Orthogonal frequency division multiplexing for next generation optical networks

Next generation optical networks will be required to provide increased data throughput on a greater number of optical channels and will also have to facilitate network flexibility in order to adapt to dynamic traffic patterns. Furthermore, the potentially wide deployment of optical Access and Metropolitan networks in particular require that these challenges are met in a cost effect manner. This thesis examines the use of Orthogonal Frequency Division Multiplexing (OFDM) as a means of helping to meet these requirements for next generation optical systems with a high market volume. OFDM is a multi–carrier modulation technique which exhibits high spectral efficiency and a tolerance to chromatic dispersion making it an excellent candidate for use in next generation optical networks. The work presented in this thesis shows how the use of OFDM in conjunction with novel laser devices and direct detection can be used to construct cost effective, low footprint optical systems. These systems are capable of providing >10Gb/s per optical channel and are suitable for implementation as optical access networks. Furthermore, OFDM is shown to be a realistic candidate for use in an optical switching environment where external modulation is employed and, as such, can be considered for use in next generation metropolitan networks

Scalable high-capacity high-fan-out optical networks for constrained environments

The investigations carried out as part of the dissertation address the architecture and application of optical access networks pertaining to high-capacity and high fan-out applications such as in-flight entertainment (IFE) and video-gaming environment. High-capacity and high-fan-out optical networks have a multitude of applications such as expo-centers, train area networks (TAN), video gaming competitions and other applications that require large number of connected users. For the purpose of keeping the scope of the dissertation within limit however, we have concentrated this work on IFE systems. IFE systems present unique challenges at physical and application layers alike. In-flight entertainment (IFE) systems have been a part of passengers' experience for a while now. Currently available systems can be considered a bare-bone at best due to lack of adequate performance and support infrastructure. According to electronic arts (EA), one of the largest developers of video games in the world, an increase in demand for electronically distributed video games will exceed boxed games in just a matter of few years. This also shows a shifting trend towards the electronic distribution of video game content as opposed to physical distribution. Against the same backdrop, the dissertation project involved defining a novel system architecture and capacity based on the requirements for development of novel physical layer architecture utilizing optical networks for high-speed and high-fan-out distribution of content. At the physical layer of the stacked communication model a novel high-fan-out optical network was proposed and simulated for high data-rates. Having defined the physical layer, protocol stack was identified through rigorous observations and data traffic analysis from a large set of traffic traces obtained from various sources in order to understand the distribution and behavior of video game related traffic compared with regular internet traffic. Data requirements were laid down based on analysis keeping in mind that bandwidth requirements are increasing at a tremendous pace and that the network should be able to support future high-definition and 3D gaming as well. Based on the data analysis, analytical models and latency analysis models were also developed for bandwidth allocation in the high-fan-out network architectures. Analytical modeling gives an insight into the performance of the technique as a function of incoming traffic whereas latency analysis exposes the delay factors involved in running the technique over time. "State-full bandwidth allocation" (SBA) was proposed as part of the network layer design for upstream transmission. The novel technique involves keeping state information from previous states for future allocation. The results show that the proposed high-fan-out high-capacity physical layer architecture can be used to distribute video-gaming related content. Also, latency analysis and design and development of a novel SBA algorithm were carried out. Results were quiet promising, in that; a large number of users can be supported on the same single channel network. SBA criteria can be applied to multi-channel networks such as the physical architecture proposed / simulated and investigated in this project. In summary, the project involved design of a novel physical layer; network layer and protocol stack of the communication model and verification by simulations and mathematical modeling while adhering to application layer requirements

Déploiement de réseaux optiques d'accès NGPON dans des métropoles de pays en développement : proposition de nouvelles techniques d'implémentation de l'OFDM

The rapid development of multimedia services and applications such as broadband Internet, 3G, LTE, has led customers to force operators to increase throughput of all network segments, including the access network. Solutions using optical fiber tend to gradually replace cable based-copper or coaxial communications to ensure larger transfer capacity. The optical fiber is a very attractive medium because its linear attenuation is very low and its bandwidth very high. However, the chromatic dispersion of the fiber associated with the chirp of the optical sources limit the rise in flowrate in future optical access networks (beyond rates of 10 Gb/s) NG-PON (Next Generation Passive Optical Network). In this context, modulation formats with higher spectral efficiency than NRZ-OOK could be selected. OFDM is a solution to increase the spectral efficiency, while ensuring a better performance and high robustness against frequency selective channel such as fiber optics. In this thesis, we proposed a new OFDM techniques implementation for NG-PON and evaluated their performance in an IM/DD channel. We showed by simulations system of a realistic optical channel, that New DCO, New INC-ACO and DC-ACO OFDM techniques are able to increase the limited transmission distances imposed by the NRZ-OOK modulation with the use of low-cost components. Thus, we showed that using the “Minimization and E-Tight (MET)”or the Levin-Campello algorithm, the New DCO and DC-ACO techniques permit to achieve data rates of 10 Gb/s with a split ratio of 1 × 64 over a distance of 70 km with New DCO and 55 km for DC-ACO. Then we conclude that the New AMOFDM approach is a good choice for the deployment of optical access networks in metropolitan cities of developing countries.L’évolution rapide des services et applications multimédias (Internet haut débit, 3G, LTE) a entrainé un besoin chez les clients qui contraint les opérateurs à augmenter le débit de tous les segments du réseau, y compris le réseau d’accès. Les solutions utilisant la fibre optique tendent à remplacer progressivement les liaisons câblées (cuivre ou coaxial) afin de garantir des capacités de transfert plus importantes. La fibre optique est un medium très attractif car son atténuation linéique est très faible et sa bande passante importante. Cependant la dispersion chromatique de la fibre associée au chirp des sources optiques limite la montée en débit dans les futurs réseaux d’accès optiques (débits au-delà de 10 Gb/s) NG-PON (Next Generation Passive Optical Network). Dans ce contexte, des formats de modulation à efficacité spectrale meilleure que le NRZ pourraient être retenus. L’OFDM est une solution pour accroître l’efficacité spectrale, tout en garantissant une meilleure performance et une grande robustesse face aux canaux sélectifs en fréquence comme la fibre optique. Dans ce travail de thèse, nous avons proposé de nouvelles techniques d’implémentation de l’OFDM pour le NG-PON et évalué leurs performances dans un canal IM/DD. Nous avons montré par des simulations système dans un canal optique réaliste, que les techniques New DCO, New INC-ACO et DC-ACO sont capables d’augmenter les limitations de distances de transmission imposées par la modulation NRZ-OOK (Non-Return to Zero On-Off Keying) avec l’utilisation de composants bas coût. Ainsi, nous avons montré qu’avec les méthodes «MET (Minimization E-Tight)» et Levin-Campello, les techniques New DCO et DC-ACO permettent de réaliser des débits de 10 Gb/s sur une distance de 70 km en New DCO et 55 km en DC-ACO avec un taux de partage de 1×64. Cela permet d’affirmer que l’approche New AMOFDM serait un bon candidat pour le déploiement de réseaux d’accès optiques dans les métropoles de pays en développement