Abstract: A method for solving routing and wavelength assignment (RWA) problems for all-optical networks involves formulating a joint optimization problem in which the routing of lightpaths and assignment of wavelengths on links of those routes to the lightpaths is expressed jointly in terms of a single optimization criterion. The method features formulation of the joint optimization problem as a continuous variable optimization problem with a convex constraint set. Integer constraints, for example, related to the fact that any particular lightpath is not permitted to split over multiple routes or over separate wavelengths on a link of its route, are not necessarily represented explicitly by the constraint set. However, the formulation of the objective function is such that although the problem is formulated in terms of continuous optimization variables, optimal solutions to the problem are integer or equivalent to an integer solution, thereby satisfying the integer constraints.