| 摘要 |
PURPOSE:To make constant the light output of a laser diode, to improve an extinction ratio at high temperature and to inhibit the light output of the laser diode within an allowable range at low temperature by a method wherein both of a laser diode AC controlling circuit and a laser diode DC controlling circuit are simultaneously controlled by the output voltage signal of a photodiode. CONSTITUTION:A switching transistor 8 is turned-ON/OFF by data and clock signals on an input signal converting circuit 7. Moreover, the back emitted light of a laser diode 6 is detected by a photo diode 1, the output is compared with the average value of input electrical signals, which are used as a reference voltage, by a differential amplifier 3 and the difference signal is inputted in the bases of a laser diode DC controlling transistor 10 and a laser diode AC controlling transistor 9. The DC of the driving current of the diode 6 and the AC of the driving current of the diode 6 are respectively changed simultaneously in the transistors 10 and 9. That is, the driving current of the diode 6 is increased or decreased by an increase or decrease in the light output to make the light output constant. |
