Patent ID: 7609438

Claim:
An optical amplifier comprising: (1) a plurality of amplification units optically cascade-connected so as to sequentially amplify signal light of one or more signal channels having mutually different wavelengths, each amplification unit of said plurality of amplification units comprising: an optical input end for receiving signal light; an optical output end for outputting the amplified signal light; an amplifying optical fiber provided on an optical path between said optical input end and said optical output end; and a pumping light source for supplying pumping light entering a light incident end of said amplifying optical fiber together with the signal light; and (2) a timing adjustment system, in each of first and second amplification units selected from said plurality of amplification units, the timing adjustment system setting a delay time of a variation timing of pumping light power with respect to a variation timing of signal light power, wherein the delay time of said first amplification unit is set to positive and the delay time of said second amplification unit is set to negative.