ELECTROOPTIC CONVERTING CIRCUIT

PURPOSE:To generate a stable pulse and to improve the reliability of an optical transmission system by detecting the voltage level of a light emitting element provided to a converting circuit and monitoring the lighting state of light. CONSTITUTION:The light emitting element 2 is connected to an electrooptic converting circuit 1 and the terminal voltage across this light emitting element 2 is monitored by two input amplifiers 3. The output of this amplifier 3 after differential amplification is applied to one input terminal of a comparator 4 and compared with a reference voltage 6 applied to the other input terminal, and the comparison result is applied to the converting circuit 1 through a feedback circuit 5. Then, the voltage level of the light emitting element 2 is detected to monitor the lighting state of the light all the time, and the stable pulse is outputted to improve the reliability of the optical transmission system.