Impact of in-band crosstalk in an optical network based on multi-degree CDC ROADMs

he most common optical networks nodes are known as reconfigurable optical add/drop multiplexers (ROADMs). The architecture and components of these nodes have evolved over the time to become more flexible and dynamic. Particularly, the wavelength add/drop structures of these nodes have become more complex and with new features such as colorless, directionless and contentionless (CDC). One of the main limitations of the optical networks physical layer, the in-band crosstalk, is mainly due to the imperfect isolation of the components inside these nodes. This crosstalk is enhanced, when an optical signal traverses a cascade of ROADM nodes. In this work, the impact of in-band crosstalk, optical filtering and amplified spontaneous emission (ASE) noise on the performance of an optical communication network based on a cascade of CDC ROADMs with coherent detection and the modulation format quadrature phase-shift keying with polarization-division multiplexing (PDM-QPSK) at 100-Gb/s is studied through Monte-Carlo simulation. Two architectures, broadcast and select (B&S) and route and select (R&S), and two possible implementations for the add/drop structures, the multicast switches (MCSs) and the wavelength selective switches (WSSs), were considered. The degradation of the optical communication network performance due to in-band crosstalk is assessed through the optical-signal-to-noise ratio (OSNR) calculation. In particular, an OSNR penalty of 1 dB due to in-band crosstalk is observed when the signal passes through a cascade of 19 CDC ROADMs with 16-degree, based on a R&S architecture and with add/drop structures implemented with WSSsOs nós das redes de comunicação ótica mais comuns são os multiplexadores óticos de inserção/extração reconfiguráveis (ROADMs – acrónimo anglo-saxónico de reconfigurable optical add/drop multiplexers). A arquitetura e componentes destes nós têm evoluído ao longo do tempo no sentido de se tornarem mais flexíveis e dinâmicos. Em particular, as estruturas de adição/extração destes nós, tornaram-se mais complexas e detêm novas características que oferecem as funcionalidades CDC (acrónimo anglo- -saxónico de colorless, directionless e contentionless). Uma das principais limitações do nível físico das redes óticas, o crosstalk homódino, deve-se principalmente ao isolamento imperfeito dos componentes presentes dentro destes nós. Este tipo de crosstalk tem um impacto ainda mais significativo quando o sinal ótico atravessa uma cadeia de nós baseados em ROADMs. Nesta dissertação, o impacto do crosstalk homódino, filtragem ótica e ruído ASE (acrónimo anglo-saxónico de amplified spontaneous emission) no desempenho de uma rede de comunicação ótica baseada numa cadeia de CDC ROADMs com deteção coerente e usando o formato de modulação PDM-QPSK (acrónimo anglo-saxónico de polarization-division multiplexing quadrature phase-shift keying) a um ritmo binário de 100-Gb/s é investigado através de simulação Monte-Carlo. Consideraram-se duas arquiteturas, B&S e R&S (acrónimos anglo-saxónicos para broadcast and select e route and select), e duas possíveis implementações para a estruturas de inserção/extração, os MCSs e os WSSs (acrónimos anglo-saxónicos de multicast switches e wavelengh selective switches). A degradação do desempenho da rede ótica devido ao crosstalk homódino foi obtida através do cálculo da relação sinal-ruído ótica. Em particular, obteve-se uma penalidade de 1 dB para esta relação devido ao crosstalk homódino quando o sinal percorre uma cadeia de 19 CDC ROADMs com grau 16, uma arquitetura R&S e estruturas de inserção/extração baseadas em WSSs

Exploiting optical signal analysis for autonomous communications

(English) Optical communications have been extensively investigated and enhanced in the last decades. Nowadays, they are responsible to transport all the data traffic generated around the world, from access to the core network segments. As the data traffic is increasing and changing in both type and patterns, the optical communications networks and systems need to readapt and continuous advances to face the future data traffic demands in an efficient and cost-effective way. This PhD thesis focuses on investigate and analyze the optical signals in order to extract useful knowledge from them to support the autonomous lightpath operation, as well as to lightpath characterization. The first objective of this PhD thesis is to investigate the optical transmission feasibility of optical signals based on high-order modulation formats (MF) and high symbol rates (SR) in hybrid filterless, filtered and flexible optical networks. It is expected a higher physical layer impairments impact on these kinds of optical signals that can lead to degradation of the quality of transmission. In particular, the impact of the optical filter narrowing arising from the node cascade is evaluated. The obtained simulation results for the required optical-signal-to-noise ratio in a cascade up to 10 optical nodes foresee the applicability of these kinds of optical signals in such scenarios. By using high-order MF and high SR, the number of the optical transponders cab be reduced, as well as the spectral efficiency is enhanced. The second objective focuses on MF and SR identification at the optical receiver side to support the autonomous lightpath operation. Nowadays, optical transmitters can generate several optical signal configurations in terms of MF and SR. To increase the autonomous operation of the optical receiver, it is desired it can autonomously recognize the MF and SR of the incoming optical signals. In this PhD thesis, we propose an accurate and low complex MF and SR identification algorithm based on optical signal analysis and minimum Euclidean distance to the expected points when the received signals are decoded with several available MF and SR. The extensive simulation results show remarkable accuracy under several realistic lightpath scenarios, based on different fiber types, including linear and nonlinear noise interference, as well as in single and multicarrier optical systems. The final objective of this PhD thesis is the deployment of a machine learning-based digital twin for optical constellations analysis and modeling. An optical signal along its lightpath in the optical network is impaired by several effects. These effects can be linear, e.g., the noise coming from the optical amplification, or nonlinear ones, e.g., the Kerr effects from the fiber propagation. The optical constellations are a good source of information regarding these effects, both linear and nonlinear. Thus, by an accurate and deep analysis of the received optical signals, visualized in optical constellations, we can extract useful information from them to better understand the several impacts along the crossed lightpath. Furthermore, by learning the different impacts from different optical network elements on the optical signal, we can accurately model it in order to create a partial digital twin of the optical physical layer. The proposed digital twin shows accurate results in modeled lightpaths including both linear and nonlinear interference noise, in several lightpaths configuration, i.e., based on different kind of optical links, optical powers and optical fiber parameters. In addition, the proposed digital twin can be useful to predict quality of transmission metrics, such as bit error rate, in typical lightpath scenarios, as well as to detect possible misconfigurations in optical network elements by cooperation with the software-defined networking controller and monitoring and data analytics agents.(Español) Las comunicaciones ópticas han sido ampliamente investigadas y mejoradas en las últimas décadas. En la actualidad, son las encargadas de transportar la mayoría del tráfico de datos que se genera en todo el mundo, desde el acceso hasta los segmentos de la red troncal. A medida que el tráfico de datos aumenta y cambia tanto en tipo como en patrones, las redes y los sistemas de comunicaciones ópticas necesitan readaptarse y avanzar continuamente para, de una manera eficiente y rentable, hacer frente a las futuras demandas de tráfico de datos. Esta tesis doctoral se centra en investigar y analizar las señales ópticas con el fin de extraer de ellas conocimiento útil para apoyar el funcionamiento autónomo de las conexiones ópticas, así como para su caracterización. El primer objetivo de esta tesis doctoral es investigar la viabilidad de transmisión de señales ópticas basadas en formatos de modulación de alto orden y altas tasas de símbolos en redes ópticas híbridas con y sin filtros. Se espera un mayor impacto de las degradaciones de la capa física en este tipo de señales ópticas que pueden conducir a la degradación de la calidad de transmisión. En particular, se evalúa el impacto de la reducción del ancho de banda del filtro óptico que surge tras atravesar una cascada de nodos. Los resultados de simulación obtenidos para la relación señal óptica/ruido requerida en una cascada de hasta 10 nodos ópticos prevén la aplicabilidad de este tipo de señales ópticas en tales escenarios. Mediante el uso de modulación de alto orden y altas tasas de símbolos, se reduce el número de transpondedores ópticos y se mejora la eficiencia espectral. El segundo objetivo se centra en la identificación de formatos de modulación y tasas de símbolos en el lado del receptor óptico para respaldar la operación autónoma de la conexión óptica. Para aumentar el funcionamiento autónomo del receptor óptico, se desea que pueda reconocer de forma autónoma la configuración de las señales ópticas entrantes. En esta tesis doctoral, proponemos un algoritmo de identificación de formatos de modulación y tasas de símbolos preciso y de baja complejidad basado en el análisis de señales ópticas cuando las señales recibidas se decodifican con varios formatos de modulación y tasas de símbolos disponibles. Los extensos resultados de la simulación muestran una precisión notable en varios escenarios realistas, basados en diferentes tipos de fibra, incluida la interferencia de ruido lineal y no lineal, así como en sistemas ópticos de portadora única y múltiple. El objetivo final de esta tesis doctoral es el despliegue de un gemelo digital basado en aprendizaje automático para el análisis y modelado de constelaciones ópticas. Una señal óptica a lo largo de su trayectoria en la red óptica se ve afectada por varios efectos, pueden ser lineales o no lineales. Las constelaciones ópticas son una buena fuente de información sobre estos efectos, tanto lineales como no lineales. Por lo tanto, mediante un análisis preciso y profundo de las señales ópticas recibidas, visualizadas en constelaciones ópticas, podemos extraer información útil de ellas para comprender mejor los diversos impactos a lo largo del camino propagado. Además, al aprender los diferentes impactos de los diferentes elementos de la red óptica en la señal óptica, podemos modelarla con precisión para crear un gemelo digital parcial de la camada física óptica. El gemelo digital propuesto muestra resultados precisos en conexiones que incluyen ruido de interferencia tanto lineal como no lineal, en varias configuraciones basados en diferentes tipos de enlaces ópticos, potencias ópticas y parámetros de fibra óptica. Además, el gemelo digital propuesto puede ser útil para predecir la calidad de las métricas de transmisión así como para detectar posibles errores de configuración en los elementos de la red óptica mediante la cooperación con el controlador de red, el monitoreo y agentes de análisis de datosPostprint (published version

An autoencoder-based solution for IQ constellation analysis

A method for IQ constellation analysis based on Autoencoders is proposed. Exhaustive numerical results show accurate physical metric prediction and large data compression, while providing useful model explainability.This work has been partially supported by the EC through the MSC REAL-NET project (G.A. 813144), by the AEI/FEDER through the TWINS project (TEC2017- 90097-R), and by the ICREA institution.Peer ReviewedPostprint (author's final draft

Lightweight optical constellation modeling by concatenating artificial neural networks

A lightweight optical constellations modeling method based on concatenating ANNs is proposed. Statistical validation of the reproduced constellations is shown. The method accelerates data generation and facilitates detecting (un)intentioned misconfigurations, among others.This work has been partially supported by the EC through the MSC REAL-NET project (G.A. 813144), by the AEI/FEDER through the TWINS project (TEC2017-90097-R), and by the ICREA institution.Peer ReviewedPostprint (author's final draft

Deep learning-based real-time analysis of lightpath optical constellations [Invited]

© [2022 Optical Society of America]. Users may use, reuse, and build upon the article, or use the article for text or data mining, so long as such uses are for non-commercial purposes and appropriate attribution is maintained. All other rights are reserved.Optical network automation requires accurate physical layer models, not only for provisioning but also for real-time analysis. In particular, In-Phase (I) and Quadrature (Q) constellation analysis enables deep understanding of the characteristics of optical connections (lightpaths), e.g., their length. In this paper, we present methods for modeling lightpaths based on deep learning. Specifically, we propose using autoencoders (AE) and deep neural networks (DNN). Models are trained and composed in a sandbox domain with the information received from the network controller and sent to the node agent that uses them to compare the features extracted from the received signal and the expected features returned by the models. We investigate two different use cases for lightpath analysis focused on lightpath length and optical signal power. The results show a remarkable accuracy for the lightpath modelling and length prediction and a noticeable performance of the AEs for unsupervised IQ constellation features extraction and relevance analysis. © 2021 Optical Society of AmericaEuropean Commission (H2020 B5G-OPEN (G.A. 101016663), MSCA REAL-NET project (G.A. 813144)); Agencia Estatal de Investigación (IBON (PID2020-114135RB-I00)); Institució Catalana de Recerca i Estudis AvançatsPeer ReviewedPostprint (published version

OCATA: A deep-learning-based digital twin for the optical time domain

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 propose a deep-learning-based digital twin for the optical time domain, named OCATA. OCATA is based on the concatenation of deep neural network (DNN) modeling of optical links and nodes, which facilitates representing lightpaths. The DNNs model linear and nonlinear noise, as well as optical filtering. Additional DNN-based models are proposed to extract useful lightpath metrics, such as lightpath length, number of optical links, and nonlinear fiber parameters. OCATA exhibits low complexity, thus making it ideal for real-time applications. Illustrative results for the application of OCATA to disaggregated and mixed disaggregated-proprietary optical network scenarios reveal remarkable accuracy.The research leading to these results has received funding from the MSCA REAL-NET (G.A. 813144), the H2020 B5G-OPEN (G.A. 101016663), and the AEI IBON (PID2020-114135RB-I00) projects and from the ICREA Institution.Peer ReviewedPostprint (author's final draft

Autonomous and energy efficient lightpath operation based on digital subcarrier multiplexing

The massive deployment of 5G and beyond will require high capacity and low latency connectivity services, so network operators will have either to overprovision capacity in their transport networks or to upgrade the optical network controllers to make decisions nearly in real time; both solutions entail high capital and operational expenditures. A different approach could be to move the decision making toward the nodes and subsystems, so they can adapt dynamically the capacity to the actual needs and thus reduce operational costs in terms of energy consumption. To achieve this, several technological challenges need to be addressed. In this paper, we focus on the autonomous operation of Digital Subcarrier Multiplexing (DSCM) systems, which enable the transmission of multiple and independent subcarriers (SC). Herein, we present several solutions enabling the autonomous DSCM operation, including: i) SC quality of transmission estimation; ii) autonomous SC operation at the transmitter side and blind SC configuration recognition at the receiver side; and iii) intent-based capacity management implemented through Reinforcement Learning. We provide useful guidelines for the application of autonomous SC management supported by the extensive results presented.The research leading to these results has received funding from the European Community's through the MSCA REAL-NET project (G.A. 813144), by the AEI/FEDER through the TWINS project (TEC2017-90097-R), and by the ICREA institution.Peer ReviewedPostprint (author's final draft

HIPTCN: Estudo Prospetivo Observacional de Doentes Traumatizados Cranioencefálicos Hipocoagulados com Tomografia Computorizada Inicial Normal

Introduction: Our national protocol for traumatic brain injury dictates that hypocoagulated patients with mild trauma and initial tomography scan with no intracranial traumatic changes must be hospitalized for 24 hours and do a post-surveillance tomography scan. The main goal of this study was to evaluate the clinical relevance of these measures. Material and methods: A prospective observational study was undertaken in four hospitals. Adult hypocoagulated traumatic brain injury patients with a normal tomography scan were included. The main outcomes evaluated were rate of delayed intracranial hemorrhage, rate of admission in a neurosurgical department, rate of complications related with surveillance and rate of prolonged hospitalization due to complications. An analysis combining data from a previously published report was also done. Results: A total of 178 patients were included. Four patients (2.3%) had a delayed hemorrhage and three (1.7%) were hospitalized in a neurosurgery ward. No cases of symptomatic hemorrhage were identified. No surgery was needed, and all patients had their anticoagulation stopped. Complications during surveillance were reported in seven patients (3.9%), of which two required prolonged hospitalization. Discussion: The rate of complications related with surveillance was higher than the rate of delayed hemorrhages. The initial period of in-hospital surveillance did not convey any advantage since the management of patients was never dictated by neurological changes. Post-surveillance tomography played a role in deciding about anticoagulation suspension and prolongation of hospitalization. Conclusion: Delayed hemorrhage is a rare event and the need for surgery even rarer. The need for in-hospital surveillance should be reassessed.Introdução: O nosso protocolo nacional para traumatismos cranioencefálicos recomenda que doentes hipocoagulados com trauma craniano ligeiro e tomografia inicial sem alterações traumáticas intracranianas sejam hospitalizados 24 horas e façam uma tomografia computorizada pós-vigilância. O principal objetivo deste estudo foi avaliar a relevância clínica dessas medidas. Material e Métodos: Foi realizado em quatro hospitais um estudo prospetivo e observacional. Foram incluídos adultos hipocoagulados com trauma craniano e tomografia normal. Os principais outcomes avaliados foram: taxa de hemorragia intracraniana tardia, taxa de internamento numa enfermaria de neurocirurgia, taxa de complicações relacionadas com a vigilância e taxa de hospitalização prolongada por complicações. Resultados: Foram incluídos um total de 178 doentes. Quatro doentes (2,3%) apresentaram hemorragia tardia e três (1,7%) foram mantidos hospitalizados numa enfermaria de Neurocirurgia. Não foram documentados casos de hemorragia tardia sintomática. Nenhuma cirurgia foi necessária e em todos estes doentes a anticoagulação foi interrompida. Durante a vigilância, foram relatadas complicações em sete doentes (3,9%), dos quais dois exigiram hospitalização prolongada. Discussão: A taxa de complicações relacionadas com a vigilância foi maior do que a taxa de hemorragia tardia. O período inicial de vigilância intra-hospitalar não trouxe qualquer vantagem, já que o manejo dos doentes nunca foi ditado por alterações neurológicas. A tomografia pós-vigilância desempenhou um papel importante na decisão sobre a suspensão da anticoagulação e o prolongamento da hospitalização. Conclusão: A hemorragia tardia é um evento raro e a necessidade de cirurgia ainda mais. Deve ser reavaliada a necessidade de vigilância intra-hospitalar.info:eu-repo/semantics/publishedVersio