星地光通信中大气湍流影响的模拟与实验研究

发布时间：2018-03-10 01:30

本文选题：星地光通信　切入点：大气湍流　出处：《武汉大学》2014年博士论文　论文类型：学位论文

【摘要】：随着信息获取类卫星的数据量剧增及传输实时性需求增强,对天基信息系统提出了速率超过1Gbps的明确需求。相对于微波通信方式,光通信可以提供更高的传输速率,更小的功耗和载荷,不受其他频段的干扰。目前国际上对卫星光通信技术的研究已经成为一个热门的研究领域。在卫星与地面的激光通信中,载有信息的光波在大气中传播时会受到大气湍流影响,引起光强闪烁、到达角起伏、光束漂移等一系列大气湍流效应,造成接收端光斑抖动、接收光功率起伏,降低通信指标。为提高空间光通信系统性能,必须对湍流大气中的光束传播特性开展专门研究,寻找克服大气湍流效应的方法,最终实现稳定通信。在科学研究以及工程设计中人们迫切需要能模拟大气湍流扰动的大气湍流模拟器,以便在室内开展相关实验。本文针对湍流大气中激光传播理论特性,讨论了湍流相位屏的数值模拟方法,基于液晶空间光调制器(LC-SLM)设计了室内大气湍流模拟器,验证了不同湍流下的光强闪烁及到达角起伏效应的影响。本文首先讨论了湍流大气中激光传播问题。从湍流统计理论出发,介绍了Kolmogorov与Non-Kolmogorov湍流功率谱模型以及各自模型下激光传输的弱起伏、强起伏理论,重点分析了光强闪烁与到达角起伏效应。研究了静态相位屏的数值模拟方法,包括功率谱反演法、Zernike多项式法和分形法,从时间复杂度、模拟精度及适用范围上对比分析了三种方法优缺点。推导了Non-Kolmogorov湍流下离散相位屏的普适表达式,针对已有随机中点位移算法(RMD)的不足,提出了一种改进RMD算法,提高了模拟精度。介绍了动态湍流相位屏的仿真方法,针对湍流冻结法产生的相位屏数量有限这一缺点,给出了样条插值法的一种实现方案,实现了长时间动态模拟。基于LC-SLM设计了室内湍流模拟器并搭建了仿真平台,分析了仿真平台与外场实验平台的等效性。详细讨论了远场光斑放大的理论基础以及室内模拟的可行性,根据透镜成像放大原理设计了级联光放大系统,以模拟不同距离的激光大气传输。模拟了Kolmogorov与Non-Kolmogorov湍流中不同湍流强度下的到达角起伏以及3.4km链路光强起伏情况。开展了外场远距离激光大气传输与激光通信实验。针对3.4km水平链路进行了长期观测实验,得到了大气折射率结构常数、大气相干长度的日平均变化规律,同时测量并分析了该链路下的光强起伏时间功率谱。介绍了一种卫星光通信终端地面演示系统,进行了链路预算分析。开展了40km激光大气传输实验及激光通信实验,从理论上分析了Gamma-Gamma信道下,误码率与信噪比的关系。讨论了星地链路与水平远距离链路大气衰减及大气湍流的关系。本文的工作为星地链路大气湍流效应的研究提供了理论基础,同时对星地链路中室内湍流模拟器的设计以及远场激光传输的模拟提供了实验依据。
[Abstract]:With access to information like satellite data and increase the real-time transmission demand, put forward a clear demand rate of more than 1Gbps of space-based information system. Compared with microwave communication, optical communication can provide higher transmission rate, power consumption and the load is smaller, no interference from other bands. The current international research on satellite technology optical communication has become a hot research field.
In satellite laser communication with the ground, the light with the dissemination of information in the atmosphere is affected by atmospheric turbulence, caused by scintillation, arrival angle fluctuation, beam drift and a series of effects of atmospheric turbulence, caused by the receiving end spot jitter, receiving light power fluctuation, reduce the communication index. In order to improve the performance of space optical communication system. We must carry out special research on the characteristics of beam propagation in the atmospheric turbulence, looking for ways to overcome the effects of atmospheric turbulence, finally realize the stable communication. In scientific research and engineering design in the urgent need of atmospheric turbulence simulator can simulate the atmospheric turbulence, so as to carry out related experiments indoors. According to the characteristics of laser propagation in atmospheric turbulence theory, discussion a numerical simulation method of turbulent phase screen, liquid crystal spatial light modulator (LC-SLM) based on the design of the indoor atmospheric turbulence simulator to verify the different The effect of light intensity flicker and angle of arrival fluctuation in turbulence.
This paper first discusses the laser propagation in the atmospheric turbulence problem. Starting from the statistical theory of turbulence, introduces Kolmogorov and Non-Kolmogorov turbulence power spectrum model and the weak fluctuation model of laser transmission, strong fluctuation theory, focusing on analysis of the scintillation and angle of arrival fluctuation effect.
The numerical simulation of the static phase screen, including power spectrum method, Zernike polynomial method and fractal method, from the time complexity, simulation accuracy and scope of application of comparative analysis of the advantages and disadvantages of the three methods are carried out. The Non-Kolmogorov turbulence phase screen discrete general expression, the random midpoint displacement algorithm (RMD) deficiencies, proposed an improved RMD algorithm, improving the accuracy of the simulation. The simulation method of dynamic turbulence phase screen method, for frozen turbulence phase screen generated by a limited number of this shortcoming, a scheme of spline interpolation method is given, the long time dynamic simulation.
The design of LC-SLM indoor turbulence simulator is built based on the simulation platform, analyzed the equivalent experimental platform simulation platform and the outfield. The far field spot to enlarge the theoretical basis and feasibility of simulation is discussed in detail according to the design principle of lens imaging amplification cascade optical amplification system, the simulation of laser propagation in different distances is simulated. Kolmogorov and Non-Kolmogorov turbulence in different turbulence intensity under the angle of arrival fluctuation and 3.4km link intensity fluctuation.
The distance field of laser atmospheric transmission and laser communication experiment. According to the level of 3.4km link long-term observation experiment, the atmospheric structure constant of refractive index is obtained, the atmospheric coherence length on average variation at the same time, measurement and analysis of the link between the power spectral intensity fluctuation is introduced. A satellite optical communication terminal ground the demo system, the link budget analysis. 40km carried out the experiment of laser propagation in atmosphere and laser communication experiment, analyzes theoretically the Gamma-Gamma channel, the relationship between BER and SNR. And discussed the relationship between the atmospheric turbulence attenuation of satellite ground link and level range link of the atmosphere.
The work in this paper provides a theoretical basis for the study of the atmospheric turbulence effect in the satellite earth link, and provides experimental evidence for the design of the indoor turbulence simulator and the simulation of far-field laser transmission in the satellite link.

【学位授予单位】：武汉大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TN929.1

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