Minimizing number of wavelengths in multicast routing trees in WDM networks

In a WDM network under multihop architecture, each link is associated with a set of wavelengths available for channel connections, and in the network, the number of wavelengths that can be used is limited. Data transmission o ver one wavelength to another requires wavelength conversion, which causes a long delay. Given a multicast connection, routing is to construct a tree for the connection that is rooted from the source and connects all destinat ions. In this paper, we consider the problem of constructing a routing tree with a minimal number of wavelengths on the tree. We first prove that this problem is NP-hard and then propose an approximation algorithm, which prod uces a routing tree that has not only a small number of wavelengths but als o a short delay from the source to all destinations. (C) 2000 John Wiley & Sons, Inc.