We consider the routing and wavelength assignment (RWA) problem for large-scale WDM optical networks where each transmission request is served by an all-optical lightpath without wavelength conversion. Two heuristic RWA algorithms are proposed in order to minimize the number of wavelengths required for a given set of connection requests. The proposed algorithms are evaluated and compared with the existing algorithms for two realistic networks constructed based on the locations of major cities in Ibaraki Prefecture and those in Kanto District in Japan.

In optical networks, wavelength converters are required to improve the efficiency of wavelength-division multiplexing. In this paper, we propose a genetic algorithm to determine the optimal locations of the nodes in the network where a given number of converters are placed. Optimality is achieved by the minimum wavelength blocking probability. Our algorithm is applied to two realistic networks constructed from the locations of major cities in Ibaraki Prefecture and from those in Kanto District in Japan and is shown to reach the nearly optimal solution in a limited number of generations. The accuracy is verified by simulation. The computational time is compared with that of an exhaustive search algorithm.

We consider the multicast routing problem for large-scale wavelength division multiplexing (WDM) optical networks where transmission requests are established by point-to-multipoint connections. To realize multicast routing in WDM optical networks, some nodes need to have light (optical) splitting capability. A node with splitting capability can forward an incoming message to more than one output link. We consider the problem of minimizing the number of split-capable nodes in the network for a given set of multicast requests. The number of wavelengths is fixed and given a priori. We propose a genetic algorithm that exploits the combination of alternative shortest paths for the given multicast requests in order to minimize the number of required split-capable nodes. This algorithm is examined for two realistic networks constructed based on the locations of major cities in Ibaraki Prefecture and those in Kanto District in Japan. Our experimental results show that the proposed algorithm can reduce more than 10% of split-capable nodes compared with other routing algorithms whereby the optimization for the split-capable node placement is not taken into account.