POLARIZATION VARIANCE COMPENSATOR

摘要

PURPOSE:To compensate the degradation in transmission characteristic due the polarization variance of an optical transmission line only on the reception side and to follow up the secular change of the polarization variance characteristic of the optical transmission line. CONSTITUTION:An optical transmitter 61 includes the means to which a modulated signal having a prescribed frequency (f) is inputted and which superposes the frequency modulated signal on the optical signal, which has the intensity modulated by a transmission signal, and sends this optical signal to an optical transmission line 62. A polarization variance giving part 10 which gives the polarization variance of the characteristic opposite to that of the line 62 is provided in the preceding stage of an optical receiver 63. A polarization control circuit 20 which controls the polarization state of the optical signal passing the line 62 in accordance with a control signal and, a transmission line polarization main axis detector 30 which detects the difference between the output polarization main axis of the system consisting of the line 62 and the polarization control circuit 20 and that of the polarization variance giving part 20 from the frequency modulation component of the output optical signal of the circuit 20 and gives it to the circuit 20 as the control signal are provided.