Dense wavelength division multiplexing (DWDM) is becoming the technology of choice for meeting the increasing bandwidth demands in optical networks. DWDM has been used to increase the capacity of long-haul optical transport systems. Efforts are being made to move DWDM into the broadband access network serving residential and business subscribers. First, a new centralized DWDM PON scheme is demonstrated for bi-directional upstream and downstream transmissions. The proposed DWDM PON scheme is implemented using optical carrier suppression and separation (OCSS) technology to generate a wavelength pair from a single laser source at the central office. This method enables the co-location of both upstream and downstream DWDM transmitters in the central office. In addition, the complexity, cost, and maintenance of the optical network unit are reduced by enabling wavelength independent operation. Second, a new multistage architecture is proposed for the delivery of information to groups of subscribers located at different distances from the central office. A 25 GHz DWDM comb is generated using OCSS technology, and error-free transmission of four 10 Gbps channels is demonstrated. Finally, a new wide area access network with bi-directional DWDM amplification using semiconductor optical amplifiers (SOAs) is demonstrated. The detrimental effect of SOA crosstalk resulting from cross gain modulation can be suppressed using a constant intensity modulation format such as differential phase shift keying (DPSK). The feasibiity of bi-directional DPSK transmission of 16 interleaved DWDM channels using an in-line SOA has been studied experimentally. In addition, the reduction of bi-directional SOA reflections has been realized by optimizing the SOA bias current and facet reflectivities.

Performance of neural network based restoration of optical networks is evaluated and a few possible improvements are proposed. Neural network based restoration is simulated with optical link capacities assigned by a new method. Two new improvement methods are developed to reduce the neural network size and the restoration time of severed optical connections. Cycle based restoration is suggested, which reduces the neural network structure by restoring the severed connections for each optical node, iteratively. Additionally, to reduce the restoration time, the necessary waiting time before the neuron outputs fire for the propagation delay over the network is computed and embedded in the control structure of the neural network. The improvement methods are evaluated by simulations in terms of restorability, restoration time, network redundancy and average length of restoration paths for different failure cases and different security requirements.

The current prospects in wired and wireless access networks, it is becoming increasingly important to address potential convergence in order to offer integrated broadband services. These systems will need to offer higher data transmission capacities and long battery life, which is the catalyst for an everincreasing variety of air interface technologies targeting local area to wide area connectivity. Current integrated industrial networks do not offer application aware context delivery and enhanced services for optimised networks. Application aware services provide value-added functionality to business applications by capturing, integrating, and consolidating intelligence about users and their endpoint devices from various points in the network. This thesis mainly intends to resolve the issues related to ubiquitous application aware service, fair allocation of radio access, reduced energy consumption and improved capacity. A technique that measures and evaluates the data rate demand to reduce application response time and queuing delay for multi radio interfaces is proposed. The technique overcomes the challenges of network integration, requiring no user intervention, saving battery life and selecting the radio access connection for the application requested by the end user. This study is split in two parts. The first contribution identifies some constraints of the services towards the application layer in terms of e.g. data rate and signal strength. The objectives are achieved by application controlled handover (ACH) mechanism in order to maintain acceptable data rate for real-time application services. It also looks into the impact of the radio link on the application and identifies elements and parameters like wireless link quality and handover that will influence the application type. It also identifies some enhanced traditional mechanisms such as distance controlled multihop and mesh topology required in order to support energy efficient multimedia applications. The second contribution unfolds an intelligent application priority assignment mechanism (IAPAM) for medical applications using wireless sensor networks. IAPAM proposes and evaluates a technique based on prioritising multiple virtual queues for the critical nature of medical data to improve instant transmission. Various mobility patterns (directed, controlled and random waypoint) has been investigated and compared by simulating IAPAM enabled mobile BWSN. The following topics have been studied, modelled, simulated and discussed in this thesis: 1. Application Controlled Handover (ACH) for multi radios over fibre 2. Power Controlled Scheme for mesh multi radios over fibre using ACH 3. IAPAM for Biomedical Wireless Sensor Networks (BWSN) and impact of mobility over IAPAM enabled BWSN. Extensive simulation studies are performed to analyze and to evaluate the proposed techniques. Simulation results demonstrate significant improvements in multi radios over fibre performance in terms of application response delay and power consumption by upto 75% and 15 % respectively, reduction in traffic loss by upto 53% and reduction in delay for real time application by more than 25% in some cases.

Στην εργασία αυτή ασχολούμαστε με το πρόβλημα της δρομολόγησης ενός συνόλου αιτήσεων επικοινωνίας σε WDM (Wavelength Division Multiplexing) πλήρως οπτικά δίκτυα από την άποψη της θεωρίας παιγνίων. Αν θεωρήσουμε κάθε αίτηση δρομολόγησης (ζεύγος κόμβων αφετηρία-προορισμός) ως παίκτη, τότε μία στρατηγική περιλαμβάνει ένα μονοπάτι από τον κόμβο-αφετηρία στον κόμβο-προορισμό και μία συχνότητα (χρώμα). Λαμβάνοντας υπόψη τον περιορισμό ότι δύο παίκτες δεν μπορούν να χρησιμοποιήσουν την ίδια συχνότητα στην ίδια ακμή, θεωρούμε ότι το κόστος δύο αλληλοσυγκρουόμενων στρατηγικών είναι απαγορευτικά μεγάλο. Στο παραπάνω πλαίσιο, μελετάμε διάφορες φυσικές συναρτήσεις κόστους επικεντρώνοντας στην ύπαρξη αμιγών σημείων ισορροπίας Nash και στην υπολογιστική πολυπλοκότητα αναγνώρισης και υπολογισμού τους. / We consider the problem of routing a number of communication requests in WDM (wavelength division multiplexing) all-optical networks from the standpoint of game theory. If we view each routing request (pair of source-target nodes) as a player, then a strategy consists of a path from the source to the target and a frequency (color). To reflect the restriction that two requests must not use the same frequency on the same edge, conflicting strategies are assigned a prohibitively high cost. Under this formulation, we consider several natural cost functions focusing on the existence of Nash equilibria and on the complexity of recognizing and computing them.

In recent years, the ever-increasing environmental friendliness concern has made energy efficiency in telecom networks as an important theme in their operations. Meanwhile, mission-critical (MC) services and systems (such as healthcare, police, and firefighting) have been acquiring special attention from telecom designers and operators. The currently deployed MC network technologies are indigent in terms of bandwidth capacity, and thus they are not able to support the emerging MC multimedia applications. Therefore in this thesis, we first explore the possibility of provisioning the MC services over the integration of fiber-wireless (FiWi) technologies, which has been considered as a promising candidate for the deployment of high-speed and mobile broadband access networks. We then investigate the energy efficiency problem in the FiWi integration, which consists of WiMAX in the wireless plane, and of Ethernet Passive Optical Network (EPON) - the most popular variant of the next-generation PON (NG-PON) technology, in the optical plane. In WiMAX, the energy saving protocol has been extensively investigated and standardized. Conversely, it has been recently studied in NG-PON, which currently consumes the least power among all the high-speed access networks. However, NG-PON has notably matured in the past few years and is envisioned to massively evolve in the near future. This trend will increase the power requirements of NG-PON and make it no longer coveted. Therefore we address the energy efficiency problem in NG-PON. For each of our contributions, we conduct extensive simulations to demonstrate the effectiveness and advantages of the proposed solutions.

This thesis evaluates the performance of service differentiation with different class of services namely protection, reservation and the best effort services on the NxN meshed torus and the ring topology, which are established as survivable all&amp / #8208 / optical WDM networks. Blocking probabilities are measured as performance criteria and the effects of different number of wavelengths, different type of services and different topology size with wavelength selective lightpath allocation schemes are investigated by simulations with respect to increasing load on the topologies.

Thesis (M.Eng.). / Written for the Dept. of Electrical and Computer Engineering. Title from title page of PDF (viewed 2008/07/29). Includes bibliographical references.

[pt] Neste trabalho, uma análise do fenômeno de mistura de quatro ondas (FWM) em sistemas ópticos multicanais é apresentada. Inicialmente, uma série de simulações determina as limitações impostas aos sistemas ópticos, sendo adotado um nível máximo de crosstalk permitido. Em seguida, os diversos parâmetros que influenciaram a eficiência da geração de FWM são estudados detalhadamente, com resultados apresentados em forma de gráficos. Nestes últimos, o nível de FWM obtido é especificado em função da potência de entrada por canal, comprimento do enlace, número de canais, presença de amplificadores, número de amplificadores e dispersão cromática da fibra utilizada. Um breve estudo discute a deterioração da qualidade do serviço, causada pro FWM, em redes ópticas. O trabalho se encerra com algumas aplicações que utilizam, de forma favorável, o fenômeno de FWM. / [en] This work adresses the four-wave mixing (FWM) issue in optical multichannel systems. First, some simulations are carried out for specifying which are the optical system limitations coping with a maximum allowed crosstalk level. Next, the different parameters affecting the FWM are throughly studied, with these last pertinent results being graphicallly presented. In these, the obtained FWM levels are specified as a function of the channel input power, link span, channel rumber, presence of amplifiers, number of amplifiers and fiber chromatic dispersion. A concise discussion, concerning the quality of service deterioration on optical networks, due to FWM, is also presented. The work is finally closed by presenting some applications that favorably use the FWM phenomena.

[pt] Este trabalho estuda o efeito de conversores de comprimento de onda em nós de redes multiplexadas por divisão de comprimento de onda totalmente ópticas ou transparentes. Foram executadas simulações para estudar os benefícios da introdução de conversores nas arquiteturas de rede. Ademais, são propostas heurísticas para alocação de conversores de comprimento de onda, baseadas na utilização destes. Os desempenhos das heurísticas são avaliados comparando-as com outros algoritmos estabelecidos na literatura. / [en] This work studies the effect of wavelength converters at nodes of wavelength division multiplexed all-optical networks. Simulations were performed to study the benefit of wavelength converters on network architectures. Moreover, wavelength converter placement heuristics based on the utilization of these devices are proposed. The performances of the heuristics are tested against existing converter placement algorithms in literature.

[pt] Este trabalho investiga o problema de alocação sub-óptima de conversores de comprimento de onda em nós de redes ópticas parciais, através da proposição de 3 algoritmos baseados nas metaheurísticas GA (Algoritmo Genético), PSO (Optimização por Enxame de Partícula) e SA (Recozimento Simulado). Simulações são apresentadas para ratificar os benefícios com a introdução de conversores nas arquiteturas de rede. Os desempenhos dos algoritmos são mensurados via um simulador, comparando-os com outros algoritmos estabelecidos na literatura. / [en] This work investigates the problem of suboptimally placing wavelength converters at nodes of partial optical networks, through the proposition of 3 algorithms based on the metaheuristics GA (Genetic Algorithm), PSO (Particle Swarm Optimization) and SA (Simulated Annealing). Simulations are presented to ratify the benefits with the introduction of wavelength converters on networks architectures. The results of these algorithms are measure by a simulator, comparing them with other algorithms in literature.