Minimizing the number of optical crossconnect ports in mesh networks based on bidirectional line-switched WDM self-healing ring protection

The design of survivable all-optical mesh networks based on bidirectional line-switched WDM (wavelength division multiplexed) self-healing rings (SHR/WDM) to provide full protection against any single line fault requires the solution of three sub-problems: determining the ring cover of the mesh topology, determining the routing of the working lightpaths (paths of light) between the node pairs that originate traffic demands, determining the allocation of the spare wavelengths in each ring required to protect every line in the mesh that supports traffic. A working lightpath can span over multiple rings, thus requiring one crossconnect I/O port at each node that connects two adjacent rings along its path. This paper addresses the problem of minimizing the total number of optical crossconnect I/O ports that are required in the mesh to support a set of traffic demands. The problem is solved under two design scenarios. In the first scenario we derive the minimum number of crossconnect ports necessary in a mesh network with a given ring cover and given routes for the working lightpaths. Once the number of crossconnect ports are minimized, the network total (working and protection) wavelength mileage is minimized by balancing the traffic in each ring. In the second scenario the ring cover, the routing for the working lightpaths and the spare wavelengths in each ring are first computed in such a way to minimize the total wavelength mileage. With this network configuration we then minimize the number of crossconnect ports. The presented solutions provide the designer with two alternative approaches that trade one cost function, i.e., the number of crossconnect ports, for the other, i.e., the total wavelength mileage.