INITIAL VALUE SETTING TYPE OPTICAL OUTPUT CONTROL CIRCUIT

摘要

PURPOSE:To raise an APC system without a time delay even when a repetitive period of a burst signals is long or at application of power by providing a initial voltage generating function and an initial voltage application function to a circuit for transmitting a burst signal. CONSTITUTION:A burst depending optical output control circuit (APC circuit) is newly provided with an analog switch SW 4, an analog switch control circuit SCNT, an APC initial voltage generating circuit ORG and a high input impedance amplifier A2. The SW 4 (between contact points 1 and 2) is closed in the APC system operation and open in the light interruption by an optical output control signal CONT. A voltage of a capacitor C2 is received by an amplifier A2 in a high impedance state and the voltage is given to a constant current circuit Cb. An output voltage Vi of the APC initial voltage generating circuit ORG is set so that an output light from a laser diode is over-powered and to be close to a voltage when the APC circuit is stable. The control circuit SCNT returns a potential to a stable potential when it is deviated from the stable potential due to a long burst period or at application of power.