| 摘要 |
PURPOSE:To enable the reduction in the overshoot of photo output, without the decrease in the efficiency of network, by slackening the speed of bias increase only in the neighborhood of set levels. CONSTITUTION:The current value of a current source 13 that charges a capacitor 11 is controlled by means of a difference circuit 14 receiving the difference signal between the detected output of a semiconductor laser 5 and the reference signal. When the photo output is small, i.e., the difference between the reference signal is large, the current value of the source 13 is large. Therefore, its charging speed is high, and the potential increases rapidly; however, the access of the photo output to the set level slackens the speed. Accordingly, the increase in the photo output nearly in uniformity from beginning without rapid increase in the neighborhood of the set level is enabled. Since the bias increase is duller in the neighborhood of the set level, even when the loop has some delay, the overshoot of output due to it is hardly observed. |
