| 摘要 |
PURPOSE:To simplify the design of a receiving circuit and to reduce its size by generating light, holding the interference characteristics of a signal and by supplying accurate local oscillation light by performing injection synchronizing operation by using a semiconductor laser for a local oscillator. CONSTITUTION:A modulated signal from a transmitted-light source system 1 is transmitted to a receiving circuit 10 through an optical transmission line system 2. Then, the modulated light is split into two by a half-mirror 3; one is supplied to a square-law detector 9 through a half-mirror 6, and the other is supplied to an jnjection synchronizing semiconductor laser 7 by being reflected by a mirror 4. Injection synchronization is performed at the carrier frequency of the signal, and an oscillation frequency from the laser 7 becomes equal to the carrier frequency in terms of interference. Light from the laser 7 is incident to a shifter 8, whose modulation frequency is modulated by a value equal to an intermediate frequency fIF, and at a carrier frequency, output light fL=fC+fIF is incident to the detector 9 via mirrors 5 and 6. The detection output is a signal having a base-band frequency centering on the fIF. |
