OPTICAL TRANSMISSION EQUIPMENT

摘要

PURPOSE:To output an optical signal having always a prescribed S/N even at a high speed operation by setting a bias current automatically near a threshold voltage of a laser diode independently of the ambient temperature condition and the element characteristic of the laser diode. CONSTITUTION:A laser diode drive circuit 2 is switched by an input signal 1 and a laser diode 3 generates an optical output in response to the input signal 1. The backward optical output of the laser diode 3 is detected by a photodetector 4, an integration circuit 5 averages the output of the photodetector 4 and a comparator circuit 6 compares the output with a reference voltage 7 and a control signal is given to a bias drive circuit 8 so that the average optical output of the laser diode 3 is constant and a bias control signal 9 from the bias drive circuit 8 controls the bias current of the laser diode 3.