| 摘要 |
The interference phases of two optical delay line interferometers of an optical receiver adopting the DQPSK or the like are stabilized at points, which have a difference of 90°, without bifurcation of a receiving signal or receiving data. A low-speed photocurrent flowing through the current source terminal of a photodetector that receives interfering light outputted from an optical delay line interferometer is detected. The interference phase is identified by utilizing a variation in the AC or DC component of the photocurrent dependent on the interference phase of the optical delay line interferometer. The difference between the interference phases of two optical delay line interferometers is controlled to be 90°.
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