【作者】 郭磊；

【导师】 于思源；

【作者基本信息】 哈尔滨工业大学 ， 物理电子学， 2010， 硕士

【摘要】 卫星光通信以其通信速率高、通信容量大、防截获能力和抗干扰能力强、体积小、重量轻和低功耗等优点,在卫星通信、本地宽带接入和军事通信领域具有极大的应用价值和发展潜力。为了解决通信过程中大气湍流对通信质量影响的问题,自适应光学技术被引入通信系统。经过研究人们发现,常规自适应光学技术对于解决上行链路、下行链路中的畸变问题可以取得一定效果,但是在水平链路,由于大气强湍流的影响,自适应光学计算的补偿效果会严重下降。本文采用CCD作为探测器,相位恢复GS算法作为控制算法,液晶空间光调制器作为校正器建立了基于强度探测的自适应光学系统。与目前常规自适应光学系统普遍使用的变形镜相比,液晶空间光调制器具有空间分辨率高、成本低、可靠性好、体积小、低能耗、易于控制等优点,而且由于系统通过相位恢复算法直接将测得的光强分布转化为相位分布,无需对波前进行探测,故非常适用于闪烁问题较为严重的大气光通信等应用领域。为了实现对系统的控制,本文利用图形化编程语言LabVIEW开发了控制系统。在掌握LabVIEW语言的语法以及设计流程后,完成了基于强度探测的自适应光学控制系统设计。根据系统各部分功能的不同将系统分为图像采集模块,GS算法运算模块,算法控制模块以及控制信号输出模块。其中图像采集模块控制CCD探测器采集图像,图像转换成二维矩阵后送至GS算法运算模块,算法控制模块控制算法的迭代次数,控制信号输出模块计算出液晶空间光调制器的控制量后输出。最后,为了精确控制液晶空间光调制器,对其相位调制特性进行测试,并通过实验研究了系统在简单畸变条件下迭代初值相同、迭代次数不同,和迭代次数相同、迭代初值不同时系统对畸变的校正能力,以及对复杂畸变的校正能力。本文建立了一种基于强度探测的自适应光学系统,并在LabVIEW平台完成了系统的设计和开发,为系统在光通信中的应用提供了一定的参考价值。更多还原

【Abstract】 Intersatellite optical communications, known with high communication speed, large capacity, strong anti-interception and anti-interference capability, small and lightweight, also with lower power consumption, are widely used in intersatellite communication and local broadband access technology, as well as in the field of military anti-jamming communication and also have a great development potential. Optical adaptive technique is brought into the communication system to solve the problem of atmospheric turbulence affecting the communication quality.The conventional optical adaptive technique is effective in solving the distortion of uplink and downlink. However, when used in horizontal-link, the optical adaptive calculations of compensation effect weakened much due to the effect of atmospheric turbulence.In this article, CCD was adopted as the detector , the phase retrieval GS algorithm as the control algorithm, and Liquid Crystal Spatial Light Modulator (LC-SLM) as the calibrator. Thus, we were able to establish optical adaptive system based on the intensity-investigation. LC-SLM has a better spatial resolution and reliability, smaller size, lower cost and consumption and is easier to control, when compared with the commonly used deformable mirror. Furthermore, the system is well applied to atmosphere optical communications with severe scintillation, because the system can directly transform the detected light distribution into the phase distribution through the iterative phase retrieval algorithm, without wavefront detection.We developed a control system using the LabVIEW to realize the well control of the new system. We completed the new system after master the LabVIEW.For the software part, the system was divided into four parts according to their various functions, which were respectively acquisition image module, operation of the module, output precision and the control module of the algorithm. Besides, CCD was controlled by the acquisition image module to capture images. The captured images were transformed into two-dimensional matrix and then delivered to the module of GS algorithm. The control module of the algorithm had control over the times of GS algorithm.The controlled quantity of the liquid crystal spatial light modulator was calculated and was put out by the output module.Finally, we tested the characteristics of phase modulation of the liquid crystal spatial light modulator to obtain the accuracy control. We also studied the ability of the system to correct the simple distortion and complex distortion. For the former, we tested the condition of the same iterated initial values and different iterations, and also the condition of the same iterations and different iterated initial values.In this article, we proposed optical adaptive system based on the intensity-investigation, designed and completed the new system by LabVIEW. This is a reference value of the application of the system in the optical communications.更多还原