A Survey on Routing and Wavelength Assignment in WDM Optical Networks

This survey deals with the routing and Wavelength-Assignment (RWA) problem in wavelength-routed optical WDM networks. Most of the attention is devoted to such networks operating under the wavelength-continuity constraint, in which lightpaths are set up for connection requests between node pairs, and a single lightpath must occupy the same wavelength on all of the links that it spans. In setting up a lightpath, a route must be selected and a wavelength must be assigned to the lightpath. If no wavelength is available for this lightpath on the selected route, then the connection request is blocked. The RWA problem is examined and various routing and wavelength assignment approaches proposed in the literature are reviewed. This paper briefly considers the characteristics of wavelength-converted networks (which do not have the wavelength-continuity constraint), and examines the associated research problems and challenges.