| 摘要 |
PROBLEM TO BE SOLVED: To eliminate phase noise and to discriminate modulation signals by heterodyne-receiving modulated waves, obtaining difference frequency signals from beat signals due to carrier frequency components and modulation side band wave components and sending them to a signal receiver. SOLUTION: A receiver A sends out carrier waves from a laser light source 101 through an isolator 102, an optical multiplexing/branching circuit 103 and an optical transmission line 108 to respective transmitters 1 and 2. In the meantime, the respective transmitters 1 and 2 modulate the carrier waves in a modulator 111 and outputs the modulated waves through the optical multiplexing/ branching circuit 109 and the isolator 110. The modulated waves reach the receiver A and are inputted through the optical multiplexing/branching circuit 103 to a heterodyne receiver 105. In this case, heterodyne reception is performed by using a carrier wave frequency from a local light source 104 and the beat signals due to the carrier frequency components and the modulation side band wave components are obtained. A difference frequency signal detection circuit 106 obtains the difference frequency signals from the beat signals and sends them to the signal receiver 107. Thus, the phase noise is eliminated and the modulation signals are discriminated. |
