A Genetic Algorithm for Routing in WDM Optical Networks with Power Considerations Part I: The Unicast Case

Routing and wavelength assignment (RWA) is an important problem that arises in wavelength division multiplexed (WDM) optical networks. Previous studies have solved many variations of this problem under the assumption of perfect conditions regarding the power of a signal. In this paper, we investigate this problem while allowing for degradation of routed signals by components such as taps, multiplexers, switching elements, fiber links, etc. It is assumed that inline optical amplifiers are preplaced on individual fiber links at the physical design stage. We investigate the problem of routing the maximum number of connections while maintaining proper power levels. The problem is formulated as a mixed-integer nonlinear program. To overcome the complexity of the problem, we divide the problem into two parts. First, we solve the pure RWA problem using fixed routes for every connection. Second, power assignment is accomplished by either using the smallest-gain first (SGF) heuristic or using a genetic algorithm. Numerical examples on a wide variety of networks show that (a) the number of connections established without considering the signal attenuation was most of the time greater than that achievable while considering the power and (b) given adequate time, the genetic solution quality was much better than that of SGF, especially when the conflict graph of the connections generated by the linear solver is denser.