Abstract: The current fast-growing Internet and multimedia applications are demanding more and more network capacity every day. Wavelength division multiplexing (WDM) appears to be the solution of choice for multiplying network capacity. Wavelength conversion is the key technology in contention resolution for WDM switching networks. In this paper, we introduce a systematic approach to the analysis of the permutation capability of WDM switching networks with limited-range wavelength conversion. Such analysis requires nontrivial extensions from that of a traditional electronic switching network. Using our model we demonstrate that the performance of a WDM network with limited-range wavelength conversion is greatly improved over that of a WDM network with no wavelength conversion in terms of permutation capacity.