Physical layer impairments in optical networks can cause significant degradation of signal quality.In order to ensure QoS
it is necessary to consider these impairments and the resulted variations in the Routing and Wavelength Assignment(RWA)algorithm.This paper proposes an impairment-aware differentiated RWA algorithm and conducts numerical simulations of regular Mesh networks and Cernet networks.The results show that in the case of satisfying QoS demands
giving priority to ensuring the wavelength assignment for the high-class services in the networks reduces their blocking probability and improves the overall network resource utilization rate.