| 摘要 |
PURPOSE:To obtain intensity-modulated light with a small noise by amplifying a weak signal in an optical fiber by using a backward Brillouin scattered light and amplifying some frequency component of signal light on an optical transmission line after modulation is imposed variously. CONSTITUTION:Signal light from a coherent signal light source 1 to which an oscillator 2 is connected so as to modulate the light source 1 is made incident on one end of an optical fiber 3 as the optical transmission line and output light from the other end is sent to a detector 7 as a demodulator through a photodetector 6. This constitution is provided with an optical multiplexer demultiplexer 4 which multiplexes or demultiplexes light waves between the light source 1 and photodetector 6, and an exciting light source 5 with good coherency for exciting induced Brillouin scattered light is connected thereto. Thus, a method which amplifies the whole signal light is not employed and the degree of modulation of the intensity-modulated light which is made incident on the photodetector 6 is made to correspond to the degree of amplification, thereby improving the ratio of the amplified part and unamplified part, i.e. SN ratio.
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