| 摘要 |
PURPOSE: To compensate element temperature drift and non-linearity by providing an attenuator feedback control loop, wherein an average light detector current which passes through a negative resistor is kept constant for maintaining a constant link RF gain. CONSTITUTION: An amplitude-stabilizing circuit 70 is connected between the anode of a photodetector diode 60 and an RF output load circuit 90. An attenuator 72 has a characteristic so as to equally attenuate an RF modulation signal and average light current. The circuit 70, further, compares the voltage generated between the both ends of a load resistor 76 to a reference voltage at a node 75, while a feedback differential amplifier 78 which generates an error signal for controlling attenuation given by the attenuator 72 is contained. Since the RF signal and average light current are equally attenuated by the attenuator 72, the feedback amplifier 78 maintains a constant average current at the load resistor 76, thereby the RF gain of link 50 is kept constant. |
