POLARIZATION CONTROLLER WITH AUTOMATIC PHASE MODULATOR

摘要

PURPOSE: A polarization controller is provided to always separate the output light of an incident light by 50% by means of a characteristic of a mode separator by electrically negative-feedbacking the intensity of the output light until the intensity of the output light becomes identical so as to automatically control phases of the incident light. CONSTITUTION: A polarization controller includes an optical fiber polarization separator(2). The optical fiber polarization separator(2) outputs an input light having a given polarization to two ports having a linear polarization state. A waveguide type 2x2 mode separator(6) receives the two outputs from the optical fiber polarization separator(2) to separate of the two input lights with the difference in the phase of the two input light by 90 degree maintained, so that the power of the output light becomes 50% of the input lights regardless of the polarization state of the input lights. A phase matching feedback circuit(16) detects the intensity of the two output lights from the waveguide type 2x2 mode separator(6) to differential-amplify the intensity by the difference between them and then controls the phase of the input lights inputted to the waveguide type 2x2 mode separator(6) to obtain a stable output power regardless of the polarization of the input light.