| 摘要 |
PURPOSE:To reduce residual phase noise which can not be suppressed until now by providing a light phase modulator which controls phase of an output light of a light frequency variable oscillator based on an output of a light phase difference detecting means. CONSTITUTION:Phase of output light of a light frequency variable oscillator 1 is changed so that residual phase noise which can not be suppressed by a feedback loop 3 is canceled by adding newly a light phase modulator 4. In this case, residual phase noise having fast variation which can not be suppressed by the feedback loop 3 is canceled by the light phase modulator 4 by setting delay time so that delay time due to light path length from the light frequency variable oscillator 1 to the light phase modulator 4 is equal to delay time due to optical-electrical path length from the light frequency variable oscillator 1 to the light phase modulator 4 via a light phase difference detecting means 2. Also, in a light phase synchronous receiver, since light synchronous detection is performed after residual phase noise is reduced, a receiver can be constituted even if the light frequency variable oscillator 1 which has comparatively large phase noise is used. |
