| 摘要 |
PURPOSE:To secure a satisfactory range of identification against the fluctuation of the mark rate of an input signal by applying the output signal of a surface acoustic wave SAW filter to a peak value detecting circuit to obtain the output voltage corresponding to the mark rate and applying the output voyage to an identification reproduction circuit. CONSTITUTION:The received optical signal is converted into an electric signal by a photodetecting element 1 and then amplified by a main amplifier circuit 4, etc. The electric signal received from the circuit 4 is inputted to an identification circuit 5 via a capacitor 13 as well as to a SAW filter 6. The output of the filter 6 is distributed via a distribution circuit 7 to be set at a prescribed amplitude via an amplitude limiting circuit 8 and inputted to the circuit 5. At the same time, a peak value detecting circuit 10 produces the DC voltage in response to the set amplitude. The DC voltage undergoes the level conversion via a DC-DC converter 11 and is applied to an amplified current signal. Thus, it is possible to apply an identification level corresponding to the input mark rate to the circuit 5 against an input signal having a fluctuating mark rate. |
