| 摘要 |
PURPOSE:To enable the stabilization of action to the variation in ambient temperature and the variation in mark rate by providing a bias current control means and a modulation current control means. CONSTITUTION:The photo signal output of a semiconductor laser element 1 is converted into photoelectricity by a light receiving element 3, and its DC component is detected by a DC component detection circuit 15. On the other hand, the DC component of modulation signals inputted from a signal input terminal 4 is detected by a DC component detection circuit 13. Comparing these outputs by a comparator 16 enables the detection of the average photo signal output without effects of the mark rate and the like of modulation signals. The peak value of electrical signals outputted by the light receiving element 3 is detected by a peak value detection circuit 19. On the other hand, the peak value of modulation signals inputted from the signal input terminal 4 is detected by the peak value detection circuit 14. Comparing these outputs by a comparator 20 enables the detection of the peak value of the photo signal output corresponding to the variation in peak value of input signals. |
