This paper proposes a routing and wavelength assignment (RWA) scheme that minimizes the number of required wavelengths for wavelength-reusable multi-carrier-distributed (WRMD) mesh networks. These networks have two unique features. First, only one light source, called the multi-carrier light source (MCLS), is required, which eases the difficulty of controlling many light source devices. Second, optical carriers are reused to improve the efficiency of wavelength usage. Since there are differences between the WRMD network and the conventional network, an efficient RWA scheme for the WRMD network is needed for wavelength-resource-efficient lightpath establishment. To realize efficient wavelength usage, we first formulate the RWA problem as an integer linear programming (ILP) problem of obtaining the minimum number of required wavelengths to satisfy the given requests. For large-scale networks, the ILP approach is not practical solution times. A heuristic RWA scheme is introduced in this paper to solve the RWA problem. Simulation results show that the proposed heuristic scheme with two carrier regenerations for the WRMD network approaches the near-optimum number of wavelengths. In addition, the optimum placement of the MCLS node is shown to reduce the number of required wavelengths for lightpath establishment, and achieve the optimum number of wavelengths. (C) 2014 Elsevier B.V. All rights reserved.