星地相干激光通信中的大气扰动问题研究
文献类型：学位论文
| 作者 | 李佳蔚 |
| 学位类别 | 博士 |
| 答辩日期 | 2016 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 陈卫标 |
| 关键词 | 星地激光通信 相干通信 大气湍流 自适应光学 |
| 其他题名 | Study of atmospheric perturbation of satellite-ground coherent laser communication |
| 中文摘要 | 由于具有高容量、低能耗和高安全性等优势，自由空间相干激光通信近些年越来越受到重视，可以作为传统微波通信的发展和补充，高码率星间相干激光通信也已经获得了巨大成功，欧洲已经开展了自由空间激光通信的商用推广，然而在星地相干激光通信方面一直进展艰难，这主要是来源于大气湍流扰动对相干激光通信系统的影响。 本论文首先介绍了自由空间激光通信的应用背景和技术发展作了介绍，介绍了国内外具有代表性的星地激光通信系统，对系统的组成和原理进行了介绍，然后分析了星地相干通信面临的问题和挑战。对目前流行的DPSK和BPSK相干通信制式的优势和劣势进行了分析，讨论了大气湍流的成因以及其对星地相干激光通信系统产生影响的几个方面，并分别对光强闪烁、光束漂移、到达角起伏、波前畸变等问题提出了解决方案。 针对大气湍流引起的波前畸变问题，研究了自适应光学波前校正的方法。介绍了自适应光学系统的构成和波前重建、校正原理和方法，对自适应光学系统的参数设计进行了介绍。理论分析了不同湍流条件下自适应光学系统的带宽需求，针对二阶控制系统提出了校正带宽不足引起的时延波前误差的计算模型。讨论了低轨卫星和同步卫星对地激光通信链路对自适应光学系统带宽的不同需求。 理论分析了星地相干激光通信中，大气湍流引起的信号光强度和相位起伏。在不同天顶角和不同闪烁强度下，利用Gamma-Gamma数学模型分析了光强闪烁对通信系统误码率的影响，讨论了孔径平均效应在抑制光强闪烁上的作用，提出了无自适应光学系统校正情况下最佳的接收望远镜口径。理论分析了不同D/r0情况下和不同Greenwood频率，自适应光学波前校正对相干通信系统误码率的改善。 利用自行设计的自适应光学系统进行了实验室环境下的波前校正实验，波前校正剩余残差小于七分之一波长并利用相位屏研究了不同Greenwood频率下波前校正残差的变化。在城市环境下搭建了1.2Km激光收发链路，开展了水平大气激光链路的自适应光学校正实验。经过系统校正后，光斑的Strehl Ratio可以从~0.15提高至~0.6，波面剩余残差降低至七分之一波长以下。并研究了不同的自适应光学系统校正带宽对光斑Strehl Ratio的影响。 开展了城市环境下1.2Km和高海拔20Km的水平大气链路相干激光通信实验，研究了实际大气环境对DPSK相干激光通信系统的影响，并对星地相干激光通信接收终端提出优化设计方案。 |
| 英文摘要 | With several advantages, such as much higher date rate, better security and lower energy consumption, free-space laser communication has attracted more and more attentions in recent years. Inter-Satellite coherent laser communication has been verified successfully. It is already planned to extend to commercial areas in Europe. However, Satellite-Ground coherent laser communication is developed difficultly because of the influence of the atmospheric turbulence. First of all, this thesis summarized the development of free-space laser communication technology comprehensively, especially on the typical Satellite-Ground coherent laser communication terminal developed in the world. The composition and the working principle of the Satellite-Ground coherent laser communication system are presented and the challenges this technology faced are introduced. The features of the atmospheric turbulence are discussed and the influences on the coherent laser system are analyzed. In order to deal with the wave-front aberration caused by the turbulence, the adaptive optics (AO) system is investigated. The system composition and working principle is introduced. The method of wave-front reconstruction and correction is studied. Under different turbulence strength and zenith angle, the relationship between the servo bandwidth of AO system and mixing efficiency of coherent laser receiver is simulated and a mathematical model of time-delay phase error for two-order AO control system is proposed. We have also discussed the different servo bandwidth requirement of AO system for LEO-Ground and GEO-Ground coherent laser communication. The fluctuation of signal amplitude and phase caused by the turbulence is analyzed in theory. For different scintillation and zenith angle, the influence of amplitude fluctuation to communication bit-error-rate is simulated by Gamma-Gamma model, the aperture-average-effect on restraining scintillation is also investigated. For the Satellite-Ground receiver without AO, the optimal size of receiving aperture is obtained. Under different D/r0, scintillation and Greenwood frequency, it is proved that the AO system is able to improve the performance of Satellite-Ground coherent laser communication. Under laboratory environment, the RMS of wave-front aberration is able to down to after correction by a self-designed AO system. The fluctuation of residual wave-front aberration increased with the Greenwood frequency. In urban environment， we set up 1.2Km transmit-receive horizontal laser link in order for the experiment of AO correction in real atmosphere. It is shown that the Strehl Ratio can be improved from 0.15 to 0.6. The residual wave-front error can be lower than . We also investigated the influence of servo bandwidth of AO system to the Strehl Ratio after correction. The atmospheric coherent laser communication is performed in urban 1.2Km and high altitude 20Km horizontal laser links. The influence of real atmospheric turbulence to the DPSK receiver is studied and adptive optics system is proved to be effective in compensating the wave-front aberration. Then we give the suggestions on the optimal design to Satellite-Ground coherent laser communication terminal. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15988]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 李佳蔚. 星地相干激光通信中的大气扰动问题研究[D]. 中国科学院上海光学精密机械研究所. 2016. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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