| 摘要 |
PURPOSE:To save the power consumption of an optical transmitter by controlling a lighting power of the optical transmitter so that a reception section is operated at a minimum photodetection level. CONSTITUTION:When a peak value of a reception signal detected by a peak detection circuit 50 is higher than a threshold voltage set by a reference voltage generating circuit 52, a level comparator 52 takes it that the photodetection power is excessive and a detection signal 70 is outputted. A coder 53 inputs the detection signal 70 to code it and the coded detection signal 71 is outputted. A multiplexer 90 applies time division multiplex to the coded detection signal 71 and a digital signal from an input terminal 1', a drive circuit 10' and an LED 20' convert the signal into an optical signal of wavelength lambda2, which is received by a photodiode 21'. A demultiplexer 91 outputs the original coded detection signal 71' and the digital signal 2' from the input terminal 1' separately. A drive circuit 10 uses a control signal 80 to decrease a drive current flowing to the LED 20 thereby decreasing the light emitting power. |
