基于光强传感的相位恢复方法与实验研究

发布时间：2018-04-05 09:09

本文选题：自适应光学　切入点：信标光　出处：《西安电子科技大学》2014年硕士论文

【摘要】：自由空间光通信(freespace optical communication,FSO),由于光束能量密度高、指向性好、具有很高的保密性,与微波通信具有很强互补性得到广泛重视并进入实用化阶段,但是,湍流大气对激光传输特性的影响限制了FSO系统性能的提高。近些年,基于对大气湍流特性实时探测和光学系统补偿的自适应光学得到快速发展及天文、激光光束整形的领域成功应用。在大气激光通信系统中引入自适应光学技术(adaptive optics,AO)可有效抑制大气湍流影响,降低误码率提高通信性能。传统AO方法是基于哈特曼波前进行传感,成本高,系统复杂,其应用受到局限,有必要探索无波前的实用型AO方法扩大基于自适应光学的FSO应用场合。由于FSO系统中用于APT(acquisition pointing and tacking,APT)的信标光中包含大气湍流信息,研究基于信标光强度分布的相位恢复方法,对于无波前探测的自适应光学在FSO中的应用具有理论意义和实用价值。论文首先开展基于光强分布相位恢复算法的研究,光强分布迭代法(classical Gerchberg-Saxton algorithm-transport of intensity equation,GS-PTIE)是波前畸变相位恢复的有效方法。采用相位屏法模拟湍流中激光传输特性,并与GS-PTIE算法结合,系统地分析两个迭代面和三个迭代面时,在弱湍流、中湍流、强湍流下的相位恢复效果。结果表明,在弱湍流、中湍流、强湍流下使用三个迭代面GS-PTIE算法相位恢复残差分别为-0.03~0.06rad、-0.1~0.1rad、-1.16~0.85rad,恢复效果优于两个迭代面算法。论文模拟仿真相位补偿之后,远场的光强分布,以及接收机探测器上的桶中功率(power-in-bucket,PIB)对相位补偿效果进行衡量评估,结果表明在不同湍流情况下,相位补偿之后接收端的PIB相较于补偿之前明显增大。在实验室环境下,搭建两个迭代面相位恢复方法的实验系统,对空间滤波器后的球面光波场,开展基于光强传感的相位恢复方法实验研究和理论验证,多组数据分析结果表明恢复精度高,基于光强传感的相位恢复方法可行。上述理论研究与实验为基于信标光的大气湍流波前补偿提供了方法和实验依据。
[Abstract]:Freespace optical communication FSOs, due to their high beam energy density, good directivity and high confidentiality, have been widely paid attention to and have entered the practical stage of microwave communication.The effect of turbulent atmosphere on laser propagation limits the performance of FSO system.In recent years, adaptive optics based on real-time detection of atmospheric turbulence characteristics and optical system compensation has been rapidly developed and applied successfully in the field of laser beam shaping.The introduction of adaptive optics (AOO) technology in atmospheric laser communication systems can effectively suppress the atmospheric turbulence and improve the communication performance by reducing the bit error rate (BER).The traditional AO method is based on the Hartmann wavefront sensing, which has high cost, complex system and limited application. It is necessary to explore the practical AO method without wavefront to expand the application field of FSO based on adaptive optics.Because the beacon light used for APT(acquisition pointing and tracking in FSO system contains atmospheric turbulence information, it is of theoretical and practical value to study the phase recovery method based on the intensity distribution of beacon light for the application of adaptive optics without wavefront detection in FSO.In this paper, the phase recovery algorithm based on intensity distribution is studied. The classical Gerchberg-Saxton algorithm-transport of intensity equationGS-PTIEs is an effective method for phase restoration of wavefront distortion.The phase screen method is used to simulate the laser propagation characteristics in turbulent flow, and the phase recovery effect under weak, medium and strong turbulence is analyzed systematically with two iterative surfaces and three iterative surfaces combined with GS-PTIE algorithm.The results show that the phase recovery residuals of the GS-PTIE algorithm with three iterative surfaces are -0.03 ~ 0.06 rad-0.1 ~ (0.1) ~ (0.1) radan ~ (-1.16) ~ (0.85) rada in weak, medium and strong turbulence respectively, and the recovery effect is better than that of two iterative surface algorithms.After simulating the phase compensation, the intensity distribution of the far field and the power in the bucket PIBs of the receiver detector are used to evaluate the phase compensation effect. The results show that the effect of phase compensation is evaluated under different turbulence conditions.The PIB of the receiver after phase compensation is obviously larger than that before compensation.In the laboratory environment, the experimental system of two iterative surface phase recovery methods is built, and the experimental research and theoretical verification of the phase recovery method based on the light intensity sensing are carried out for the spherical light wave field behind the spatial filter.The results of multi-group data analysis show that the recovery accuracy is high and the phase recovery method based on light intensity sensing is feasible.The above theoretical research and experiments provide a method and experimental basis for wavefront compensation of atmospheric turbulence based on beacon light.
【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN929.1

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