| 摘要 |
PURPOSE:To prevent fluctuation in temperature and decrease in optical output, by deforming a modulating signal in a rectangular wave into a form, in which a corner at a rising part is removed, so as to obtain a driving signal, applying the signal to a semiconductor laser, and suppressing the temperature increase, when the driving signal is applied, to the utmost. CONSTITUTION:A driving signal (c) in pulse waveform, which undergoes modulation, is applied to a semiconductor laser LD. At the time of rising of the modulating signal (a), an edge signal (b), whose polarity is reverse with respect to the modulating signal, is generated in synchronization with the rising timing of the modulating signal. The edge signal is superimposed on the modulating signal. Then the driving signal has a slowly increasing waveform. The driving signal is applied to the semiconductor laser LD before the rectangular wave reaches a peak. For example, when the modulating signal in rectangular waveform is inputted to a differential circuit 14, a differential waveform is generated and rectified in a rectifier circuit 15. The differential waveform at the falling part is removed. The differential waveform at the rising part becomes the waveform, whose polarity is inverted by an inverter circuit 16. The result is inputted into a superimposing circuit 17. The modulating signal is also inputted to the superimposing circuit 17. The differential waveform, whose polarity is inverted, is superimposed to the modulating signal. The driving signal 12, whose corner at the rising part is removed, is obtained and applied to the semiconductor laser LD. |
