Constraint Satisfaction in Optical Routing for Passive Wavelength-Routed Networks

Awavelength-routed, optical network employs all-optical channels (lightpaths) on multiple wavelengths to establish a rearrangeable interconnection pattern (virtual topology) for transport of data. A lightpath may span multiple ber-links, and may be routed optically at an intermediate node without undergoing electronic conversion. We examine the problem of establishing a set of lightpaths in an optical network, which employs a passive wavelength routing device called a Latin Router (LR). Latin Routers are attractive for optical network design because of their fault-tolerance and low cost, but make traditional routing algorithms difcult to implement due to the complexity of the constraints they impose on legitimate routes and colors. We employ a local search algorithm to search the space of virtual topologies in order to satisfy a maximum number of given lightpath requests. We use the same algorithm to maximize the number of single-hop connections for a given network. We show that the algorithm can satisfy a high percentage of lightpaths under low to moderate network loads. Experiments reveal that we can establish O(N) lightpaths in an optical network with N nodes. We believe that our work is the rst known attempt at designing optical wide-area networks using Latin Routers.