| 摘要 |
PURPOSE:To enable the transmission of a burst signal by integrating an input burst signal and making a bias current flowing to a laser nearly zero when a level of the input signal is a prescribed value or below based on the result of integration. CONSTITUTION:A resistor R11 and a capacitor C2 form an integration circuit to integrate input signals to terminals SD, the inverse of SD. The integrated signal is inputted to a noninverting input terminal of a comparator 4. An inverted output signal of the comparator 4 is inputted to a noninverting input terminal of an operational amplifier 3. When a Ve (bias of laser LD) source is set properly in advance, a transistor(TR) Q3 is turned on when an output of the operational amplifier 3 is at a high level and the TR Q3 is turned off when at a low level. Thus, since a bias current of the laser is 0A and a modulation current is also 0A at the terminal SD with no signal, the laser LD is extinguished completely. Moreover, when a signal is inputted to the terminal SD, since a bias current flows to the laser LD and the modulation current also flows, the normal signal transmission can be implemented. |
