| 摘要 |
PURPOSE:To provide a laser diode driving circuit and method which making a bias current to drive a laser diode automatically biased to an oscillation threshold value, and light transmitting system using the same. CONSTITUTION:A lower frequency signal from a low frequency oscillator 7 is superposed on a bias current which drives a laser diode LD. An output optical waveform detection level of the laser diode LD corresponding to the low frequency signal is detected by a photodiode PD, a band passing filter 8 and a peak detector 6. A comparison amplifier 4 makes a bias current close to an oscillation threshold value to make the detection level constant. In this way, even if a temperature, etc., varies thereby changing an oscillation threshold value, a current is always biased to an oscillation threshold value and the laser diode can respond to a signal input promptly and a signal is not lost. |
