The focus of this chapter is to provide an analytical framework and to obtain some insight into how traffic grooming affects performance in terms of the call blocking probability in different network topologies. Specifically, the performance of constrained and sparse grooming networks are compared using simulation-based studies. Constrained grooming corresponds to the case where grooming is performed only at the SONET-ADMs on an end-to-end basis. Sparse grooming corresponds to the case where, in addition to grooming at the SONET-ADMs, the cross-connects at some or all of the nodes are provided with a traffic stream switching capability. The goal is to develop techniques to minimize electronic equipment costs and to provide solutions for efficient WDM network designs.

It has been established that wavelength conversion, that is, the ability of a routing node to convert one wavelength to another, reduces wavelength conflicts and improves the performance by reducing the blocking probability. Lower bounds on the blocking probability for an arbitrary network for any routing and wavelength assignment algorithm are known. It is further shown that the use of wavelength converters results in a 10–40% increase in wavelength reuse. A reduced load approximation scheme to calculate the blocking probabilities for the optical network model for two routing schemes, fixed routing and least-loaded routing, has been used in. This model does not consider the load correlation between the links. Analytical models of networks, using fixed routing and random wavelength assignment, taking wavelength correlation into account, have been developed in.