Wavefront Correction Technique Of Spatial Coherent Optical Com-Munication With LC-SLM

With the rapid development of information technology,the wireless optical communica-tion system based on traditional intensity modulation/direct detection method has been unable to meet the current user's requirements for communication rate.In recent years,the space co-herent optical communication technology has attracted wild attention of academic researchers.Especially by using the heterodyne detection method in space coherent optical communication technology can effectively enhance the sensitivity of signal detection and realize the detection of weak optical signals.However,how to effectively solve the wavefront distortion caused by turbulent atmospheric channel in the detection process has become an urgent matter for the ap-plication and promotion of this technology.In this thesis,on the premise that the output power and linewidth of lase source meet the experimental requirements,the effect of wavefront distor-tion caused by atmospheric turbulence on heterodyne efficiency of spatial coherent optical communication system is analyzed and discussed.Furthermore,theoretical research and ex-perimental verification of the wavefront correction technology in space coherent optical com-munication which based on beacon light and liquid crystal spatial light modulator(LC-SLM)are also carried out.The four main research contents of this thesis are as follows.1?Based on the beacon light and LC SLM for wavefront correction space coherent optical heterodyne detection method.To study the direct detection,heterodyne detection,and balance of heterodyne detection system SNR and bit error rate and detection sensitivity.As well as the generating principle of wavefront aberration and the influence of wavefront aberration external differential detection experiment laid a good theoretical basis for the system.2?The influence of laser light source stability on the performance of spatial coherent op-tical communication system is studied,and the mathematical model of system under the in-fluence of atmospheric turbulence is established.In addition,the experiment verifies that there is an optimal value of local vibration light power in heterodyne detection,and the wider the la-ser line width is,the smaller the SNR of the system is and the larger the bit error rate is,which provides a powerful theoretical basis for the system experiment.3?The phase modulation characteristics of LC-SLM are measured and calibrated,and the gray value lookup table is established.That is,when the same phase delay is obtained,the driv-ing grayscale is added to the LC-SLM when the different wavelengths beams are inci-dent.Which provided experimental basis for wavefront correction experiment.4?The wavefront correction simulation experiment and 1300m link outfield experiment of spatial coherent optical communication based on beacon light and lc-slm were carried out,and the wavefront correction simulation experiment and outfield experiment were completed.The experimental results show that the voltage amplitude of the output differential frequency signal in the simulation experiment is about 1.7 times higher than that before correction,and the SNR is about 3 times higher than that before correction.The voltage amplitude of the output differ-ential frequency signal after correction in the field experiment is about 2 times higher,and the SNR is about 3 db higher,providing experimental basis for the engineering application of this method.The research results of this paper provide a new way to correct the wavefront distortion caused by atmospheric turbulence and improve the sensitivity of heterodyne detection.