Patent ID: 7286758

Claim:
A method for switching a transmission route for use in transmission from a transmission station to a receiver station in an optical network in which the transmission station and the receiver station are connected through a plurality of transmission routes with redundancy, comprising the steps of: (a) in a switch unit of a regenerator station disposed between the transmission station and the receiver station, extracting a main signal having a predetermined wavelength from a first one of the plurality of transmission routes, receiving a first optical signal, and inserting the first optical signal into the predetermined one of the plurality of transmission routes; (b) converting the main signal extracted from the predetermined one of the plurality of transmission routes into an electric signal, and detecting an input level of the main signal, in the regenerator station; (c) in a transmitter of the regenerator station, converting the electric signal into a second optical signal, inputting the second optical signal into the switch unit of the regenerator station as the first optical signal when the input level is equal to or higher than a predetermined level, and stopping output of the second optical signal when the input level is lower than the predetermined level; (d) transmitting a control signal indicating occurrence of a failure, from the regenerator station through a transmission route to the receiver station, when the input level is lower than the predetermined level; and (e) in the receiver station, switching a transmission route from which the receiver station acquires the main signal, from the first one of the plurality of transmission routes to a second one of the plurality of transmission routes, when an input level of the main signal at the receiver station is lower than a predetermined level or when the receiver station receives the control signal.