Design Problems in Robust Optical Networks DESIGN PROBLEMS IN ROBUST OPTICAL NETWORKS

The goal of the paper is two-fold. First, the paper formulates a set of optimization problems relevant for the design of optical WDM networks robust to failures, encompassing demand routing, wavelength assignment and link dimensioning. Two basic protection mechanisms are considered: path diversity and single backup path restoration. The design problems, taking directly into account a scenario of assumed failure situations, are formulated as mixed linear integer programming tasks. For small networks these tasks can be solved directly with the branch and bound approach available e.g. in the CPLEX optimization package. As the considered problems are NP-complete, for networks of realistic size heuristic methods are called for. Accordingly, the second goal of the paper is to demonstrate how to apply two proposed stochastic heuristic approaches, namely Simulated Annealing and Simulated Allocation, to the specified problems. It is shown using large network configurations that the latter approach, although not commonly known, turns out to be superior to the former, and yields good sub-optimal solutions in reasonable time. Our numerical results also show what extra spare capacity volume is required by the considered protection mechanisms. This can help solving the tradeoff between the reconfiguration complexity and the extra link and node capacity cost. Acknowledgement This work was partly carried out under the Explain project sponsored by the Danish Academy of Technical Sciences. Design Problems in Robust Optical Networks