摘要 |
PROBLEM TO BE SOLVED: To prevent the degradation of signal quality of a DPD signal even when regenerating the point where reflectivity falls off due to the adhesion of a smudge etc. SOLUTION: The apparatus includes gain variable amplifiers 1A to 1D which correspond respectively to four regions of a photodetector 5, binarization circuits 2A to 2B which binarize the outputs of the gain variable amplifiers 1A to 1D. a first phase comparison circuit 11 which detects the phase difference between the outputs of the binarization circuits 2C to 2D, a second phase comparison circuit 12 which detects the phase difference between the outputs of the binarization circuits 2C to 2D, and an adder circuit 13. The apparatus in the above described configuration is equipped with a gain controller 4 which increases the gain of the gain variable amplifiers 1A to 1D when the signal level inputted to the gain variable amplifiers 1A to 1D gets small. COPYRIGHT: (C)2007,JPO&INPIT
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