1. A method for minimizing the cost of an optical network, the optical network having a plurality of nodes connected by interconnecting optical fibers, and wherein a plurality of parameters are associated with the nodes and the fibers, the method comprising steps of: determining values for a first portion of the plurality of parameters; restricting values for a second portion of the plurality of parameters to have integer values; and solving a minimization objective function that includes at least some of the first and second portions of the plurality of parameters, to determine values for a third portion of the plurality of parameters, wherein a solution to the minimization objective function allows the cost of the optical network to be minimized.