watt School of Engineering, University of Glasgow, UK
³Now with Lumensisty Ltd, Romsey, UK
Spatial modes provide a potential dimension to boost the capacity of free-space optical (FSO) communication systems. Various modal basis sets can be used. For a given aperture size, complete orthogonal modal basis sets can provide higher capacity compared to incomplete modal basis sets, but are more sensitive to FSO channel impairments, such as atmospheric turbulence. In this invited paper, we review our recent progress in using advanced digital signal processing algorithms for the implementation of high-capacity mode-division multiplexed FSO communication systems when employing complete modal basis sets. Besides turbulence, the relatively high inter-mode crosstalk from a commercial multiplexer/demultiplexer has been taken into account. By employing adaptive loading at the transmitter side and/or advanced multiple-input multiple-output detection algorithms at the receiver side, record-high single-wavelength transmission data rates and spectral efficiency have been achieved over both turbulence-free and turbulent FSO links, where all key devices are commercially available.
Keywords: atmospheric turbulence, digital signal processing, free-space optics, mode-division multiplexing, multiple-input multiple-output, optical wireless communication.

Vincenzo Petruzzelli
Integrated optical phased arrays for on-chip communication
M. Khalid¹, G. Calò¹, G. Bellanca², J. Nanni³, M. Barbiroli³, F. Fuschini³, V. Tralli², D. Bertozzi², and V. Petruzzelli^1
1Department of Electrical and Information Engineering, Polytechnic University of Bari, Italy
²Department of Engineering, University of Ferrara, Italy
³Department of Electrical, Electronic and Information Engineering, University of Bologna, Italy
The realization of efficient interconnections is one of the important challenges either in long-haul optical communications or in short-reach optical interconnects. As an example, in chip multiprocessors, the efficient interconnection of cores is becoming a major challenge and it is necessary to avoid communication bottleneck and to meet high bandwidth, low-power and low-latency requirements. Wireless optical on-chip communication is a promising technology to overcome these communication issues at the chip level. In this context, here we propose a new approach based on the use of optical wireless switches based on thin-film lithium niobate on insulator (LNOI) technology. In particular, the radiation characteristics of reconfigurable optical phased arrays are investigated for the realization of integrated optical switches for wireless on-chip interconnection.
Keywords: optical wireless interconnects, on-chip photonics, taper antennas, lithium niobate.

Henrique Salgado
Sigma-delta modulation for enhanced underwater optical communication systems
J. H. Araújo^1,2, H. J. Rocha^1,2, J. S. Tavares^1,2, and H. M. Salgado^1,2
1INESC TEC—Institute for Systems and Computer Engineering, Technology and Science, Porto, Portugal
²Faculty of Engineering, University of Porto, Porto, Portugal
This paper presents an experimental investigation of sigma-delta modulation (SDM) as a means of improving the performance of underwater optical communication systems. The study considers the impact of the key parameters of SDM, including oversampling ratio, the system’s signal-to-noise ratio, bandwidth, and optical link distance.  The results of this study provide insights into the design and optimization of SDM-based underwater optical communication systems, paving the way for future research in this field. A fully digital solution, albeit operating at a lower bit rate than previously published OFDM counterparts, provides immunity against nonlinearities of the system and robustness to noise, which is relevant in harsh environments. Moreover, the proposed solution based on a first-order bandpass SDM architecture avoids the employment of a DAC at the receiver, simplifying its operation and reducing costs. An experimental investigation is carried out for the transmission of 16-QAM over SDM, and a transmission distance of 4.8 m over the underwater channel is achieved with a maximum transmission rate of 400 Mbit/s with an MER of 28 dB.
Keywords: underwater optical wireless link, 16-QAM, sigma-delta modulation, oversampling ratio, MER.

Eszter Udvary
A portable ambient optical noise measurement station
Á. Schranz^1,2, E. Udvary^1,2, B. Matolcsy¹, L. Bacsárdi¹, and A. Nagy^3
1Budapest University of Technology and Economics, Hungary
²ELKH-BME Information Systems Research Group, Budapest, Hungary
³ATL Zrt., Budakalász, Hungary
Optical background radiation measurement to characterize the optical noises is essential because the ambient light can be a degradation and limiting factor of classical and quantum free-space optical communication. A measurement setup for ambient optical noise measurement was designed and developed, and it is realized in a protective housing. The measurement unit is equipped with a camera with the same orientation as the detectors and takes photos of the sky. The optical power measurement was performed at different locations and different wavelength ranges, including 1550 nm and 810 nm optical bands. The measured results show that a clouded sky attenuates the signal heavily, and at the same time it increases the amount of noise at the receiver. The effects of the movement of clouds and dark rain clouds are also presented.
Keywords: satellite ground stations, optical background noise, free space quantum key distribution.

Scott Watson
Blue lasers for optical wireless communication
S. Watson¹, S. P. Najda², P. Perlin^2,3, T. Suski², L. Marona^2,3, M. Leszczynski^2,3, S. Stanczyk², D. Schiavon^2,3, T. J. Slight⁴, and A. E. Kelly^1
1James Watt School of Engineering, University of Glasgow, UK
²TopGaN Ltd, Warsaw, Poland
³Institute of High Pressure Physics PAS, Warsaw, Poland
⁴Sivers Photonics Ltd, Blantyre, UK)
Distributed feedback (DFB) lasers based on gallium nitride (GaN) have been fabricated and characterised for use in optical wireless communications. These devices find applications in free space visible light communication, but also play a fundamental role in underwater and space environments due to the low loss transmission at blue wavelengths. Devices have shown Gbit/s performance making them ideal candidates for low-cost, high speed data transmission.

Changyuan Yu
Multi-user visible light communication and positioning system based on multiplexing technology
Changyuan Yu^1,2, Zhongxu Liu¹, and Jing Zhou^1
1Department of Electronic and Information Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong, China
²Shenzhen Research Institute, The Hong Kong Polytechnic University, Shenzhen, China
Visible light communication and positioning (VLCP) is a promising technology for constructing a multi-functional wireless network that provides simultaneous high-speed communication and high-precision positioning functions. To simultaneously transmit various and complex visible light communication (VLC) and visible light positioning (VLP) signals of multiple users, multiplexing technologies are necessarily adopted in VLCP systems. In this paper, we first review and analyze the VLCP system designs based on conventional multiplexing technologies, including time division multiplexing, frequency division multiplexing, and code division multiplexing. Then, we propose a multi-user VLCP system based on the dual-domain multiplexing scheme, where the VLC and VLP signals of multiple users are effectively integrated and transmitted through multiplexing the time and code resources. The proposed method can make full use of transmission resources to offer simultaneous VLC and VLP functions for multiple users.
Keywords: visible light communication and positioning, visible light communication, visible light positioning, multiplexing technology.

Guoping Lin
Exploring Kerr frequency comb generation with Yttria Stabilized Zirconia (YSZ) crystalline microcavities
Guoping Lin, Harbin Institute of Technology, Shenzhen, China
Microcavity Kerr frequency comb devices have been emerging as promising compact comb sources for a wide range of applications. Considering the oxide crystalline material platform, yttria-stabilized zirconia (YSZ) has a high refractive index of 2.1 at the telecom wavelength and a Kerr nonlinear coefficient similar to that of the silicon nitride platform. Here, we fabricated sub-millimeter size YSZ crystalline microcavities with Q factors above ten million and explored Kerr frequency comb generation at the telecom wavelengths with YSZ.

Juan Pedro Fernandez-Palacios
Investigation of mid-term migration scenarios to multi-band solutions in metropolitan networks
J. P. Fernández-Palacios¹, F. Arpanaei^1,2, J. M. Rivas-Moscoso¹, J. A. Hernández², and D. Larrabeiti^2
1Telefónica Research and Development, Madrid, Spain
²Department of Telematic Engineering, Universidad Carlos III de Madrid, Madrid, Spain
The evolution toward beyond-5G/6G services and applications requiring very high bandwidths will put ever-growing pressure on deployed optical networks to provide the spectral resources needed to accommodate such traffic loads. This is particularly true for the metro/regional segments, where expected traffic CAGR exceeding 40%, primarily driven by CDN traffic confined to the network segments closer to the end users, will push the fiber capacity to its fundamental limits on a number of “hot” links in the short to medium term, irrespective of the use of spectrally efficient modulation formats, especially suited for short-haul transmission. It is therefore critical to evaluate migration scenarios to expand spectral resources beyond the extended C-band (4.8 THz) mainly in use today. In this paper, we conduct multi-homed edge-to-core routing, modulation-level and spectrum-assignment simulations over Telefónica reference metropolitan networks, considering bandwidth-variable coherent transmission with per-channel capacity of 100-400 Gbps in 50 GHz and link-by-link C+L-band migration, while ensuring optimal GSNR performance. Results show that the rollout of L-band equipment over a reduced number of links can efficiently extend the lifespan of current networks, guaranteeing congestion-free operation with minimal intervention, and can be a suitable transitional capacity-stretching solution prior to undertaking more disruptive multi-fiber deployments.
Keywords: multi-band, spectrum assignment, network migration, metropolitan networks.

Mario Nicola Armenise
Flexible photonic integrated circuits: A new paradigm to process data on-board satellites
M. N. Armenise, A. di Toma, G. Brunetti, N. Saha, and C. Ciminelli
Optoelectronics Laboratory, Politecnico Di Bari, Italy
Photonic Integrated Circuits (PICs) are an enabling technology for a large range of field applications, also including Space. In this context, New Space Economy sets several constraints mainly in terms of reliability and flexibility of on-board systems, taking into account the need for small size and low weight, low propagation losses, immunity to electromagnetic disturbances, high processing speed, wide bandwidth, and radiation resistance. Reconfigurable PICs are one of the most promising technologies to fulfil all those requirements. In particular, system flexibility could be achieved by means of programmable or tuneable application-specific PICs (ASPICs). A tuneable ASPIC should be tailored according to the targeted applications, also by reconfiguring itself in relation to the user demands or external environment, at the expense of recursive designing costs, and low flexibility. On the other hand, a programmable PIC performs several functions on a single chip, even if targeted to different applications, with a resulting larger flexibility although with high power consumption and worst performance with respect to ASPIC. Synthetic Aperture Radar (SAR) systems can benefit from these technologies to process on-board image data with a severe reduction of data transfer to the ground station. In this framework, an innovative reconfigurable Ka-band LiNbO3 ASPIC has been proposed, acting as an 8-bit Fourier Transform Spectrometer, to compress echo data and process directly on-board, with a significant improvement of the performance (e.g., footprint, processing time) with respect to the standard counterparts (MMIC, ASIC, FPGA).
Keywords: photonic integrated circuits, flexibility, photonics for space, AWGs.

Tigran Baghdasaryan
Direct laser writing of photonic waveguide components in polymer
T. Baghdasaryan, K. Vanmol, F. Berghmans, H. Thienpont, and J. Van Erps
Vrije Universiteit Brussel, Department of Applied Physics and Photonics, Brussels Photonics (B-PHOT) and Flanders Make, Belgium
Here we report our recent progress in fabrication of optical waveguide building block components for 3D-printed photonic circuits. We used sub-micrometer resolution two photon polymerization based direct laser writing technology to demonstrate waveguides that are mode matched with standard single mode optical fibers, as well as high aspect ratio adiabatic tapers and S-bends. Low-loss performance of these crucial building block components allowed us to further elaborate on the design and fabrication of multimode interferometer couplers, waveguide Bragg gratings and ring resonators.
Keywords: direct laser writing, two-photon polymerization, adiabatic tapers, S-bends, ring resonators, multimode interferometer couplers.

Jonathan Bradley
Measured anomalous dispersion, Kerr comb, and lasing in hybrid TeO₂-coated Si₃N₄ waveguides
H. M. Mbonde¹, B. L. Segat Frare¹, T. Wildi², P. T. Ahmadi¹, B. Hashemi¹, D. B. Bonneville¹, T. Herr², and J. D. B. Bradley^1
1Department of Engineering Physics, McMaster University, Hamilton, Canada
²Centre for Free Electron Laser Science (CFEL)-DESY and University of Hamburg, Germany
We report measured anomalous dispersion, Kerr comb generation, and lasing on hybrid waveguides based on a standard wafer scale 400-nm Si₃N₄ coated with the TeO₂ film. The use of thin Si₃N₄ ensures reduced stress and film crack and therefore fabrication of scalable and high yield waveguides through conventional CMOS process. On the other hand, the highly nonlinear TeO₂ film is added to enhance nonlinearity and engineer waveguide dispersion while also acting as a host of rare-earth dopants for amplification and lasing. Experimental results are presented showing that the normal dispersion of 400 nm-thick Si₃N₄ waveguides can be engineered to anomalous by adding the TeO₂ film. For a 1.6-µm wide, 500 µm bend radius ring resonator with a 424-nm thick TeO₂ coating, dispersion values of ~25 and ~78 ps/nm∙km was measured at 1552 nm for the TE and TM-modes, respectively. Also, by exploiting the rare-earth solubility of the TeO₂ film and depositing an Er-doped TeO₂ coating, a microdisk laser was observed at pump power of 12 mW. These results show a promising route to potentially monolithic integration of linear, nonlinear and active functionalities in a single photonic chip.
Keywords: silicon nitride, monolithic integration, microdisk laser, dispersion engineering, nonlinear photonics, Kerr combs.

Susobhan Das
All-optical control of nonlinear optics of 2D-materials
S. Das¹, Yi Zhang¹, Yadong Wang², Yunyun Dai³, and Zhipei Sun^1
1Aalto University, Espoo, Finland
²The University of Sheffield, Sheffield, UK
³Beijing Institute of Technology, Beijing, China
All-optical control of nonlinear photonic processes in nanomaterials is of significant interest from a fundamental viewpoint and with regard to applications ranging from ultrafast data processing to spectroscopy and quantum technology. Despite of second and third harmonic generation, high-harmonic generation, an extreme nonlinear optical phenomenon beyond the perturbation regime, is of great significance for various potential applications, such as high-energy ultrashort pulse generation with excellent spatio-temporal coherence. However, efficient control of different harmonic generation is still challenging due to the typical weak light-matter interaction. Here, we demonstrate giant and broadband all-optical ultrafast modulation of second, third, fourth and fifth harmonic generation in monolayer transition-metal dichalcogenides mediated by the modified excitonic oscillation strength produced upon optical pumping. Our results indicate that the multiple order of nonlinear optical susceptibility of monolayer molybdenum disulfide (MoS2) can be controlled optically. All-optically tunable nonlinear optical susceptibility is not only a promising technique for the characterization and study of intriguing exciton dynamics, but also a potential platform for disruptive photonic and optoelectronic applications, including all-optical modulation and imaging.
Keywords: transition metal dichalcogenides monolayers, nonlinear optical susceptibility, ultrafast all-optical modulations.

Onur Düzgöl
Calibration of a photonic neural network considering fabrication tolerances
O. Düzgöl and A. Richter
VPIphotonics, Berlin, Germany
Photonic integrated circuits (PICs) offer high-speed and wide-bandwidth hardware solutions for deep learning applications. However, phase mismatches resulting from fabrication tolerances can significantly degrade the accuracy of these networks. Calibration is essential before network operation to address this issue. This study presents a novel circuit-level simulation technique for photonic neural networks. Furthermore, we propose a method to calibrate the linear component of the neural network, a step that can significantly improve accuracy.
Keywords: neuromorphic computing, photonic integrated circuits, simulation, fabrication tolerances.

Marco Grande
Design and optimization of broadband optical duplexer and triplexer couplers
A. Thottoli¹, A. S. Vorobev^1,2,3, G. Biagi^2,4, S. ladanza^5,6, G. Magno¹, L. O’Faolain^2,3, and M. Grande^1
1Department of Electrical and Information Engineering, Politecnico di Bari, Bari, Italy
²Centre for Advanced Photonics and Process Analysis, Munster Technological University, Cork, Ireland
³Tyndall National Institute, Cork, Ireland
⁴PolySenSe Lab, Physics Department, University of Bari, Italy
⁵Laboratory of Nano and Quantum Technologies, Paul Scherrer Institut, Villigen, Switzerland
⁶IBM Research Zurich, Switzerland
On-chip optical combiners with high coupling efficiency can be fully exploited in both multiple gas/liquid sensing devices and telecommunication applications. In this paper, we will review the enabling technologies and discuss the basic operating characteristics of ultra-broadband optical couplers. The design and preliminary fabrication results of optimized optical duplexers and triplexers based on angled multimode interference (AMMI) and directional coupler (DC) configurations will be also detailed.

Haroldo Hattori
Opto-electronic devices based on refractory and 2D materials
I. A. M. Al-Ani¹, K. As’ham¹, S. Akter¹, S. Abdo¹, Ziyuan Li², and H. T. Hattori^1
1School of Engineering and Information Technology, UNSW Canberra, Australia
²MoE Key Lab of Photoelectronic Imaging Technology and Systems, Beijing Institute of Technology, China
In this article, we highlight our current work on optoelectronic devices based on 2D and refractory materials. We initially present our past work on nano-antennas based upon refractory materials and show how they can handle higher fluences than noble metals. We then show how refractory ceramics can be applied to ultraviolet and visible photodetectors based on refractory carbides/borides, with potential integration to silicon carbide power electronic devices. Finally, we exploit 2D dichalcogenides and show how to achieve perfect absorbance and efficient strong coupling in the materials, when combined with nanostructures such as nano-cylinders and meta-gratings.
Keywords: nonlinear analysis, laser, arrayed waveguide gratings, Fabry-Perot filters.

Kambiz Jamshidi
Numerical modelling and characterization of active silicon ring resonators
K. Jamshidi¹, M. Catuneanu¹, Menglong He¹, A. Shetewy¹, A. Zarif¹, S. Dev¹, H. Vithalani¹, Shiyao Fang¹, D. Heydari², R. Hamerly^3,4, and H. Mabuchi^2
1Integrated Photonics Devices Group, Chair of RF and Photonics, TU Dresden, Germany
²E. L. Ginzton Laboratory, Stanford University, USA
³Physics and Informatics Laboratories, NTT Research Inc., Sunnyvale, USA
⁴Research Laboratory of Electronics, MIT, Cambridge, USA
Silicon ring resonators are important components that can be fabricated using photonic IC (PIC) technologies and have found several applications in the realization of high-speed modulators, all-optical filters, reservoir computing, and photon pair generation. Several nonlinear effects like thermal, free-carrier, Kerr, and two-photon absorption affect the performance of these resonators. The dynamical modeling of ring resonators is necessary to characterize the fabricated rings and to use the proper physical parameters for the desired application. This paper will review recent progress in static and dynamic modeling of ring resonators. These models are used to characterize the active silicon ring resonators which were previously designed and fabricated.
Keywords: ring resonators, silicon photonics, photonic ICs, optical bistability, nonlinear dynamics, self-pulsing, free carrier oscillation.

Andrew Katumba
Using Bayesian techniques to accelerate the design of silicon photonics reservoirs
A. Katumba^1,2, J. Mikelson¹, M. P. Matovic¹, J. Dambre², and P. Bienstman^2
1Makerere University, Kampala, Uganda
²Ghent University, Ghent, Belgium
Silicon photonics reservoirs have shown incredible promise as high-speed, energy-efficient neuromorphic processors for optical communications networks. However, achieving high performance on practical tasks tends to be both computationally expensive and storage intensive.  In this work we employ Bayesian techniques to i) optimize reservoir hyper-parameters and ii) reduce the number of expensive, physical propagation results required to obtain an accurate estimate on the task with a small number of evaluations. We will use the case of numerical simulations of silicon photonics reservoir signal equalization in a 56 Gbaud PAM-4 100 km transmission system and report symbol and bit level performance metrics with appropriate error bounds.

Kenji Kintaka
Research progress on cavity-resonator-integrated guided-mode resonance mirror for Gaussian beam
K. Kintaka¹, A.Watanabe², J. Inoue², and S. Ura^2
1National Institute of Advanced Industrial Science and Technology, Ikeda, Japan
²Kyoto Institute of Technology, Japan
A guided-mode resonance filter integrated in a waveguide resonator on a reflective substrate can present highly efficient reflection with a steep reflection-phase change. Recent research work on improvement of characteristics of the device for small-diameter Gaussian beam will be introduced and discussed.

Sylwester Latkowski
Standardization and automation of test processes in the production flow of integrated photonics
S. Latkowski, D. Pustakhod, R. Jansen,  X. Leijtens, and K. Williams
Institute for Photonic Integration, Eindhoven University of Technology, The Netherlands
Global technology roadmaps for semiconductor electronics (HIR) and integrated photonic systems (IPSR-I) widely highlight demands for increased automation and standardization of electronic-photonic testing  across the production flow. Test processes at all stages, including front-end,  back-end, outsourced semiconductor assembly and test (OSAT) suppliers, module, and system integrators are deemed to be one of the top contributors to the manufacturing costs of integrated photonics. Current developments of test processes towards Test-as-a-Service, and standardization efforts carried out at Photonic Integration Technology Center and TU/e will be presented.

Alessio Lugnan
Silicon ring resonator with phase-change material as a plastic dynamical node for scalable all-optical neural networks with synaptic plasticity
A. Lugnan¹, S. Garcia-Cuevas Carrillo², J. Song², S. Aggarwal³, F. Brückerhoff-Plückelmann⁴, W. H. P. Pernice⁴, H. Bhaskaran³, C. D. Wright², and P. Bienstman^1
1Photonics Research Group, INTEC Department, Ghent University – imec, Belgium
²Department of Engineering, University of Exeter, UK
³Department of Materials, University of Oxford, UK
⁴Department of Physics, University of Münster, Germany
Synaptic plasticity, that is the ability of connections in neural networks to strengthen or weaken depending on their input, is a fundamental component of learning and memory in biological brains. We present a numerical and experimental investigation of an integrated photonic plastic node, consisting of a silicon ring resonator enhanced by phase-change materials (GST). This all-optical device is capable of dynamical nonlinear behaviour, multi-scale volatile memory, non-volatile memory and multi-wavelength operations. We discuss its employment as a building block in scalable all-optical dynamical neural networks that can adapt to their input via synaptic plasticity.

Liam O’Faolain
Refractive index sensing using a photonic crystal hybrid external cavity laser
L. O’Faolain^1,2, T. Oliveira¹, F. Atar², Y. Arafat², M. Grande³, S. ladanza^5,6, and B. Corbett^2
1Centre for Advanced Photonics and Process Analysis, Munster Technological University, Cork, Ireland
²Tyndall National Institute, Ireland
³Department of Electrical and Information Engineering, Politecnico di Bari, Italy
⁴PolySenSe Lab, Physics Department, University of Bari, Italy
⁵Laboratory of Nano and Quantum Technologies, Paul Scherrer Institut, Villigen, Switzerland
⁶IBM Research Zurich, Rüschlikon, Switzerland
In this work, we show a photonic crystal hybrid external cavity laser (HECL) that can be used for refractive index sensing applications. To demonstrate its potential for integration we present the first demonstration of a fully integrated hybrid external cavity laser (HECL) in edge-coupling configuration by means of micro-transfer printing. The HECL is able to achieve single-mode regime over a wide range of driving currents with SMSR in the range of 40 dB. This platform provides a RI sensor characterized its compactness, simplicity of fabrication, compatibility with high throughput integration processes.
Keywords: photonic integrated circuits, hybrid external cavity laser, photonic crystal, silicon photonics, silicon nitride.

Christos Riziotis
Design and fabrication challenges of integrated optical circuits for quantum computing applications
S. I. Tsintzos¹, K. Tsimvrakidis¹, A. Sinani^1,2, A. Bogris², J. C. Gates³, P. G.R. Smith³, A. W. Elshaari⁴, V. Zwiller⁴, and C. Riziotis^1,5
1National Hellenic Research Foundation, Theoretical and Physical Chemistry Institute, Athens, Greece
²Department of Informatics and Computer Engineering, University of West Attica, Egaleo, Greece ³Optoelectronics Research Centre, University of Southampton, UK
⁴Department of Applied Physics, Royal Institute of Technology, Stockholm, Sweden
⁵Institute for Advanced Modelling and Simulation, University of Nicosia, Cyprus
The paper presents current design issues, limitations, and fabrication challenges towards the development of hybrid integrated optical circuits with embedded single photon sources, which are critical components for future quantum computing, sensing, and communication systems. Optical nanowires with embedded quantum dots (NWQD) are very promising single photon sources, with several reported results of integration in high index platforms like silicon or silicon nitride. Silica on silicon is a favorable platform for optical computing, providing the high degree of customization when combined with direct laser writing techniques for definition of optical structures with refractive index modification. However, the low 10^-3 achievable refractive index contrast imposes strict limitations on the compatibility with NWQD resulting in general in low coupling efficiency as shown in this work. Consideration of several design and fabrication issues demonstrates the potential for NQWD integration in laser written silica based optical circuits with adequate efficiency for practical applications.
Keywords: nanowires, quantum dot, waveguides, integrated optical circuit, quantum photonics, computing.

David Rowe
Group IV mid-infrared photonic devices and applications
D. J. Rowe, L. Reid, Chen Wei, C. J. Stirling, C. J. Mitchell, Han Du, Xingzhao Yan, D. T. Tran, Yangbo Wu, M. Banakar, Yanli Qi, A. Osman, Ke Li, J. Soler Penades, Longqi Zhou, K. M. Groom, J. Heffernan, C. G. Littlejohns, M. Nedeljkovic, and G. Z. Mashanovich
Optoelectronics Research Centre, University of Southampton, UK
We present our recent results on mid-infrared photonic devices, including component optimisation, circuit design and their application to sensing. We show the performance of an on-chip FTIR microspectrometer implemented in silicon-on-insulator. A self-referenced switching sensor in germanium-on-silicon (GoS) improves noise rejection by a factor of 11 compared to a regular waveguide sensor. We demonstrate waveguides with single-moded guidance over an octave of frequency at mid-infrared wavelengths to enable on-chip spectroscopy by suppressing higher-order modes. We apply a noise model to evaluate the performance of our waveguide sensors for therapeutic drug monitoring. Flip-chip bonding has been used to integrate quantum cascade lasers onto a GoS platform and we report further advances in coupling efficiency, structural integrity, process design and real-time laser monitoring. Final, we discuss recent progress on detectors, included bolometers and defect-mediated methods.

Alejandro Sánchez-Postigo
Enhancing the performance of waveguide-integrated superconducting nanowire single-photon detectors using subwavelength grating metamaterials
A. Sánchez-Postigo, C. Graham-Scott, and C. Schuck
Institute of Physics, University of Münster, Germany
The integration of quantum photonics devices in nanophotonic platforms is a promising approach for implementing scalable quantum systems for quantum sensing and communications applications. Superconducting nanowire single-photon detectors (SNSPDs) have developed into the most popular photon counting devices due to their high detection efficiency, low dark count rates, and time uncertainty (jitter). As many integrated structures, waveguide-coupled SNSPDs can benefit from the use of subwavelength gratings, which are periodic planar structures that enable the synthesis of metamaterials with tailorable optical properties, namely refractive index, wavelength dispersion, and anisotropy. In this work, we report on our latest advances regarding single-photon detection in silicon nitride waveguides, including the novel use of subwavelength grating metamaterials to enhance the performance of SNSPDs.
Keywords: superconducting nanowire single-photon detectors, SNSPD, SWG metamaterials, SWG, NbTiN.

Isaac Suárez
Waveguide amplifiers and lasers based on FASnI₃ perovskite thin films
I. Suárez¹, H. P. Adl², V. S. Chirvony², J. Sánchez-Díaz³, R. S. Sánchez³, I. Mora-Seró³, and J. P. Martínez-Pastor^2
1Escuela Técnica Superior de Ingeniería, Universidad de Valencia, Spain
²UMDO, Instituto de Ciencia de los Materiales, Universidad de Valencia, Spain
³Institute of Advanced Materials (INAM), Universitat Jaume I, Castelló, Spain
The integration of optical functionalities in flexible substrates has become in an important trend in the optoelectronics community. However, the sophisticated technology to fabricate suitable optical architectures in a flexible substrate limits its demonstration to extremely few reports, which becomes even more challenging for active devices, where the appropriate integration of a material with high efficiency of emission is also necessary. In this work, a FASnI₃ (FA, formamidinium) lead-free perovskite thin films are incorporated in a flexible polyethylene terephthalate (PET) substrate and cladded by a polymethylmethacrylate(PMMA) thin film. The structure conforms a planar waveguide where the geometrical parameters (i.e. thicknesses of the films) are properly chosen to: (i) allow the single mode propagation at the photoluminescence (PL) wavelength, (ii) provide an optimum excitation of the FASnI3 by end-fire coupling the pump beam, (iii) enhance the light-matter interaction in the semiconductor and with it the optical gain, (iv) provide preferable direction for the emitted light and a direct outcoupling. As a result, amplified spontaneous emission is demonstrated with an extremely low threshold, about 1 µJ/cm², and a strong polarization anisotropy preferable to the transverse electric (TE) polarization. Moreover, the device exhibits narrow lasing lines (< 1 nm) caused by the formation of random cavity loops in the polycrystalline grains. The operation of the device is analyzed under bending conditions demonstrating that the figures of merit can be tuned with the curvature radius.  The proposed device represents an important step towards the development of future cheap and green flexible/wearable technology.

David Thomson
High efficiency and high-speed silicon optical modulators
D. J. Thomson, W. Zhang, M. Ebert, K. Li, B. Chen, S. Liu, W. Cao, F. Meng, X. Yan, H. Du, M. Banakar, D. T. Tran, C. G. Littlejohns, and G. T. Reed
Optoelectronics Research Centre, University of Southampton, UK
Optical modulators built in a CMOS compatible silicon photonics platform allow the potential for high data rate communication at low cost. Here our recent progress in high efficiency and high-speed silicon optical modulators is presented, including mechanisms for enhancing the performance of devices beyond previous limitations.

Jarosław Turkiewicz
Coupled aperture VCSELs suitable for 100 GHz intensity modulation
M. Lindemann¹, N. C. Gerhardt¹, M.R. Hofmann¹, N. Ledentsov jr.^2,3, V. A. Shchukin³, O. Yu. Makarov², N. N. Ledentsov², Ł. Chorchos^2,3, and J. P. Turkiewicz^3
1Photonics and Terahertz Technology, Ruhr-Universität Bochum, Germany
²VI Systems GmbH, Berlin, Germany
³Warsaw University of Technology, Poland
Search for novel approaches to reach and exceed 100 GHz modulation bandwidth applying vertical cavity surface emitting lasers (VCSELs) became an important subject due to the continuously growing bandwidth demand in data centers and a need in low-cost energy-efficient solutions.  In this work we consider coherent VCSEL mini-arrays composed of two 3µm-diameter oxide-confined apertures at a 7µm center-to-center distance. We demonstrate intensity modulation in the range of up to ~100 GHz through coherent interaction of the coupled modes in the neighboring cavities. Applying 2ps pulse excitation and a streak camera detection we observe resonance high frequency (HF) features corresponding to the resonant oscillation frequency (ROF) resonance and a much stronger photon-photon (PP). The intensity modulation in each of the cavities occurs in anti-phase as evidenced by selective light outcoupling. The intensity of the PP resonance is only weakly dependent on the polarization of the excitation pulse. Spin-related features are observed through circular polarization studies indicating additional polarization oscillations at lower frequencies. The PP intensity modulation frequency is defined by the frequency splitting of the cavity modes and can be tuned within 35-75 GHz by current tuning 0.5-8 mA.

Carlos Alonso-Ramos
Optomechanical and nonlinear applications in silicon photonics
P. Nuño Ruano¹, J. Zhang^1,2, T. T. D. Dinh¹, D. González-Andrade¹, X. Le Roux¹, M. Montesinos-Ballester¹, C. Lafforgue¹, D. Medina-Quiroz¹, D. Benedikovic³, P. Cheben^2,4, S. Edmond¹, D. Bouville¹, N. D. Lanzillotti-Kimura¹, D. Marris-Morini¹, E. Cassan¹, L. Vivien¹, and C. Alonso-Ramos^1
1Université Paris-Saclay, CNRS, Centre de Nanosciences et de Nanotechnologies, Palaiseau, France
²National Research Council Canada, Ottawa, Canada
³University Science Park, University of Zilina, Slovakia
⁴Dept. Electronics, Carleton University, Ottawa, Canada
Periodically patterning silicon with a subwavelength pitch opens new degrees of freedom to control the propagation of light and sound in silicon photonic circuits with unprecedented flexibility. In this invited presentation, we will show our most recent results on the use suspended silicon waveguides for supercontinuum generation in the near-IR and mid-IR. We will also discuss our recent demonstrations of subwavelength engineering of photons and phonons in suspended and non-suspended silicon optomechanical cavities.

Stéphane Calvez
Nonlinear conversion in Cavity-Resonant Integrated Grating Filters
S. Calvez¹, F. Renaud¹, E. Hemsley¹, A. Monmayrant¹, O. Gauthier-Lafaye¹, E. Popov², and A.-L. Fehrembach^2
1LAAS-CNRS, Université de Toulouse, CNRS, Toulouse, France
²Aix Marseille Univ, CNRS, Centrale Marseille, Marseille, France
In this presentation, we will review our recent progress in nonlinear conversion in grating-coupled Fabry-Pérot planar microcavities also known as Cavity-Resonant Integrated Grating Filters. Having established that enhanced second harmonic generation is obtained in these resonators, we will discuss the design and experimental demonstration of technical implantations allowing the achievement of critical coupling and improved conversion efficiencies.

Xianfeng Chen
Manipulation of second harmonic generation in nanoscale nonlinear scattering media
Xianfeng Chen, Shanghai Jiao Tong University, China
The interaction between light and media is the eternal topic of light physics research. In recent years, nonlinear nanophotonics have gradually become the focus of modern optics. In this report, we focus on the second-harmonic generation in nanoscale nonlinear scattering media. Radom cavity-enhanced second-harmonic generation was demonstrated. By using feedback-based wavefront shaping, we have realized second-harmonic spatial focusing and spectral control. Besides, we have further proposed a completely new nonlinear-scattering-matrix method to cope with the second-harmonic wave manipulation. All these studies open a path towards nonlinear signal recovery, nonlinear imaging, and complex environment quantum information processing.

Francesco De Lucia
Poled fibers for nonlinear photonics: Recent advances and future perspectives
F. De Lucia¹, N. Englebert¹, P. Parra-Rivas¹, C. Mas Arabí¹, R. Bannerman², M. I. M. A. Khudus², S.-P. Gorza¹, G. Brambilla², J. Gates², P. Sazio², and F. Leo^1
1Service OPERA-Photonique – Université libre de Bruxelles, Brussels, Belgium
²Optoelectronics Research Centre, University of Southampton, UK
Silica fibers thermally poled possess a non-null second order nonlinear susceptibility and can consequently be exploited for the realization of parametric processes usually prohibited, such as for example second harmonic generation or parametric down conversion. In this talk we present their most recent applications, ranging from high harmonics generation to the implementation of an all-fiber optical parametric oscillator, and discuss some future perspectives of what we still consider a reliable technological platform for nonlinear photonics applications.

Yannick Dumeige
GaP WGM microdisks for second order nonlinear optics
R. Saleem-Urothodi¹, P. Guillemé¹, J. Le Pouliquen², T. Rohel², R. Bernard², L. Bramerie¹, C. Velly¹, A. Lorenzo-Ruiz², A. Beck², A. Létoublon², O. De Sagazan³, C. Cornet², Y. Dumeige¹, Y. Léger^2
1Univ Rennes, CNRS, Institut FOTON, Lannion, France
²Univ Rennes, INSA de Rennes, CNRS, Institut FOTON, Rennes, France
³Institut d’Électronique et des Télécommunications de Rennes, CNRS, Rennes, France
III-V semiconductor whispering gallery mode (WGM) microdisks have many assets for second order nonlinear optics. Their large nonlinear susceptibility combined with their high refractive index allows us to consider low power optical function based on nonlinear effects in a broad spectral range.  In this paper, we will review our recent results on WGM GaP microdisks. After having recalled the different phase matching scenarios achievable in this material, we will present our experimental results on Q-factor characterization and second harmonic generation measurements. Finally, we will discuss other device configurations based on coupled microdisks.

François Sanchez
A review of dissipative soliton resonance in fiber lasers
F. Sanchez¹, A. Komarov^1,2, and G. Semaan^1,3
1Laboratoire de Photonique d’Angers, Université d’Angers, France
²Institute of Automation and Electrometry, Russian Academy of Sciences, Novosibirsk, Russia
³Service OPERA-Photonique, Université Libre de Bruxelle, Belgium
Due to the quantization of the pulse energy in fiber lasers, it is challenging to find effective ways to increase the pulse energy directly from a fiber laser oscillator. One efficient and promising technique is based on the dissipative soliton resonance (DSR) effect which is a special solution of the nonlinear propagation equation manifesting as a square-wave pulse with a constant peak power and increasing pulse energy and duration when the pumping power increases. Experimentally, DSR is favored with the use of long or ultra-long cavities and has been observed in many optical configurations with various rare-earth doped fibers. In this communication we give a review of DSR in fiber lasers.

Concita Sibilia
Linear and nonlinear optical properties of Zno-ZnWO4 eutectic composites
C. Sibilia¹, G. Leahu¹, R. Li Voti¹, E. Petronjievic¹, M. C. Larciprete¹, M. Centini¹, A. Belardini¹, and D. Pawlak^2
1Dept SBAI, University of Roma La Sapienza, Italy
²Ensemble3 – Center of Excellence, Warsaw, Poland
Many different optical interesting and unusual properties of eutectics [1] ZnO/ZnWO₄ have been studied ranging from linear up to nonlinear optical properties in the visible range. The optical linear properties evidencing a strong polarization dependence of transmitted and reflected signal have been analyzed [2]. For example, the photodeflection method utilized for those sample was able to put into evidence the excitonic resonance in the blue region. Also, the nonlinear optical behavior was studied looking at the Second Harmonic generation: we used a set-up based on a pulsed Ti:Sapphire laser with 130 fs pulse duration, wavelength of 800 nm and repetition rate of 1 kHz as a pump light source. The polarization of the fundamental beam at the laser’s output was in p-state and it can be tuned by means of a rotating a half-wave plate at 800 nm. In order to suppress the SHG signal generated from the half-wave plate, a long pass filter was placed after the plate. The sample was placed on a rotational stage which enables tuning of the angle of incidence α. The light coming out of the sample was then filtered by a short pass filter and set to p or s state by a polarization analyzer before the detector. With this set-up the intensity of s or p SHG signal at the output as a function of the input polarization or α was detected and the corresponding conversion efficiency was estimated. The conversion efficiency was attributed to a phase matching condition enhancement due to the effective dispersion low of the eutectic compound [3,4]. The complex geometry of the eutectic composite reveals peculiar properties both in the visible and in the IR ranges acting as natural polarizing filters opening the way to new interesting photonics applications.
[1] D. A. Pawlak et al., Advanced Functional Materials 20, 1116-1124 (2010).
[2] P. Osewski et al., Advanced Optical Materials 8,1901617 (2020).
[3] C. J. Spengler, S. O’Hara, App. Optics vol. 3, no. 9 (1964).
[4] P. Osewski et al., Sci. Rep. 7, 45247 (2017).

Misha Sumetsky
SNAP platform: New ultraprecise fabrication methods and devices
M. Sumetsky, Aston Institute of Photonics Technologies, Aston University, Birmingham, UK
SNAP platform enables exceptionally precise fabrication of microresonators and microresonator circuits at the optical fibre surface with the subangstrom and, potentially, picometer fabrication precision. Here, the recently developed experimental approaches in SNAP technology and recently invented new SNAP devices are reviewed. The new approaches include fabrication of optical microresonators by lithographic methods, annealing in a flame, slow cooking, fibre bending, and fibre side-coupling. The new devices include microwave photonic filters, optical frequency comb generators, and bat microresonators.

Xuezong Yang
Recent progress on continuous-wave single frequency diamond Raman lasers
Xuezong Yang¹, Muye Li¹, Yuxiang Sun¹, D. J. Spence², R. P. Mildren², and Yan Feng^1,3
1Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou, China
²MQ Photonics Research Centre, Department of Physics and Astronomy, Macquarie University, Sydney, Australia
³Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, China
Diamond Raman lasers provide an efficient scheme for achieving continuous-wave (CW) single-frequency high-power output in both visible and near-infrared bands based on the spatial-burning-hole free gain and the intracavity χ2 crystal nonlinear loss. Maximum single-frequency powers of 20 W at Stokes and 22 W at SHG were demonstrated by tuning the phase matching of the χ² crystal and changing the Stokes output coupling. A spectral linewidth of a CW single-frequency diamond Raman laser was measured to be about 100 kHz at the power of 20 W by using the delayed self-heterodyne interferometric method. We also quantified the level of SHG coupling necessary to suppress secondary axial-modes including the parasitic stimulated Brillouin scattering.

Yuanlin Zheng
Nonlinear optics applications on the lithium niobate-on-insulator platform
Yuanlin Zheng, State Key Laboratory of Advanced Optical Communication Systems and Networks, School of Physics and Astronomy, Shanghai Jiao Tong University, China
Integrated photonics on the lithium niobate-on-insulator platform has attracted significant interest in recent years. Dense photonic integrated circuits, benefiting from its high refractive index contrast, can be realized to harness the versatile linear and nonlinear optical functionalities of lithium niobate for various optical effects. In this talk, I will present our recent work on the fabrication of micro/nano structures on LNOI, and the application of LNOI ridge waveguides and whispering-gallery-mode (WGM) microdisks for efficient nonlinear photonics. Efficient frequency conversion and bright heralded single-photon generation is demonstrated, which holds great promise for integrated nonlinear photonics and devices.

Anthony Bennett
Colour centres in aluminium nitride are bright, room-temperature quantum light sources
J. K. Cannon^1,2, S. G. Bishop^1,2, Yanzhao Guo^1,2, H. B. Yağcı^1,2, R. N. Clark^1,2, . P. Hadden^1,2, and A. J. Bennett^1,2
1School of Engineering, Cardiff University, UK
²Translational Research Hub, Cardiff, UK
Red colour centres in AlN are bright room-temperature quantum light sources emitting anti-bunched light under optical excitation. We study the temporal, spectral and polarisation behaviour of emitters in commercially supplied AlN on sapphire. The high refractive index limits the photon collection efficiency for a lens above the sample, through refraction and total internal reflection. Applying a macroscopic solid immersion lens which is almost index matched to the semiconductor we achieve a 4.2-fold increase in collection efficiency, yielding nearly one megacount per second detected photon rate.
Keywords: single photon, quantum emitter, colour centre, aluminium nitride.

Adrien Bensemhoun
Bright multimode entanglement out of a SiN microring
A. Bensemhoun¹, V. D’Auria¹, M. Melalkia¹, G. Esposito¹, Y. Désières², S. Guerber², Q. Wilmart², K. Roux², S. Olivier², A. Zavatta^5,6, C. Gonzalez-Arciniegas³, O. Pfister³, A. Martin¹, J. Etesse¹, L. Labonté¹, G. Patera⁴, and S. Tanzilli^1
1Université Côte d’Azur, CNRS, Institut de Physique de Nice (INPHYNI), UMR 7010, Nice,France
²Université Grenoble Alpes, CEA LETI, Grenoble, France
³Department of Physics, University of Virginia, Charlottesville, USA
⁴Université Lille, CNRS, PhLAM – Physique des Lasers Atomes et Molécules, Lille, France
⁵Istituto Nazionale di Ottica, Florence, Italy
⁶LENS and Department of Physics Astronomy, University of Firenze, Italy
We investigate, in continuous variable regime, multimode entanglement among different frequency components generated in a Silicon Nitride (SiN) micro-ring above its oscillation threshold. Entangled spectral modes at the micro-ring output form a frequency comb and generated in an extremely compact configurations (micro-rings with radius of about ten micrometers). The multimode structure opens up the possibility of connecting multiple users to a quantum network and/or increasing channel capacity across a set of users and can be exploit for quantum computing. In this work, we study multimode quantum states generated by four-wave mixing pumped by a continuous wave laser. In the regime of continuous variables, some pioneering works, all based on the SiN platform, have been reported, showing bi-partite quantum correlations in intensity or among field quadratures. Here, we present a theoretical analysis aiming at quantifying quadrature entanglement in different frequency comb regimes and show a transition between bi-partite to multipartite entanglement as a function of increased pump power and of the measurement parameters. In the simulations, multipartite entangled states are considered to be emitted in the telecommunication C-band so as to be compatible with standard optical fibers and off-the-shelf fiber-based components. We also present an experimental setup built to measure intensity correlations that are directly linked to quadratures and highlight multimode entanglement. Results on two mode intensity squeezing will be presented and discussed in the context of multimode dynamics.

Ortwin Hess
Nanoplasmonics as enabler of room-temperature quantum nanophotonic networks
O. Hess^1,2, ¹School of Physics and CRANN Institute, Trinity College Dublin, Ireland, ²The Blackett Laboratory, Imperial College London, UK
Quantum technologies are widely expected to bring a revolution in communications and information technologies in the coming decade allowing, for example, un-paralleled levels of secure communications. For quantum communication, photonic quantum effects have played a central role, but most photonic solutions and systems based on light-matter interaction also require cryogenic environments. Strong coupling of light and matter at the single emitter level is a fundamental quantum resource offering deterministic energy exchange between single photons and a two-level system, and the possibility to achieve single-photon nonlinearities via the anharmonicity of the Jaynes-Cummings ladder. Until recently, however, the conditions for achieving strong-coupling were most commonly met at cryogenic temperatures such that de-coherence processes are suppressed. As a major step forward, we have recently demonstrated room-temperature strong coupling of single molecules [1] and single quantum dots [2] to ultra-confined light fields in plasmonic resonators at ambient conditions. The fact that strong-coupling conditions may be reached at room temperature is of immense interest because it represents a clear route to a practical implementation and use of quantum behaviour in nanophotonic systems and its application in bio-sensing  [3]. The talk will discuss how nanoplasmonics can be an enabler of ultrafast room-temperature quantum nanophotonic networks via strong coupling and ultrafast quantum dynamics [4]. We will highlight the physics associated with recently demonstrated room-temperature strong coupling of single molecules in a plasmonic nano-cavity  [1] and near-field generated strong coupling of single quantum dots  [2] and single quantum emitter Dicke enhancement [5] paving the road towards single-photon quantum nonlinearities. The presentation will also explain near-field enhanced single-photon emission in near-zero index materials  [6] and ultrafast multi-partite quantum entanglement  [7]. This provides the foundation for unprecedented control over photon number, single photon dynamics, and dynamic multi-photon coherence. These properties are all imperative for the development of next-generation, nanoscale building blocks in ambient-temperature photonic quantum communication technologies. ACKNOWLEDGEMENTS: Supported by the Science Foundation Ireland (SFI) via grants 18/RP/6236 and 22/QERA/3821.
[1] R. Chikkaraddy, B. de Nijs, F. Benz, S. J. Barrow, O. A. Scherman, E. Rosta, A. Demetriadou, P. Fox, O. Hess, and J. J. Baumberg, Single-molecule strong coupling at room temperature in plasmonic nanocavities, Nature 535, 127 (2016).
[2] H. Groß, J. M. Hamm, T. Tufarelli, O. Hess, and B. Hecht, Near-field strong coupling of single quantum dots, Science Advances 4, eaar4906 (2018).
[3] N. Kongsuwan, X. Xiong, P. Bai, J.-B. You, C. E. Png, L. Wu, and O. Hess, Quantum plasmonic immunoassay sensing, Nano Lett. 19, 5853 (2019).
[4] X. Xiong, N. Kongsuwan, Y. Lai, C. E. Png, L. Wu, and O. Hess, Room-temperature plexcitonic strong coupling: Ultrafast dynamics for quantum applications, Appl. Phys. Lett. 118, 130501 (2021).
[5] T. Tufarelli, D. Friedrich, H. Groß, J. Hamm, O. Hess, and B. Hecht, Single quantum emitter Dicke enhancement, Phys. Rev. Research 3, 033103 (2021).
[6] F. Bello, N. Kongsuwan, J. F. Donegan, and O. Hess, Controlled cavity-free, single-photon emission and bipartite entanglement of near-field-excited quantum emitters, Nano Lett. 20, 5830 (2020).
[7] F. D. Bello, N. Kongsuwan, and O. Hess, Near-field generation and control of ultrafast, multipartite entanglement for quantum nanoplasmonic networks, Nano Lett. 22, 2801 (2022).
Keywords: quantum nanophotonic networks, nanoplasmonics, room-temperature strong coupling, single-emitter Dicke enhancement, single photon quantum nonlinearity, quantum entanglement

Branislav Jelenković
Entangled pairs of photons for squeezed light: Generation and application
M. Ćurčić, D. Arsenović, and B. Jelenković
Institute of Physics Belgrade, Serbia
We discuss methods of generation of quantum entangled pairs of photons and present results obtained by non-linear process of four way mixing (FWM) in alkali atoms. Two-mode squeezing, known also as  relative amplitude squeezing, by a pair of photons generated by FWM has been thoroughly investigated because of important applications of such paired photons. We show strong intensity squeezing in potassium vapour and also dependence of IDS on FWM parameters.  Experimental results are compared with calculated IDS by the model of operators. Examples of application of twin photons for quantum enhanced sensing and quantum imaging and microscopy will be given.
Keywords: four wave mixing, amplitude squeezing, correlated photon pairs, entanglement, quantum imaging.

Marco Liscidini
Efficient generation of squeezed light via spontaneous four-wave mixing in integrated structures
A. Viola, L. Zatti, and M. Liscidini, Università degli Studi di Pavia, Italy
We investigate the use of integrated structures for the efficient generation of squeezed light via dual-pump spontaneous four-wave mixing. We consider the case of ring resonators, in which resonant field enhancement is typically used to greatly increase the efficiency of nonlinear interactions. We show that in these structures the presence of a comb of equally spaced resonances can also lead to the enhancement of parasitic processes that can degrade the quality of the generated light, thus limiting the available squeezing. Here, we discuss possible solutions to this issue, and we introduce a device comprising of a ring resonator and a resonant interferometric coupler able to selectively control the resonant field enhancement. We show that through this structure one can strongly limit the effect of parasitic processes and overcome the intrinsic limitations of a single ring resonator. Finally, we model the effect of nonlinear parasitic processes and provide an analytic expression of the achievable squeezing.

Khaled Mnaymneh
Silicon nitride integrated quantum photonics
K. Mnaymneh¹, E. Yeung^1,2, D. B. Northeast¹, Jeongwan Jin¹, P. Laferrière^1,2, S. Haffouz¹, P. J. Poole¹, D. Dalacu^1,2, and R. L. Williams^1
1National Research Council Canada, Ottawa, Canada
²Dept. of Physics, University of Ottawa, Canada
In this talk, we present our recent work in field-ready quantum technologies. Using silicon nitride as a materials platform for scalable quantum optics, we demonstrate in-plane, high-quality non-classical light from our III-V nanowire sources integrated on pre-fabricated photonic circuits. We conclude with future directions and next steps.

Eilon Poem-Kalogerakis
Photon synchronization with a room-temperature atomic quantum memory
O. Davidson, O. Yogev, E. Poem, and O. Firstenberg
Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot, Israel
Efficient synchronization of single photons that are compatible with narrowband atomic transitions is an outstanding challenge, which could prove essential for photonic quantum information processing.  Here, we report on the synchronization of independently-generated single photons using room-temperature atomic quantum memory. The photon source [1,2] and the memory [3,4] are interconnected by fibers and employ the same `ladder' atomic-level scheme. We store and retrieve the heralded single photons with end-to-end efficiency of 25% and final anti-bunching of g=0.023. Our synchronization process increases the photon-pair coincidence rates by a factor of about 30, reaching over 1000 detected synchronized photon pairs per second. The fidelity of the synchronized photons and their indistinguishability from the unstored photons are quantified by a Hong-Ou-Mandel interference measurement, yielding less than 10% fidelity degradation, due mostly to temporal-shape change during retrieval.
[1] O. Davidson et al., New J. Phys 23, 073050 (2021).
[2] O. Davidson et al., arXiv:2301.06049 (2023).
[3] R. Finkelstein et al., Science Adv. 4, eaap8598 (2018).
[4] O. Davidson et al., arXiv:2212.04263 (2022).

Markus Pollnau
Quantum-optical principle for photons/bosons, equivalent to Pauli’s exclusion principle
M. Pollnau, University of Surrey, Guildford, UK
By exploiting Einstein’s rate-equation approach [A. Einstein, Phys. Z. 18, 121 (1917)] to Planck’s law of blackbody radiation [M. Planck, Ann. Phys. 309, 553 (1901)], we obtain a simple relation between the population densities of the two energy levels of the atomic oscillators in the walls of the black body, as assumed by Einstein in his paper from 1917, and the occupation numbers in a photonic excited and ground state. This relation establishes a quantum condition for photons and, more generally, all bosons, which has the same physical relevance as Pauli’s exclusion principle [W. Pauli, Z. Phys. 31, 765 (1925)], the quantum condition for fermions. We then derive a differential equation of thermal equilibrium, which is independent of the nature of particles involved and, hence, of general validity. Simple integration delivers the Boltzmann distribution [L. Boltzmann, Sitzungsber. Kais. Akad. Wiss. Wien Math. Naturwiss. Classe 76, 373 (1877)], which therefore emerges as the most general distribution that quantifies a thermal equilibrium. Exploiting the established quantum conditions for fermions or bosons, simple integration of the same general differential equation of thermal equilibrium delivers the Fermi-Dirac [E. Fermi, Rendiconti Lincei 3, 145 (1926)] and Bose-Einstein [Bose, Z. Phys. 26, 178 (1924)] distribution, respectively. Since these two distributions each require an additional condition, they emerge as special cases of the general Boltzmann distribution. This result is further underlined by the fact that inserting either quantum condition directly into the Boltzmann distribution transforms it directly into either the Fermi-Dirac or the Bose-Einstein distribution. This finding implies that fermions and bosons simultaneously obey both their own specific and the general Boltzmann distribution. The results presented in this paper raise serious questions about the concept of distinguishable classical particles and indistinguishable quantum particles. It would imply that fermions and bosons are simultaneously distinguishable and indistinguishable particles.

Constantin Simovski
Spatial Fano resonance and its implication for a glass microsphere
V. Klimov¹, R. Heydarian², and C. Simovski^2
1Lebedev Physical Institute, Russia
²Aalto University, Finland
The well-known Fano resonance (a rather broad maximum adjacent to a sharp narrow minimum) was initially discovered in quantum mechanics, but, nowadays, it is well known also in classical optics. In optics, it is commonly thought as a kind of resonant frequency dispersion of absorption or extinction cross section of resonant scattering objects. Sometimes, it is also revealed for electric or magnetic polarizabilities of nanoparticles, but, in any case, it is considered as a feature of a parameter and not of a field. However, if we look at the underlying physics of this resonance, we will see that this resonance can nicely refer to the light itself. Really, it results from the interference of a continuum of the object eigenstates with its resonant state. Conventionally, these are either energy states or eigenfrequencies. However, in the diffraction by an optically substantial object, such as a microsphere illuminated by visible light, all non-resonant terms of the Mie expansion form the quasi-continuum in space and can nicely interfere with the resonant multipole field. If this interference is pronounced, we must observe the Fano resonance is space. Moreover, we may engineer this resonance so that the Fano maximum is inside the sphere and the sharp minimum is outside it, in free space. Indeed, for a pronounced interference we need the approximate equivalence of the magnitudes of the resonant mode and the quasi-continuum. For a single plane wave impinging on the sphere this equivalence is not achievable. We have shown that this condition is respected when the sphere is illuminated by a hollow wave beam, e. g. by the 1st order Bessel beam. In this case the spatial Fano resonance is present, and its minimum located behind the sphere is a subwavelength spot, in which electromagnetic field nullifies. Since this region in free space is tiny and cold, it is suitable for trapping not only small nanoparticles but also molecules and atoms. This claim is confirmed by calculations of the operational parameters of the trap. An experimental demonstration of this unique and simple trap would open new doors in optical trapping.

Gustavo Anjos
An FPGA-based physical layer approach for a CV-QKD transmitter
G. Anjos¹, M. Almeida², J. Martins², N. Silva¹, N. Muga¹, and A. N. Pinto^2
1Instituto de Telecomunicações, University of Aveiro, Portugal
²Department of Electronics, Telecommunications and Informatics, University of Aveiro, Portugal
Quantum key distribution (QKD) provides a secure and effective way of exchanging cryptographic symmetric keys without the possibility of an eavesdropper being undetected. The transmission and detection of the quantum states at the physical layer is the first step to defining a common source of entropy, where both parties will extract a raw key. Over the last few years, continuous variable quantum key distribution (CV-QKD) protocols have become an attractive technology for QKD, providing a low-cost solution that can be easily integrated with the current optical network devices and infrastructure. Unlike other QKD technologies, a CV protocol requires complex and highly computationally demanding digital signal processing (DSP) operations. In that sense, parallel computation tools such as field programmable gate arrays (FPGAs) represent a key element for the practical implementation of this quantum technology and to scale its performance in terms of distance and secret key rate indicators. This work presents an FPGA-based implementation of the physical layer of a CV-QKD transmitter. The proposed architecture and employed protocols are described, and hardware implementation aspects are discussed, including resource occupation analysis, configuration parameters, and timing issues.
Keywords: information theoretic security, quantum communications, CV-QKD, physical layer, FPGA.

Ramon Aparicio-Pardo
Quantum virtual link generation via reinforcement learning
R. Aparicio-Pardo, A. Cousson, and R. A. Alliche
Université Côte d’Azur, CNRS, I3S, France
Quantum networks make use of the quantum entanglement as building block. When two qubits are entangled, their state changes exhibit non-classical correlations used to design new applications not possible with classical communication, such us quantum key distribution or distributed quantum computation. Unfortunately, quantum entanglement is a probabilistic process strongly dependent on the features of involved devices (optical fibers, lasers, quantum memories, ...). The management decisions (i.e., the control policy) to set up and keep the entanglement as long as possible with the highest quality constitutes a stochastic control problem. This process can be modelled as Markov Decision Process (MDP) and solved via the Reinforcement Learning (RL) framework (a form of Machine Learning). In this work, we apply this RL framework to learn an entanglement management policy outperforming the State-of-the-Art policy when models characterising precisely the involved quantum devices are not known.
Keywords: Quantum communications, quantum swapping, deep reinforcement learning.

Davide Bacco
BB84 decoy-state QKD protocol over long-distance optical fiber
G. Guarda^1,2, D. Ribezzo^2,3, D. Salvoni⁴, C. Bruscino³, P. Ercolano³, M. Ejrnaes⁵, L. Parlato^3,5, I. Vagniluca⁶, C. De Lazzari⁶, T. Occhipinti⁶, G. Piero Pepe^3,5, A. Zavatta^2,6 and D. Bacco^6,7
1European Laboratory for Non-Linear Spectroscopy, Sesto Fiorentino, Italy
²Istituto Nazionale di Ottica, Consiglio Nazionale delle Ricerche, Firenze, Italy
³Department of Physics, Universit`a degli Studi di Napoli Federico II, Italy
<sup>4</sup>PHOTEC L.d., 80146, Napoli, Italy
<sup>5</sup>Istituto Nazionale di Ottica, Consiglio Nazionale delle Ricerche, Napoli, Italy
<sup>6</sup>QTI S.r.l., Firenze, Italy
<sup>7</sup>Department of Physics and Astronomy, Universit`a degli Studi di Firenze, Italy
Quantum key distribution represents one of the most mature and well-studied advances in quantum technologies. Many protocols have been implemented, breaking record distances both employing satellites and fiber-based systems. However, there still are open challenges in achieving long distance links without implementing quantum repeaters. One of the main limiting factors comes from the non-ideality of detection systems, in particular from intrinsic dark counts. As the covered distances increase, the signal decreases in intensity and the noise in the detector prevails, hindering the extraction of a secret key. In this work, we propose the use of high-performance state-of-the-art superconducting nanowire single-photon detectors (SNSPD) showing ultra-low dark count rates to reduce the quantum bit error rate (QBER) in the detection system. The transmitter adopts the well-tested three-state BB84 protocol with the decoy-state method and the signal travels through an optical fiber channel.

Massimo Borghi
Programmable silicon photonic sources of frequency bin entangled qubits and qudits
M. Borghi¹, N. Tagliavacche¹, M. Clementi², F. A. Sabattoli³, L. Gianini⁹, H. El Dirani⁴, L. Youssef⁵, N. Bergamasco¹, C. Petit-Etienne⁶, E. Pargon⁶, J. E. Sipe⁷, M. Liscidini¹, C. Sciancalepore⁸, M. Galli¹, and D. Bajoni^9
1Dipartimento di Fisica, Università di Pavia, Italy
²Photonic Systems Laboratory, École Polytechnique Fédérale deLausanne, Switzerland
³Advanced Fiber Resources Milan S.r.L, Italy
⁴LIGENTEC SA, Corbeil-Essonnes, France
⁵IRCER, Centre Europeen de la Ceramique, Limoges, France
⁶Univ. Grenoble Alpes, CNRS, CEA/LETI-Minatec, France
⁷Department of Physics, University of Toronto, Toronto, Canada
⁸SOITEC SA, Parc Technologique des Fontaines, Chemin des Franques, Bernin, France
⁹Dipartimento di Ingegneria Industriale e dell’Informazione, Università di Pavia, Italy
Frequency bin encoding is becoming of widespread use in photonic quantum applications due to its strong noise resilience, the large information content that can be encoded per photon, and the inherent parallelism through which gates can be applied over multiple frequency modes. Ideally, sources of frequency bin qubits and qudits should be programmable, have high brightness, and have tightly spaced spectral modes to be useful for quantum algorithms.  Here we present an integrated photonic device that simultaneously met all these requirement. We exploit the coherent generation of photon pairs over multiple ring resonators to overcome the trade-offs that hurdle single resonators.  Harnessing the dense integration and phase stability of silicon photonics, we demonstrate a photon pair source of frequency bin qudits and qudits with simultaneously high brightness, fidelity, and purity.
Keywords: quantum photonics, silicon photonics, photon-pair sources, resonators, frequency bin quantum states, programmable devices.

Hans Brunner
CV-QKD design for network integration
H. H. Brunner, C.-H. F. Fung, and M. Peev, Huawei Technologies Düsseldorf GmbH, Germany
Continuous-variable quantum key distribution (CV-QKD) has reached a maturity that requires to consider its integrability into optical communication networks. As a key exchange, QKD cannot take the central role in optical network design but has to adapt to the requirements of the network. In this article compact CV-QKD prototypes, which have been demonstrated in operational environments, and several of their key features for facilitating network integration are presented. Among these features are the coverage of typical metro link losses with automatic adaptation to the channel conditions as well as in-channel synchronization, which reduces the spectral needs to a single dense-wavelength-division-multiplexing (DWDM) channel. In many situations, this fully C-band tunable channel can simply be connected to a free multiplexer port of an existing DWDM infrastructure. Any-to-any connectivity between many QKD transmitters and receivers can reduce the number of devices, while dynamic protocol switching allows to address different security requirements and cryptographic tasks.
Keywords: QKD, CV-QKD, quantum cryptography, quantum communications.

Goran Djordjevic
Effect of pointing errors on BER performance of multidimensional LDPC-coded OAM modulation with direct detection over turbulent FSO channels
G. T. Djordjevic¹ and I. B. Djordjevic^2
1Faculty of Electronic Engineering, University of Niš, Serbia
²University of Arizona, Tucson, USA
In this invited paper, we study orbital angular momentum (OAM) - based signal transmission over free-space optical (FSO) link. After low-density parity-check (LDPC) encoding and multidimensional mapping, intensity modulation is implemented, and OAM multiplexing is performed. Signal is transmitted over FSO channel with atmospheric turbulence, pointing errors, and atmospheric loss. At the receiver end, signal is firstly demultiplexed by OAM demultiplexer, detected by photodiode, and further decoded by applying the multidimensional posterior-probability demapper and LDPC decoder. The bit-error rate (BER) performances are estimated by Monte Carlo simulations. The numerical results show that even when there is a strong misalignment between transmitter and receiver apertures, BER of the system can be reduced by applying appropriate quasi-cyclic LDPC codes. We show that BER values under 10-6 can be achieved for some typical values of electrical energy per information bit - to - noise spectral density ratio even when turbulence is strong.
Keywords: free-space optics, atmospheric turbulence, pointing errors, error performance, LDPC codes, orbital angular momentum.

Verónica Fernández
Photonic integrated circuits and components for quantum key distribution
D. Cano, D. Balado, and V. Fernández, Instituto de Tecnologías Físicas y de la Información, CSIC, Madrid, Spain
In this talk, we present designs of photonic integrated circuits and components for applications in quantum communications. The goal is to miniaturize the instrumentation while optimizing the security of various quantum key distribution protocols, such as BB84 with different qubit encodings, and measurement-device-independent protocols (MDI-QKD). The proposed components include diffraction gratings for polarization coupling, on-chip path-polarization interconverters, nanoantennas, and graphene nanocavities for coupling individual photon emitters. We simulate the behavior of the proposed circuits and components, and analyze the quantum key error for different parameters, comparing the advantages of single photons and weak coherent states.

Tawfik Ismail
Feasibility analysis of uplink quantum communication with hap considering beam wandering and weather dependence
N. Alshaer¹ and T. Ismail^2,3
1Department of EEC, Faculty of Engineering, Tanta University, Gharbiya, Egypt
²Department of EAL, National Institute of Laser Enhanced Sciences, Cairo University, Giza, Egypt
³Wireless Intelligent Networks Center (WINC), Nile University, Giza, Egypt
Software Defined Networking is increasingly seen as one of the best choices to create a Quantum Key Distribution (QKD) Network, especially if the aim is also its integration into a standard telecommunications network. The degree of flexibility afforded by this paradigm allows the creation of a network whose control mechanisms can be made aware simultaneously of the capabilities installed at the classical optical transport level as well as those at the quantum level. This is interesting not only to manage the coexistence between a classical and a quantum network sharing the same infrastructure, but also for future applications beyond QKD. This flexibility is due to a formal separation between the control and data forwarding planes. The logically centralized SDN controller gathers all relevant information monitoring the behavior of the hole network. It can act on the programmable quantum or classical devices opening many possibilities to share a common infrastructure, that can reach even the level of a single fiber strand to manage the signals that go through it in a compatible way. The same controller can use this information to manage the fundamental task of a QKD network, namely the key transport. Here we briefly report on the implementation of the SDN-QKD controller used in the Madrid testbed and its use to allow multi-vendor end-to-end key transport between any two nodes in the network.
Keywords: quantum key distribution, quantum networks, software-defined networking, key management.

Vicente Martin
The Madrid testbed: QKD SDN control and key management in a production network
V. Martin¹, J.P. Brito¹, L. Ortíz¹, R. Brito-Méndez¹, R. Vicente¹, J. Saez-Buruaga¹, A.J. Sebastian¹, D.G. Aguado¹, M. I. García-Cid¹, J. Setien¹, P. Salas¹, C. Escribano¹, E. Dopazo¹, J. Rivas-Moscoso², A. Pastor-Perales², and D. Lopez^2
1Center for Computational Simulation, DLSIIS, DMATIC and DATSI, ETSI Informáticos, Universidad Politécnica de Madrid, Spain
²Telefonica Investigación y Desarrollo y gCTIO/I+D, Madrid, Spain
Software Defined Networking is increasingly seen as one of the best choices to create a Quantum Key Distribution (QKD) Network, especially if the aim is also its integration into a standard telecommunications network. The degree of flexibility afforded by this paradigm allows the creation of a network whose control mechanisms can be made aware simultaneously of the capabilities installed at the classical optical transport level as well as those at the quantum level. This is interesting not only to manage the coexistence between a classical and a quantum network sharing the same infrastructure, but also for future applications beyond QKD. This flexibility is due to a formal separation between the control and data forwarding planes. The logically centralized SDN controller gathers all relevant information monitoring the behavior of the hole network. It can act on the programmable quantum or classical devices opening many possibilities to share a common infrastructure, that can reach even the level of a single fiber strand to manage the signals that go through it in a compatible way. The same controller can use this information to manage the fundamental task of a QKD network, namely the key transport. Here we briefly report on the implementation of the SDN-QKD controller used in the Madrid testbed and its use to allow multi-vendor end-to-end key transport between any two nodes in the network.
Keywords: quantum key distribution, quantum networks, software-defined networking, key management.

Roberto Morandotti
Scalable quantum signal processing with integrated photonics and fiber-based modules
N. Montaut¹, P. Roztocki¹, Hao Yu^1,2, S. Sciara^1,3, M. Chemnitz¹, Y. Jestin^1,4, B. MacLellan¹, B. Fischer¹, M. Kues^1,5, C. Reimer^1,6, L. Romero Cortes¹, B. Wetzel^1,7, Yanbing Zhang¹, S. Loranger⁸, R. Kashyap⁸, A. Cino³, Sai T. Chu⁹, B. E. Little¹⁰, D. J. Moss¹¹, L. Caspani¹², W. J. Munro^13,14, J. Azaña¹, and R. Morandotti^1
1Institut National de la Recherche Scientifique - Centre Énergie, Matériaux et Télécommunications, Varennes, Canada
²Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Sichuan, China
³Department of Energy, Information Engineering and Mathematical Models, University of Palermo Italy
⁴Ki3 Photonics Technologies Inc., Montreal, Canada
⁵Institute of Photonics, Leibniz University Hannover, Germany
⁶HyperLight Corporation, Massachusetts, USA
⁷Xlim Research Institute, CNRS, Université de Limoges, France
⁸Department of Engineering Physics, Department of Electrical Engineering, Polytechnique Montreal, Canada
⁹Department of Physics, City University of Hong Kong, China
¹⁰University of Chinese Academy of Sciences, Beijing, China
¹¹Optical Sciences Centre, Swinburne University of Technology, Hawthorn Australia
¹²Institute of Photonics, Department of Physics, University of Strathclyde, Glasgow, UK
¹³NTT Basic Research Laboratories and NTT Research Center for Theoretical Quantum Physics, Kanagawa, Japan
¹⁴National Institute of Informatics, Tokyo, Japan
Quantum photonic resources are critical for advanced applications such as quantum computation, communication, and information processing. Efficient generation and detection of quantum states, as well as reliable photon manipulation techniques, are essential for the development of practical quantum technologies. Integrated photonic platforms offer attractive solutions due to their stability, small device footprint, and improved power efficiencies. However, optical loss and environmental noise hinder their capability to transmit, measure, and detect quantum states with high accuracies. To tackle these limitations, we have developed robust solutions for quantum signal processing by leveraging infrastructures from telecommunications and integrated photonics. These approaches focus on the use of silicon-based photonic sources for entanglement generation in the time and frequency degrees of freedom, as well as chip- and fiber-based architectures for entanglement verification via quantum interference and tomography measurements. Our photonic schemes allow for high-dimensional entanglement processing, demonstrating their versatility in developing scalable and cost-efficient quantum signal processing platforms.
Keywords: integrated quantum photonics, quantum signal processing, on-chip interferometers, microring resonators, entangled photons, fiber-based optical modules.

Michał Parniak-Niedojadło
Atomic ensembles as nodes of quantum and classical optical networks
M. Parniak¹, M. Mazelanik^1,2, A. Leszczyński^1,2, M. Lipka¹, M. Jastrzębski^1,2, S. Kurzyna^1,2, B. Niewelt^1,2, J. Nowosielski^1,2, S. Borówka^1,2, and U. Pylypenko^1,2, and W. Wasilewski^1,2
1Centre for Quantum Optical Technologies, Centre of New Technologies, University of Warsaw, Poland
²Faculty of Physics, University of Warsaw, Poland
Photons are excellent carriers of information as they can be easily transmitted over long distances. However, in quantum information science we often cannot accept almost any loss of light, and direct amplification is forbidden as it would introduce noise, which would in turn compromise security of the quantum link. This issue led to the invention of quantum repeaters, which may probabilistically repeat a weak quantum signal without introducing noise. Atomic ensembles can serve as physical implementations of quantum repeaters, as they can generate, process and store the optical photons travelling along the link. I will present our recent advances in introducing multiplexing into the atomic-ensemble technology, and our ideas how those systems well known in fundamental physics can be applied in quantum communications. In most recent times a need arises also to connect remote quantum computers, often based on superconducting qubits operating with GHz microwave photons. Our atomic ensembles, when excited to Rydberg states, may serve as interconnects between those microwave devices and optical networks.

Paola Parolari
Integration of the QKD layer in fibre networks using multicore fibres
A. Gagliano¹, A. Gatto¹, P. Martelli¹, P. Boffi¹, T. Hayashi², A. Mecozzi³, C. Antonelli³, and P. Parolari^1
1Dip. di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Italy
²Sumitomo Electric Industries, Ltd., Yokohama, Japan
³University of L’Aquila, Italy
Uncoupled multicore fibres (MCFs) are a suitable solution for integrating the quantum communication systems in WDM networks. The performance of the QKD layer is in fact impaired by nonlinear effects generated by the classical channels. MCFs allow a smart management of  classical and quantum key carriers coexistence, preserving the secret key rate generation thanks to a proper choice of the wavelength-core allocation plan.

Armando Nolasco Pinto
Oblivious keys for secure multiparty computation obtained from a CV-QKD
A. N. Pinto^1,2, M. B. Santos³, N. A. Silva², N. J. Muga², and P. Mateus^3
1Departamento de Eletrónica, Telecomunicações, e Informática, Universidade de Aveiro, Portugal
²Instituto de Telecomunicações, Universidade de Aveiro, Portugal
³Departamento de Matemática, Instituto Superior Técnico, Universidade de Lisboa, and Instituto de Telecomunicações, Portugal
We analyze the use of a Quantum Key Distribution (QKD) system to generate and distribute oblivious keys. Oblivious keys can be used to implement secure multiparty computation services. After defining oblivious keys, we show how they can be reduced to symmetric keys and used to implement secure links, and how they can also be used to implement secure computation services. Oblivious keys can also be reversed. In this context, we analyze the advantages of using quantum resources to generate oblivious keys. Particularly, we analyze a protocol to generate oblivious keys, considering both the efficiency and security of the process. We show that by using QKD, we can simultaneously obtain an efficient and quantum-resistant solution to generate and distribute oblivious keys. Finally, we discuss a field trial where a quantum secure multiparty computation service for calculating phylogenetic trees was implemented in the Quantum Madrid Network.
Keywords: quantum cryptography, quantum key distribution, quantum oblivious keys, secure multiparty computation.

Matteo Schiavon
High-speed continuous-variable quantum key distribution with advanced digital signal processing
M. Schiavon¹, Y. Piétri¹, L. Trigo Vidarte², D. Fruleux¹, M. Huguenot³, B. Gouraud³, A. Rhouni¹, P. Grangier⁴, and E. Diamanti^1
1Sorbonne Universitè, CNRS, Paris, France
²ICFO - Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Castelldefels, Spain
³Exail, Modulation Solution Division, Besancon, France
⁴Universitè Paris-Saclay, Institut d’Optique Graduate School, CNRS, Laboratoire Charles Fabry, Palaiseau, France
Continuous-variable quantum key distribution (CV-QKD) is a promising solution for providing high secure key rates in moderate channel loss regime. A great advantage with respect to discrete-variable (DV) systems is the use of a technology similar to the one use in classical coherent communication, in particular for the detection system, which can operate at room temperature and benefits from an easier integration process. In addition to this, the use of advanced digital signal processing (DSP) techniques developed for classical communication allows for bandwidth-efficient temporal shaping, which optimizes the performance of the CV-QKD system. These techniques applied to the detected signal are also fundamental for using a locally generated local oscillator, correcting frequency and phase differences using frequency-multiplexed pilots generated by the transmitting laser. In this presentation, we will describe how these techniques can be applied to a CV-QKD system and show some recent experimental results obtained by our research group, including results for a receiver based on a Photonic Integrated Circuit (PIC).

Gabriel Senno
On the proper quantification of the randomness produced by QRNGs
G. Senno^1,2, T. Strohm³, and A. Acín^1,4
1ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Spain
²Quside Technologies S.L., Barcelona, Spain
³Corporate Research, Robert Bosch GmbH, Renningen, Germany
⁴ICREA-Institucio Catalana de Recerca i Estudis Avançats, Barcelona, Spain
An ideal QRNG, such as one that prepares spin-1/2 states in the +Z direction and measures them in the X direction, produces bits that are uniformly random and independent of any pre-existing information. However, the prepared states and the measurements performed in real quantum devices are always imperfect or noisy. This introduces an unavoidable element of stochasticity that leads to an apparent randomness not intrinsic to quantum theory. Operationally, this stochasticity is modeled through correlations with an external observer, Eve, whose goal is to make the best guess about the device’s outcomes. In the quantum information literature, the so-called side information provided to Eve has usually been limited to the state. In this talk, we will present a general framework for the quantification of quantum randomness accounting for arbitrary noise both in the state and in the measurements. Finally, we will report on the recent progress in applying this theoretical framework to Quside’s QRNGs.

Grzegorz Sęk
Towards practical QD-based single photon sources in the telecom range
G. Sęk, Wroclaw University of Science and Technology, Poland
Secure quantum communication requires on-demand bright sources of single photons with ultra-low probabilities of multiphoton events and very good emission extraction efficiency to provide high transmission rates. It is of particular importance to transfer the developments from proof-of-principle experiments at shorter wavelengths to telecom wavelengths for compatibility with the existing low-loss fiber networks, especially for long-haul communication. In that respect, semiconductor nanostructures have been proven as prospective and flexible solid-state platform, which is a mature nanotechnology allowing for scalability and integration. It already enabled realization of many fundamental quantum optics experiments revealing the potential of epitaxial quantum dots for quantum communication and quantum networks applications. Nowadays much effort is devoted to improvement of the emitters’ performance and realization of more practical devices. In this contribution there will be overviewed our recent results on engineering and investigation of the electronic and optical properties of quantum emitters suitable for the 1.3-1.55 µm spectral range, made of two different material systems of InGaAs on GaAs and InAs on InP, and further on development of efficient quantum-dot-based single photon sources within such platforms. For various classes of quantum dot materials there will be discussed the currently achievable single photon emission purity and its temperature stability, always in conjunction with the underlying physics of excitonic complexes confined in such nanostructures or the related fundamental limitations on the side of technology and fabrication. In addition, there will be elaborated the issue of photonic confinement engineering and placing quantum dots in especially designed, spectrally broadband photonic structures of various geometries for controlling the emission rates, linear polarization degree as well as improving the extraction efficiency. Possibility to generate entangled photon pairs for selected examples of telecom quantum dots will also be discussed. Eventually, there will be described a solution for constructing compact, robust, portable and cryogenic-free plug and play fiber-based sources operating at telecom wavelengths.

Nuno Silva
A network server for distributing quantum random numbers
N. A. Silva¹, M. Ferreira^1,2, M. A. Carvalho¹, A. Souto^3,4, N. Paunković³, P. Mateus^2,4, A. Teixeira^1,2, and A. N. Pinto^1,2
1Instituto de Telecomunicações, University of Aveiro, Portugal
²Department of Electronics, Telecommunications, and Informatics, University of Aveiro, Portugal
³Instituto de Telecomunicações, Lisbon, Portugal
⁴LASIGE, Departamento de Informática, Faculdade de Ciências, Universidade de Lisboa, Portugal
⁵Departamento de Matemática, Instituto Superior Técnico, Universidade de Lisboa, Portugal
Quantum random number generators (QRNGs) based on homodyne detection have a potential to be a cost-effective solution to deploy random numbers at high-speed rates over networks. The new information technologies, such as quantum key distribution, cloud computing, and big data, demands true randomness for those cryptosystems to be secure and private. This is incompatible with known security loopholes of classical pseudo-random number generators.  In this work, we discuss our recent advances in the implementation of a vacuum-based QRNG service to be used in a distributed network environment. We will also highlight the advantages of using quantum technologies to generate random numbers in comparison with classical approaches.

Michela Svaluto Moreolo
Efficient solutions for quantum secure communications in future optical networks
M. Svaluto Moreolo, Centre Tecnològic de Telecomunicacions de Catalunya (CTTC/CERCA), Spain
To face the quantum era and the prospect or threat of quantum computing, especially in a disaggregated network environment, the design and implementation of efficient quantum secure communication systems facilitating their integration in the optical network infrastructure is key. Quantum key distribution (QKD) is one of the most promising technologies to ensure long-term security. In particular, continuous-variable QKD results an efficient solution more compatible and suitable to be integrated with conventional optical systems. In this invited talk, quantum secure systems based on QKD for enabling a smooth and sustainable integration in optical networks are introduced, considering the related challenges, towards future secure 6G networks.

Idelfonso Tafur Monroy
Prospects of chip-based multi-protocol quantum key distribution transceivers
A. Grebenchukov, Hui Lui, G. Nazarikov, B. Cimoli, S. Rommel, and I. Tafur Monroy
Department of Electrical Engineering, Eindhoven University of Technology, The Netherlands
Quantum communications enable the transmission of information in a secure way that is ensured by the laws of quantum physics. Quantum-safe communication technologies are based on quantum key distribution (QKD) systems at their core. There is a growing number of remarkable QKD research implementations, some of which are becoming commercially available. However, even with ongoing development of QKD systems, there are efforts toward their miniaturization, power efficiency improvement, and enhancement of their performance and functionality.  In this paper, we outline major QKD protocols, followed by reviewing the recent advances in QKD systems based on photonic integrated circuits. Finally, we will discuss the potential feasibility of multi-protocol QKD chips leveraging the advantages of different protocols in one solution.
Keywords: quantum key distribution, photonic integrated circuits, multi-protocol QKD.

Alessandro Zavatta
Advances on the feasibility analysis of underwater optical communications
M. Pinel^1,3,4, S. Cocchi^2,3, C. De Lazzari³, M. Menchetti³, T. Occhipinti³, A. Zavatta^3,4, and D. Bacco^2,3
1Università degli Studi di Napoli Federico II, Italy
²Department of Physics and Astronomy, Università degli Studi di Firenze, Italy
³QTI S.r.l., Firenze, Italy
⁴Istituto Nazionale di Ottica del Consiglio Nazionale delle Ricerche (CNR-INO), Firenze, Italy
In this work we study the underwater optical channel, making a feasibility analysis on the development of a high-speed communication system with security guaranteed by Quantum Key Distribution (QKD).
In particular, we introduce a new model for the attenuation of the underwater medium which includes the effect of turbulence within the marine environment.  We report the performance of the system focusing on the most important figures of merit, such as the Secret Key Rate of the quantum channel and the bit rate of the classical channel at the physical layer as a function of the total link range. We carried out these analyzes depending on various environmental conditions, such as the geographical area, depth, path-loss and turbulence models. The communication protocols are BB84 with time-bin encoding for QKD and baseband On-Off Keying (OOK) modulation for classical data communication for a maximum link range of 100 meters.

Marcelo Abbade
Enhancing inter-data centre link security with spectral polarisation shuffling and phase encoding
M. Pereira Nogueira¹, N. J. Badue², L. H. Bonani², I. Aldaya¹, and M. L. F. Abbade^1
1São Paulo State University, School of Engineering, São João da Boa Vista, Brazil
²Universidade Federal do ABC, Santo André, Brazil
In this work, we propose a strategy for encrypting dual polarisation optical signals. The scheme is based on shuffling the spectral samples of baseband signals that further modulate the orthogonal polarisations of an optical carrier. Additionally, the samples phases are also encoded. We investigate the performance of the encryption scheme in a scenario where data centres are connected by a cascade of standard fibre optical links. Simulation results indicate that the encrypted versions of 448 Gb/s 16 quadrature amplitude modulation (QAM) signals may be properly propagated by distances of up to 420 km.
Keywords: network security, signal cryptography, optical communications.

Khouloud Abdelli
Fault monitoring in passive optical networks using machine learning techniques
K. Abdelli¹, C. Tropschug², H. Griesser³, and S. Pachnicke^4
1Nokia Bell Labs, Germany
²ADVA Optical Networking SE, Germany
³Adva Network Security GmbH, Germany
⁴Christian-Albrechts-Universität zu Kiel, Germany
Passive optical network (PON) systems are vulnerable to a variety of failures, including fiber cuts and optical network unit (ONU) transmitter/receiver failures. Any service interruption caused by a fiber cut can result in huge financial losses for service providers or operators. Identifying the faulty ONU becomes difficult in the case of nearly equidistant branch terminations because the reflections from the branches overlap, making it difficult to distinguish the faulty branch given the global backscattering signal. With increasing network size, the complexity of fault monitoring in PON systems increases, resulting in less reliable monitoring. To address these challenges, we propose in this paper various machine learning (ML) approaches for fault monitoring in PON systems, and we validate them using experimental optical time domain reflectometry (OTDR) data.
Keywords: passive optical networks, fault monitoring, machine learning, optical time domain reflectometry.

Marija Furdek
Proactive spectrum defragmentation leveraging spectrum occupancy state information
E. Etezadi¹, C. Natalino¹, R. Diaz², A. Lindgren², S. Melin², L. Wosinska¹, P. Monti¹, and Marija Furdek^1
1Department of Electrical Engineering, Chalmers University of Technology, Gothenburg, Sweden
²Telia AB, Solna, Sweden
One of the main obstacles to efficient resource usage under dynamic traffic in elastic optical networks (EONs) is spectrum fragmentation (SF), leading to blocking of incoming service requests. Proactive spectrum defragmentation (SD) approaches periodically reallocate services to ensure better alignment of available spectrum slots across different links and alleviate blocking. The services for reallocation are commonly selected based on their properties, e.g., age, without detailed consideration of prior or posterior spectrum occupancy states.  In this paper, we propose a heuristic algorithm for proactive SD that considers different spectrum fragmentation metrics to select services for reallocation. We analyze the relationship between these metrics and the resulting service blocking probability. Simulation results show that the proposed heuristic outperforms the benchmarking proactive SD algorithms from the literature in reducing blocking probability.
Keywords: elastic optical networks, fragmentation metric, proactive spectrum defragmentation.

Shabnam Sultana
Resilient control-plane design for T-SDN based optical transport networks
S. Sultana^1,2, R. Romero Reyes¹, K. T. Nguyen¹, and T. Bauschert^1
1Chair for Communication Networks, Technische Universität Chemnitz, Germany
²highstreet technologies GmbH Berlin, Germany
With the emerging focus on the control plane design of SDN-based networks, numerous studies have solved the controller placement problem with diverse objectives.  However, the design of the control plane itself has not been thoroughly studied, especially for Transport (T-SDN) based networks. To close this gap, we proposed in our previous work a heuristic method for the design of a centralized control plane for T-SDN networks. The approach determines the optimal number and placement of control-plane interfaces as well as the routing of the control-plane traffic. The objective is to minimize the cost of the control-plane w.r.t. the number of control plane interfaces and the capacity consumed by the control plane traffic. For that, the assumption was made that only a subset of transport nodes is directly connected to a single central controller through the control interfaces, while the control traffic of the remaining nodes is forwarded via dedicated connections. In this paper, we consider the extended control plane design problem by assuming a distributed T-SDN control-plane consisting of multiple interconnected controllers and extend our method accordingly so as to determine the optimal number and placement of the controllers as well as the optimal routing of the controller-node traffic and the controller-controller traffic considering reliability constraints (i.e., robustness w.r.t. single node or single link failures). The performance of the method is assessed for selected transport network topologies for which we analyse the impact of the cost parameters on the control-plane network design.

Luca Valcarenghi
A flexible forecasting platform enabling zero touch networking and digital twinning
L. Valcarenghi, A. Sgambelluri, E. Paolini, and A. Pacini
Scuola Superiore Sant'Anna, Pisa, Italy
A proactive approach could bring several advantages in network operations to meet the increasingly strict requirements (e.g., in terms of latency, reliability) of emerging applications (e.g., XR-VR, xURLLC). This paper, describes a flexible forecasting platform that provides estimates of performance parameters involved in the closed-loop utilized in Zero Touch Networking and Digital Twin. The advantages of using parameter estimation within the closed-loop in reducing performance violations are also shown.

Tiago Alves
On the use of feedforward neural networks to improve the ICXT tolerance in self-coherent MCF systems
T. M. F. Alves, D. Piedade, T. Brandão, J. L. Rebola, and A. V. T. Cartaxo
Instituto de Telecomunicações-IUL, Iscte - Instituto Universitário de Lisboa, Portugal
In this work, machine learning techniques based on artificial neural networks are investigated to improve the performance of self-coherent short-reach weakly-coupled multicore fibre (WC-MCF) systems. Particularly, a feedforward neural network is proposed to mitigate the performance degradation induced by the random variation of the intercore crosstalk (ICXT) along time in 200 Gb/s quadrature amplitude modulation WC-MCF  systems. A product between the skew and the symbol rate much lower than one and a self-coherent receiver based on Kramers-Kronig technique, are considered.
Keywords: intercore crosstalk, multicore fibres, neural networks, self-coherent receivers, space-division multiplexing.

Adolfo Cartaxo
Effect of core-dependent loss on the intercore crosstalk in multicore fiber systems with concatenated random loss fiber segments
J. L. Rebola and A. V. T. Cartaxo
Instituto de Telecomunicações, Iscte – Instituto Universitário de Lisboa, Portugal
We investigate the impact of core-dependent loss (CDL) on the signal and crosstalk (XT) powers at the output of a link composed by several concatenated multicore fiber (MCF) segments, by considering random CDL in each MCF segment. We show that, with random CDL, for a 100 km optical link and specific arrangements of MCF segments, the forward, signal, coupled and direct XT powers may increase around 1 dB (with respect to the absence of CDL). We show also that, at the output of the concatenated MCF segments, the probability density functions of these powers follow a Gaussian distribution with random CDL generated from different statistical distributions.
Keywords: coupled power, intercore crosstalk, multicore fiber, space-division multiplexing.

Ivana Gasulla
Dispersion-diversity signal processing in space-division multiplexing fibers
S. García, E. Nazemosadat, M. Ureña, and I. Gasulla
Photonics Research Labs, iTEAM Research Institute, Universitat Politecnica de Valencia, Spain
Beyond high-capacity digital communications, space-division multiplexing fibers bring significant benefits to microwave signal distribution and processing, as not only space but also chromatic dispersion are introduced as new degrees of freedom. The key lies in developing new fibers where each individual core/mode is tailored to provide parallel dispersion-diversity signal processing.

Nelson Muga
Self-coherent detection in multicore fiber systems impaired by intercore crosstalk
N. J. Muga¹, T. M. F. Alves², R. K. Patel¹, I. A. Alimi¹, A. N. Pinto^1,2, and A.V. T. Cartaxo^3,4
1Instituto de Telecomunicações, University of Aveiro, Portugal
²Department of Electronics, Telecommunications and Informatics, University of Aveiro, Portugal
³Instituto de Telecomunicações, Lisbon, Portugal
⁴Iscte - Instituto Universitário de Lisboa, Portugal
Space division multiplexing transmission, employing multicore fibers, as well as simplified coherent detection technologies have been intensively investigated in recent years to accommodate the demand for energy-efficient short-reach fiber-optic communication systems with extremely high capacity. Indeed, the conjugation of multicore fibers and simplified coherent receivers can be explored as a promising scheme to tackle the problems of capacity constraints in data center networks. This paper presents our recent investigations on the exploitation and optimization of novel simplified coherent detection techniques, e.g. Kramers-Kronig and DC-Value methods, and on the performance assessment of weakly-coupled MCF-based systems employing such new coherent detection receivers.
Keywords: self-coherent receivers, digital signal processing, multi-core fibers, space-division multiplexing, weakly-coupled.

Suresh Subramaniam
Advanced resource allocation strategies for MCF-based SDM-EONs: Crosstalk aware and machine learning assisted algorithms
S. Petale and S. Subramaniam
Lab for Intelligent Networking and Computing, George Washington University, Washington DC, USA
In space division multiplexed elastic optical networks (SDM-EONs), parallel transmission of lightpaths is enabled using multicore fibers (MCFs) in the network. However, the intercore crosstalk (XT) between parallel transmissions degrades the quality of service and reduces the utilization of available capacity. This impairment results in a tradeoff between spectrum utilization and XT accumulation. In this work, we discuss various approaches to solve the routing, modulation, core, and spectrum assignment (RMCSA) problem while balancing the tradeoff, viz., Tridental Resource Assignment algorithm (TRA), translucency-aware TRA, and Spectrum Wastage Avoidance based Resource Allocation (SWARM) algorithm. We also propose offline optimizations such as machine learning (ML)-aided optimization, and integer linear programming-based priority path selection (PPS) for routing to improve the performance of TRA. The ML-aided optimizer and PPS guarantee the improvement in the performance of "any" RMCSA. Extensive simulation experiments show significant reductions in bandwidth blocking probability, by several orders of magnitude for a variety of scenarios.

Masatoshi Suzuki
High-capacity and ultra-long-haul transmission over transoceanic distances using coupled and uncoupled 4-core fibers with standard cladding diameter
M. Suzuki, D. Soma, S. Beppu, Y. Wakayama, N. Yoshikane, and T. Tsuritani, Waseda University, Japan
High-capacity transmission experiments using coupled and uncoupled 4-core fibers with standard cladding diameter are discussed. 62.9 Tbit/s and 50.4 Tbit/s transmissions over 9150 km have been achieved with uncoupled and coupled 4-core fibers, respectively.  Real-time MIMO processing for coupled 4-core fiber transmission over 7200 km and FIFO less EDFAs for submarine cable systems are also discussed.

Filipe Ferreira
On the scaling of the number of modes in mode division multiplexing systems
F. M. Ferreira, F. A. Barbosa, and R. Yadav
University College London, UK
We review our recent advances on the design of multimode fibres with hundreds of spatial pathways for reduced differential mode delay in the C-band and on the development of adaptable spatial multiplexing techniques to enable scalability of all data pathways.

Norbert Hanik
Optimization of ultra-broadband optical wavelength conversion in nonlinear multi-modal silicon-on-insulator waveguides
T. Kernetzky¹, N. Hanik¹, Yizhao Jia¹, U. Höfler¹, R. Freund^2,3, C. Schubert³, I. Sackey³, G. Ronniger³, L. Zimmermann^2,3
1TU München, Munich, Germany
²TU Berlin, Germany
³Fraunhofer Gesellschaft, Heinrich Hertz Institut Berlin, Germany
³IHP Leibnitz-Institut für innovative Mikroelektronik Frankfurt (Oder), Germany
Ultra-Broadband Wavelength Conversion is identified as one of the key issues in future high-capacity, flexible optical networks. In this contribution, methods to optimize the design of Multi-Modal high-nonlinear SOI-Waveguides to achieve broadband wavelength conversion between extreme optical wavelength-bands are presented. Finally, measurements and experimental results are discussed that prove ultra-broadband conversion of data signals between different l-bands.

Georg Rademacher
Petabits/s transmission over multimode fibers
G. Rademacher, R. S. Luis, B. J. Puttnam, and H. Furukawa
National Institute of Information and Communications Technology, Japan
Optical fiber transmission systems using space division multiplexing (SDM) over multi-mode fibers (MMFs) potentially offer the highest spatial density, especially considering fibers with the current standard cladding diameter. In this talk, we discuss the principles of SDM transmission in MMFs and report on recent transmission demonstrations, including the transmission of more than 1.5 Peta-bit/s over a 55 mode MMF.

Stefan Rothe
Achieving information security in spatially multiplexed communication systems by harnessing disorder of multimode fibres
S. Rothe, K.-L. Besser, D. Krause, D. Pohle, R. Kuschmierz, N. Koukourakis, E. Jorswieck, and J. W. Czarske
Technical University of Dresden, Germany

Ioannis Roudas
Mode vector modulation: A review
I. Roudas, J. Kwapisz, and E. Fink
Montana State University, Bozeman, USA
The use of multidimensional modulations can significantly reduce the energy consumption of optical networks. In this invited paper, we review Mode Vector Modulation (MVM), a generalized polarization modulation technique for transmission over multimode/multicore optical fibers or free space. MVM, like Polarization Shift Keying (PolSK) and Stokes Vector Modulation (SVM), can be combined with direct detection and is thus appropriate for future high-capacity, short-haul optical interconnects. The MVM transceiver design, the analytical evaluation of the performance of the optically-preamplified MVM direct-detection receiver, the optimization of MVM constellations using geometric shaping, and the associated bit-to-symbol mapping are the main topics of this review. We demonstrate that, in terms of receiver sensitivity, MVM outperforms traditional single-mode, direct-detection-compliant, digital modulation formats by several dB's, and the SNR gain increases with the number of spatial degrees of freedom.

Pedro Vaz
Single-pixel imaging: Concepts and application to imaging through scattering media
P. G. Vaz, B. Guerra, and J. Cardoso
LIBPhys, University of Coimbra, Portugal
Imaging through scattering media using conventional systems is a significant challenge. Pixaleted systems struggle to handle the light wavefront scrambling that occurs when light is scattered before reaching the detector. This paper presents an imaging technique called single-pixel imaging which is more robust to scattering and allows better image quality when imaging through scattering media. Simulation and experimental works are used to show the capacities of SPI to reconstruct images acquired when a scattering medium is placed between the imaging sensor and the sample. Their results are compared with the images taken using a conventional pixelated system. The implications and limitations of these results are then discussed.
Keywords: single-pixel imaging, Hadamard patterns, scattering media, microscopy.

Piero Castoldi
Network programmability for smart factory mobile robotics: The SmartEdge project approach
P. Castoldi1, A. Sgambelluri1, L. Ismail2, F. Paolucci2, F. Cugini2, and D. Bowden3
¹Scuola Superiore Sant’Anna, Italy
²CNIT, Italy
³DELL Technologies, Ireland
In this paper we show how P4-based network programmability is exploited to enable swarm formation and reliable communications in decentralized smart factory scenarios including mobile robots. In band telemetry will be extensively used by all network nodes to provide for dynamic aggregation/disaggregation of connected entities to perform different augmented functions: computing, massive data-delivery, time-sensitive networking.
Keywords: network programmability, network telemetry, edge processing, packet processing.

João Pedro
Complexity and accuracy trade-off for quality of transmission estimation in wideband optical systems
A. Souza¹, N. Costa¹, J. Pedro^1,2, and J. Pires^2
1Infinera Unipessoal Lda., Carnaxide, Portugal
²Instituto de Telecomunicações, Instituto Superior Técnico, Lisboa, Portugal
This paper investigates the computational time and accuracy of several alternatives for the estimation of the GSNR of coherently detected signals in multi-band transmission (MBT) systems. The considered optical performance estimation methods are the closed-form ISRS-GN, the FWM, the enhanced FWM, and the numerical GGN (used as a reference). A comprehensive set of results suggests that the closed-form ISRS-GN model has the best trade-off between computation time and accuracy in the evaluated scenarios, enabling fast but still reasonably accurate optical performance estimation for MBT systems with transmission bandwidths up to 20 THz.
Keywords: Multi-band transmission, quality of transmission, nonlinear interference.

Trevor Benson
Fiber optic sensor systems without using spectral analysis
T. Benson¹, J. Palmowski², N. Kubicka³, F. Gołek⁴, L. Benson⁵, S. Phang¹, and E. Bereś-Pawlik^1,2
1George Green Institute for Electromagnetics Research, Faculty of Engineering, University of Nottingham, UK
²RELS Limited, Wrocław, Poland
³Faculty of Electronics and Information Technology, Warsaw University of Technology, Poland
⁴Institute of Experimental Physics, University of Wroclaw, Poland
⁵School of Physics and Astronomy, University of Leeds, UK
The paper describes our investigations of some Fibre Bragg Grating (FBG) systems for measuring basic environmental parameters where a simple measurement of transmitted or reflected power provides an alternative to specialist interrogators. The work targets a low-cost sensor configuration, capable of operating in remote environments and of storing and/or communicating sensing information to a base station.
Keywords: fibre Bragg gratings, fibre optic sensing, strain measurement, environmental sensing.

Elżbieta Bereś-Pawlik
Simultaneous study of fluorescence and transmission based on a sensor with a doped optical fibre
N. Kubicka¹, F. Gołek², J. Palmowski³, S. Phang⁴, T. Benson⁴, and E. Bereś-Pawlik^3,4
1Faculty of Electronics and Information Technology, Warsaw University of Technology, Poland
²Institute of Experimental Physics, University of Wroclaw, Poland
³RELS Limited, Wrocław, Poland
⁴George Green Institute for Electromagnetics Research, Faculty of Engineering, University of Nottingham, UK
The paper presents a model sensor system for the simultaneous measurement of fluorescence and transmission for potential application in medical diagnostics. The paper presents results connected with the test substance, fluorescein. The sensor used in the paper includes a neodymium-doped optical fibre to build an asymmetric coupler. The dependence of the intensity of the fluorescence power and transmission on the concentration of fluorescein placed at the end of the system was investigated. Measurements for the presented system were made using UV diode with a wavelength of 415 nm. For the UV source, the effect of fluorescein exposure time on the fluorescence and transmission signals was analysed for different concentrations of fluorescein.
Keywords: optical fibre sensor, asymmetric coupler, fluorescence, transmission.

Wilfried Blanc
Tailoring oxide nanoparticles in optical fibers
Zhuorui Lu^1,2, M. Cabié³, M. Guzik⁴, M. Ude¹, T. Neisius³, D. Tosi^5,6, C. Molardi⁵, F. Pigeonneau², and W. Blanc^1
1Université Côte d'Azur, INPHYNI, CNRS, Nice, France
²MINES ParisTech, PSL Research University, CEMEF – Centre for material forming, Sophia‑Antipolis, France
³Aix Marseille Univ, CNRS, Centrale Marseille, France
⁴Faculty of Chemistry, University of Wrocław, Poland
⁵Nazarbayev University, School of Engineering and Digital Sciences, Nur-Sultan, Kazakhstan
⁶National Laboratory Astana, Laboratory of Biosensors and Bioinstruments, Nur-Sultan, Kazakhstan
Optical fibers containing nanoparticles were proposed twenty years ago to develop new applications in lasers and amplifiers. By encapsulating luminescent ions in the nanoparticles, new emission properties can then appear. However, the particles must be small in size to limit the optical losses by light scattering. More recently, this type of optical fiber has shown a strong potential for application as sensors. These exploit the light scattering properties induced by nanoparticles. Then, the development of these fibers for these different applications depends on our ability to control the characteristics of the nanoparticles in the optical fibers. During this presentation, we will show how the drawing step is a crucial step to achieve this goal.

Pierpaolo Boffi
Fiber interferometric sensors for monitoring the telecom infrastructure integrity
M. Fasano¹, M. Brunero², A. Madaschi¹, J. Morosi², M. Ferrario², and P. Boffi^1
1Dipartimento di Elettronica Informazione e Bioingegneria, PoliCom Lab, Politecnico di Milano, Italy
²Cohaerentia s.r.l., Milano, Italy
Fiber sensing can be used for structural health monitoring and for diagnostics and surveillance of the infrastructure integrity by giving sensing functionalities to the fiber cables, already deployed for telecom purposes. Their sustainability in system implementation and data processing is achieved by means of a suitable interferometric approach, assuring the coexistence of telecom data propagation with sensing signals. Keywords: fiber networks, fiber sensors, interferometric sensors, fiber cables.

Muriel Botey
Self-cleaning in non-Hermitian linear multimode fibers
M. N. Akhter¹, S. B. Ivars¹, R. Herrero¹, K. Staliunas^1,2, and M. Botey^1
1Departament de Fisica, Universitat Politecnica de Catalunya, Terrassa, Spain
²Institucio Catalana de Recerca i Estudis Avancats, Barcelona, Spain
We propose a self-cleaning mechanism in linear non-Hermitian graded index multimode fibers. The proposal is based a unidirectional coupling among transverse modes, induced by the introduction of a non-Hermitian potential, i.e. by the simultaneous modulation of the propagation constant and of the gain/loss coefficient along the fiber. The effect is semi-analytically predicted on a simplified Gaussian beam approximation and numerically proven by solving the wave propagation equation. As the main result, we demonstrate a substantial condensation of the radiation into the lowest order mode; resulting in a linear non-Hermitian self-cleaning. The demonstrated scheme could be experimentally realized within the current nanofabrication technologies.
Keywords: multimode fibers, non-Hermitian, mode-cleaning.

Reinhard Caspary
Automatisation steps for laser direct writing
R. Caspary¹, Lei Zheng^1,2, A. Günther^1,2,3, and B. Roth^1,2
1Cluster of Excellence PhoenixD, Leibniz University Hannover, Germany
²Hannover Centre for Optical Technologies (HOT), Leibniz University Hannover, Germany
³Institute of High Frequency Technology, Technical University Braunschweig, Germany
Two-photon polymerisation (TPP) is an additive manufacturing tool based on laser direct writing with sub-wavelength resolution. It has received enormous attention in recent years because it enables the production of precision polymer micro-optics without post-processing steps as well as three-dimensional diffractive optical structures. However, TPP is still a lab-technology which requires elaborate and time-consuming alignment steps. This talk will present our approach to automise many of these steps.

Pavel Cheben
Subwavelength-engineered metamaterial devices for integrated photonics
P. Cheben¹, J. H. Schmid¹, P. Ginel-Moreno², S. Khajavi³, R. Korček⁴, W. Fraser³, D. Sirmaci⁵, A. F. Hinestrosa², J. M. Luque-González², D. Pereira-Martín², A. Sánchez-Postigo², A. Hadij-ElHouati², D. Benedikovič⁴, A. Ortega-Moñux², J. G. Wangüemert-Pérez², I. Molina-Fernández², R. Halir², W. N. Ye³, D. Melati⁶, C. Alonso-Ramos⁶, D. González-Andrade⁶, L. Vivien⁶, I. Staude⁵, J. Zhang¹, M. Milanizadeh¹, D.-X. Xu¹, Y. Grinberg¹, R. Cheriton¹, S. Janz¹, S. Wang¹, M. Vachon¹, M. Dado⁴, R. Fernández de Cabo⁷, and A. V. Velasco^7
1National Research Council Canada, Ottawa, Canada
²University of Malaga, Malaga, Spain
³Carleton University, Ottawa, Canada
⁴Dept. Multimedia and Information-Communication Technologies, University of Zilina, Slovakia
⁵Institute of Solid State Physics, Friedrich-Schiller-University Jena, Germany
⁶Centre de Nanosciences et de Nanotechnologies, CNRS, Universite Paris-Saclay, Palaiseau, France
⁷Instituto de Óptica Daza de Valdés, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
Incorporating subwavelength grating metamaterials in nanophotonic waveguides has opened new degrees of freedom to control light propagation on a photonic chip. In this invited contribution, we will present our recent advances in development of subwavelength-engineered metamaterial devices for silicon photonics, including fiber-chip couplers, nanophotonic waveguides with controlled anisotropy, resonant waveguides, complex spectral filers and nanoantennas for Optical Phased Arrays (OPAs).
[1] P. Cheben, D-X. Xu, S. Janz, A. Densmore, Subwavelength waveguide grating for mode conversion and light coupling in integrated optics, Opt. Express 14(11), pp. 4695-4702 (2006).
[2]. P. Cheben, P. J. Bock, J. H. Schmid, J. Lapointe, S. Janz, D.-X. Xu, A. Densmore, A. Delâge, B. Lamontagne, T. J. Hall, Refractive index engineering with subwavelength gratings for efficient microphotonic couplers and planar waveguide multiplexers, Opt. Lett. 35(15), pp. 2526-2528 (2010).
[3] P. Cheben, R. Halir, J. H. Schmid, H. A. Atwater, D. R. Smith, Subwavelength integrated photonics, Nature 560(7720), 565–572 (2018).
[4] R. Halir, A. Ortega-Moñux, D. Benedikovic, G. Z. Mashanovich, J. G. Wangüemert-Pérez, J. H. Schmid, Í. Molina-Fernández, P. Cheben, Subwavelength-grating metamaterial structures for silicon photonic devices,” Proc. IEEE 106(12), 2144–2157 (2018).
[5] J. M. Luque-González, A. Sánchez-Postigo, A. Hadij-ElHouati, A. Ortega-Moñux, J. G. Wangüemert-Pérez, J. H. Schmid, P. Cheben, Í. Molina-Fernández, R. Halir, A review of silicon subwavelength gratings: building break-through devices with anisotropic metamaterials, Nanophotonics 10(11), pp. 2765–2797 (2021).

Caterina Ciminelli
Lab-On-Chip for liquid biopsy: A new approach for the detection of biochemical targets
C. Ciminelli, P. Colapietro, G. Brunetti, and M. N. Armenise
Optoelectronics Laboratory, Politecnico di Bari, Italy
The biomedical research community is looking for non-invasive diagnostic tools for early screening, diagnosis, prognosis prediction, early relapse detection, and follow-up of cancer diseases. In this context, Liquid Biopsy (LB) is emerging as a new minimally invasive diagnostic method that allows reliable analysis and diagnosis of diseases, mainly cancerous diseases, from several biological fluids instead of a fragment of cancer tissue. The capability of performing LB using Lab-On-Chip (LOC) technologies allows for minimizing the invasiveness and risks of tissue biopsy. Here, we review LOCs, designed to achieve a system for personalized medicine capable of performing detection, capture, and analysis of liquid cancer biomarkers (ctDNA, cfDNA, CTCs, exosomes, EVs, etc.). The overview is focused on the photonic sensing section that could ensure high specificity and sensitivity of the system to a selected biomarker and remarkable limit-of-detection (LOD). We provide an overview of biosensor technologies for Personalized Medicine applications, critical and comprehensive evaluations regarding the prospects of the LOC operating platform, and optimization methods for its future applications.
Keywords: liquid biopsy, Lab-On-Chip, biomarkers, biosensing.

Svatopluk Civiš
Origin of water bound on the surface of oxygen containing minerals – Stellar wind contribution
S. Civiš1, J. Kubišta1, J. Plšek, and D. Balakin
J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic
The origin of water and volatile compounds on Earth and other planets is a hotly debated topic in planetary science, with many dynamic models suggesting that the majority of Earth's water and volatile elements were added later from an external source, likely from C-type asteroids located in the Jupiter-Saturn region and beyond. The volatile source is believed to have shared a common parent population with carbonaceous chondrite meteorites, which contain up to 10 wt% H2O. Recent studies suggest that enstatite chondrites and Itokawa particles may be more water-rich than previously thought, but they contain sufficient water for only the lowest estimate of Earth's water budget. The Earth's mantle and standard mean ocean water are lighter in D/H than the average of CI, CR, and CM chondrite groups. The volatile isotopic composition of the Earth remains a mystery, and it is likely that at least one other light isotope reservoir contributed to our planet's water budget, such as the Sun and/or the solar nebula. The solar wind irradiation of rocky oxygen containing  materials results in a reaction between H ions and silicate minerals to produce water and OH, which could explain the presence of water in the regoliths of airless worlds such as the Moon, as well as the water abundances in asteroids. To investigate water abundances, the method of High-resolution Infrared Fourier Transform spectroscopy and thermal programmable desorption with mass spectroscopy techniques have been used  to measure the abundance of water and OH molecules within minerals.
Keywords: astrochemistry, solar system, high resolution FT spectroscopy, hydrogen isotopes, terrestrial planets, meteorites, origin of water.

Crina Cojocaru
Large nonlinear efficiency enhancement in the visible and UV range from plasmonic gold nanogratings
C. Cojocaru¹, S. Mukhopadhyay¹, L. Rodriguez-Suné¹, M. A. Vincenti², R. Vilaseca¹, M. Scalora³, and J. Trull^1
1Department of Physics, Universitat Politècnica de Catalunya, Terrassa (Barcelona), Spain
²Department of Information Engineering – University of Brescia, Italy
³Aviation and Missile Center, US Army CCDC, Redstone Arsenal, USA
We report a combined experimental/theoretical investigation on second and third harmonic generation from a plasmonic gold nanograting, that exhibits a plasmonic resonance in the near IR. The intense field localization leads to significant enhancement in the efficiency of nonlinear optical processes from the UV to the near IR range: second harmonic generation (SHG) conversion efficiencies increase three orders of magnitude compared to a flat gold mirror, while third harmonic generation (THG) conversion efficiency increases by nearly four orders of magnitude. The spectral and angular dependence (qualitative and quantitative) of the harmonics were experimentally recorded and validated within the framework of our own theoretical model, that we employ to simulate SHG and THG efficiencies. Our approach consists of an expanded microscopic hydrodynamic model that captures the dynamics of both free and bound electrons, and faithfully describes the basic electrodynamic behaviour of linear and nonlinear optics of metals at the nanoscale.
Keywords: nanophotonics, nonlinear optics, plasmonic resonance, harmonic generation enhancement.

Massimo De Vittorio
Nanostructured fiber optics for high sensitivity, minimally invasive, spatially-resolved, plasmonic diagnosis and therapeutics
L. Collard¹, F. Pisano¹, Di Zheng¹, A. Balena¹, M. F. Kashif¹, M. Pisanello¹, B. Spagnolo¹, R. Mach-Batlle¹, A. D'Orazio², F. De Angelis¹, M. Valiente³, L. M. de la Prida⁴, C. Ciracì¹, M. Grande², F. Pisanello¹, and M. De Vittorio^1,5
1Center for Biomolecular Nanotechnologies, Istituto Italiano di Tecnologia, Arnesano, Italy
²Dipartimento di Ingegneria Elettrica e dell’Informazione, Politecnico di Bari, Italy
³Brain Metastasis Group Spanish National Cancer Research Center (CNIO), Madrid, Spain
⁴Instituto Cajal, CSIC, Madrid, Spain
⁵Dipartimento di Ingegneria Dell’Innovazione, Università del Salento, Lecce, Italy
Plasmonic fiber optics have attracted considerable research interest from perspectives ranging from fundamental physics to biomedical optics. However, across all fields, researchers face two distinct but strongly connected challenges. First, a nanofabrication challenge: integrating nanostructures on a substrate fiber; second, a photonic problem: engineer the interaction between the plasmonic structures and the modal patterns of light propagation. In this work we aim to show how both state-of-the-art fabrication approaches and optical techniques may be used to resolve these issues for plasmonic endoscopy in both deep and shallow brain regions. By applying wavefront shaping, we show that either a sub-region or entire plasmonic structure on a flat fiber facet can be holographically activated. We have applied this method to a wide range of plasmonic structures including periodic nanostructures for EOT and sub-diffraction beam formation and nanoislands for Surface Enhanced Raman Spectroscopy (SERS), resulting in a multifunctional plasmonic endoscope targeted at shallow brain regions. Alternatively, we show how a tapered optical fiber can also be used as a substrate of plasmonic structures targeted at detection of neurotransmitters in deep brain regions.
Keywords: multimode fiber endoscopy, plasmonics, SERS, wavefront shaping, Raman spectroscopy, tapered fibers.

Antonio Díez
Modal analysis of acoustic resonances in an optical fiber: All-optical excitation and detection
L. A. Sánchez, C. A. Álvarez-Ocampo, M. Delgado-Pinar, A. Díez, J. L. Cruz, and M. V. Andrés, Universidad de Valencia, Burjassot, Spain
Opto-mechanical interactions in optical fibers based on Forward Brillouin Scattering (FBS) can lead to a new paradigm for the optical fiber sensing technology, since it allows monitor the surroundings of the fiber without requiring light interaction with the fiber outer medium. Point and distributed sensing schemes have been demonstrated based on FBS. FBS consists on the interaction of an optical signal (the “probe”) with opto-excited transverse acoustic mode resonances (TAMRs) of the optical fiber. TAMRs are typically excited via electrostriction by an optical beam that propagates in the fiber (the “pump”). The development of applications based on this nonlinear effect requires accurate knowledge of the properties of such acoustic modes. In this work, different all-optical approaches for the excitation and detection of TAMRs in optical fibers will be presented and discussed.

Antonella D'Orazio
Guided mode resonance-based transparent metasurfaces for selective multi-color reflection
G. Magno¹, M. Grande¹, B. Dagens², O. Gauthier Lafaye³, and A. D'Orazio^1
1Department of Electrical and Information Engineering), Polytechnic University of Bari, Italy
²Université Paris-Saclay, CNRS, Centre de Nanosciences et de Nanotechnologies, Palaiseau, France
³LAAS-CNRS, Université de Toulouse, CNRS, INSA, UPS, Toulouse, France
Metasurfaces enable precise and efficient control over light's angular-spectral properties, making them crucial for developing augmented reality displays for information visualization. In this contribution, we will focus on the design of transparent metasurfaces that use guided mode resonances to achieve polychromatic selective reflection, specifically for wearable augmented reality systems. These metasurfaces may be valuable in the realization of near-eye visual aids in support of individuals with cognitive impairment issues.

Iker García
Partial least squares and partial least squares-discriminant analysis to detect and quantify adulterations in olive oil using optical methods of analysis. A comparative study between NIR and UV-Vis spectroscopy
D. Castro^1,2, M. C. Ortiz¹, S. Sanllorente¹, I. García², I. Ayesta³, M. Azkune⁴, and  J. Zubia^5
1University of Burgos, Dep. Chemistry, Spain
²AOTECH (Advanced Optical Technologies S.L.), Escuela Ing. de Bilbao, Spain
³University of the Basque Country, UPV-EHU, Dpto. de Matemática Aplicada, Escuela de Ingeniería de Bilbao, Spain
⁴University of the Basque Country, UPV-EHU, Dpto. de Ingeniería Electrónica, Escuela de Ingeniería de Bilbao, Spain
⁵University of the Basque Country, UPV-EHU, Dpto. de Ingeniería de Comunicaciones, Escuela de Ingeniería de Bilbao, Spain
Due to its high nutritional value, olive oil (OO) is more expensive than most of other vegetable oils, making it the most common edible oil to be adulterated by many merchants or oil suppliers in small percentages in order to obtain economic benefits. These fraudulent practices become more sophisticated every day, which gives rise to the necessity of the implementation of new more innovative and efficient methodologies.  For that reason, in this work, the great advantages of some optical methods of analysis combined with chemometrics are used to study the possibilities they present in the determination of adulterants in OO [1-6].  In this work, the presence of five different adulterants (vegetable oils) in OO has been evaluated using different spectroscopic techniques (UV-Vis, NIR and Raman spectroscopy) by applying chemometric methods. One the one hand, the percentage of adulterants was calculated using Partial Least Squares (PLS). In addition, qualitative classification models (PLS-Discriminant Analysis) have been proposed to distinguish between adulterated and unadulterated samples of intense OO. Using these techniques, it is possible to classify between unadulterated samples of OO and those that have been adulterated, obtaining almost a hundred percent both for sensitivity and specificity. Within the adulterated, it is also possible to identify which is the vegetable oil (adulterant) in the sample. A good estimation of the adulterant percentage in OO was also achieved, obtaining the best results when UV-Visible spectroscopy was used.
[1] X. Meng, et al., Rapid detection of adulteration of olive oil with soybean oil combined with chemometrics by Fourier transform infrared, visible-near-infrared and excitation-emission matrix fluorescence spectroscopy: A comparative study, Food Chemistry, 405, 134828 (2023).
[2] P. Fang, H. Wang, X. Wan, Olive oil authentication based on quantitative β-carotene Raman spectra detection, Food Chemistry, 397, 133763 (2022).
[3] I.uisánchez, G. Rovira,  M. P. Callao, Multivariate qualitative methodology for semi-quantitative information. A case study: Adulteration of olive oil with sunflower oil, Analytica Chimica Acta, 1206, 339785 (2022).
[4] J. Zhang, H. Sun, W. Lu, Recent advances in analytical detection of olive oil adulteration. ACS Food Science and Technology, 2(3), 415-424 (2021).
[5] S. A. Ordoudi, O. Özdikicierler,  M. Z. Tsimidou, Detection of ternary mixtures of virgin olive oil with canola, hazelnut or safflower oils via non-targeted ATR-FTIR fingerprinting and chemometrics, Food Control, 142, 109240 (2022).
[6] S. A. Ordoudi, L. Strani,  M. Cocchi, Toward the non-targeted detection of adulterated virgin olive oil with edible oils via FTIR spectroscopy and chemometrics: Research methodology trends, gaps and future perspectives, Molecules, 28(1), 337 (2023).

Dominique Guichaoua
Phase-matched magnetization-induced second-harmonic generation in epitaxial iron garnet thin films
D. Guichaoua¹, I. Syvorotka², N. Syvorotka², R.  Wielgosz³, A. Andrushchak⁴, H. El Karout^1,5, and B. Sahraoui^1
1Laboratory of Photonics LPhiA, University of Angers, France
²Scientific Research Company “Electron-Carat”, Lviv, Ukraine
³ENERGIA OZE Sp. z o.o ,Konopiska, Poland
⁴Lviv Polytechnic National University, Ukraine
⁵University of Angers, MOLTECH Anjou - UMR CNRS 6200, SFR MATRIX, Angers, France
Bismuth-free yttrium iron garnet and Bismuth-doped iron garnet magnetic thin films have grown on gadolinium gallium garnet single crystal substrates by means of the liquid phase epitaxy method. Faraday rotation measurement results show clearly a strong enhancement with bismuth doped sample. The second harmonic generation measurements in transmission show a relation with the orientation of the spontaneous magnetization vector of films and the second harmonic intensities.
Keywords: magneto-optical devices, magneto-photonic crystals, optical propagation in nonlinear media.

Ramon Herrero
Stabilization of laser emission by non-Hermitian potentials
R. Herrero¹, S. B. Ivars¹, M. Botey¹, and K. Staliunas^1,2,3
1Universitat Politecnica Catalunya, Dep. de Fisica, Terrassa, Spain
²ICREA, Passeig Lluís Companys 23, 08010, Barcelona, Spain
³Faculty of Physics, Laser Research Center, Vilnius University, Lithuania
Light emission from single lasers and laser arrays can suffer from dynamical spatiotemporal instabilities leading to emitted beams temporally unstable and with low spatial quality. We propose a feasible stabilization mechanism for laser emission based on non-Hermitian potentials, i.e. simultaneous modulations of refractive index and gain-loss. The proposed spatiotemporal modulations can be introduced by a potentials directly acting on the field or on carriers. The stabilization can be based on the suppression of the modulation instability, on the stabilization of specific stationary solutions or on field localization. These stabilization mechanisms are applied in vertical-cavity semiconductor lasers, single units and arrays of Edge Emitting Lasers.

Jian-Jang Huang
Electrical manipulation of plasmonic relaxation and the application of voltage-modulated plasmon resonance to biosensing
K. Barman¹, Syu-Cing Ma¹, R. Gupta¹, Liang-Yun Lee¹, and Jian-Jang Huang^1,2
1Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei, Taiwan
²Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan
This paper reveals two studies on electrical controlled plasmonic responses, one for understanding the plasmon-phonon interactions and the other for demonstrating high-sensitivity EC (electrochemical)-SPR biosensors. In the first part, we experimentally study the effect of voltage controlled surface acoustic waves on localized surface Plasmon (LSP), which unveils exceptional properties of plasmon-phonon interaction.  The experiment was conducted by depositing gold nanoparticles on an X-cut LiNbO3 to generate plasmonic oscillation, and fabricating an interdigital transducer monolithically to create surface acoustic wave pulses. The interaction between amplitude acoustic wave and plasmonic oscillation affects different plasmon dynamics and relaxation gradients, leading to a systematic change in LSP absorption. Second, we designed and investigated a novel voltage modulated optical biosensor based on a hybrid plasmonic and electrochemical phenomenon. The SPR (surface plasmon resonance) was generated from a thin layer of gold nanohole array on a glass substrate.  The optical response under various voltage bias conditions were tested using the target analyte, C-Reactive Protein (CRP). We observed that SPR response is concentration-dependent and can be modulated by varying DC voltages or AC bias frequencies. The phenomenon is due to spatial re-distribution of electron concentration at the metal-solution interface.  Our proposed voltage actuated sensor is permissible for various future optoelectronic integration for plasmonic and electrochemical sensing.
Keywords: localized surface plasmon, interdigital transducer, surface acoustic waves, surface plasmon resonance, nanohole arrays, biosensors, C-reactive protein.

José Javier Imas
Optical fiber sensors based on lossy mode resonances (LMRs): Fundamentals and recent developments
J. J. Imas, I. Del Villar, C. R. Zamarreño, and I. R. Matías, Electrical, Electronic and Communications Engineering Dept., Public University of Navarre, Pamplona, Spain
Lossy mode resonance (LMR)-optical sensing technology has consolidated in the last years in the field of the resonance-based sensors, which rely on the utilization of a thin film that affects the propagation of the light through the waveguide, thus generating a resonance. Optical fibers have been the most commonly employed waveguide for the development of LMR-based sensors, including applications such as refractive index sensing, gas detection, humidity sensing, pH sensing or biosensing, among others. In this work, the fundamentals of LMR-based optical fiber sensors are reviewed, as well as some of the main lines of research that are currently being pursued in order to improve their performance: development of multisensing platforms on fiber to simultaneously measure several variables, and increase of the resolution by either improving the sensitivity or the figure of merit (FOM) of the LMR based sensor.
Keywords: optical fiber, sensors, thin-films

Bhupesh Kumar
Disorder enhanced-photonic crystal based on-chip spectrometer
B. Kumar and S. Schulz
SUPA, School of Physics and Astronomy, University of St. Andrews, Fife, UK
Spectrometers are commonly used for various purposes such as chemical and biological sensing and characterizing light sources. However, traditional grating-based spectrometers are large and expensive. To reduce the size, the effective path length must be increased while maintaining a small footprint. This can be achieved through the use of multiple light scattering in a random structure. However, current disorder-based speckle spectrometers have low efficiency and poor signal-to-noise ratios due to high optical losses [1]. To overcome this issue, the controlled disorder is superimposed on a photonic crystal to increase wavelength separation and suppress out-of-plane scattering[2,3,4], leading to improved performance. The device is fabricated using electron beam lithography on a Silicon on Insulator (SOI) wafer. Simulation results show that a combination of disorder and periodicity enhances throughput by 30% compared to only disorder, without compromising spectral resolution. Future plans include optimizing hyper uniform disorder-based configurations for enhanced throughput and higher resolution.
[1] B. Redding et al., Nat. Photon. 7, 746 (2013).
[2] J. P. Vasco and S. Hughes, ACS Photonics ,6 (11), 2926-2932 (2019).
[3]. L. O’Faolain et al., Opt. Express 18, 27627 (2010).
[4] J. Li et al., Photonic Nanostruct. 10, 589 (2012).

Igor Meglinski
Spin and orbital angular momenta in biomedical diagnosis and tissues characterisation
I. Meglinski^1,2,3, I. Lopushenko³, A. Sdobnov³, and A. Bykov^3
1College of Engineering and Physical Sciences, Aston University, Birmingham, UK
²Aston Institute of Photonics Technologies, Aston University, Birmingham, UK
³Optoelectronics and Measurement Techniques, University of Oulu, Finland
We explore the potential of structured vortex laser beams, known also as shaped light with orbital angular momentum (OAM), for diagnosis of cells and cells cultures, as well as for quantitative characterization of biological tissues. The structured vortex beams contains a spin contribution, conditioned by the polarization of the electromagnetic fields and an orbital contribution, related to their spatial structure. When the shaped light propagates in a homogeneous transparent medium, both spin and orbital angular momenta are conserved. In order to study a conservation of spin and orbital angular momenta of the shaped light propagation in a homogeneous transparent medium we have built a Mach-Zehnder-like interferometer featuring spatial light modulator (SLM) for generating Laguerre-Gaussian (LG) light beams with different momenta. The LG beam passes through a tissue sample and the interference with reference plane wave is detected on the camera. We show that when the LG beam propagates through normal and cancerous tissue samples the OAM is preserved with the noticeably different phase shift – twist of light. We also demonstrate that the twist of light is up to ∼ 1000 times more sensitive to the refractive indices changes within the tissue samples and, therefore, has a high potential to revolutionize the current practices of tissue diagnosis, e.g. histology examination. The results of our experimental studies are well agreed with the results obtained with newly developed by Monte Carlo code developed in-house. Finally, we conclude that the application of OAM for biomedical diagnosis offers fascinating opportunities for both new fundamental biological studies and practical clinical applications.

Jean-Michel Nunzi
Advanced photodetectors, sensors and energy harvesting devices
J.-M. Nunzi, Queen's University, Quebec, Canada
Several approaches are currently explored to build devices exploiting size-effects in nano-sciences. Self-assembling emerges as a master bottom-up technique to enable the applications of nanomaterials into the real world. Among these applications, image sensing and processing requires capabilities that are beyond the technology of current image sensors, such as automated color-based quality inspection systems operating under varying levels of illumination [1] or laser-based satellite communication systems using parallel optical processing functions [2]. I will describe the recent outcomes of our network of collaborative research aimed at exploiting the benefits of organic [3], perovskite [4], graphene [5] and plasmonic photodetectors [6,7] for sensing [8], detecting, and harvesting light and solar energy.
[1] R. D. Jansen-van Vuuren, J.-M. Nunzi, S. N. Givigi, Frontiers in photosensor materials and designs for new image sensor applications, IEEE Sensors J. 21, 11339 (2021).
[2] I. M. Kislyakov et al., Nonlinear optical fullerene and graphene based polymeric 1D photonic crystals: Perspectives for slow and fast optical bistability, J. Opt. Soc. Am. B 38 C198-C209 (2021).
[3] E. V. Verbitskiy et al., Pyrimidine-based push-pull systems with a new anchoring amide group for dye-sensitized solar cells, Electronic Materials 2, 142–153 (2021).
[4] L. L. Wang et.al., Double-layer CsI intercalation into an MAPbI3 framework for efficient and stable perovskite solar cells, Nano Energy 86, 106135 (2021).
[5] S. Aynehband, M. Mohammadi, R. Poushimin, J.M. Nunzi, A. Simchi, Efficient FAPbI3-capped PbS-quantum dot graphene-based phototransistors , New J. Chem. 45, 15285–15293 (2021).
[6] D. Salem, M. Shalabi, F. Souissi, F. Nemmar, M. Said Belkaid, M. Aamir, J. M. Nunzi, Ag nanoparticle-based efficiency enhancement in an inverted organic solar cell, Eur. Phys. J. Appl. Phys. 90, 30201 (2020).
[7] S. M. A. Mirzaee, O. Lebel, J.M. Nunzi, Simple unbiased hot-electron polarization-sensitive near-infrared photo-detector, ACS Appl. Mater. Inter. 10, 11862-11871 (2018).
[8] M. Aamir, M. Shahiduzzaman, T. Taima, J. Akhtar, J. M. Nunzi, It is an all-rounder! On the development of metal halide perovskite-based fluorescent sensors and radiation detectors, Adv. Opt. Mater. (2021).

Dorota Pawlak
Novel photonic materials enabled by crystal growth
D. A. Pawlak^1,2,3, P. Paszke^1,2, P. Piotrowski^1,2, M. Tomczyk^1,2, K. Sadecka¹, K. Bandopadhay¹, K. Markus¹, H. B. Surma¹, A. Materna¹, and J. Toudert^1
1ENSEMBLE3 Centre of Excellence, Warsaw, Poland
²Faculty of Chemistry, University of Warsaw, Poland
³Lukasiewicz Research Network - Institute of Microelectronics and Photonics, Warsaw, Poland
We will demonstrate how to utilize the crystal growth methods for manufacturing of novel composite materials for various applications, especially photonics (metamaterials, plasmonic materials), topological insulators, energy conversion. We will focus on two novel bottom-up manufacturing methods: (i) method based on directionally-grown self-organized eutectic structures; and (ii) NanoParticles Direct Doping meth-od (NPDD) based on directional solidification of dielectric matrices doped with various nanoparticles.

Giovanni Pellegrini
Photonic multilayers for broadband and large area superchiral surface waves
G. Pellegrini¹, E. Mogni², J. Jil-Rostra³, F. Yubero^2,3, G. Simone^2,4, S. Fossati⁵, J. Dostálek^5,6,7, R. Martinez Vázquez⁸, R. Osellame⁸, M. Celebrano², M. Finazzi², and P. Biagioni^2
1Dipartimento di Fisica,Università degli studi di Pavia, Italy
²Dipartimento di Fisica, Politecnico di Milano, Italy
³Instituto de Ciencia de Materiales de Sevilla, CSIC-Universidad de Sevilla, Spain
⁴School of Mechanical Engineering, Northwestern Polytechnical University Xi’an, Shaanxi, China
⁵Biosensor Technologies, AIT-Austrian Institute of Technology GmbH, Tulln an der Donau, Austria
⁶FZU-Institute of Physics, Czech Academy of Sciences, Prague, Czech Republic
⁷Laboratory for Life Sciences and Technology (LiST), Faculty of Medicine and Dentistry, Danube Private University, Krems, Austria
⁸Istituto di Fotonica e Nanotecnologie (IFN)-CNR, Milano, Italy
Chirality is omnipresent in chemistry and of paramount importance in the modern pharmaceutical industry. Chiroptical analysis techniques allow for a flexible and low-cost molecular structure characterization, but their limited sensitivity prevents on-chip integration. We overcome these limitations by introducing the concept of superchiral surface waves, and design photonic multilayers capable of a two orders of magnitude chiral signal enhancement compared to standard techniques [1–3]. We design structures displaying broadband spectral operation over arbitrarily large areas and compatibility with lab-on-a-chip setups. The structural and optical characterizations of the realized platforms shows excellent agreement with the design [4]. We finally adopt optimization and machine learning techniques to design multilayers operating from the ultraviolet to the near infrared regime, with great flexibility in terms of adopted materials. These findings pave the way towards the integration of chiroptical techniques with microfluidic networks, enriching the widespread lab-on-chip technology with new functionalities.
[1] G. Pellegrini, M. Finazzi, M. Celebrano, et al., Chiral surface waves for enhanced circular dichroism, Phys. Rev. B 95:241402 (2017).
[2] G. Pellegrini, M. Finazzi, M. Celebrano, et al., Surface-enhanced chiroptical spectroscopy with superchiral surface waves, Chirality 30:883–889 (2018).
[3] G. Pellegrini, M. Finazzi, M. Celebrano, et al. Superchiral surface waves for all-optical enantiomer separation, J. Phys. Chem. C 123:28336–28342 (2019).
[4] E. Mogni, G. Pellegrini, J. Gil-Rostra, et al., One-dimensional photonic crystal for surface mode polarization control, Advanced Optical Materials 10:2200759 (2022).

Przemysław Płóciennik
Examples of perovskite solar cells construction and techniques for measuring their basic electrical parameters
P. Płóciennik^1,4, A. Zawadzka^2,4, K. Wiśniewski², A. Laouid^2,3, A. Marjanowska^2,4, and Z. Łukasiak^5
1Institute of Engineering and Technology, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University in Toruń, Poland
²Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University in Toruń, Poland
³National School of Applied Sciences, Engineering Science for Energy Laboratory, Chouaib Doukkali University of El Jadida, Morocco
⁴Centre for Modern Interdisciplinary Technologies, Nicolaus Copernicus University in Toruń, Poland
⁵Archimedes Sp. z o.o., R&D Department, Toruń, Poland
This work contains a description of the production of perovskite photovoltaic cells and their structure. We present the results of measurements of the basic parameters of cells, obtained by examining the current-voltage characteristics. Photovoltaic cells were manufactured in the process of physical vapor deposition (PVD) by the co-deposition method, which allowed to obtain hybrid structures with various compositions and parameters. The evaporation unit NANO36 (Kurt&Lesker) allows real-time control of such parameters as the rate of layer growth, the composition of the obtained structure and its resultant thickness. The tests of the current-voltage characteristics were performed by typical source measure unit KEITHLEY 4200-scs system. In addition, we present a simple measurement system built for the initial selection of prototype photovoltaic cells.
Keywords: perovskite solar cells, physical vapor deposition, electrical properties.

Alexander Quandt
Basic theoretical and numerical concepts of photovoltaics
A. Quandt, School of Physics, NRF-DST Centre of Excellence in Strong Materials and Materials for Energy Research Group, University of the Witwatersrand, Johannesburg, South Africa
Solar cell simulations have become an essential tool for the development of novel types of photovoltaic devices. Many of the standard software packages currently in use are very mature numerical tools. They are easy to understand and easy to apply. This led to a development, where simulations make up for a good fraction of the literature about photovoltaics, and they even tend to substitute more and more of the experimental work and the practical development of real working devices. I would like to give an overview of the basic theoretical and numerical concepts underlying solar cell simulations. Then I will discuss some typical examples to point out the advantages, but also the practical limitations of standard photovoltaic device simulations. Furthermore, I will suggest several promising theoretical and numerical extensions, which could change the current focus of the field towards more fundamental aspects of light-matter interactions, rather than using solar cell simulations only as a virtual tool to explore variations in the key device components of standard types of solar cells.

Ivan Richter
Analysis of plasmonic interactions in nonlocal and nanosnowman structures
P. Kwiecien, M. Burda, P. Klajs, L. Marešová, and I. Richter
Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic
Nonlocal interactions of plasmonic nanostructures are currently being intensively investigated. Nonlocal interactions are generally believed to be most noticeable in structures with unit dimensions of the order of nanometers and affect the shape of spectral functions characterizing quantities in the resonance region. However, the numerical analysis of nonlocal phenomena is very complicated. At first, this contribution deals with the analytical solution of the nonlocal process of a planar metal layer using a hydrodynamic model. This model is further extended to the more general case of two adjacent nonlocal layers (bilayers). Results for both the single-layer and the bilayer case are presented and discussed in detail. In the second part, we discuss the incorporation of a suitable hydrodynamic model into the Fourier modal method (FMM). This implementation is able to numerically analyze periodic plasmonic systems such as nonlocal periodic multilayers and resonant lattices. The implementation has been done in such a way that possible future generalization of the hydrodynamic nonlocal description as well as aperiodization of the technique (aFMM) will be possible. In the third part, in agreement with the growing scientific interest in nanoplasmonic structures, together with the increasing possibility of their fabrication using suitable nanotechnologies, and the current interest in various plasmonic-based sensors, we have further focused on the theoretical assessment of linear chains of several metallic nanospheres. By modifying the original design, new "nanosnowman" structures were obtained, and they were analyzed to maximize the resonance effect. We have effectively used our portfolio of simulation methods, based on both our own Fourier modal methods and commercial numerical tools. Selected promising results along with optimizations will be presented, enabling potential applications of resonances in sensors and other fields.

Giuseppe Rizzelli
Early-warning debris flow and avalanches detection system based on optical fiber polarization sensing
G. Rizzelli¹, S. Pellegrini², Marco Lacidogna², S. Aiassa³, F. Antolini³, M. Barla⁴, and R. Gaudino^2
1Links Foundation, Torino, Italy
²Dipartimento di Elettronica e Telecomunicazioni, Politecnico di Torino, Italy
³Geosolving srl, Torino, Italy
Landslides, avalanches and debris flows are common hazards in the mountain environment that can endanger people and infrastructures. The existing monitoring systems in the geotechnical field are often unsuitable for real-time applications, such as early-warnings of the aforementioned events [1]. We present an optical fiber system [2-3] able to give an alarm when some anomalous event is detected [4]. Experiments have been carried out on a reduced scale model of the slope of a mountain, showing that state of polarization monitoring [5] is a reliable way to early-detect anomalous vibrations.
[1] M. Hürlimann, V. Coviello, C. Bel, X. Guo, M. Berti, C. Graf, J. Hübl, S. Miyata, J. B. Smith, and H.-Y. Yin, Debris-flow monitoring and warning: Review and examples, Earth-Science Reviews, vol. 199, p. 102981 (2019).
[2] L. Schenato, A review of distributed fibre optic sensors for geo-hydrological applications, Applied Sciences, vol. 7, no. 9 (2017).
[3] I. Di Luch, P. Boffi, M. Ferrario, G. Rizzelli, R. Gaudino, and M. Martinelli, Vibration sensing for deployed metropolitan fiber infrastructure, Journal of Lightwave Technology, vol. 39, no. 4, pp. 1204–1211 (2021).
[4] S. Aiassa, F. Antolini, M. Barla, A. Insana, R. Gaudino, G. Rizzelli Martella, and S. Pellegrini, A new real-time debris flow and avalanches detection system based on optical fiber sensing, in Proceedings of the 8th International Conference on Debris Flow Hazard Mitigation (2023).
[5] A. Mecozzi, M. Cantono, J. C. Castellanos, V. Kamalov, R. Muller, and Z. Zhan, Polarization sensing using submarine optical cables, Optica, vol. 8, no. 6, pp. 788–795 (2021).

Bouchta Sahraoui
Optical properties of some selected organometallic compounds
A. Aamoum¹, S. Taboukhat², Y. El Kouari³, A. Zawadzka¹, A. Andrushchak⁴, and B. Sahraoui^2
1Institute of Physics, Faculty of Physics, Astronomy, and Informatics, Nicolaus Copernicus University in Toruń, Poland
²University of Angers, LPHIA, SFR MATRIX, Angers, France
³Laboratory of Materials, Energy and System Control, Faculty of Sciences and Technology, Hassan II University of Casablanca, Mohammedia, Morocco
⁴Lviv Polytechnic National University, Ukraine
Research for nonlinear optical properties of highly conjugated organometallic compounds and self-assembled photonic architectures is growing very rapidly and play a major role in emerging photonic technologies. Innovative compounds for communications, optical switching, optical data information storage and optical limiting require an important development of materials based on molecular engineering of advanced molecular systems with exceptional nonlinear optical (NLO) responses. Thus, organic materials, polymeric materials, organometallic or coordination metallic complexes have been the subject of both experimental and theoretical investigations during last recent years because of their valuable potential applications in photonics and optical devices. The aim of the present work is to study the impact of the chemical structure on the photoluminescence response of Znq2, Cuq2 and Alq3 studied organometallic compounds. These ones were deposited as thin layers by using the Physical Vapor Deposition (PVD) apparatus. The photoluminescence gives information about the photophysical properties of studied thin layers. The time-resolved photoluminescence was used to measure the decay time in the real time precisely. The chemical structure has an important impact on the photoluminescence. However, the important photoluminescence results in visible range allow the studied complexes to be used as a good material for the production of Organic Light Emitting Diode (OLED). The effect of magnetic field and its role in controlling nonlinear optical properties will be also discussed.
Keywords: physical vapor deposition (PVD), photoluminescence (PL), decay time.

Marco Saldutti
Lasing threshold in nanolasers with extreme dielectric confinement
M. Saldutti, Yi Yu, and J. Mørk, DTU Fotonik, Department of Photonics Engineering, Technical University of Denmark, Lyngby, Denmark
Today, most of the energy in computer chips is wasted for data communications through electrical wires. Not only does ohmic heating hamper further miniaturization and integration, but it also limits the data processing speed. On the other hand, on-chip optical interconnects are advantageous in terms of energy consumption and bandwidth, thus being a real keystone for information and communication technologies with higher energy efficiency and more complex functionalities. However, this dense integration of electronics and photonics requires new semiconductor lasers, with ultra-small footprint, low noise and reduced energy consumption. Nanolasers based on emerging dielectric cavities with deep sub-wavelength optical confinement may offer unprecedented light-matter coupling rate, near-unity spontaneous emission factor and ultra-low threshold current. However, the extreme dielectric confinement encountered in these nanolasers calls for a reconsideration of the standard approach to identifying the lasing threshold. In this presentation, we discuss a new threshold definition, valid all the way from the macro to the nanoscale and reflecting the recycling process that photons undergo in nanolasers with extreme dielectric confinement. By utilizing a Langevin approach and a more fundamental stochastic simulation scheme, we discuss quantum noise and photon statistics in relation to this generalized threshold definition.

Salvador Sales
Real-time monitoring systems using fiber optic sensors
S. Sales, D. Barrera, J. Madrigal, D. Maldonado-Hurtado, and V. Hernández-Ambato
ITEAM Research Institute, Universitat Politècnica de València, Spain
Fiber optics Sensors are widely used today. We will present our latest developments to monitor real-time systems in applications ranging from civil engineering to medical or aerospace applications. Our sensors can monitor temperatures ranging from cryogenic temperatures to very high temperatures (over 2000 K).

Marina Simović Pavlović
Holographic and nonlinear optical study of natural photonic structures: Where biology meets physics
M. Simović Pavlović¹, B. Bokić², C. Verstraete³, D. Vasiljević², S. R. Mouchet^4,5, T. Verbiest³, and B. Kolarić^2,6
1Faculty of Mechanical Engineering, University of Belgrade, Serbia
²Photonics Center, Institute of Physics, University of Belgrade, Serbia
³Molecular Imaging and Photonics, Department of Chemistry, KU Leuven, Heverlee, Belgium
⁴School of Physics, University of Exeter, UK
⁵Department of Physics andNamur Institute of Structured Matter, University of Namur, Belgium
⁶Micro- and Nanophotonic Materials Group, University of Mons, Belgium
Nano-optics exploits linear and nonlinear phenomena at the nanoscale to advance our understanding of materials and their interaction with light in both classical and quantum domains. This not only deepens our fundamental knowledge but also drives new photonics-based technologies, from sensing to communication. Nonlinear optics further offers a way to explore and leverage the complexity of natural structures for technological advancement. The presented research investigates natural photonic structures through holographic and nonlinear optical studies, revealing the correlations among their geometries, optical, and dynamic responses. These findings will inspire novel designs for optical devices and systems.
Keywords: nonlinear analysis, nonlinear optics, holography, natural photonics, biophotonics, optics.

Vincenzo Luigi Spagnolo
Latest advances in quartz enhanced photoacoustics spectroscopy for environmental and industrial applications
A. Zifarelli, G. Menduni, M. Giglio, A. Sampaolo, P. Patimisco, Hongpeng Wu, Lei Dong, and V. Spagnolo, Technical University of Bari, Italy
Environmental monitoring, as well as safety and security, and industrial applications demand for real time and in-situ solutions capable to unambiguously identify and quantify chemical analytes composing the investigated samples. Starting from the basic physical principles governing the quartz tuning fork physics, I will review the main results achieved by exploiting custom QTFs in QEPAS sensing for real-world applications.

Łukasz Szostkiewicz
From smart materials for space industry to soil temperature gauges for climate change monitoring: A review of new applications of distributed optical fiber sensors
Ł. Szostkiewicz, InPhoTech sp. z o.o, Ołtarzew, Poland
Distributed optical fiber sensors (DOF’s) are usually associated with strain and temperature measurements of long linear constructions. Within this paper we demonstrate how alterations in sensing schemes and application of specialty optical fibers allow to broaden the applications of DOF’s. One of those is an multi line underground temperature monitoring in arctic environment which demonstrates the possibility to remotely interrogate multiple sensing fibers with centimeter spatial resolution. We will also discuss the possibilities of distributed optical fiber sensing embedded in composites and metal alloys.
Keywords: distributed optical fiber sensors, specialty optical fibers.

Mikhail Vasilevskiy
Generation of hot surface plasmons in graphene by a powerful optical beam
R. Dias¹, D. Cunha¹, and M. Vasilevskiy^1,2
1Centro de Física das Universidades do Minho e do Porto and Laboratory of Physics for Materials and Emergent Technologies, University of Porto, Portugal
²National International Iberian Nanotechnology Laboratory, Braga, Portugal
Resonant interaction of two optical beams, with specially adjusted frequencies and wavevectors, mediated by graphene surface plasmons (SPs) and eventually leading to their all-optical generation, was demonstrated experimentally several years ago by measuring the differential reflectance of the probe beam. However, the quantitative explanation of these results requires much larger second-order optical conductivities of graphene than calculations based on standard perturbation theory approaches can yield. We suggest that the observed effect can be understood by considering, in addition to the second-order frequency-difference process, the generation of SPs via interband relaxation of hot electrons created by the powerful pump pulse. We calculate the generation rate of out-of-equilibrium plasmons by the latter mechanism and compare it to other mechanisms of hot carrier relaxation in graphene described in the literature.
Keywords: graphene, optical pumping, hot electrons, surface plasmons.

Aiguo Wu
Nanoparticles for optical sensing detection, tumor imaging and therapy in biomedicine
Aiguo Wu, Cixi Institute of Biomedical Engineering, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, China
Photoactive or photofunctional nanoparticles are widely used in many research fields such as storing, transporting, analyzing, sensing, imaging, and therapy. Particularly, there are so many applications in biomedicine based on photoactive or photofunctional nanoparticles. In this presentation, we will discuss some progress in optical sensing applications based on noble metal nanoparticles for detection of various types of cations/anions, small organic molecules, and cancer cells [1-3]; a various of biomedical applications in tumor imaging, therapy and therapeutic visualization based on different kinds of metal oxide nanoparticles for example iron oxide nanoparticles, titanium oxide nanoparticles, zinc oxide nanoparticles and their nanocomponents with metal nanoparticles etc. [4-10].
[1] F. Q. Zhang, L. Y. Zeng, Y. X. Zhang, H. Y. Wang, and A. G. Wu, Nanoscale, 3, 2150-2154 (2011).
[2] Y. X. Gao, X. Li, Y. L. Li, T. H. Li, Y. Y. Zhao, and A. G .Wu, Chem. Commun., 50, 6447-6450 (2014).
[3] J. Lin, O. U. Akakuru, and A.G. Wu, View, 2, 20200146 (2021).
[4] Z. Y. Shen, T. X. Chen, X. H. Ma, W. Z. Ren, Z. J. Zhou, G. Z. Zhu, A. Zhang, Y. J. Liu, J. B. Song, Z. H. Li, H. M .Ruan, W. P. Fan, L. S. Lin, J. Munasinghe, X. Y. Chen, and A. G. Wu, ACS Nano, 11, 10992-11004 (2017).
[5] Z. Y Shen, J. B. Song, Z. J. Zhou, B. C. Yung, M. A. Aronova, Y. Li, Y. L. Dai, W. P. Fan, Y. J. Liu, Z. H. Li, H. M. Ruan, R. D. Leapman, L. S. Lin, G. Niu, X. Y. Chen, and A. G. Wu, Adv. Mater., 30, 1803163 (2018).
[6] C. Liu, J. Xing, O. U. Akakuru, L. J. Luo, S. Sun, R. F. Zou, Z. S. Yu, Q. L. Fang, and A. G. Wu, Nano Lett., 19, 5674-5682 (2019).
[7] Z. Q. Jiang, B. Yuan, Y. J. Wang, Z. N. Wei, S. Sun, O. U. Akakuru, Y. Li, J. Li, A. G. Wu, Nano Today, 34,100910 (2020).
[8] X. W. Xu, J. Lin, Y. H. Guo, X. X. Wu, Y. P. Xu, D. H. Zhang, X. Z. Zhang, Y. J. Xie, J. Wang, C. Y. Yao, J. L. Yao, J. Xing, Y. Cao, Y. Y. Li, W. Z. Ren, T. X. Chen, Y. Ren, A. G. Wu, Biosensors and Bioelectronics, 210, 114305 (2022).
[9] H. Du, F. Yang, C. Y .Yao, W. H Lv, H. Peng, S. G. Stanciu, H. A. Stenmark, Y. M. Song, B. Jiang, A. G. Wu, Biomaterials, 2022, 291,121868.
[10] H. Du, F. Yang, C. Y. Yao, Z. C. Zhong, P. H. Jiang, S. G .Stanciu, H. Peng, J. P. Hu, B. Jiang, Z. H. Li, W. H. Lv, F .Zheng, H. A. Stenmark, and A. G. Wu, Small, 18, 220166 (2022).

Guang Wu
Evolutional analysis of coronavirus spike proteins with big-data
Shaomin Yan and Guang Wu
Institute of Bio-Science and Technology, Guangxi Academy of Sciences, Nanning, Guangxi, China
The pandemic of COVID-19 has overrun for three years, however, the systematic evolution of coronaviruses is still unclear. In this study, all 3227 unique CoV spike proteins from 1941 to 2019 plus the spike protein of the first sequenced SARS-CoV-2 were aligned based on seven different algorisms, of which each was constructed five types of phylogenetic trees. The generated 70 phylogenetic trees were compared, and 84 branch levels of ME and NJ phylogenetic trees were dissected to determine each spike protein at which branch level for each clade. Finally, the common evolutionary path was found out from the 70 phylogenetic trees. This big-data analysis provides the whole picture of coronavirus evolution over 80 years.
Keywords: coronavirus, evolution, phylogenetic analysis, SARS-CoV-2, spike protein, tree comparison.

Anna Zawadzka
Hybrid perovskites thin films – Temperature changes of properties
A. Zawadzka^1,2, A. Marjanowska^1,4, A. Laouid^1,5, K. Wiśniewki^1,2, and P. Płócennik^2,3
1Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Torun, Poland
²Centre for Modern Interdisciplinary Technologies, Nicolaus Copernicus University, Torun, Poland
³Institute of Engineering and Technology, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Torun, Poland
⁴University of Angers, MOLTECH-Anjou, UMR CNRS 6200, Angers, France
⁵National School of Applied Sciences, Engineering Science for Energy Laboratory, Chouaib Doukkali University of El Jadida, Morocco
Hybrid organic-inorganic halide perovskites have become the most promising materials in the field of photovoltaics. In just few years, the power conversion efficiency of solar cells based on hybrid perovskites has rapidly increased from an initial promising value of 9% to over 24%. Their extraordinary properties, including high carrier mobility, low carrier recombination rate and the tunable spectral absorption range are attributed to the unique electronic properties of these materials. The application field of hybrid perovskites has also rapidly expanded because replacing one or more organic or inorganic ions in the hybrid molecule's structure may lead to its different optical and electrical properties. Moreover, such substitution also leads to different structural properties of the hybrid halide perovskites thin films.  Despite undoubted progress in conversion efficiency of perovskite solar cells, understanding the basic structural, optical and electrical properties of hybrid perovskites is somewhat limited. The presentation will contain investigation results of the temperature dependences of the structural, electrical and optical properties for the multifunctional hybrid perovskites thin films fabricated by the Physical Vapor Deposition technique. Structural properties of the films were investigated by the AFM technique. Optical and electrical properties were examined by temperature-dependent transmittance, photoluminescence and current-voltage measurements.
Keywords: physical vapor deposition, hybrid organic-inorganic halide perovskites, thin films, atomic force microscopy, absorbance, photoluminescence.

Xavier Hesselbach
Intelligent network slicing in the multi-access edge computing for 6G networks
X. Hesselbach, Dept. Network Engineering, Universitat Politècnica de Catalunya, Barcelona, Spain
Multi-access Edge Computing (MEC) provides a service environment at the edge of the network where the latency it is expected to be extremely reduced and the overall performance is tuned to support cloud computing and new services. This type of network architecture is critical to deploy the next generation of pre-6G networks. The behavior must be optimized to exploit the capacity of the core optical fiber network. This paper proposes a network slicing aware intelligent queueing theory architecture for the MEC in order to optimize the performance metrics, in online and offline scenarios.

Hamzeh Khalili
Dynamic service placement in 6G multi-cloud scenarios
F. Tabatabaei, H. Khalili, M. Requena, S. Kahvazadeh, and J. Mangues-Bafalluy
Centre Tecnològic de Telecomunicacions de Catalunya, Castelldefels, Spain
The rapid development of 6G technology promises to revolutionize wireless communication and bring significant advancements in various industries. Public Protection and Disaster Relief (PPDR) applications require cutting-edge communication technology to meet their low latency, high-speed, and bandwidth requirements for effective decision-making support during emergencies. This paper presents a federated framework for the 5G-EPICENTRE project that allows various testbeds to federate and share resources for emergency situations. The proposed federated framework can provide flexible and efficient utilization of resources, enabling more effective PPDR applications to be connected and utilized.  To further enhance the performance of PPDR applications, we propose a scheduler that optimizes Network Service (NS) placement for Cloud and Multi-access Edge Computing (MEC) resources to improve the overall performance of PPDR applications. Our approach aims to reduce latency and efficiently offload services to empower first responders to make critical decisions during emergencies. This approach is expected to improve the overall performance of the PPDR applications and empower first responders to make critical decisions in emergency situations.
Keywords: 6G, autonomous network management, multi-cloud, federation, Karmada, scheduler.

David Rincón
Optimizing resource allocation in long reach PONs for improved performance in 6G networks
A. Haastrup¹, M. Zehri^1,2, D. Rincón¹, and J. R. Piney^1
1Dept of Networking Engineering, Universitat Politècnica de Catalunya – BarcelonaTech, Castelldefels, Spain
²Dept of Computer and Communication Eng., Lebanese International University, Beirut, Lebanon
Next-generation cellular networks, such as 6G, will require high-speed, low-latency connectivity to support advanced services and applications. To meet the bandwidth and latency demands of these networks, Passive Optical Networks (PONs) have emerged as a promising solution. Long Reach PONs (LR-PONs) have further extended the reach of PONs, making them ideal for remote and rural areas, as well as providing high-speed connectivity to buildings and homes. LR-PONs have the potential to play a critical role in the Radio Access Network (RAN) of any mobile communication system, specifically in Centralized Radio Access Network (C-RAN) architectures. In this paper, we present a new dynamic bandwidth allocation algorithm specifically enhanced for LRPONs based on the Longest Processing Time (LPT) scheduling policy, where the farthest ONUs are not penalized because of their distance to the OLT. The proposed algorithm optimizes resource allocation to maximize bandwidth capacity while minimizing delay and jitter. We evaluate the performance of the algorithm through simulations under various traffic scenarios. Our results demonstrate that the proposed algorithm outperforms other algorithms in terms of throughput and queue delay, which ultimately reduces the end-to-end delay especially under heavy traffic loads.
Keywords: 6G, 5G, dynamic bandwidth allocation, passive optical network, LR-PON, LPT.

Idelfonso Tafur Monroy
Secure and agile 6G networking – Quantum and AI enabling technologies
C. R. García¹, O. Bouchmal¹, C. Stan¹, P. Giannakopoulos1, B. Cimoli¹, J. J. Vegas Olmos², S. Rommel¹,and I. Tafur Monroy^1
1Department of Electrical Engineering, Eindhoven University of Technology, The Netherlands
²NVIDIA Corporation, Yokneam, Israel
This paper proposes a novel architecture for enabling ultra-fast and ultra-safe 6G networks that can support complex and challenging real-time applications based on four key enabling technologies: 1) performance prediction, 2) AI-enabled task offloading, 3) quantum machine learning, and 4) quantum-resistant communication. With the emergence of 6G applications where the real-time quality of experience is prioritized, AI-enabled task offloading leverages the benefits of edge computing. Moreover, the execution time of complex applications can be reduced by using quantum computers at the edge or in the cloud. In addition, by incorporating quantum key distribution and post-quantum cryptography, we can ensure the safety of mobile networks in the quantum computing era. Collectively, these technologies will provide ultra-fast and ultra-safe 6G networks, meeting the requirements of challenging real-time applications that were not supported in the previous generations, thus advancing the state of the art of mobile communication networks.
Keywords: 6G, edge computing, performance prediction, task offloading, QML, QKD, PQC.

Samira Mansourzadeh
New opportunities open by advances in table-top, high-power, and broadband terahertz sources
S. Mansourzadeh, T. Vogel, C. Millon, M. Khalili, R. Löscher, and C. J. Saraceno, Ruhr-Universität Bochum, Germany
The "terahertz" frequency range extends from about 100 GHz to 30 terahertz (THz). Long unexplored because of the difficulties of their generation, giving the well-known term “terahertz gap”; there is now a various explored way to generate them: plasma, optical rectification in organic and inorganic crystals, photoconductive antenna. We are developing high-power, broadband, and high dynamic range laser-based THz sources. These sources operate within the range of MHz / hundreds of kHz of repetition rate. This enables applications like THz time domain spectroscopy or pump-probe spectroscopy to be massively accelerated. Application fields such as the investigation of water molecular dynamics or THz imaging benefit enormously from these sources. In particular, samples with large absorption index in the THz range have been very difficult to characterize so far. Our high- power sources often make an efficient investigation with simultaneously high signal strength possible.

Christian Meineke
Intense sub-half-cycle terahertz waveforms for lightwave-driven scanning tunnelling microscopy
C. Meineke¹, M. Prager¹, J. Hayes¹, Q. Wen², L. Z. Kastner¹, D. Bougeard¹, M. Kira², and R. Huber^1
1Department of Physics, University of Regensburg, Germany
²Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, USA
Intense phase-locked terahertz (THz) pulses form the foundation of THz lightwave electronics, where the carrier field acts as transient bias and controls electrons on sub-cycle time scales. Major applications such as THz scanning tunnelling microscopy require ultimately short, ideally unipolar waveforms, at megahertz (MHz) repetition rates. In this work, we introduce a novel, flexible and fully scalable THz source of intense, phase-stable and strongly asymmetric sub-cycle field transients. Making use of shift currents in type-II aligned epitaxial semiconductor heterostructures we generate THz waveforms exhibiting only 0.45 optical cycles at their centre frequency, peak fields above 1.1 kV cm^-1 and spectral components up to the mid-infrared, at a repetition rate of 4 MHz. The only positive half-cycle of this transient exceeds the negative half-cycles by a factor of almost four, which is unexpected from shift currents alone. Our detailed quantum mechanical analysis reveals that local charging dynamics causes the dominant positive field peak as spatially separated electrons and holes are pulled back together after photoexcitation. Our emission scheme marks a landmark for scalable, next-generation high-repetition-rate sources of intense and strongly asymmetric electric field waveforms.
Keywords: lightwave electronics, terahertz generation, nonlinear optics, semiconductor heterostructures.

Daniel Mittleman
Conformal leaky-wave antennas for terahertz networks
H. Guerboukha, R. Shrestha, J. Neronha, Zhaoji Fang, and D. M. Mittleman
School of Engineering, Brown University, Providence, USA
We explore the performance of curved leaky-wave antennas in the terahertz range. We identify two distinct regimes in which the far-field emission pattern varies relative to that of a planar leaky-wave antenna. We show that a curved multi-aperture leaky-wave antenna can be used for agile far-field beam forming, and demonstrate high-gain wireless links at gigabit-per-second data rate with low bit error rate, in multiple directions simultaneously. This work lays the foundation for the implementation of terahertz leaky-wave structures in conformal geometries.

Mauro Pereira
Superlattices: From nonequilibrium Green’s functions to medical physics and integrated photonics applications
M. F. Pereira^1,2, V. Vaks³, V. Anfertev³, and H. Zafar^2
1Department of Physics, Khalifa University of Science and Technology, Abu Dhabi, UAE
²Department of Condensed Matter Theory, Institute of Physics, Czech Academy of Sciences, Czech Republic
³Institute for Physics of Microstructures of RAS, Nizhny Novgorod, Russia
In this talk we will summarize our recent theoretical and experimental studies of different types of superlattices.  We start with a summary of the predictive theory used to simulate giant control of THz nonlinearities and demonstrate its validity per direct comparison with experiments [1-3]. Next the same semiconductor superlattices are used for the detection of nitriles, showing potential as diagnostic method for cancer patients treated with chemotherapy.  In the second part of the talk, we focus on compact and broadband adiabatically bent superlattice-waveguides with negligible insertion loss and ultra-low crosstalk. Our numerical simulations also predict accurately the experiments based on a silicon-on-insulator platform. The approach is applicable to other waveguide geometries and integrated photonic platforms [5-6].
[1] M. F. Pereira et al., Sci Rep 10, 15950 (2020).
[2] V. Vaks et al., Sci Rep 12, 18117 (2022).
[3] M. F. Pereira, Nanomaterials 12, 1504 (2022).
[4] H. Zafar et al., in IEEE Journal of Selected Topics in Quantum Electronics, doi: 10.1109/JSTQE.2023.3241617.
[5] H. Zafar et al., Opt. Express 30, 10087-10095 (2022).
[6] H. Zafar et al., AIP Advances 10, 125214 (2020).

Jasmin Smajic
Plasmonic antennas for the reception of millimeter and THz waves
J. Smajic, H. Ibili, T. Blatter, M. Baumann, B. Vukovic, and J. Leuthold
Institute of Electromagnetic Fields, ETH Zurich, Switzerland
On-chip systems comprising a plasmonic THz antenna with an integrated electro-optical modulator are a very promising solution for sensing or future high-speed wireless communication links. In this context, we will present a modeling and simulation method for the optimization of THz-antennas. The model is capable of revealing the influence of the integrated modulator to the antenna parameters and its field enhancement capabilities essential for electro-optical modulation. Ultimately, we will present an in-detail antenna optimization approach for a given modulator design based on the accurate antenna’s equivalent circuit that eliminates  the need for computationally very expensive 3-D FEM antenna simulations.

Andreas Stöhr
High output power broadband 1.55 μm waveguide-integrated terahertz MUTC-photodiodes
E. Abacıoğlu¹, M. Grzeslo¹, T. Neerfeld¹, J. L. Fernández Estévez¹, and A. Stöhr^1,2
1University of Duisburg-Essen, Optoelectronics, Duisburg, Germany
²Microwave Photonics GmbH, Oberhausen, Germany
Photonic generation of millimeter- and terahertz-waves (30 GHz - 10 THz) has gained increasing interest and photodiodes have become key components in this regard. Among other photodiode technologies, the uni-travelling carrier photodiode (UTC-PD) has been a breakthrough in reaching high speed and high output power simultaneously. Consequently, UTC-PDs have been employed in numerous photonic applications ranging from spectroscopic sensing to wireless communications. In this work, we present broadband waveguide-type modified uni-traveling-carrier photodiodes (MUTC-PDs) providing mW output power levels up to the terahertz range. The fabricated MUTC-PDs are indium phosphide (InP) based photodiodes with coplanar waveguide (CPW) outputs. Maximum output power levels measured by using a calorimeter (PM5B) at 30 GHz, 150 GHz and 320 GHz are +12.2 dBm, +6.1 dBm and −4.6 dBm, respectively. KEYWORDS: High speed, high power, uni-traveling-carrier photodiode, THz photomixer.

Naoya Wada
New ICT devices enabled by organic electro-optic polymers
N. Wada, T. Kaji, T. Yamada, and A. Otomo
Advanced ICT Research Institute, National Institute of Information and Communications Technology, Tokyo, Japan
In 6G and beyond 6G ICT systems, the radio-over-fiber (RoF) technology that transmits signal waveforms of terahertz waves using optical fibers is attracting much attention. In the receivers of the radio sections of the mobile fronthaul and the remote antennas in the RoF systems, there is a need to develop low-cost, high-performance devices that convert wireless signals to optical signals. Organic electro-optic (EO) polymers can have large EO coefficients compared with nonlinear optical crystals such as lithium niobate (LiNbO3) and realize ultra-high-speed optical modulation of several hundred GHz or more. It is expected to realize devices that directly convert terahertz signals into optical signals by using the EO polymers. We will show recent research activities on new ICT devices enabled by organic electro-optic polymers.

Redha Alliche
prisma-v2: Extension to cloud overlay networks
R. A. Alliche¹, T. Da Silva Barros¹, R. Aparicio-Pardo¹, and L. Sassatelli^2
1Université Côte d’Azur, CNRS, Inria, I3S, France
²Université Côte d’Azur, CNRS, I3S, Institut Universitaire de France, France
An artificial neural network is investigated to improve the performance of self-coherent weakly-coupled multicore fibre (WC-MCF) systems. Particularly, a feedforward neural network (FNN) is proposed to mitigate the performance degradation induced by the random variation of the intercore crosstalk along time in 64 Gbaud quadrature amplitude modulation WC-MCF systems. A product between the intercore skew and the symbol rate much lower than one and a self-coherent receiver based on Kramers-Kronig technique, are considered. Compared with the reference system without neural networks, an improvement of the tolerable ICXT level close to 12 dB is achieved with the proposed shallow FNN.
Keywords: intercore crosstalk, multicore fibres, neural networks, self-coherent receivers, space-division multiplexing.

Samael Sarmiento
Low-cost all-optical switching nodes for ultra-dense optical metro-access networks
S. Sarmiento and J. A. Lázaro, Altran Innovación, Barcelona, Spain
Optical metro-access networks (OMANs) must enable connectivity among 5G-based radio stations, edge datacentres, businesses, and home users. In such a heterogeneous scenario, greater scalability, higher levels of dynamic connectivity and flexibility, reduced end-to-end latency, and increased energy efficiency are required. Mesh-based ultra-dense wavelength division multiplexing (u-DWDM) OMANs using reconfigurable optical switching nodes are a promising solution. However, the designs of traditional optical switching nodes relay on wavelength-selective switches (WSSs), which provide high network reconfigurability only at a high cost, making them prohibitive for OMANs. Moving away from this design approach, we proposed a novel cost-effective and energy-efficient design based on a modular DWDM structure for reconfigurable optical add-drop multiplexer (ROADM) and optical cross-connects (OXC) nodes compatible with mesh-based u-DWDM OMANs. Results show that proposed solutions can provide performance close to that of WSS-based OXCs but with a switching node cost reduction of one order magnitude.

Helio Waldman
A minimal idleness algorithm for spectrum assignment on a single elastic link under dynamic traffic
H. Waldman¹, R. C. Bortoletto², V. F. de Souza¹, R. C. A. Almeida Jr^3
1Fac. de Eng. Elétrica e de Computação, UNICAMP, Campinas, Brazil
²Instituto Federal de Educação, Ciência e Tecnologia de São Paulo, Brazil
³Universidade Federal de Pernambuco, Brazil
This paper presents an analytical derivation of an optimal spectrum assignment algorithm that minimizes spectral resource idleness in a single elastic link. The algorithm is aware of the requestable connection sizes and rates thereof. This awareness enables the calculation, for each possible void size and assignment policy, of the expected idle slot-time integral until the void is either fully occupied or coalesced into a new void by the termination of a neighboring connection. Idleness minimization may then be obtained by comparison among all possible on-arrival assignment policies when starting at each possible void size and choosing among all available voids the one that yields maximal reward in terms of reduction of the expected idleness, assuming the new connection is placed next to one of its edges. Since the number of policies grows exponentially with the number of requestable connection sizes, a scalability issue is identified.
Keywords: elastic optical networks, optical fiber networks, single link, maximal idleness reduction, reward tabulation.

Krzysztof Walkowiak
Performance analysis of multilayer optical networks with time-varying traffic
A. Knapińska¹, P. Lechowicz¹, S. Spadaro², and K. Walkowiak^1
1Wroclaw University of Science and Technology, Poland
²Universitat Politècnica de Catalunya, Barcelona, Spain
In this paper, we examine a multilayer packet-over-optical network. The packet layer is used to provision time-varying traffic, i.e., traffic that changes over time (day) due to the different popularity of various services and applications at different times of the day. In turn, the optical layer provides a virtual topology of lightpaths transmitting aggregated requests from the packet layer. The proposed algorithm allows to establish traffic in both analyzed layers and  utilizes  cross-layer  information  what  enables  traffic  grooming.  In  addition,  traffic prediction provided by ML algorithms is applied to improve routing and grooming decisions. The main objective of this paper is to make a comparison of various transceiver models in a multilayer optical network provisioning time-varying traffic. In more details, the key goal of is to examine what are the potential benefits of updating the transceivers to new models offering better performance in terms of spectral efficiency and transmission reach. We present and discuss results of extensive simulations run on a representative network topology with realistic physical assumptions and under diversified dynamic time-varying traffic patterns. As the main performance metric, we use bandwidth blocking probability (BBP). In addition, we estimate and 1% threshold of BBP defined as the maximum traffic that can be provisioned in the network with BBP not greater than 1%, which is a commonly acceptably threshold for BBP.  Furthermore,  we  report  other  metrics  including  spectrum  usage  and  number  of reallocations.

Molka Gharbaoui
Intent-based networking: Current advances, open challenges, and future directions
M. Gharbaoui, B. Martini, and P. Castoldi, Scuola Superiore Sant'Anna, Pisa, Italy
5G and beyond networks aim at provisioning a variety of services with different characteristics that require complex network configuration operations, which increases the risk of human error. This brings the necessity for the design and implementation of a flexible and programmable architecture that allows for an easy and automated network configuration, thus paving the way for self-managing and self-optimizing networks. In this context, Intent-based Networking (IBN) is emerging as a novel approach that facilitates network management and automates the implementation of network operations required by applications. The aim is to use a simple declarative approach while unburdening applications to deal with technology-specific low-level networking directives.  The objective of the paper is three folds: first reviewing the current advances in the IBN architecture and its building blocks; second discussing the open issues and challenges that still need to be addressed to further improve it and third presenting some future directions to overcome those challenges.

Brigitte Jaumard
Efficient 5G network slicing provisioning under dynamic traffic
B. Jaumard, J. Momo Ziazet, and N. Huin
CSE, Concordia University, Montréal Canada

Carmen Mas Machuca
Long-term capacity planning in flexible optical networks
C. Mas Machuca, Technische Universität München, Germany
Operators are continuously analyzing the most efficient solution to cope with their increasing demands in terms of investments, spectrum efficiency, over- and under-provisioning, etc. This talk will propose and compare different alternatives for operators to increase the capacity of flexible optical core networks.

Hailey Shakespear-Miles
Dynamic subcarrier allocation for P2MP connections
H. Shakespear-Miles, M. Ruiz, and L. Velasco Universitat Politècnica de Catalunya Barcelona, Spain
This paper details a solution for dynamically allocating subcarriers in a point-to-multipoint connection in the upstream direction. Using Digital Subcarrier Multiplexing a single carrier can be divided into several subcarriers. An ILP was used to dynamically allocated subcarriers in various traffic scenarios allowing for an increased number of edge nodes serviced. Significant capital and energy cost reductions were shown in comparison to traditional methods.

Michela Svaluto Moreolo
Photonic and quantum communication technologies for optical networks evolution
M. Svaluto Moreolo, L. Nadal, J. M. Fabrega, and J. Vílchez
Centre Tecnològic de Telecomunicacions de Catalunya (CTTC/CERCA), Spain
The role of photonic technologies and optical communications, including quantum communications, is particularly relevant to address the societal challenges posed by 6G networks and for a sustainable network evolution. This work focuses on recent advances in programmable multi-dimensional (spectrally and spatially multiplexed) transmission systems and adaptive high-capacity (multi-Tb/s) photonic transceivers to address a sustainable capacity scaling and the need of future optical networks. In particular, it is discussed how to enable high-performance, flexibility, agility, cost/power efficiency and security, promoting an optimal resource usage. To address security aspects, quantum key distribution is considered in coexistence with classical/conventional systems.