Impairment-aware protection in optical WDM networks

In WDM networks, optical reachability is limited by physical impairments introduced by fibers and cascading optical components. In the network design phase, 3R regeneration (reamplifying, reshaping, and retiming) can be placed sparsely at a set of network nodes in WDM networks for extending optical reach and is currently realized by converting the optical signal to the electronic domain and optically retransmitting the signal. Regenerators used for 3R regeneration are expensive. It is very important to find protected paths with the minimum number of regenerators in order to reduce the total network cost. In this talk, we consider the problem of finding two disjoint paths in an optical WDM network with optical reachability constraints that are imposed by physical impairments. Routing for disjoint paths with the minimum number of regenerators is shown to be a NP-complete problem. We propose heuristic algorithms to find disjoint working and protection paths whose total number of regenerators is minimal. The proposed algorithms are able to verify the optimality of the solution if a pair of disjoint paths is found.