Due to the high computational complexity of exact methods (e.g., integer programming) for routing and wavelength assigment in optical networks, it is beneficial to decompose the problem into a routing task and a wavelength allocation task. However, by this decomposition it is not necessarily possible to obtain a valid wavelength assignment for a given routing because of wavelength continuity constraints in the network. This paper proposes an extension of the routing and network dimensioning subproblem that facilitates a subsequent wavelength assignment in the absence of wavelength converters. The extension anticipates wavelength continuity conflicts by limiting the maximum number of traversing lightpaths at each node. Such a limitation is derived from a lower bound on the number of conflicts, given a routing and network configuration. Preliminary computational experiments indicate that our approach can reduce the number of lightpath blockings significantly.
Appeared in Proceedings of the International Network Optimization Conference (INOC 2007), Spa, Belgium, April 2007.