Sparse placement of electronic switching nodes for low blocking in translucentoptical networks

We evaluate the performance of optical network designs using relatively few switch nodes at which wavelength conversion and electronic regeneration is possible. A simple heuristic for placing the fewest such nodes to reach a given blocking probability is based on the ranked frequency of shortest-path routes transiting each node. This strategy is found to be efficient in designing a translucent optical network with sparse electronic switch placement that performs very close in blocking to that of an opaque optical network. In addition, we apply a new two-dimensional Dijkstra algorithm for routing and wavelength assignment in the resultant translucent optical network. Simulation results indicate that a translucent optical network with sparse electronic switch placement based on the heuristic has much lower blocking than a fully transparent optical network when the constraint of the maximum transparent distance before regeneration is also considered. Moreover, when the switches are placed according to the heuristic, lightpath blocking can approach that of a fully opaque network with significantly fewer total electronic switches. In our results, lightpath blocking as low as that with the fully opaque network case was obtained with electronic switches selectively placed at approximately one node in three on average. The heuristic also performs well against random searching for an effective subset of electronic switch nodes and performs better than a prior optimal method that is based on a combinatorially exhaustive search and that is limited to assuming fixed shortest-path routing.