A New Algorithm for Reducing the Number of Add-Drop Multiplexers in WDM Optical Ring Networks

This paper considers a network design problem introduced in 11,12 in which resource allocation is performed within a Wavelength Division Multiplexing (WDM) optical ring network to reduce overall equipment cost. The problem can be summarized as follows. The Add-Drop Multiplexers (ADM's) that are used to terminate lightpaths in an optical (SONET/SDH) ring are expensive and therefore a naive implementation that places ADM's for each wavelength at every node would waste expensive resources. However, by carefully assigning connections to wavelengths and routing the resulting lightpaths, one may avoid terminating all wavelengths at every node, and thereby reduce the number of ADM's needed. While Gerstel et al 11 consider wavelength assignment with respect to this problem, they do not consider the additional complication of routing. In this paper, we consider joint routing and wavelength assignment, and show that the number of ADM's required is signiicantly less than the number resulting from applying the heuristics in their paper. 11 Our algorithm analyzes connection requirements and, using a decomposition based on Euler paths, performs routing and wavelength assignment.