| 摘要 |
PURPOSE: To provide a demodulator circuit of a simple constitution which can properly demodulate the monitor signal component that is superposed in response to the strength of an optical signal. CONSTITUTION: A monitor signal component is extracted out of the optical signal that is converted into an electric signal by a photodiode 106 by means of a BPF 108 and an envelope detection circuit 111. The output of the photodiode 106 is smoothed by a capacitor 12 via a buffer amplifier 11. A threshold voltage control circuit 13 converts the smoothed signal voltage into the threshold voltage in the prescribed ratio. An identifier 115 binarizes the extracted monitor signal component based on the threshold voltage. As the smoothed voltage varies according to the mean strength or the optical signal, the monitor signal can be properly binarized in response to the strength of the receiving optical signal. Furthermore this smoothing can be attained by a capacitor, etc., so that the constitution of a demodulator circuit is simplified. |
