PURPOSE: To prevent the fluctuation of phase difference by splitting returned light and locally oscillated light into orthogonal polarized-light components, performing optical heterodyne detection, offseting the phase difference between the orthogonal polarized-light components at the optical wave stage in the state of the electric signal after the detection, and performing addition.
CONSTITUTION: Returned light 13 in the state of polarized light and locally oscillated light are split into the polarized-light components in the directions X and Y in a polarized-light beam splitter 2 through an optical directional coupler 1E. The polarized-light components of the returned light 13 in the directions X and Y and the polarized-light components of the locally oscillated light 12 in the directions X and Y are synthesized. The optical heterodyne detections are performed in photodetectors 3A and 3B. The signal of the frequency difference Δf between the returned light 13 and the locally oscillated light 12 is obtained. The outputs from the photodetectors 3A and 3B are inputted 5A and 5B into a phase corrector 5 through detectors 4A and 4B. In adder 6, the outputs from the detector 4A and the corrector 5 are added. Thus, the fluctuation of the phase difference between the orthogonal components of the polarized lights is prevented.
TAKEDA TOSHIYUKI
MATSUURA SATOSHI
