A post-optimization method to route scheduled lightpath demands with multiplicity

We consider a NP-hard problem related to the routing and wavelength assignment (RWA) problem in optical networks, dealing with scheduled lightpath demands (SLDs) with multiplicity. A SLD is a connection demand between two nodes of the network, during a certain time. Each SLD requires a given number of wavelengths (its multiplicity). Given a set of SLDs, we want to assign a lightpath (i.e. a routing path and the necessary wavelengths) to each SLD, so that the total number of required wavelengths is minimized. To solve the problem, we design a post-optimization method allowing to improve the solutions provided by a heuristic. Experimental results show that this post-optimization method is quite efficient to reduce the number of necessary wavelengths.