Patent ID: 7664392

Claim:
An automatic power restoring method, in which, in an optical communication system for supplying a pumping light for Raman amplification from an optical receiving station side to an optical transmission path connecting between an optical transmitting station and an optical receiving station, and for transmitting a main signal light sent out from the optical transmitting station to the optical receiving station via the optical transmission path while amplifying the main signal light, a power state at an occurrence of line fault in which the power of a light output from the optical transmitting station or the optical receiving station to the optical transmission path is suppressed to a predetermined level or lower, is restored to a power state at a time of normal operation according to a detection of continuity by dissolution of line fault, comprising: when a line fault occurs, controlling said pumping light for Raman amplification at the power of said predetermined level or lower to switch to a pilot signal light, to send out the pilot signal light from the optical receiving station to the optical transmission path; and detecting continuity by receiving at the optical transmitting station the pilot signal light sent out to the optical transmission path, to restore the power state at the occurrence of line fault to the power state at the time of normal operation.