| 摘要 |
PROBLEM TO BE SOLVED: To improve the distortion characteristic without losing the high C/N characteristic of an optical reception circuit. SOLUTION: The circuit has a photoelectric conversion circuit 1 converting a received optical signal into an electric signal, plural (n staves of variable gain control circuits 21 -2n each consisting of a variable attenuator and an amplifier circuit, a peak detection circuit 5 detecting an output level of an electric signal at an output terminal 10 of the final stage variable gain control circuit 2n , a comparator circuit 6 comparing an output level detected by the peak detection circuit 5 with each of reference comparison levels v1 ,v2 -vn and control circuits and control circuits 71 -7n comparing the outputs of the comparator circuit 6 with the reference comparison levels v1 ,v2 -vn to control the variable gain control circuits 21 -2n . Then the 1st stage variable control circuit 21 just after the photoelectric conversion circuit 1 is finally controlled by the increase in the attenuation of the variable attenuator. |
