| 摘要 |
PROBLEM TO BE SOLVED: To provide an automatic optical output control circuit whereby a constant optical output is obtained without taking a high frequency countermeasure as against a high bit rate signal with the large fluctuation of a signal mark rate m. SOLUTION: A driving part 5 driving a light emitting element LD based on an input signal so as to execute light emitting, a photodetector PD monitor- receiving light from the light emitting element LD and converting a light quantity into an electric signal and a driving control part 3 comparing the electric signal from the photodetctor PD with a previously set reference electric signal and outputting a control signal for controlling the driving part 5 based on a comparison result are provided in the automatic optical output control circuit 1. The circuit 1 is constituted in such a way that a gain variable differential amplifier circuit 3 varying gain based on the fluctuation of the signal mark rate m in the input signal and a definitive convertion means for making tour gain inside a negative feedback loop definite is provided. |
