The all-optical transparent wavelength routed network is a promising candidate for the next-generation backbone network to provide large bandwidth at low cost. Due to transmission impairments, present in fibers and optical components, may significantly affect the quality of a lightpath, and, hence, in wavelength routed transparent optical networks, the best routing optimization, which is determined only by network-layer performance, might not be the best one or even worse after physical-layer performance taken into account. In order to overcome the above limitation, in this paper, we propose that routing optimizations should be evaluated from both network-layer performance and physical-layer performance and the best routing optimization should be chosen based on the overall performances, not just the networklayer performance.