| 摘要 |
PURPOSE:To obtain a wavelength multiplex receiving device of a coherent detecting system which can control a transmission wavelength characteristic with high accuracy by using a local oscillation light itself as a wavelength reference and aligning the transmission wavelength of a branching means with said wavelength. CONSTITUTION:Signal light beams 1-4 of four waves which is propagated through an optical fiber 50 are coupled to local oscillation light beams 6-9 of four waves in the same way by a directional coupler 5 and led into a branching filter 10. In the branching filter 10, the respective corresponding signal light beam and local oscillation light beams are branched together with each other, made incident on each receiving circuit 11-14 and brought to heterodyne detection. An average current of photodetectors of each circuit 11-14 is proportional to the intensity of the light beams 6-9 which are made incident on the respective circuits, therefore, a transmission wavelength characteristic of the branching filter 10 is adjusted by detecting by a current detecting part 37 so that said average current shows the maximum value. This adjustment can be controlled by changing a current of a control electrode 18 being a thermal resistance electrode attached on one waveguide 16 of two branch light beams and adjusting the optical length of the waveguide 16. |
