| 摘要 |
PROBLEM TO BE SOLVED: To provide a light amplifier stably having a large gain, even when the intensity of an input signal light is small. SOLUTION: A closed loop constituted of a pre-light amplifying part 30, an optical demultiplexer 40, a light feedback part 60, and an optical multiplexer 20 constitutes a traveling wave type laser oscillator, and laser oscillation is operated with the passage wavelength of an optical band pass filter 62 of the light feedback part 60. Inversion distribution in an EDF 34 of the pre-light amplifying part 30 is fixed, and the gain of a signal light in the pre-light amplifying part 30 is maintained to be constant according to the laser oscillation. A signal light outputted from the pre-light amplifying part 30 is allowed to pass through an optical filter 70, inputted to a post-light amplifying part 80, further amplified with a constant gain, and outputted. |
