| 摘要 |
PURPOSE:To inhibit the amplification of spontaneous emission light, which is generated by an optical amplification fiber, to make it possible to obtain a low noise and a high gain in an optical fiber amplifier. CONSTITUTION:When excitation lights, which are generated by excitation light sources 2 and 4, are introduced into an optical amplification fiber part 1 through multiplexer/branching filter 3 and 5, the excitation lights are by-pass via a multiplexer/branching filter 9, an optical fiber 12 and a multiplexer/branching filter 10 and optical amplification fibers 6 and 7 are excited. When signal light is inputted in the fiber part 1 in this state, the signal light is amplified by an induced emission while being propagated in the interior of the fiber 6 and moreover, the signal light is further amplified and is outputted while being propagated in the interior of the fiber 7 via the filter 9, an optical isolator 11 and the filter 10. Spontaneous emission light generated by the fiber 7 is intercepted by the isolator 11 via the filter 10 and is not propagated to the fiber 6 and an increase in a noise in the fiber 6 is prevented. |
