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 over 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 destinations. 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 produces a routing tree that has not only a small number of wavelengths but also a short delay from the source to all destinations. © 2000 John Wiley & Sons, Inc.