| 摘要 |
PROBLEM TO BE SOLVED: To prevent a transient response at the time of changing over a frequency band by charging a setting capacitor while the capacitor for changing over a control band by turning on-off a servo system is switched off from a feedback system. SOLUTION: A system controller supplies a laser level setting signal SLV to a non-reverse-input of an error amplifier 31 as a reference voltage signal via a D-A converter 33. The error amplifier 31 receives an output of a monitor PD22 via a monitor amplifier 30, and compares it with the reference voltage signal, and supplies an output of the result to a laser diode(LD) 4 as its driving current via a laser driver 18. The system controller sends a band change-over signal SFB to a switch 32, and changes over a switch terminal from a terminal (b) to a terminal (a), to turn on a capacitor C2 into a feedback system for changing over the frequency band. As long as the switch terminal is staying on the terminal (b), the capacitor C2 is connected with the non-reverse input of the error amplifier 31 and charged with the reference voltage signal. |
