| 摘要 |
PURPOSE:To prevent deterioration in the reception sensitivity of a digital data signal due to superimposition of a sub signal. CONSTITUTION:A light receiving element 1 converts an optical signal subject to amplitude modulation through the superimposition of a main signal being a digital data signal and a sub signal having a lower frequency component into an electric signal. A preamplifier circuit 2 amplifies the electric signal and outputs the signal into two ways, A band stop filter 4 receives one of the branched electric signals resulting from being amplified by a main amplifier circuit 3 and outputs it while stopping the sub signal. An identification circuit 5 identifies a signal outputted from the band stop filter 4 to reproduce the main signal A1. The other branched electric signal is given to a low pass filter 6, in which the low frequency component is extracted and it is amplified by a low frequency amplifier circuit 7 and the sub signal B1 is outputted. |
