Routing in wavelength routed optical networks

We consider the routing problem that arises in the design of a virtual logical topology over a wavelength division multiplexed all optical network (AON). The logical topology is created by setting up lightpaths-end-to-end optical channels-created over the AON by suitable optical switching and routing. These lightpaths form the directed arcs of the logical topology. The combined problem of setting up lightpaths and routing of traffic over these lightpaths, in an optimal manner, is called the virtual topology design problem. The problem of designing such a topology and routing traffic over this topology with the objective of minimizing the network congestion while restricting the average propagation delay between source-destination pairs, and the degree of the logical topology, has been considered by Ramaswamy and Sivarajan (1996), and formulated as a large mixed linear integer program (MILP). For a given logical topology, the problem of optimal routing of traffic becomes a large linear program. We show that, by exploiting the special structure of this linear program, the routing problem can be managed and solved much more efficiently.