An effective approach to the connection routing problem of all-optical wavelength routing DWDM networks with wavelength conversion capability

The emergence of DWDM (dense wavelength-division multiplexing) technology has provided the network designer great convenience in constructing a wavelength routing optical network. In this paper, we study the problem of routing and wavelength assignment (RWA) in an all-optical DWDM network. We formulated the problem into a constrained integer linear problem (ILP) and the objective is to minimize the overall cost of the routing scheme over the DWDM network. Considering the complexity of the RWA problem, a decomposition approach using Lagrangean relaxation is proposed to simplify the solution procedure. The overall problem is decomposed into semi-lightpath level subproblems for the wavelength and route selection from the source to the destination. The multipliers are then updated at high level. To optimize the dual function, subgradient approach is used. Also, a heuristics algorithm is proposed to generate a feasible RWA scheme based on the dual solution. The performance evaluation for the optimization result of one network example indicates that the algorithm we used can achieve very good near-optimum solution, and the influence from the changing of the number of resources is also studied.