自由空间光通信若干关键技术研究

发布时间：2018-04-01 04:29

本文选题：空间光通信　切入点：大气信道　出处：《北京邮电大学》2015年硕士论文

【摘要】：自由空间光通信(Free Space Optical Communication, FSO)是一种以激光作为载波,在自由空间中传输信息的无线通信方式。与传统的射频(Radio Frequency, RF)无线通信相比,FSO具有可用频谱宽、保密性好、抗电磁干扰能力强、功耗低、体积小和传输容量大等优点。因此,FSO在星间、星地和地面通信中都极具应用潜力。国内外对自由空间光通信的研究已经进行了很多年,包括发射光源、调制格式、大气信道、跟踪捕获技术及接收技术。然而,激光在大气信道中传输会受到湍流的严重影响。湍流是造成FSO信道畸变的最主要原因,会对激光产生一系列的影响,从而导致通信质量降低,严重时甚至可能造成通信的中断。因此,研究大气信道模型具有重要意义。由于大气信道的影响,提高接收端灵敏度对FSO系统性能的提升也至关重要。因此,研究接收技术和调制格式以提高灵敏度很有必要。另外,相比于光纤信道,FSO信道更适于使用空间模式复用技术,以提高传输容量。本文主要从大气信道、接收技术和复用技术三个方面研究了空间光通信的关键技术。主要工作如下：一、研究大气信道模型。基于Kolmogorov大气湍流理论,利用相位屏法建立了大气信道模型,对激光在湍流中的传输进行了数值仿真。利用空间光调制器搭建了室内大气湍流仿真平台,实验研究了不同强度湍流对激光束的影响,包括远场强度分布和接收光功率。二、研究了接收技术。仿真分析了空间分集接收,实现并比较了三种常用合并算法在BPSK和QPSK调制格式下的性能。分析了相干接收技术及数字信号处理算法,并进行了数字相干高速空间光通信实验,研究了相干接收技术在空间光通信中的性能。对比和分析了多种常用调制格式的接收灵敏度。三、研究了轨道角动量(Orbit Angular Momentum, OAM)在空间光通信中的应用。介绍了基于OAM的空间复用技术,设计了相应的相位灰度图,利用空间光调制器成功将普通高斯光束转换成任意阶的OAM光束。
[Abstract]:Free Space Optical Communication (FSO) is a wireless communication mode in which laser is used as carrier to transmit information in free space.Compared with the traditional radio frequency communication, FSO has the advantages of wide spectrum, good confidentiality, strong anti-electromagnetic interference, low power consumption, small volume and large transmission capacity.Therefore, FSO has great potential in intersatellite, terrestrial and terrestrial communications.The research on free space optical communication has been carried out for many years, including emission light source, modulation format, atmospheric channel, tracking and capturing technology and receiving technology.However, laser propagation in atmospheric channels will be seriously affected by turbulence.Turbulence is the main cause of FSO channel distortion, which will have a series of effects on the laser, which leads to the decrease of communication quality and even the interruption of communication.Therefore, it is of great significance to study the atmospheric channel model.Because of the influence of atmospheric channel, it is also important to improve the performance of FSO system by improving the sensitivity of the receiver.Therefore, it is necessary to study the receiving technique and modulation format to improve the sensitivity.In addition, space mode multiplexing is more suitable than fiber channel FSO to improve transmission capacity.In this paper, the key technologies of space optical communication are studied from three aspects: atmospheric channel, receiving technology and multiplexing technology.The main tasks are as follows:First, the model of atmospheric channel is studied.Based on the Kolmogorov theory of atmospheric turbulence, the model of atmospheric channel is established by using phase screen method, and the propagation of laser in turbulence is simulated numerically.An indoor atmospheric turbulence simulation platform is built using a spatial light modulator. The effects of different intensity turbulence on the laser beam are experimentally studied, including the far-field intensity distribution and the received optical power.Second, the receiving technology is studied.The spatial diversity reception is simulated and analyzed, and the performance of three common merging algorithms in BPSK and QPSK modulation formats is compared.The coherent reception technology and digital signal processing algorithm are analyzed, and the digital coherent high-speed space optical communication experiments are carried out, and the performance of coherent reception technology in space optical communication is studied.The receiving sensitivity of various modulation schemes is compared and analyzed.Thirdly, the application of orbit angular momentum (Orbit Angular momentum) in space optical communication is studied.The spatial multiplexing technology based on OAM is introduced, and the corresponding phase grayscale map is designed. The ordinary Gao Si beam is successfully converted into an arbitrary order OAM beam by using spatial light modulator.
【学位授予单位】：北京邮电大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN929.1

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