| 摘要 |
PURPOSE:To attain driving which does not exceed the maximum rating of a laser diode by comparing the threshold current of the laser diode with the detection output of a photo diode and a set point and controlling the current value of a current source. CONSTITUTION:A second current switch part 9 is provided without providing a high frequency oscillator outside and a high frequency modulation current is caused to flow when write data is not generated. The threshold current is caused to flow from the current source 2b, the monitor detection output of the photo diode PD is compared with the set point and automatic power control is attained with setting the compared result as a base current. When write data is generated, a write addition current is added from a first current switch part 1. When write data is not generated, the high frequency modulation current is added from a second current switch part 9. Thus, a high frequency can be overlapped in a read level, noise can be reduced and driving is attained without exceeding the maximum rating value of the laser diode LD. |
