BATCH POLARIZATION CONTROL METHOD

摘要

PURPOSE:To suppress the influence of polarization dispersion by allowing the relative polarization states of the locally oscillated light in respective signal receivers which respectively separately receive plural beams of signal light to coincide with each other. CONSTITUTION:Three beams of the signal light 1 of the 1st to 3rd channels subjected to frequency multiplexing are passed through a 1st polarization controller 2 which controls the polarization by impressing a pressure to optical fibers and are then separated by an optical branching circuit 7 to be made incident to 1st to 3rd signal receiving systems 4 to 6 where the respective beams are subjected to optical heterodyne detection and reception. The level of the IFA signal obtd. by the optical heterodyne detection is detected and outputted by an envelope detecting circuit at the 2nd receiving system 5. A 1st controller 3 controls the operation of the 1st polarization controller 2 in such a manner that the IFA signal levels attains always the max. level. The polarization maintaining optical fibers 9 are used between a local oscillation light source 8 and the signal receiving circuit as the means for allowing the polarization states of the locally oscillated light to coincide with each other. The deterioration in the sensitivity of the signal reception induced by the polarization dispersion of the optical fibers is minimized in this way.