| 摘要 |
PURPOSE:To control the peak value of a light output pulse constantly even for the variation in the mark rate and duty ratio of a modulation signal by controlling the reference value of a bias controlling circuit of a laser diode in accordance with the average value of the modulation signal. CONSTITUTION:A bias current is supplied to a laser diode 1 formed of amplifier A having transistors 3, 10 grounded in AC manner at the input side, the light output of the diode 1 is partly fed back to a photodiode 2 provided at the input side of the amplifier A, and the photodetecting current is inputted to the amplifier A, thereby stabilizing the optical output of the diode 1 by providing a differential amplifier 12, a reference voltage supply terminal 13, a resistor 14, a capacitor 15, and a modulation signal (voltage signal) supply terminal 16. The modulation signal supplied to the terminal 16 by the resistor 14 and the capacitor 15 is averaged, and a DC voltage is outputted. This DC voltage and the reference voltage from the terminal 13 are supplied to the amplifier 12, which amplifies the difference between the voltages as the bias voltage of the diode 2. |
