The Research About Electro-optic Modulator Automatic Bias Control System And Control Device

At present, owing to the space laser communications experiment continuous progress in the settlement of laser communication some of the key technology becomes imperative. The electro-optic modulation technique as a kind of the indirect modulation of laser technology is widely used because of its unmatched advantages by any other modulation. However, the quiescent operating point of the electro-optic modulator been controlled at the laser modulation become one of the key issues, if it can't be properly solved, the modulated signal would seriously distortion, leading to communication failure.The Electro-optical modulator's operating point at the establishment of two methods often used: 1) To the electro-optic crystal plus a fixed DC bias (A half of electro-optic modulator half-wave voltage), the electro-optic modulator can works the linear regional. 2) Inserted a 1 / 4 wave plate in the optical path may also work linear modulator district. But in the harsh conditions, such as the becoming temperature in free space experiments, these two methods can not guarantee linear laser modulation, effects of poor communication.In this paper, a program on electro-optic modulator automatic bias control is proposed on basis of the first method. The method is that to detect the laser power in real-time through the electro-optic modulator before and after, monitoring the change of the modulator's operating point , then pass DC bias voltage by feedback control system, result the operating point of modulator always maintain the linear regional, not realizing the signal modulation distortion. Experiments prove the feasibility of the program.