SUMMARYThe exchanged hypercube, denoted by EH(s, t), is a graph obtained by systematically removing edges from the corresponding hypercube, while preserving many of the hypercube's attractive properties. Moreover, ring-connected topology is one of the most promising topologies in Wavelength Division Multiplexing (WDM) optical networks. Let R n denote a ring-connected topology. In this paper, we address the routing and wavelength assignment problem for implementing the EH(s, t) communication pattern on R n , where n = s + t + 1. We design an embedding scheme. Based on the embedding scheme, a near-optimal wavelength assignment algorithm using 2 s+t−2 + 2 t /3 wavelengths is proposed. We also show that the wavelength assignment algorithm uses no more than an additional 25 percent of (or 2 t−1 /3 ) wavelengths, compared to the optimal wavelength assignment algorithm.