| 摘要 |
PURPOSE:To prevent code error rate characteristics from being degraded caused by disabling the keeping of a clamp state when a transmitting signal is a random waveform and caused by making a state not optimum for the threshold voltage of an identifying and reproducing circuit concerning the optical receiver of 3R provided with a clamp circuit. CONSTITUTION:A transmitting signal D1 inputted to an APD 5 is amplified by an equalizing amplifier circuit 6 and inputted to a clamp circuit 2. An output D3 of the clamp circuit 2 is branched into two signals and inputted to an identifying and reproducing circuit 4 and an average value detection circuit 1. At the average value detection circuit 1, the DC level of the transmitting signal is detected and outputted to a threshold value level control circuit 3. Corresponding to the detected DC level, the control circuit 3 sets the identifying and reproducing circuit 4 at a threshold voltage so that the best code error rate can be provided. Thus, the code error rate can be prevented from being degraded. |
