Network architectures for supporting survivable WDM rings

Wavelength division multiplexing (WDM) based networks consist of a logical topology, defined by a set of nodes and lightpath connections and a physical topology, defined by the set of nodes and the fiber connecting them. Although both the logical and physical topologies may be independently tolerant to single link failures, once the logical topology is embedded on the physical topology, the logical topology may no longer be survivable to single physical link failures. Each physical fiber link may carry multiple lightpaths. Hence, the failure of a single physical link, can lead to the failure of multiple links in the logical topology which may subsequently leave the logical topology disconnected. Our focus is on the design of physical topologies capable of supporting ring logical topologies in a survivable manner. While there has been a great deal of work in the area of optical layer protection, this survivable routing formulation is a new approach to network protection that has significant implications on the design of future WDM-based networks.