PURPOSE: To stabilize the intermediate frequency(IF) signal power of an optical heterodyne polarization diversity receiver by measuring the power of the IF signal corresponding to each polarized wave of signal light and selecting only the IF signal having the higher IF signal power.
CONSTITUTION: A part of the IF signals of p-polarized and s-polarized wave components is branched by branching parts 4 and 4', and a part of branched signals is branched by branching parts 41 and 41' furthermore. Signals branched by branching parts 41 and 41' are inputted to power detectors 61 and 61' in a measuring means 6 to monitor the IF signals of respective polarized waves. IF signal powers detected by the measuring means 6 are inputted to a switch control circuit 71 in a selective means 7, and the IF signal having the higher power is outputted from a micro wave switch 72 in accordance with magnitudes of IF signal powers. The frequency of a local light source is automatically controlled by this signal.
NAITO TAKAO
ONAKA HIROSHI
KUWABARA HIDEO
IMAI TAKAMASA
NIPPON TELEGRAPH & TELEPHONE