| 摘要 |
PURPOSE:To obtain an optical modulator with which waveform deterioration and extinction ratio deterioration hardly occur by comparing the output of a mean value detecting circuit with a set value and controlling the operating potential of a modulation driving circuit so that the difference signal between the output and set value can become the minimum. CONSTITUTION:This optical modulator is provided with a coupled optical switch 1 equipped with two input ports and two output ports, modulation driving circuit 2 which distributes the light of a fixed intensity level inputted to one of the input ports of the switch 1 to both of the output ports in time series in accordance with modulate signals, and a photodetector 3 which detects the intensity of the optical output from one of the output ports of the optical switch 1. In addition, a mean value detecting circuit 4 which detects the mean level of the output of the photodetector 3, comparison circuit which compares the output of the circuit 4 with a set value and outputs a difference signal, and operating potential control circuit 6 which controls the operating potential of the modulation driving circuit 2 so as to minimize the difference signal are also provided. Therefore, an optical modulator with which deterioration of waveform and extinction ratio hardly occurs is obtained. |
