| 摘要 |
PROBLEM TO BE SOLVED: To reduce a gain difference between wavelengths as small as possible and also to increase a conversion efficiency from an excitation light input to a signal light output, by a method in which preceding-stage and succeeding-stage amplifying parts are respectively composed of each optical coupler for introducing excitation light from each excitation light source in an optical fiber for preceding-stage or succeeding-stage amplification use. SOLUTION: An optical amplifier 1 has preceding and succeeding amplifying parts 2a and 2b and the preceding and succeeding amplifying parts 2a and 2b are connected with each other via an isolator 4. The preceding-stage amplifying part 2a is provided with an excitation light source 7a for pumping an optical fiber 6a for preceding-stage amplification use and an optical coupler 8a for introducing excitation light from the light source 7a in the optical fiber 6a, while the succeeding-stage amplifying part 2b is also provided with an optical fiber 6b for succeeding-stage amplification use, an excitation light source 7b and an optical coupler 8b like the amplifying part 2a. As excitation light from the light source 7b of the amplifying part 2b is intercepted by the isolator 4 and exerts no effect on the amplifying part 2a, such excitation light power as to become proper gain wavelength characteristics can be independently set for making small to the utmost a gain difference between wavelengths in the amplifying part 2a. |
