| 摘要 |
PROBLEM TO BE SOLVED: To obtain an optical amplifier which can obtain a function equal to that in a case in which an optical isolator and an optical multiplexer are used by a method wherein a three-port optical circulator is arranged on the output side of signal light from a rare-earth-doped optical fiber. SOLUTION: An optical amplifier 10 is provided with a rare-earth-doped optical fiber 11 which has a function to amplify a light signal, with an exciting light source 12 which generates a population inversion in the electron level of a rare-earth element in the optical fiber 11 and with a wavelength multiple optical multiplexer 13 which multiplexes an optical output with the rare-earth-doped optical fiber 11. In addition, a three-port optical circulator 14 is arranged on the output side of signal light from the rare-earth-doped optical fiber 11. Then, the signal which has been amplified by the rare-earth-doped optical fiber 11 is made incident on a first port 14A at the optical circulator 14, its signal light is output to a second port 14B and a third port 14C at the optical circulator 14, and output branched light is detected by a photodetector 19. Thereby, it is possible to realize a function which is equal to that in a case in which both an optical isolator and an optical multiplexing and branching filter are used. |
