nonlinearities [1]. Typically, systems are designed such that these degrading effects are eitherminimized or compensated (e.g., using compensation fibers and devices). It has been widelyrecognized that as domains of transparency get larger, data rates of 10 Gb/s and higher becomemore common, and channel spacings are reduced, physical impairments will become a significantissue in making routing decisions within optical transmission systems and networks [2, 3] .