Switching and Traffic Grooming in WDM Networks

We consider the role of switching in minimizing the number of electronic ports (e.g., SONET ADMs) in an optical network that carries sub-wavelength traffic. Providing nodes with the ability to switch traffic between wavelengths, such as through the use of SONET cross-connects, can reduce the required number of electronic ports. We show that only small switches distributed among the nodes in the ring are needed for significant reductions in the number of ports. We characterize a class of network architectures that use both the minimal amount ADMs and the minimal amount of switching. We also give an algorithm for designing a topology that is efficient in both the required number of electronic ports and the amount of switching used.