Placement of Mode and Wavelength Converters for Throughput Enhancement in Optical Networks

The success of recent experiments to transport data using combined wavelength division multiplexed (WDM) and mode-division multiplexed (MDM) transmission has generated optimism for the attainment of optical networks with unprecedented bandwidth capacity, exceeding the fundamental Shannon capacity limit attained by WDM alone. Optical mode converters and wavelength converters are devices that can be placed in future optical nodes (routers) to prevent or reduce the connection blocking rate and consequently increase network throughput. In this thesis, the specific problem of the placement of mode converters (MC) and mode-wavelength converters (MWC) in combined mode and wavelength division multiplexing (MWDM) networks is investigated. Four previously proposed wavelength converter placement heuristics are extended to handle the placement of MC and MWC in MWDM networks. A simple but effective method for the placement of mode and wavelength converters in MWDM networks is proposed based on ranking the nodes with respect to the volume of received connection requests. The results of extensive simulation tests to evaluate the new method and compare its performance with the performance of the other four heuristics are presented. The thesis provides extensive comparison results among the five converter placement methods using different network topologies and under different network loads. The results demonstrate the effectiveness of the new proposed method in achieving lower blocking rates compared to the other more-complex converter placement heuristics

Dynamic wavelength routing in multifiber WDM networks

The research, development, and deployment of wavelength division multiplexing (WDM) technology are now evolving at a rapid pace to fulfill the increasing bandwidth requirement and deploy new network services. Routing and wavelength assignment algorithms play a key role in improving the performance of wavelength-routed all-optical networks. We study networks with dynamic wavelength routing and develop accurate analytical models for evaluating the blocking performance under dynamic input traffic in different topologies. Two dynamic routing algorithms are first developed and the performances of the algorithms in single-fiber WDM networks are studied using both analytical models and simulation. We also develop efficient algorithms to optimally place a given number of wavelength converters on a path of a network. Finally we consider the effect of multiple fibers on WDM networks without wavelength conversion. We develop analytical models for evaluating the blocking performance of multifiber networks with fixed-path routing, alternate-path routing, and fixed-path least-congestion routing algorithms. The number of fibers required to provide high performance in multifiber networks with different routing algorithms are also studied

Contribuição ao encaminhamento de comprimentos de onda em redes opticas WDM

Orientador: Ivanil Sebastião BonattiDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de ComputaçãoMestrad

Investigation of the tolerance of wavelength-routed optical networks to traffic load variations.

This thesis focuses on the performance of circuit-switched wavelength-routed optical network with unpredictable traffic pattern variations. This characteristic of optical networks is termed traffic forecast tolerance. First, the increasing volume and heterogeneous nature of data and voice traffic is discussed. The challenges in designing robust optical networks to handle unpredictable traffic statistics are described. Other work relating to the same research issues are discussed. A general methodology to quantify the traffic forecast tolerance of optical networks is presented. A traffic model is proposed to simulate dynamic, non-uniform loads, and used to test wavelength-routed optical networks considering numerous network topologies. The number of wavelengths required and the effect of the routing and wavelength allocation algorithm are investigated. A new method of quantifying the network tolerance is proposed, based on the calculation of the increase in the standard deviation of the blocking probabilities with increasing traffic load non-uniformity. The performance of different networks are calculated and compared. The relationship between physical features of the network topology and traffic forecast tolerance is investigated. A large number of randomly connected networks with different sizes were assessed. It is shown that the average lightpath length and the number of wavelengths required for full interconnection of the nodes in static operation both exhibit a strong correlation with the network tolerance, regardless of the degree of load non-uniformity. Finally, the impact of wavelength conversion on network tolerance is investigated. Wavelength conversion significantly increases the robustness of optical networks to unpredictable traffic variations. In particular, two sparse wavelength conversion schemes are compared and discussed: distributed wavelength conversion and localized wavelength conversion. It is found that the distributed wavelength conversion scheme outperforms localized wavelength conversion scheme, both with uniform loading and in terms of the network tolerance. The results described in this thesis can be used for the analysis and design of reliable WDM optical networks that are robust to future traffic demand variations

Effective fiber bandwidth utilization in TDM WDM optical networks

Ph.DDOCTOR OF PHILOSOPH