A new partitioning configuration that divides a given network into overlapped protection areas is investigated. If two working sub-paths are in the adjacent different working areas, their corresponding protection sub-paths can share a wavelength on the link that belongs to the overlap between two adjacent protection areas. The objective of overlapping is to increase sharing of the protection sub-paths that belong to the adjacent protection areas. The performances of resource utilization and recovery time are improved without any significant degradation of other performances.

In wavelength division multiplexed networks, shared path protection provides the same level of protection against a single fiber-link failure as dedicated path protection with potentially higher network utilization. The shared path protection is more complex to provision and maintain. In this paper, we introduce a parameter, the degree of sharing, which refers to the number of protection paths that a wavelength can be assigned to on a link. We propose methods for calculating the maximum degree of sharing. We consider on-line routing and wavelength assignment (RWA) of protection paths that are established for incremental traffic using the maximum degree of sharing. Establishment of protection paths using the maximum degree of sharing can simplify the algorithm. We compare the results on the decreased calculation time with accepted connection requests for a given number of wavelengths, assuming that wavelengths are assigned according to the First-Fit policy for working paths and Last-Fit policy for protection paths. The more wavelengths are used, the more calculation time can be reduced. When the load increases, the decreasing rate of calculation time also increases.