Patent ID: 7688501

Claim:
An optical amplification method for an optical transmission system including a plurality of first light sources for Raman amplification that amplify signal light transmitted in an optical transmission line and a plurality of second light sources for Raman amplification that are disposed at positions adjoining respective members of said plurality of first light sources for Raman amplification via said optical transmission line, comprising the steps of: amplifying said signal light by said first light sources for Raman amplification; transmitting said amplified signal light through said optical transmission line; providing one or more spare pumping light sources only among said plurality of second light sources for Raman amplification, the number of said second light sources being less than the number of said first light sources, a number of said first light sources not having spare pumping light sources, interveningly positioned between two of said second light sources being determined by a permissible failure rate of the optical transmission system; detecting a deteriorated state of said signal light amplified by one or more of said first sources for Raman amplification; and restoring said deteriorated signal light to an un-deteriorated state by emitting spare pumping light from at least one of said spare pumping light sources, said spare pumping light sources being operated only when required to restore deteriorated signal light.