| 摘要 |
PURPOSE:To eliminate optical output monitor from the rear surface of a light source for APC operation and facilitate high output operation by measuring an average value of a light current generated by light absorption in an optical demodulator and controlling a DC current to be applied to a semiconductor laser always to give constant average value of light current. CONSTITUTION:Laser oscillation can be realized by applying a DC current to a laser section 100 of an integrated light source with a bias circuit 300. Random pulse modulation is carried out in an optical demodulator 200 with a signal voltage from a drive circuit 400. As a result, an optical current, generated in the optical demodulator 200, in an optical output from the optical demodulator 200 providing good modulation waveform can be measured with a monitor circuit 500. A current to the laser section 100 from bias circuit 300 is controlled by a feedback loop 600 so that such optical current can be kept constant. Thereby, APC operation can be realized easily by controlling a current to the laser section 100 so that a light current generated from the optical demodulator 200 always becomes constant. |
