Research On The Optimal Design And Performance Evaluation Methods Of The Optical System In Intersatellite Optical Communications

Intersatellite optical communications (IOC) which can establish high-speed information communication between satellites by adopting laser as the information carrier has become the research focus of space communication in the world. Along with the extension of application field of satellite optical communication, design requirements of transmitting and receiving optics are becoming more and more rigid. The catadioptric transmitting and receiving optics which can not meet the high performance requirement of terminal should be optimized using novel method. Transmitting and receiving performance of optics designed using Diffractive Optical Elements (DOE) can be improved. Furthermore, the performance of the satellite optical communication terminal must be evaluated and verified in ground laboratory. Thus, it is essential to develop high precision evaluation method and verification installation.In this dissertation, optics of IOC is research subject, and developing high performance optical subsystem and high precision evaluation method is research goal. Optimization method of designing transmitting and receiving optics and evaluation method of verifying optics high performance are proposed using diffraction optical technique and modern optoelectric detection technique, respectively. The main content of this dissertation include:(1) Optimal design method of high performance transmitting opticsConsidering the decrease of transmitting power caused by the obscuration of secondary mirror, the transmitting light is controlled by using DOE from which the efficiency of transmitting power and far field light intensity of optical communication terminal are improved. For the influence of the obscuration and truncation of antenna on the distribution of far field intensity, we simulated the far field intensity in different obscuration and truncation, and compared the optimum gain with different obscuration and truncation ratio.Considering the inconvenient of acquisition caused by the far field distribution of beaconing light, far field distribution of intensity is changed from class Gaussian to uniform, and acquisition range is enlarged and acquisition difficulty is reduced.In order to increase the beam intensity homogeneity of far field and avoid the iteration algorithm trap in a local extreme, GS (Gerchberg-Saxton) algorithm for designing DOE must be improved. The new input phase function of the improved algorithm after the kth iteration was set as the weighted sum of the two phase functions in the succeeding neighbor loops, and simultaneously the adoption of the new phase functions whether or not was determined by the comparison of the output amplitudes of the succeeding neighbor loops. In the following numerical simulation, we simulated all the two iteration algorithms to compute the phase functions, and compared the corresponding results.(2) Optimal design method of high performance receiving opticsIn the receiving optics, the requirement of precision of sensor position is very high due to the high sensitivity of sensor receiving performance to position change. To decrease the requirement of precision of sensor position and the influence of position change on receiving performance, distribution of intensity on optical axis is changed to uniform using DOE by deepening focus depth.Miniaturization and integration is an important trend of IOC terminal. To simplify optical receiving system, ESA has achieved the composite design of signal optics and tracking optics using DOE. Herein, we reproduced the design and analyzed the simulation result considering the importance and secrecy of the design.(3) High precision evaluation method for optical systemHigh precision evaluation and verification methods are indispensable to transmitting and receiving performance of optical systems. Considering the developing requirement of satellite optical communication specification, evaluation methods of divergence angle, wavefront error and coaxiality are systematically studied:â‘ proposed the method to evaluate coaxiality of transmitting axis and receiving axis;â‘¡proposed the method to evaluate coaxiality of optical axis and mechanical axis;â‘¢studied the method to evaluate the distance between primary mirror and secondary mirror which could impact the quality of wavefront, and deduced the mathematical relationship between distance error and interference stripe;â‘£studied the method to evaluate beam divergence angle and analyzed the error using this method.This research work would promote the application of novel optics in IOC and the development of miniaturization and integration of communication terminal. The evaluation methods proposed to verify optical performance could ensure the implementation of high precision optical systems.