The transmission capacity of a link in today's optical networks has increased significantly due to wavelength-division multiplexing (WDM) technology. A unique feature of optical WDM networks is tight coupling between routing and wavelength selection. A lightpath is implemented by selecting a set or sequence of physical links between the source and destination nodes, and reserving a wavelength on each of these links for the lightpath. Thus, in establishing an optical connection we must deal with both routing (selecting a suitable path, i.e., sequence of physical links) and wavelength assignment (allocating an available wavelength for the connection (source-destination pair)). The resulting problem is referred to as the routing and wavelength assignment (RWA) problem, and is significantly more difficult than the routing problem in electrical networks. In this thesis, we offer a new heuristic algorithm to solve the RWA problem using Ant Colony Optimization (ACO) meta-heuristic. An edge disjoint path problem and a partition coloring problem are used to formulate the algorithm.