Algorithms for Wavelength Assignment in All-Optical Networks

Abstract

This paper describes algorithms for solving the wavelength assignment problem in multi-wavelength transparent all-optical networks. In such networks, each connection is assigned a unique wavelength along the physical route and it is assumed that no wavelength conversion is allowed. The objective is to assign wavelengths to all connections in such a way that the number of wavelengths required, M, is minimised. Two techniques are considered in this paper. The first is based on the use of genetic algorithms (GAs) and the second is a simple heuristic algorithm. It was found that the former can be used to achieve an optimal value of M with a considerable reduction of computational time requirement compared to the extensive search approach. Hence this technique is appropriate in the case where the number of wavelengths available is strictly limited and an optimal value of M is highly desired. The heuristic algorithm does not perform as well as the genetic algorithm; although in some cases it performs exceptionally well. However, its computational time requirement is almost negligible; and results can be obtained swiftly. Therefore, it could be used to obtain a good starting value before an extensive optimisation is carried out. It also assigns wavelengths on a single connection basis which is independent of the previous connections assigned. This makes it particularly attractive in the situation where one or only a small number of new connections are to be established without having to modify the existing connections.