—Existing research demonstrated that an effective Routing and Wavelength Assignment (RWA) scheme and a wavelength converter placement algorithm are the two primary vehicles for improving the blocking performance in a wavelength-routed all-optical network. However, these issues have largely been investigated separately, in particular, the RWA has seldom considered the existence of wavelength converters. In this paper, we argue perhaps for the first time, that an effective RWA algorithm needs to take into account the presence of wavelength conversion as the later is usually done at much earlier stage during the capacity planning. We proceed to show that existing dynamic RWA algorithms largely fail in the presence of wavelength conversion. We then propose a weighted least-congestion routing and first-fit wavelength assignment (WLCR-FF) RWA algorithm in conjunction with a simple heuristic wavelength converter placement algorithm called Minimum Blocking Probability First (MBPF) that consi...