| 摘要 |
PROBLEM TO BE SOLVED: To improve the efficiency of an optical amplifier, etc. SOLUTION: In an optical amplifier, a signal light is amplified by inputting respectively to an optical amplifying medium 2 whereto the signal light is inputted first and second excitation lights in the equal and opposite directions to the signal light. In the optical amplifier, by making different the wavelengths of the first and second excitation lights from each other, the first and second excitation lights are so branched respectively from a first wavelength selecting filter 4 provided on the output side of the signal light of the optical amplifying medium 2 and from a second wavelength selecting filter 6 provided on the input side of the same as to make possible the monitorings of the excitation lights. |
