In this paper, we study routing and wavelength assignment (RWA) tasks in WDM mesh networks with wavelength conversion capabilities. For each lightpath request, we solve the routing and wavelength assignment sub-problems as a single problem, rather than separating them into two separate problems. We use four different optimization criteria: (1) minimize the number of wavelength conversions (2) minimize the number of wavelengths used (3) minimize the hop count and (4) minimize the use of scarce

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... sources (trunking). Each of these problems is solved by a Dijkstra type of algorithm, executed sequentially on one request at a time. We also develop an integer linear programming (ILP) model with the objective to minimize the number of wavelength conversions. The optimal ILP solution can only be obtained for small networks. We conduct a comprehensive simulation study of the performance of the algorithms for different network topologies and traffic scenarios.