| 摘要 |
PURPOSE:To attain on/off switching while a superimposed amplitude is gradually changed and to prevent the occurrence overshoot and undershoot by providing an amplitude adjustment circuit adjusting the amplitude of a high frequency signal in a semiconductor driving circuit superimposing the high frequency signal onto a laser driving current. CONSTITUTION:An RF amplitude adjustment circuit 4 is provided newly to a semiconductor laser driving circuit 10. When an RF superimposition switch 73 is switched from OFF to ON in the circuit 43, since a charge of a power supply 71 is gradually charged in a capacitor 74, a voltage of a point 76 is gradually increased, and when the RF superimposition switch 73 is switched from ON to OFF in the circuit 43, the charge is gradually discharged from the capacitor 74, and the voltage of the point 76 is gradually decreased. When the voltage of the point 76 is changed in such a way, a current flowing from the emitter of a 5th transistor (TR) 55 to a collector of an 8th TR 58 is changed gradually, then the amplitude of an output 53 of the adjustment circuit 43 is also changed thereby varying the amplitude of the optical output power subject to RF signal superimposition from the circuit 10 gradually. |
