Electro-Optic Modulator Of The Automatic Gain And Automatic Bias Control System

At present, because of national space laser communications experiment progresses, it is very urgent to solve some of the key laser communication technologies. An external modulation laser technology of electro-optical modulation technique has been widely used because of its advantages which can not be got by others. However, to ensure the work performance of the modulator, the electro-optic modulator required to ensure that the input drive signal should be able to be controlled and is not subject to outside influences, and the electro-optic modulator of the modulation characteristics may be also affected by temperature changes and the impact of high-frequency continuous signal change, which makes the modulator quiescent operating point deviation from the midpoint of modulation characteristics of the linear region, resulting in modulated signal distortion. Therefore, to solve the electro-optic modulator gain control and offset control of the issue has become one of the key technologies for electro-optic modulator.In this paper, on the basis of our predecessors, I proposed separately by electro-optic modulator automatic gain control and automatic bias control program. Automatic gain control design is the use of RF feedback from the performance-driven module to automatically adjust the gain control voltage Vgain, Therefore, we can change the gain of RF drive module to achieve different levels of data signal amplification. The department of automatic gain control have been completed, and the system could achieve the operating bandwidth of 75kHz to 12.2GHz, Saturated output power 22dBm, the output peak 7V, maximum input power is 24dBm, gain range of 14dB to 26dB, fast response (200ms-400ms). The automatic bias control part in this paper presents a new theoretical derivation and design program, using non-linear modulator to produce a small-amplitude disturbance signal bias point which will make minor changes in the phase, the disturbance signal will be complete feedback modulator bias point information, thereby operating point to achieve automatic control. Test results show the feasibility of this new program. The experimental results could allow bias voltage fixed at Vp/2 points (quad points), eye diagram of the Q value is 25.04.