| 摘要 |
PURPOSE: To improve the noise index of a fiber amplifier by proving an attenuating fiber means for attenuating a signal part that advances to the output terminal part of a gain fiber means, through a secondary passage. CONSTITUTION: An attenuating fiber 22 is arranged between a pump fiber 16 and a coupler fiber 12. The optical characteristic of the attenuating fiber 22 attenuates a signal beam with a wavelength ofλs , but a pumping power with a wavelength ofλp is propagated with an extremely low loss. Therefore, essentially all pump power from a source 15 reaches a gain fiber 10, but a signal beam from the gain fiber 10 is separated from the pump source. An S/P ratio (the ratio between an attenuation of a signal wavelength and that of a pump wavelength) depends on the specific amplifier. Normally, the S/P ratio must as high as possible. However, probably a pump power loss of approximately 3 dB will be allowed, when an excessive pump power exists. |
