An optical transmission apparatus connected to an optical ring network stores identification information of an optical transmission apparatus as a communication partner predetermined on a communication path. Each optical transmission apparatus includes self identification information in header information of an optical signal having a working wavelength used in normal operation, and transmits the optical signal to one of the two optical ring networks transferring optical signals in mutually opposite directions. The optical transmission apparatus determines whether the identification information included in the header information of the received optical signal having the working wavelength matches pre-stored identification information. The optical transmission apparatus thus detects a fault that occurs by the communication path. The optical transmission apparatus having detected the fault requests the communication partner to transmit the optical signal on a backup wavelength in the optical ring network opposite in direction to the optical ring network in the normal operation.