| 摘要 |
PURPOSE:To resist the fluctuation of a light receiving level without deteriorating a transmitting efficiency by photo-electrically converting a clock signal by a light receiving circuit as well as a light receiving element and a preamplifier, detecting the average value of the voltage output, and using the average value as the reference input of a comparator. CONSTITUTION:The average value of the clock signal converted into a voltage signal by a preamplifier 5c, is detected by a low pass filter constituted of a resistance R and a capacitor C, at a reception side. The average value of the clock signal is matched with the just intermediate value between the high level and the low level of a data signal output from a preamplifier 5[subscript 1-(n)]. Therefore, the average value of the clock signal is used as the reference value of a comparator 6[subscript 1-(n), and (c)] which discriminates 1.0 of the data and the clock, so that a threshold can always be held to be an optimal value without being affected by the fluctuation of a light inputting level. Thus, the threshold for discriminating the received data can be adjusted according to the fluctuation of the light inputting level, so that always stable output data can be obtained. |
