| 摘要 |
PURPOSE: To constitute the device with a minimum number of components by providing only two adjustable elements which affect a polarization state. CONSTITUTION: To achieve the best modulation transmission, the polarization state of a signal beam needs to be equalized to the polarization state of a local oscillator beam even if the signal beam changes in polarization state. To compensate their phase shift, two adjustable elements 51 and 52 which affect the polarization state are arranged in the radiation optical path of the signal beam. Then the adjustable elements 51 and 52 are controlled through connection parts 71 and 72 with the control signal from a control circuit 70. Therefore, displacement from the best adjustment state is made very small, so the best adjustment is made by detecting the change in the polarization state of the signal beam. Consequently, the device is constituted of the least number of components. |
