| With the development of space exploration and space application technology, the demand for space data transmission increases dramatically. Laser communication technology has become a research focus in countries, which has a series of advantages over microwave communication, such as larger capacity, greater security against eavesdropping, more compact terminal, lower power consumption and so on.The United States in the 60 s, Europe in the 70 s and Japan in the 80 s, respectively conducted the research of satellite laser communication technology. And they have entered the stage of space experiments in recent years. In the early 90 s, Harbin Institute of Technology firstly conducted the research of satellite laser communication technology in our country. After more than 20 years of research and development, the technology also entered the stage of space experiments. In 2011, the first laser communication experiment in space was successfully conducted in China, which made our country enter the forefront of the world in the field of satellite laser communication.One of the core technologies in laser communication is detection technology, which is mainly divided into direct detection and coherent detection. Direct detection has the characteristics of simple system structure, easy to implement in engineering. But with the improvement of communication data requirements, the detection sensitivity of direct detection is limited. Currently we are still looking for the high data rate and high sensitivity detection technology. In recent years, coherent detection technology has become a research focus, along with the gradually development of device technology. With the mature of 1550 bands fiber optic components, DPSK/self-homodying coherent detection system based on single-mode fiber-coupling has received the attention.The domestic and overseas researchers have conducted a large amount of research efforts in connection with the study of space laser communication system performance. But theoretical models of the receiving system performance are still established on the basis of fully coherent laser, the influence of laser spatial coherence degree is not in consideration. Because the laser beam transmitted from the space optical communication system is not ideal fully coherent, the characteristics of laser spatial coherence degree would influence the optical signal transmission, make the receiving optical field distribution change, and then influence the receiving laser intensity distribution, bring down the beam quality, resulting in the decline of the stability and even lead to the insufficient of the laser link system redundancy. Therefore, the influence of laser spatial coherence degree on the performance of the laser communication receiving system is the basic scientific problem which needs to be resolved urgently. In allusion to DPSK/selfhomodying coherent detection system based on single-mode fiber-coupling, the key problems that need to be solved urgently are as follows:(1) Research the influence of laser spatial coherence degree on the mean value and the statistical distribution of the central receiving optical intensity. Establish the theory model of the central receiving optical intensity based on partially coherent laser source through atmospheric turbulence.(2) Analyze the influence of laser spatial coherence degree on the mean single-mode fiber-coupling efficiency. Establish the theory model of the mean single-mode fiber-coupling efficiency based on partially coherent laser source through atmospheric turbulence.(3) Solve the influence problem of laser spatial coherence degree on the statistical distribution of the single-mode fiber-coupling efficiency and the system performance based on self-homodying detection. Establish the performance model of a DPSK/self-homodying coherent receiving system based on partially coherent laser source through atmospheric turbulence.These three important issues need to be resolved urgently. This dissertation is mainly based on the actual situation of space laser communication system(partially coherent laser source). The theory model of the central receiving optical intensity based on partially coherent laser source through atmospheric turbulence is established, the mutual restriction relation of laser spatial coherence degree and the central receiving optical intensity is gi ven, the influence rule of laser spatial coherence degree on the central receiving optical intensity through atmospheric turbulence and laser spatial coherence degree are obtained, the correctness of the theoretical model is verified by the experiments. The theory model of the mean single-mode fiber-coupling efficiency based on partially coherent laser source through atmospheric turbulence is established, the variation relation of the mean single-mode fiber-coupling efficiency with laser spatial coherence degree is given, and the experimental verification is conducted. The communication performance model of a DPSK/self-homodying coherent receiving system based on partially coherent laser source is established. The influence of laser spatial coherence degree on the system fading probability and fading redundancy, the system biterror rate(BER) and the power penalty is analyzed.In this dissertation, our works are a basic applicable investigation concerned with laser spatial coherence degree and its influence on laser communication. The research work solved the basic scientific problem in the field of laser communication, which is the influence problem of laser spatial coherence degree on the performance of laser communication receiving system. The work of this dissertation can further enrich the theory of spatial laser coupled into single-mode fiber, and provide theoretical basis for the adaptive compensation of laser spatial coherence degree and reasonable estimation of the laser link redundancy in a space laser communication receiving system.
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