| 摘要 |
PURPOSE:To realize a coherent light communication system which can be applied to a high speed system and consists of a simple constitution by multiplying a first intermediate frequency signal obtained by multiplexing a signal light and a local oscillation light by an optical coupler by a sine wave signal and a cosine wave signal from an oscillator, respectively and multiplexing its multiplication signals. CONSTITUTION:A first intermediate frequency signal is obtained by multiplexing a signal light 1 and a local oscillation light 2 to which a sufficiently small frequency difference is given against a base band zone by an optical coupler 3 and thereafter, bringing them to opto-electric conversion by a photodetector 4. This first intermediate frequency signal is multiplied by a sine wave signal and a cosine wave signal from an oscillator 5, respectively, and by multiplexing these multiplication signals by a 90 deg. hybrid coupler 6, a second intermediate frequency signal is obtained. This second intermediate frequency signal is demodulated asynchronously. In such a way, a coherent light receiving system which is suitable for improving a transmission rate, whose request to spectral line width of a light source is not strict, and also, whose constitution is simplified can be offered. |
