| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical amplifier which has a stable gain characteristic to input signal light power. SOLUTION: In this optical amplifier which has a rare earth added optical fiber 1 which is excited by a exciting light and amplifies a light, and a feedback means which selectively feedbacks a light of a part of wavelength band out of amplified wavelength band to the rare earth added optical fiber 1, a first detecting means detecting amplified signal light and a part of spontaneous emission light, and a second detecting means detecting a part of a laser- oscillation light due to feedback, are installed. The power of an excited light is controlled on the basis of outputs of the first detecting means and the second detecting means. |
