Baroni, Stefano; (1998) Routing and wavelength allocation in WDM optical networks. Doctoral thesis (Ph.D.), University College London (United Kingdom).

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Abstract

This thesis investigates routing and wavelength allocation (RWA) in wavelength-division-multiplexed (WDM), wavelength-routed optical networks (WRONs). WRONs represent the most promising solution for high-capacity transport applications, providing efficient way to satisfy the increasing demand for bandwidth requirement and network flexibility. The most critical parameter in WRONs is the network physical topology onto which traffic demand has to be mapped, since it determines RWA, and, hence, resource and WDM transmission requirements. Although numerous investigations have addressed RWA problems in WRONs, little attention has been paid to the role of physical topology. It is, therefore, the focus of this thesis to investigate relationship between physical topology and network performance, the results being crucial to enable optimal network design. First, single-fibre WRONs are systematically analysed with uniform traffic demand, the figure of merit being the wavelength requirement Nx A new integer linear program (ILP) formulation is proposed for the exact solution of the RWA problem. Lower bounds on Nx are discussed, and RWA heuristic algorithms proposed. The results quantify the relationship between Nx and physical connectivity a, and highlights the negligible benefit achievable with wavelength conversion, or interchange (Wl), in the optical crossconnects (OXCs). It is shown that WRONs allow large wavelength reuse, resulting in large network throughput with a moderate number of wavelengths Nx, even in weakly- connected topologies. The comparison with regular networks shows that arbitrarily-connected WRONs provide scalability and flexibility, whilst maintaining similar wavelength requirements. The consequence of link failure restoration is then assessed. The results demonstrate the key role of physical topology on the increase in Nx, and the limited improvement achievable with WI. WDM transmission is studied by considering physical limitations imposed by wave length-dependent gain characteristic of erbium-doped fibre amplifiers (EDFAs). A simple algorithm for the absolute-wavelength assignment is proposed to compensate for gain non-uniformities in EDFA cascades, under condition of lightpath add/drop. In addition, a WDM optical amplifier configuration providing self-regulating properties is proposed to reduce management complexity in large-scale resilient WRONs. The design of multi-fibre WRONs is then investigated, by introducing the maximum number of wavelengths per fibre, W, as a parameter. Fibre requirement, FT, and resource utilisation are derived under different network conditions, including provisioning of basic demand, restoration, and traffic growth. Different restoration strategies are studied and compared. It is shown that the increase in FT to provide for restoration is governed by network physical connectivity. The analysis of traffic growth identifies the relationship between network size and connectivity, wavelength multiplicity W, and relative merits of WI. The presented algorithms and results can be used in the analysis and optimisation of WRONs.

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