Cost-effective routing in wavelength division multiplexing (WDM) optical networks using super lightpaths

In this study, we analyze the routing and wavelength assignment problem for one of the most recent applications of wavelength division multiplexing (WDM) networks, namely super lightpaths. We assume that the traffic is static and each node has the wavelength conversion capability. We try to determine the number of fibers to open for use on each physical link and the routing of the given traffic through super lightpaths so as to minimize the network cost, composed of fiber and wavelength usage components. The problem is proved to be NP-Hard and an integer linear program is proposed as an exact methodology to solve the problem for small scale networks. For larger network sizes, different heuristic approaches are developed. To evaluate the quality of the heuristic solutions, where optimal values are not available, the LP relaxation of the proposed model is strengthened through the use of valid inequalities. The heuristics are tested on a large set of varying network topologies and demand patterns. In terms of the deviation from lower bounds, the heuristic solutions attained are promising.