Machine Learning for Multi-Layer Open and Disaggregated Optical Networks

L'abstract è presente nell'allegato / the abstract is in the attachmen

Optical packet networks : enabling innovative switching technologies

Les réseaux informatiques avec une grande capacité nécessitent des liaisons de transmission de données rapides et fiables pour prendre en charge les applications web en pleine croissance. Comme le nombre de serveurs interconnectés et la capacité de stockage des médias ne cessent daugmenter, les communications optiques et les technologies de routage sont devenues intéressantes grâce au taux binaire élevé et à lencombrement minimum offert par la fibre optique. Les réseaux optiques à commutation de paquets (OPSNs) offrent une flexibilité accrue dans la gestion de réseau. OPSNs exploitent les convertisseurs de longueur donde accordables (WC) pour minimiser la probabilité de blocage et fournir une allocation dynamique des longueurs donde. Les émetteurs optiques basés sur des sources multi-longueurs donde se présentent comme une solution intéressante en termes de coût, dencombrement et defficacité énergétique par rapport aux autres types de lasers. Les convertisseurs de longueurs donde doivent permettre des taux binaires élevés et une transparence à une grande variété de formats de modulation, tout en offrant une réponse rapide, des niveaux de puissance modérés et un rapport de signal à bruit optique (OSNR) acceptable à la sortie. Plusieurs technologies de conversion de longueur donde ont été proposées dans la littérature. Lutilisation du mélange à quatre ondes (FWM) dans les amplificateurs optiques à semi-conducteurs (SOA) permet lutilisation de faibles niveaux de puissance dentrée et offre une bonne efficacité de conversion ainsi que la possibilité dintégration photonique. Les SOAs offrent donc un excellent compromis par rapport aux autres solutions. Pour couvrir une plus large bande de conversion, nous utilisons le schéma exploitant le FWM avec doubles pompes dans les SOAs. Pour la stabilité de phase, les pompes viennent d’un laser en mode bloqué (QDMLL) qui sert comme source multi-longueurs donde. Deux modes du QDMLL sont sélectionnés par un filtrage accordable et servent comme doubles pompes. Un filtre accordable placé à la sortie du SOA sert à sélectionner le produit du FWM pour le signal final. Nous étudions le convertisseur de longueur donde proposé et comparons sa performance pour différents formats de modulation (modulation dintensité et de phase) et à différents débits binaires (10 et 40 Gbit/s). Le taux derreur binaire, lefficacité de conversion et la mesure de lOSNR sont présentés. Nous démontrons aussi la possibilité de simultanément convertir en longueurs donde les données et l’étiquette. Les données à haut débit et l’étiquette à faible débit se retrouvent dans une seule bande de longueurs d’onde, et ils sont convertis ensemble avec une bonne efficacité. Notre démonstration se concentre sur les performances de conversion, donc les données et létiquette sont des signaux continus plutôt que de paquets optiques. Des mesures de taux derreur binaire ont été effectuées à la fois pour les données et pour létiquette. Nous proposons aussi lutilisation de QDMLL comme source de transmetteurs WDM pour deux applications différentes: unicast et multicast. Nous démontrons aussi sa compatibilité avec le format de transmission DQPSK à haut débit binaire. Nous évaluons la performance du DQPSK en terme de taux derreur binaire et comparons sa performance à celle dune source laser à cavité externe.Large scale computer networks require fast and reliable data links in order to support growing web applications. As the number of interconnected servers and storage media increases, optical communications and routing technologies become interesting because of the high speed and small footprint of optical fiber links. Furthermore, optical packet switched networks (OPSN) provide increased flexibility in network management. Future networks are envisaged to be wavelength dependent routing, therefore OPSN will exploit tunable wavelength converters (WC) to enable contention resolution, reduce wavelength blocking in wavelength routing and switching, and provide dynamic wavelength assignment. Optical transmitters based on multi-wavelength sources are presented as an attrative solution compared to a set of single distributed feedback lasers in terms of cost, footprint and power consumption. Wavelength converters should support high bit rates and a variety of signal formats, have fast setup time, moderate input power levels and high optical signal-to-noise ratio at the output. Several wavelength conversion technologies have been demonstrated. The use of four wave mixing (FWM) in semiconductor optical amplifiers (SOAs) provides low input power levels, acceptable conversion efficiency and the possibility of photonic integration. SOAs therefore offer excellent trade-offs compared to other solutions. To achieve wide wavelength coverage and integrability, we use a dual pump scheme exploiting four-wave mixing in semiconductor optical amplifiers. For phase stability, we use a quantum-dash mode-locked laser (QD-MLL) as a multi-wavelength source for the dual pumps, with tunability provided by the frequency selective filter. We investigate the proposed wavelength converter and compare its performance of wavelength conversion for different non-return-to-zero (NRZ) intensity and phase modulation formats at different bit rates (10 and 40 Gbit/s). Bit error rate, conversion efficiency and optical signal-to-noise ratio measurements are reported. We demonstrate the possibility of tightly packed payload and label wavelength conversion at very high data baud rate over wide tuning range with good conversion efficiency. Our demonstration concentrates on conversion performance, hence continuous payload and label signals were used without gating into packets. Bit error measurements for both payload and label were performed. We propose the use of QD-MLL as multi-wavelength source for WDM unicast and multicast applications and we investigated its compatibility with DQPSK transmission at high bit rate. We quantify DQPSK performance via bit error rate measurements and compare performance to that of an external cavity laser (ECL) source

Investigation of performance issues affecting optical circuit and packet switched WDM networks

Optical switching represents the next step in the evolution of optical networks. This thesis describes work that was carried out to examine performance issues which can occur in two distinct varieties of optical switching networks. Slow optical switching in which lightpaths are requested, provisioned and torn down when no longer required is known as optical circuit switching (OCS). Services enabled by OCS include wavelength routing, dynamic bandwidth allocation and protection switching. With network elements such as reconfigurable optical add/drop multiplexers (ROADMs) and optical cross connects (OXCs) now being deployed along with the generalized multiprotocol label switching (GMPLS) control plane this represents the current state of the art in commercial networks. These networks often employ erbium doped fiber amplifiers (EDFAs) to boost the optical signal to noise ratio of the WDM channels and as channel configurations change, wavelength dependent gain variations in the EDFAs can lead to channel power divergence that can result in significant performance degradation. This issue is examined in detail using a reconfigurable wavelength division multiplexed (WDM) network testbed and results show the severe impact that channel reconfiguration can have on transmission performance. Following the slow switching work the focus shifts to one of the key enabling technologies for fast optical switching, namely the tunable laser. Tunable lasers which can switch on the nanosecond timescale will be required in the transmitters and wavelength converters of optical packet switching networks. The switching times and frequency drifts, both of commercially available lasers, and of novel devices are investigated and performance issues which can arise due to this frequency drift are examined. An optical packet switching transmitter based on a novel label switching technique and employing one of the fast tunable lasers is designed and employed in a dual channel WDM packet switching system. In depth performance evaluations of this labelling scheme and packet switching system show the detrimental impact that wavelength drift can have on such systems

Journal of Telecommunications and Information Technology, 2001, nr 2

kwartalni

Design, monitoring and performance evaluation of high capacity optical networks

Premi Extraordinari de Doctorat, promoció 2018-2019. Àmbit de les TICInternet traffic is expected to keep increasing exponentially due to the emergence of a vast number of innovative online services and applications. Optical networks, which are the cornerstone of the underlying Internet infrastructure, have been continuously evolving to carry the ever-increasing traffic in a more flexible, cost-effective, and intelligent way. Having these three targets in mind, this PhD thesis focuses on two general areas for the performance improvement and the evolution of optical networks: i) introducing further cognition to the optical layer, and ii) introducing new networking solutions revolutionizing the optical transport infrastructure. In the first part, we present novel failure detection and identification solutions in the optical layer utilizing the optical spectrum traces captured by cost-effective coarse-granular Optical Spectrum Analyzers (OSA). We demonstrate the effectiveness of the developed solutions for detecting and identifying filter-related failures in the context of Spectrum-Switched Optical Networks (SSON), as well as transmitter-related laser failures in Filter-less Optical Networks (FON). In addition, at the subsystem level we propose an Autonomic Transmission Agent (ATA), which triggers local or remote transceiver reconfiguration by predicting Bit-Error-Rate (BER) degradation by monitoring State-of-Polarization (SOP) data obtained by coherent receivers. I have developed solutions to push further the performance of the currently deployed optical networks through reducing the margins and introducing intelligence to better manage their resources. However, it is expected that the spectral efficiency of the current standard Single-Mode Fiber (SMF) based optical network approaches the Shannon capacity limits in the near future, and therefore, a new paradigm is required to keep with the pace of the current huge traffic increase. In this regard, Space Division Multiplexing (SDM) is proposed as the ultimate solution to address the looming capacity crunch with a reduced cost-per-bit delivered to the end-users. I devote the second part of this thesis to investigate different flavors of SDM based optical networks with the aim of finding the best compromise for the realization of a spectrally and spatially flexible optical network. SDM-based optical networks can be deployed over various types of transmission media. Additionally, due to the extra dimension (i.e., space) introduced in SDM networks, optical switching nodes can support wavelength granularity, space granularity, or a combination of both. In this thesis, we evaluate the impact of various spectral and spatial switching granularities on the performance of SDM-based optical networks serving different profiles of traffic with the aim of understanding the impact of switching constraints on the overall network performance. In this regard, we consider two different generations of wavelength selective switches (WSS) to reflect the technology limitations on the performance of SDM networks. In addition, we present different designs of colorless direction-less, and Colorless Directionless Contention-less (CDC) Reconfigurable Optical Add/Drop Multiplexers (ROADM) realizing SDM switching schemes and compare their performance in terms of complexity and implementation cost. Furthermore, with the aim of revealing the benefits and drawbacks of SDM networks over different types of transmission media, we preset a QoT-aware network planning toolbox and perform comparative performance analysis among SDM network based on various types of transmission media. We also analyze the power consumption of Multiple-Input Multiple-Output (MIMO) Digital Signal Processing (DSP) units of transceivers operating over three different types of transmission media. The results obtained in the second part of the thesis provide a comprehensive outlook to different realizations of SDM-based optical networks and showcases the benefits and drawbacks of different SDM realizations.Se espera que el tráfico de Internet siga aumentando exponencialmente debido a la continua aparición de gran cantidad de aplicaciones innovadoras. Las redes ópticas, que son la piedra angular de la infraestructura de Internet, han evolucionado continuamente para transportar el tráfico cada vez mayor de una manera más flexible, rentable e inteligente. Teniendo en cuenta estos tres objetivos, esta tesis doctoral se centra en dos áreas cruciales para la mejora del rendimiento y la evolución de las redes ópticas: i) introducción de funcionalidades cognitivas en la capa óptica, y ii) introducción de nuevas estructuras de red que revolucionarán el transporte óptico. En la primera parte, se presentan soluciones novedosas de detección e identificación de fallos en la capa óptica que utilizan trazas de espectro óptico obtenidas mediante analizadores de espectros ópticos (OSA) de baja resolución (y por tanto de coste reducido). Se demuestra la efectividad de las soluciones desarrolladas para detectar e identificar fallos derivados del filtrado imperfecto en las redes ópticas de conmutación de espectro (SSON), así como fallos relacionados con el láser transmisor en redes ópticas sin filtro (FON). Además, a nivel de subsistema, se propone un Agente de Transmisión Autónomo (ATA), que activa la reconfiguración del transceptor local o remoto al predecir la degradación de la Tasa de Error por Bits (BER), monitorizando el Estado de Polarización (SOP) de la señal recibida en un receptor coherente. Se han desarrollado soluciones para incrementar el rendimiento de las redes ópticas mediante la reducción de los márgenes y la introducción de inteligencia en la administración de los recursos de la red. Sin embargo, se espera que la eficiencia espectral de las redes ópticas basadas en fibras monomodo (SMF) se acerque al límite de capacidad de Shannon en un futuro próximo, y por tanto, se requiere un nuevo paradigma que permita mantener el crecimiento necesario para soportar el futuro aumento del tráfico. En este sentido, se propone el Multiplexado por División Espacial (SDM) como la solución que permita la continua reducción del coste por bit transmitido ante ése esperado crecimiento del tráfico. En la segunda parte de esta tesis se investigan diferentes tipos de redes ópticas basadas en SDM con el objetivo de encontrar soluciones para la realización de redes ópticas espectral y espacialmente flexibles. Las redes ópticas basadas en SDM se pueden implementar utilizando diversos tipos de medios de transmisión. Además, debido a la dimensión adicional (el espacio) introducida en las redes SDM, los nodos de conmutación óptica pueden conmutar longitudes de onda, fibras o una combinación de ambas. Se evalúa el impacto de la conmutación espectral y espacial en el rendimiento de las redes SDM bajo diferentes perfiles de tráfico ofrecido, con el objetivo de comprender el impacto de las restricciones de conmutación en el rendimiento de la red. En este sentido, se consideran dos generaciones diferentes de conmutadores selectivos de longitud de onda (WSS) para reflejar las limitaciones de la tecnología en el rendimiento de las redes SDM. Además, se presentan diferentes diseños de ROADM, independientes de la longitud de onda, de la dirección, y sin contención (CDC) utilizados para la conmutación SDM, y se compara su rendimiento en términos de complejidad y coste. Además, con el objetivo de cuantificar los beneficios e inconvenientes de las redes SDM, se ha generado una herramienta de planificación de red que prevé la QoT usando diferentes tipos de fibras. También se analiza el consumo de energía de las unidades DSP de los transceptores MIMO operando en redes SDM con tres tipos diferentes de medios de transmisión. Los resultados obtenidos en esta segunda parte de la tesis proporcionan una perspectiva integral de las redes SDM y muestran los beneficios e inconvenientes de sus diferentes implementacionesAward-winningPostprint (published version