Survivable WDM mesh networks. II. Restoration

This investigation considers optical networks which employ wavelength cross-connects that enable the establishment of wavelength-division-multiplexed (WDM) channels, between node-pairs. In such and other networks, the failure of a network element may cause the failure of several optical channels, thereby leading to large data losses. Ramamurthy and Mukherjee formulated integer linear programs to determine the capacity requirements for different protection schemes for a static traffic demand. In this paper, we formulate a model of protection switching times for the different protection schemes, and propose distributed control protocols for path and link restoration, assuming a fully distributed control network. Based on our assumptions, we find that when the cross connect configuration time is low (⩽10 μs), the protection schemes in increasing order of average protection-switching times are as follows: (a) shared-link, (b) dedicated-path, and (c) shared-path. When the cross-connect configuration time is high (⩾500 μs), the protection schemes in increasing order of average protection-switching times are as follows: (a) dedicated-path, (c) shared-link, and (d) shared-path. Numerical results obtained by simulating the distributed restoration protocols indicate that, for a representative network topology, path restoration has a better restoration efficiency than link restoration, and link restoration has a better restoration time compared to path restoration