Wavelength Assignment Algorithms and the Benefits of Wavelength Changers in WDM Ring Networks

Rick Barry, MIT Lincoln Laboratory

Wavelength Division Multiplexed (WDM) rings are becoming an attractive architecture for interoffice and backbone networks. In fact, commercial WDM ring network products have been anounced and will probably be available within a year from more than one vendor. WDM rings may be all-optical, where the signal remains in the optical domain from the source node (of the ring) to the destination node, or electro-optic, where conversion to electronics occurs at one or more intermediate nodes along the ring.

In either case, including the ability to change the wavelength of a signal at an intermediate node increases hardware costs. Wavelength changing is analogous to time slot interchange in TDM networks, however, unlike the latter case, wavelength changers can be prohibitively expensive.

In this talk, we will discuss the how much performance benefit wavelength changers provide for dynamic circuit switched traffic and present a wavelength assignment algorithm for operation of these networks. The algorithm is applicable to a variety of WDM ring architectures, including multifiber rings as well as rings with sparse wavelength conversion (wavelength conversion at a select number of nodes).