On design of physical and logical topologies with fault-tolerant ability in wavelength-routed optical networks

We consider the problem of designing a network consisting of optical cross connects (OXCs) to provide end-to-end lightpath services for label switched routers (LSRs). Unlike previous work, we take into account the fault-tolerant ability of both physical and logical topologies. In addition, we present a novel routing policy that combines the shortest-path principle and the minimal-congestion rule. At the same time, we employ different wavelength assignment strategies for working lightpaths and protection lightpaths. We adopt the tabu search algorithm to find out the near optimal solution. Then we explore the lower bounds for the number of OXCs. We present numerical results for up to 1000 LSRs and for a wide range of system parameters, such as the number of wavelengths supported by each fiber link and traffic. The results indicate that it is possible to build a large-scale optical network with rich connectivity in a cost-effective manner, requiring relatively few, but properly dimensioned, OXCs.