The protection lightpaths in 1∶1 protection and shared protection are "virtual" in fault-free case.Based on this,we propose a power-efficient routing and wavelength assignment approach for 1∶1 protection,called PA algorithm,which aims to maximize the usage of active fibers carrying working lightpath,minimize the number of active optical repeater devices,and hence that reduce the electricity power consumption of an optical network.Simulation results indicate that the new approach can achieve sign...