| 摘要 |
PURPOSE: To prevent light radiated from a local oscillator from being returned to a transmitting optical fiber by providing the light receiver with a means capable of preventing light radiated from the local oscillator from arriving at the input part of the receiver itself. CONSTITUTION: A signal beam is branched to two optical beams 33, 34 by a polarized beam splitter(PBS) 30 through an optical fiber 21. On the other hand, light radiated from the local oscillator 40 is branched to two straight polarized beams 43, 44 by a PBS 42. A conversion element 45 executes conversion so that the polarization of beams propagated through fibers 43, 33 and 44, 34 is made equal. Signal beams outputted from the two optical fibers 33, 34 and having an equal polarized state and beam components outputted from the oscillator 40 are coupled with each other by a coupling element 50 and mixed beams are inputted to detectors 53, 54 through fibers 51, 52 Similarly mixed beams between signal beams and local oscillator beam components are inputted from a coupling element 60 to detectors 63, 64. Output signals from the detectors 53, 54 and 63, 64 are coupled with each other by an adder 70 through respective amplifiers 55, 56 and outputted. |
