| 摘要 |
PURPOSE:To maintain the peak value of light signal pulses and light dc output at respective predetermined values and suppress chopping modulation as well, by monitoring the output light level of a light semiconductor element with a light sensor and further, causing the output of a minimum value detecting circuit to perform its feedback to a bias current source, thereby causing the output of maximum value detecting circuit to perform its feedback to a drive circuit. CONSTITUTION:When a semiconductor laser 1 is driven by a pulse drive circuit 2 and a bias current source 3, a light output pulse 4 from one-sided surface of a resonator is inputted in a light sensor 5 and waveforms are monitored. After being amplified, a monitor output 6 is inputted in maximum and minimum value detecting circuits 8 and 9 of the waveforms. The maximum value detecting circuit 8 detects a peak level of waveforms of the monitor output 6. The detection circuit 9 reads the light output level at the place of a bias current level. These outputs at the detecting circuits 8 and 9 are compared by a differential amplification circuit 10 and its output corresponds to the peak value of pulses. Thus, the pulse peak value and the dc light level of the light output are suppressed to respective predetermined values by allowing the outputs of the detecting circuit 9 and the amplification circuit 10 to perform their feedbacks as respective control signals of the current source 3 and the pulse drive circuit 2. |
