| 摘要 |
PROBLEM TO BE SOLVED: To make a large current circuit of wide band unnecessary and realize cost reduction, by driving a semiconductor laser by using a driving current of the sum of a first driving current and a second driving current. SOLUTION: A semiconductor laser driver 1 is provided with a first control loop of a comparator 3 and a current source 6 and a second control loop of an amplifier 5 and a current source 7. A semiconductor laser 1 is driven by a current of the sum of a semiconductor laser driving current I1 and a semiconductor driving current I2 . Hence the frequency characteristic of the whole control loop which controls the semiconductor laser 1 becomes summed characteristics of the gains of frequency characteristics of the first and the second control loops. The first control loop controls power change in low frequency. The second control loop restrains return light noise of the semiconductor laser. Hence laser power is controlled by a control loop of high frequency band small current driving and a control loop of low frequency band large current driving. |
