A methodology for topological design of metropolitan area networks employing optical WDM

We present a cost-efficient topology design technique for optical metropolitan area networks (MANs) using WDM. The network employs a topology with a two level hierarchy. The lower level physical topology is a passive optical star interconnecting a number of electrical local area networks (LANs), while the higher level physical topology uses a wavelength routing switch (WRS) at the center for intercluster communication. Thus the number of wavelengths as well as the optical links needed for the network has been significantly reduced as compared to that of the single level (i.e., non-hierarchical) counterparts. An algorithm has been proposed for the formation of clusters based on the geographical locations of the electrical LANs. The algorithm assigns more weightage to the total link cost as compared to the number of wavelengths required. When number of wavelength is found to be at a premium as compared to the link cost, the weightage can swung towards wavelength economy at the cost of increased overhead