 The algorithm constructs paths, starting at the source and going towards the destination.But, at each iteration, the algorithm is rid of all paths that are guaranteed to violate the constraints, thereby keeping only those partial paths that have the potential to be turned into feasible paths, from which the optimal paths are drawn.Liu also proposed a special class of Optical devices called SPIDER (2001, ); optical routers, dense wavelength division multiplexing (DWDM) systems, and cross-connects of unprecedented capacities.