Routing and Wavelength Assignment (RWA) in an arbitrary mesh network is an NP-complete problem. So far, this problem has been solved by linear programming for network topologies with a few nodes, and sub-optimally solved for larger networks by heuristic strategies and the application of optimization algorithms such as Genetic Algorithms (GA), Particle Swarm Optimization (PSO), Differential Evolution (DE), etc. In this chapter, the authors present the use of Ant Colony Optimization (ACO) to find near optimal solutions to the routing and wavelength assignment problem in real sized networks with up to 40 nodes and 65 connecting links. They compare their results to the lower bounds obtained by the Nagatsu’s method, finding them to be equal or very close (one wavelength over) to them.
