| 摘要 |
PROBLEM TO BE SOLVED: To provide a multi-stage amplifying structure which is capable of efficiently using a pumping energy and utilizes a circulator which takes advantage of access to an amplifier so as to realize a spectral shaping and a filter processing. SOLUTION: An optical amplifier is equipped with an optical circulator 1 with four ports A, B, C, and D and optical fiber amplifiers 3, 5, and 7. At least, the other ends of the two optical fiber amplifiers 3 and 5 are connected to Faraday's rotation mirrors 15 and 17, and in result, signals are made to pass through the optical fiber amplifiers 3 and 5 twice. |
