Path Protection in Translucent WDM Optical Networks

Optical noise, chromatic dispersion, nonlinear effects, polarization mode dispersion (PMD) and cross-talk cause the quality of an optical signal to degrade as it propagates through the fibers in wavelength division multiplexed (WDM) optical networks. In a translucent network, regenerators are placed ay appropriate intervals to carry out 3R regeneration (re-amplify, re-shape and re-time). Translucent WDM networks are receiving attention as long-haul back bone networks. One important aspect of such networks that has not received attention is the possibility of cycles in the path of a translucent network. This research studies how we implement path protection in translucent networks, considering the possibility of cycles. We are developing a new scheme for dynamic lightpath allocation using the idea of shared path protection. We propose to study the performance of the scheme using a number of well known networks

A Simple Approach to Dynamic Optimisation of Flexible Optical Networks with Practical Application

This paper provides an initial introduction to, and definition of, the ‘Dynamically Powered Relays for a Flexible Optical Network’ (DPR-FON) problem for opto-electro-optical (OEO) regenerators used in optical networks. In such networks, optical transmission parameters can be varied dynamically as traffic patterns change. This will provide different bandwidths, but also change the regeneration limits as a result. To support this flexibility, OEOs (‘relays’) may be switched on and off as required, thus saving power. DPR-FON is shown to be NP-complete; consequently, solving such a dynamic problem in real-time requires a fast heuristic capable of delivering an acceptable approximation to the optimal configuration with low complexity. In this paper, just such an algorithm is developed, implemented, and evaluated against more computationally-demanding alternatives for two known cases. A number of real-world extensions are considered as the paper develops, combining to produce the ‘Generalised Dynamically Powered Relays for a Flexible Optical Network’ (GDPR-FON) problem. This, too, is analysed and an associated fast heuristic proposed, along with an exploration of the further research that is required

Regenerator placement and fault management in multi-wavelength optical networks.

Shen, Dong.Thesis (M.Phil.)--Chinese University of Hong Kong, 2011.Includes bibliographical references (p. 98-106).Abstracts in English and Chinese.Abstract --- p.i摘要 --- p.ivAcknowledgements --- p.vTable of Contents --- p.viChapter Chapter 1 --- Background --- p.1Chapter 1.1 --- Translucent Optical Networks --- p.1Chapter 1.1.1 --- The Way Towards Translucent --- p.1Chapter 1.1.2 --- Translucent Optical Network Architecture Design and Planning --- p.3Chapter 1.1.3 --- Other Research Topics in Translucent Optical Networks --- p.6Chapter 1.2 --- Fault Monitoring in All-Optical Networks --- p.12Chapter 1.2.1 --- Fault Monitoring in Network Layer's Perspective --- p.12Chapter 1.2.2 --- Passive Optical Monitoring --- p.14Chapter 1.2.3 --- Proactive Optical Monitoring --- p.16Chapter 1.3 --- Contributions --- p.17Chapter 1.3.1 --- Translucent Optical Network Planning with Heterogeneous Modulation Formats --- p.17Chapter 1.3.2 --- Multiplexing Optimization in Translucent Optical Networks --- p.19Chapter 1.3.3 --- An Efficient Regenerator Placement and Wavelength Assignment Scheme in Translucent Optical Networks --- p.20Chapter 1.3.4 --- Adaptive Fault Monitoring in All-Optical Networks Utilizing Real-Time Data Traffic --- p.20Chapter 1.4 --- Organization of Thesis --- p.22Chapter Chapter 2 --- Regenerator Placement and Resource Allocation Optimization in Translucent Optical Networks --- p.23Chapter 2.1 --- Introduction --- p.23Chapter 2.2 --- Translucent Optical Network Planning with Heterogeneous Modulation Formats --- p.25Chapter 2.2.1 --- Motivation and Problem Statements --- p.25Chapter 2.2.2 --- A Two-Step Planning Algorithm Using Two Modulation Formats to Realize Any-to-Any Topology Connectivity --- p.28Chapter 2.2.3 --- Illustrative Examples --- p.30Chapter 2.2.3 --- ILP Formulation of Minimizing Translucent Optical Network Cost with Two Modulation Formats under Static Traffic Demands --- p.34Chapter 2.2.4 --- Illustrative Numeric Examples --- p.42Chapter 2.3 --- Resource Allocation Optimization in Translucent Optical Networks --- p.45Chapter 2.3.1 --- Multiplexing Optimization with Auxiliary Graph --- p.45Chapter 2.3.2 --- Simulation Study of Proposed Algorithm --- p.51Chapter 2.3.3 --- An Efficient Regenerator Placement and Wavelength Assignment Solution --- p.55Chapter 2.3.4 --- Simulation Study of Proposed Algorithm --- p.60Chapter 2.4 --- Summary --- p.64Chapter Chapter 3 --- Adaptive Fault Monitoring in All-Optical Networks Utilizing Real-Time Data Traffic --- p.65Chapter 3.1 --- Introduction --- p.65Chapter 3.2 --- Adaptive Fault Monitoring --- p.68Chapter 3.2.1 --- System Framework --- p.68Chapter 3.2.2 --- Phase 1: Passive Monitoring --- p.70Chapter 3.2.3 --- Phase 2: Proactive Probing --- p.71Chapter 3.2.4 --- Control Plane Design and Analysis --- p.80Chapter 3.2.5 --- Physical Layer Implementation and Suggestions --- p.83Chapter 3.3 --- Placement of Label Monitors --- p.83Chapter 3.3.1 --- ILP Formulation --- p.84Chapter 3.3.2 --- Simulation Studies --- p.86Chapter 3.3.3 --- Discussion of Topology Evolution Adaptiveness --- p.93Chapter 3.4 --- Summary --- p.95Chapter Chapter 4 --- Conclusions and Future Work --- p.95Chapter 4.1 --- Conclusions --- p.96Chapter 4.2 --- Future Work --- p.97Bibliography --- p.98Publications during M.Phil Study --- p.10

IMPAIRMENT AWARE DYNAMIC ROUTING AND WAVELENGTH ASSIGNMENT IN WDM NETWORKS

Optical networks play a major role in supporting the traffic in backbone computer networks. Routing and Wavelength Assignment (RWA) is the technique used to establish a light-path from a source node to a destination node in a Wavelength Division Multiplexed (WDM) optical network. As an optical signal propagates through the network, the quality of the signal degrades due to physical layer impairments. To address this problem, in translucent WDM networks, the signal is regenerated at intervals. The main objective of this research is to propose a fast heuristic for dynamic lightpath allocation in translucent WDM networks and to compare the heuristic with an optimal algorithm that was proposed recently

Survivability aspects of future optical backbone networks

In huidige glasvezelnetwerken kan een enkele vezel een gigantische hoeveelheid data dragen, ruwweg het equivalent van 25 miljoen gelijktijdige telefoongesprekken. Hierdoor zullen netwerkstoringen, zoals breuken van een glasvezelkabel, de communicatie van een groot aantal eindgebruikers verstoren. Netwerkoperatoren kiezen er dan ook voor om hun netwerk zo te bouwen dat zulke grote storingen automatisch opgevangen worden. Dit proefschrift spitst zich toe op twee aspecten rond de overleefbaarheid in toekomstige optische netwerken. De eerste doelstelling die beoogd wordt is het tot stand brengen vanrobuuste dataverbindingen over meerdere netwerken. Door voldoende betrouwbare verbindingen tot stand te brengen over een infrastructuur die niet door een enkele entiteit wordt beheerd kan men bv. weredwijd Internettelevisie van hoge kwaliteit aanbieden. De bestudeerde oplossing heeft niet enkel tot doel om deze zeer betrouwbare verbinding te berekenen, maar ook om dit te bewerkstelligen met een minimum aan gebruikte netwerkcapaciteit. De tweede doelstelling was om een antwoord te formuleren om de vraag hoe het toepassen van optische schakelsystemen gebaseerd op herconfigureerbare optische multiplexers een impact heeft op de overleefbaarheid van een optisch netwerk. Bij lagere volumes hebben optisch geschakelde netwerken weinig voordeel van dergelijke gesofistikeerde methoden. Elektronisch geschakelde netwerken vertonen geen afhankelijkheid van het datavolume en hebben altijd baat bij optimalisatie

Improving Routing Efficiency, Fairness, Differentiated Servises And Throughput In Optical Networks

Wavelength division multiplexed (WDM) optical networks are rapidly becoming the technology of choice in next-generation Internet architectures. This dissertation addresses the important issues of improving four aspects of optical networks, namely, routing efficiency, fairness, differentiated quality of service (QoS) and throughput. A new approach for implementing efficient routing and wavelength assignment in WDM networks is proposed and evaluated. In this approach, the state of a multiple-fiber link is represented by a compact bitmap computed as the logical union of the bitmaps of the free wavelengths in the fibers of this link. A modified Dijkstra\u27s shortest path algorithm and a wavelength assignment algorithm are developed using fast logical operations on the bitmap representation. In optical burst switched (OBS) networks, the burst dropping probability increases as the number of hops in the lightpath of the burst increases. Two schemes are proposed and evaluated to alleviate this unfairness. The two schemes have simple logic, and alleviate the beat-down unfairness problem without negatively impacting the overall throughput of the system. Two similar schemes to provide differentiated services in OBS networks are introduced. A new scheme to improve the fairness of OBS networks based on burst preemption is presented. The scheme uses carefully designed constraints to avoid excessive wasted channel reservations, reduce cascaded useless preemptions, and maintain healthy throughput levels. A new scheme to improve the throughput of OBS networks based on burst preemption is presented. An analytical model is developed to compute the throughput of the network for the special case when the network has a ring topology and the preemption weight is based solely on burst size. The analytical model is quite accurate and gives results close to those obtained by simulation. Finally, a preemption-based scheme for the concurrent improvement of throughput and burst fairness in OBS networks is proposed and evaluated. The scheme uses a preemption weight consisting of two terms: the first term is a function of the size of the burst and the second term is the product of the hop count times the length of the lightpath of the burst

Optimization of WDM Optical Networks

Optical network, with its enormous data carrying capability, has become the obvious choice for today\u27s high speed communication networks. Wavelength Division Multiplexing (WDM) technology and Traffic Grooming techniques enable us to efficiently exploit the huge bandwidth capacity of optical fibers. Wide area translucent networks use sparse placement of regenerators to overcome the physical impairments and wavelength constraints introduced by all optical (transparent) networks, and achieve a performance level close to fully switched (opaque) networks at a much lesser network cost. In this dissertation we discuss our research on several issues on the optimal design of optical networks, including optimal traffic grooming in WDM optical networks, optimal regenerator placement problem (RRP) in translucent networks, dynamic lightpath allocation and dynamic survivable lightpath allocation in translucent networks and static lightpath allocation in translucent networks. With extensive simulation experiments, we have established the effectiveness and efficiencies of our proposed algorithms

Estudo de caso de técnicas de utilização de transponders em redes ópticas elásticas

The growth in data traffic is mainly caused due to both the increasing number of subscriber and new applications that require high transmission rates. Optical networks have been the most suitable way to support this demand. One of the biggest challenges faced by these networks is optimizing the use of the available spectrum. The technologies that may lead to better use of the available optical spectrum is the one that allows to the divide the spectrum narrow slices. This approach is known as Elastic Optical Networks (EON), EONS are an evolution of WDM (Wavelength Division Multiplexing) networks. Moreover translucent elastic optical network may be designed from a transparent network by the addition of certain amount of regenerators 3R distributed in a strategically way in the network. In a translucent network, some nodes are transparent and other ones are opaque or translucent. Therefore, in such networks the question of deciding which nodes are translucent or transparent arises. This problem is known as Regenerator Placement (RP). The RP consists of to decide at which of EONs will be deployed 3R regenerators and as well as the number of 3R should be placed at each node. After the RP problem is solved, the regenerator allocation algorithm (RA) is responsible to determine whether to use, or not, the 3R regenerators deployed in each intermediate node of a given route. In EONs, the use of regenerators can be done by lack of quality in the transmission, by spectrum conversion or to improve modulation format. In this thesis, three algorithms to perform regenerator assignment for EONs are proposed. EONs with sparse regeneration and dynamic traffic are considered. The proposed algorithms are: The FLR-RA (First Longest Reach Regenerator Assignment), which tries to use as less as possible regenerators along a route, the FNS-RA (First Narrowest Spectrum Regenerator Assignment), which tries to use as less as possible spectrum along a route, and the exhaustive, that returns either the solution that uses the fewest possible number of regenerators or occupy fewest possible number of slots along a given route. The algorithms a simulated in two network topologies. The results show, in the simulated scenarios, that the FLR-RA reaches smaller blocking probabilities when the number of regenerators deployed in network is small, while the FNS-RA reaches smaller blocking probabilities in the cases in which many regenerators are placed in network. The FLR-RA and FNS-RA heuristics show similar results to the exhaustive, meaning that the heuristics present a good performance.O crescimento da demanda por tráfego de dados é ocasionado pelo aumento de assinantes e pelo aparecimento de novos aplicativos que exigem maiores taxas de transmissão. As redes ópticas têm sido o meio mais adequado para suportar essa demanda. Um dos grandes desafios enfrentados por essas redes é otimizar o uso do espectro disponível. Uma das tecnologias que permitem uma melhor utilização desse espectro é a que possibilita divisão do espectro em pequenas faixas espectrais. Essa abordagem conhecida como redes ópticas elásticas (EON, Elastic Optic Network). A rede óptica elástica translúcida é projetada em uma rede transparente acrescida de uma certa quantidade de regeneradores 3R distribuídos de forma estratégica na rede. Em uma rede translúcida, alguns nós são transparentes e outros são opacos ou translúcidos. Surge então a questão de decidir quais “nós” são translúcidos ou transparentes. Esse problema é conhecido como colocação de regeneradores (RP, Regenerator Placement). O RP consiste em decidir a quais “nós” das EONs serão adicionados regeneradores 3R e quantos deverão ser colocados em cada nó. Após ser resolvido o problema de RP, cabe ao algoritmo de atribuição de regeneradores (RA, Regenerator Allocation) determinar como usar esse recurso de regeneração 3R e determinar em que nó do caminho o regenerador será ou não usado. Nas EONs, o uso de regeneradores pode ser feito por falta de qualidade na transmissão, por conversão de espectro ou para melhorar o formato de modulação. Nesta dissertação, são analisados três algoritmos de atribuição de regeneradores para as EONs aplicadas à rede esparsa de tráfego dinâmico, visando à redução da probabilidade de bloqueio. O FLR-RA (First Longest Reach Regenerator Assignment), que economiza regeneradores na rede, o FNS-RA (First Narrowest Spectrum Regenerator Assignment), que economiza espectro na rede, e o exaustivo, que escolhe uma das possíveis soluções ótimas, ou uma solução que apresenta o menor número total de slots para implementá-la (FNS-RA) ou uma solução que apresenta o menor número total de regeneradores para implementá-la (FLR-RA). Os algoritmos foram simulados em duas topologias de rede. Os resultados mostram que nos cenários simulados o FLR-RA atinge uma menor probabilidade de bloqueio quando o número de regeneradores adicionado na rede é pequeno, enquanto o FNS-RA atinge menores probabilidades de bloqueio nos casos nos quais muitos regeneradores são colocados na rede. As heurísticas FLR-RA e FNS-RA apresentam resultados similares ao exaustivo, isto mostra que as heurísticas apresentam um bom desempenho

A Test-Bed for Comparing Impairment Aware Routing & Wavelength Assignment Algorithms in WDM Networks

When an optical signal propagates through optical fibers, the quality of the signal degrades due to a number of physical phenomena. Traditional Routing and Wavelength Assignment (RWA) approaches assume an ideal physical layer medium and ignore the effects of physical layer impairments on the lightpath feasibility. In the last few years investigators have started taking into account the fact that the quality of transmission (QoT) of an optical signal propagating through an optical network degrades, due to physical layer considerations. To measure the extent of this degradation due to physical layer impairments (PLI), metrics such as the Bit Error Rate (BER) used. In a translucent network, when the quality of a signal is reduced sufficiently, the signal has to be regenerated. In a transparent network, regenerators are not allowed so that lightpaths with high bit error rates are disallowed. A number of heuristic approaches for impairment aware RWA have been proposed for transparent and for translucent networks. As a result of this investigation a test-bed ahs been developed for Impairment Aware Static Route and Wavelength Assignment (IA-RWA) in transparent networks. This includes a tool for computing BER values and allows the user to run a new heuristic for IA-RWA and study its performance against a number of existing heuristics for IA-RWA

Contribution à l'amélioration de l'efficacité des réseaux IP sur WDM en évaluant et en dépassant les limites du dimensionnement multicouche

The traffic passing through core networks grows by nearly 25% each year. To bring the costs under control, the different network layers of the network should work together to include more and more parameters during the network planning phase. This is called “multilayer network planning”. We study the multilayer network planning of static networks composed of two circuit switched layers (typically IP-over-WDM). We propose a semi-analytical model explaining the behavior of algorithms responsible for aggregation and routing in both layers. This theory allows comparing multilayer planning algorithms between them, but also explaining and enhancing their efficiency. We then describe the impact of the optical reach constraint in WDM networks on the results of a multilayer planning algorithm. Finally, we explain how these results apply to the design of future networks (dynamic and with heterogeneous optical layers)La quantité de données devant être transportée via les réseaux de cœur croit de près de 25% par an. Pour maîtriser les coûts, les différentes couches du réseau doivent mettre des informations en commun pour inclure de plus en plus de paramètres lors du dimensionnement du réseau. Cela s’appelle « dimensionnement multicouche ». Nous étudions le dimensionnement multicouche de réseaux statiques composés de deux couches utilisant la commutation en mode circuit (typiquement IP-sur-WDM). Nous proposons un modèle semi-analytique expliquant le comportement des algorithmes responsables de l’agrégation et du routage dans les deux couches. Ce cadre théorique permet de comparer les algorithmes de dimensionnement multicouche entre eux, mais aussi d’expliquer et d’améliorer leur efficience. Nous décrivons ensuite comment la contrainte de portée optique affecte les résultats d’un algorithme de dimensionnement multicouche. Enfin, nous expliquons comment ces résultats s'appliquent au dimensionnement des réseaux de nouvelle génération (dynamiques et hétérogènes en capacité optique