Optimisation d'un réseau de communication par fibre optique

Le présent travail concerne la modélisation d'un réseau de communication par fibre optique. Il s'agira de modéliser une topologie virtuelle prenant en compte les noeuds, les capacités de traitement aux noeuds, les exigences de qualité ainsi que les routes virtuelles ou successions de trajets sur lesquels sont embarqués les flux de données ou la matrice de trafic. Le modèle devra aussi tenir compte de divers paramètres (longueurs d'onde, modulations, type de routage, etc..). Nous utiliserons, après la modélisation en un programme linéaire mixte en nombres entiers (MILP), un ensemble de solveurs pour nous permettre d'apprécier les performances ainsi que les limites de la résolution sur ces différentes plates-formes au fur et à mesure que le problème croît. Un autre aspect du travail sera de faire le constat de la complexité de la programmation linéaire mixte en nombres entiers. Cela va d'ailleurs susciter le passage d'un MILP dit fort à un MILP dit faible. Un autre volet du travail sera la formalisation du MILP dit faible par une approche de décomposition structurée, prenant en compte la structure du modèle ainsi que des caractéristiques de certaines variables avec pour objectif ultime d'améliorer le processus d'optimisation

Digital signal processing optical receivers for the mitigation of physical layer impairments in dynamic optical networks

IT IS generally believed by the research community that the introduction of complex network functions—such as routing—in the optical domain will allow a better network utilisation, lower cost and footprint, and a more efficiency in energy usage. The new optical components and sub-systems intended for dynamic optical networking introduce new kinds of physical layer impairments in the optical signal, and it is of paramount importance to overcome this problem if dynamic optical networks should become a reality. Thus, the aim of this thesis was to first identify and characterise the physical layer impairments of dynamic optical networks, and then digital signal processing techniques were developed to mitigate them. The initial focus of this work was the design and characterisation of digital optical receivers for dynamic core optical networks. Digital receiver techniques allow for complex algorithms to be implemented in the digital domain, which usually outperform their analogue counterparts in performance and flexibility. An AC-coupled digital receiver for core networks—consisting of a standard PIN photodiode and a digitiser that takes samples at twice the Nyquist rate—was characterised in terms of both bit-error rate and packet-error rate, and it is shown that the packet-error rate can be optimised by appropriately setting the preamble length. Also, a realistic model of a digital receiver that includes the quantisation impairments was developed. Finally, the influence of the network load and the traffic sparsity on the packet-error rate performance of the receiver was investigated. Digital receiver technologies can be equally applied to optical access networks, which share many traits with dynamic core networks. A dual-rate digital receiver, capable of detecting optical packets at 10 and 1.25 Gb/s, was developed and characterised. The receiver dynamic range was extended by means of DC-coupling and non-linear signal clipping, and it is shown that the receiver performance is limited by digitiser noise for low received power and non-linear clipping for high received power