Chapter 10 - WDM Network Design

Abstract

This chapter studies the design of wavelength-routing networks. There is a clear benefit to building wavelength-routing networks, as opposed to simple point-to-point WDM links. The main benefit is that traffic, which is not to be terminated within a node, can be passed through by the node, resulting in significant savings in higher-layer terminating equipment. The design of these networks is more complicated than the design of traditional networks. It includes the design of the higher-layer topology (IP or SONET), which is the lightpath topology design problem, and its realization in the optical layer, which is the routing and wavelength assignment problem. These problems may need to be solved in conjunction if the carrier provides IP or SONET VTs over its own optical infrastructure. A practical approach may be to iteratively solve these problems. The chapter also discusses the wavelength-dimensioning problem. The problem is to provide sufficient capacity on the links of the wavelength-routing network to handle the expected demand for lightpaths. This problem is solved today by periodically forecasting a traffic matrix and (re)designing the network to support the forecast matrix. Alternatively, one can employ statistical traffic demand models to estimate the required capacities, and two such models are discussed. The absence of wavelength conversion in the network can be overcome by providing more wavelengths on the links. This trade-off under various models is studied in the chapter.