A Route Assignment Algorithm for Fault-tolerant Clos Networks in Optical Switches

A route assignment algorithm for fault-tolerant Clos networks, which is commonly used for design of optical switches, is proposed in this paper. The algorithm is based on a newly proposed edge coloring method, called complex coloring. The route assignment in three-stage fault-tolerant Clos networks is formulated as an edge coloring problem of bipartite graphs. The extra switch modules in the middle stage of fault-tolerant Clos networks provide additional colors for edge coloring. In complex coloring, those redundant colors help to reduce the running time of the coloring process. Therefore, as the number of extra switch modules increases, the time complexity can be substantially improved along with the reliability of switching systems. The performance of our algorithm has been verified by extensive simulation experiments.