| 摘要 |
PURPOSE:To demodulate an optical phase modulation signal by using a single light source and a transmission line by dividing light modulated in phase to two beams of light, by synthesizing both of them after giving an optical path difference to each beam and by permitting them to interfere with each other. CONSTITUTION:Light emitted from a laser light source 1 is modulated with a phase modulator 7 according to a transmission signal. For the phase modulator, a crystal with refractive index changed according to an external electric field is used, and in coincidence of an optical axis of the crystal with a polarization direction of light, polarization directions of both input and output lights are made not to change. Light modulated in phase is sent through a transmission medium 3 to a receiving end, and after making it parallel beams of light by using a lens 10, enters an interferometer formed with reflection mirrors 11, 12 and a semitransparent mirror 13. A phase modulated signal can be reproduced from a detected signal by giving a constant difference to optical path length extending to an optical intensity detector 4, i.e., to a difference between an optical path passing a mirror 11 and an optical path passing a mirror 12. |
