| 摘要 |
PURPOSE:To make the pulse width of a PIM light waveform invariably constant by comparing the pulse width of a semiconductor laser driving signal with the pulse width of an LD light output monitor and controlling the DC bias current of an LD. CONSTITUTION:An input signal 1 is PMF-modulated by a PFM modulator 2 and E/O-converted by an LD driving circuit 3. The rear light of a laser diode LD 4, on the other hand, is monitored by a photodiode PD 5 to reproduce the monitor waveform into a PFM signal by a discriminator 6. Then the PFM waveform which is discriminated and reproduced by the discriminator 6 to a constant amplitude and the PFM waveform from the modulator 2 are detected by mean value detectors 7 and 9, whose pulse widths are compared by a compa rator 8 with each other to control the DC bias current. Thus, APF (automatic optical control) is realized and the pulse width of the PIM light waveform is made invariably constant. |
