Optical path managing device in an optical transmission network and a method thereof

A WDM communications line is used as a trunk to which an IP network or a SONET/SDH network is connected as a tributary. Additionally, an ID for identifying each wavelength or path, which is accommodated by a WDM communications line, is assigned to a frame of each wavelength. The ID for identifying a wavelength or a path, and the number held by a transmission device that configures the path are managed. When a fault occurs, the wavelength or the path on which the fault occurs is identified, and the identified wavelength or path is displayed on the screen of a supervisory control device that monitors the entire network. An administrator can recognize at first sight the path influenced by the fault other than the point at which the fault occurs, thereby efficiently maintaining and managing the network.