Analysis About Influence Of Annular Beam Used On Satellite Optical Communication Transmission System

With the continuous development of the information society,the research of satellite laser communication has been paid more and more attention by all countries.As indicators of the terminal optical system really influences laser communication,and it's very important to optimize its optical system to enhance the terminal performance.When using hollow beam to avoid the blocking of sub-mirror in Cassegrain antenna,the model of the input hollow beam and the parameters matching between the hollow beam and the antenna have a great influence on the communication performance.The double-Gaussian hollow beam which has caused a lot of interest in recent research was chosen to replace the double-half-Gaussian hollow beam which was earlier raised,and take these two model compared with the flat top hollow beam model which also has been in the high researching heat in recent years.It is important to select the appropriate model and analyze the optimal matching parameters between the incident ring light and the aperture to improve the encircled energy of the antenna,and it also make sense to deeply understand the characteristics of the hollow beam when it is transmitted.Focusing on optimization the ring light model of Satellite Laser Communication and achieving ring laser shaping the following work has been done:(1)In order to study the hollow beam model which is more suitable for satellite laser communication,the two kinds of hollow beam models which have been used in satellite optical communication and one kind of efficient double-Gaussian hollow beam model proposed in recent years are compared and analyzed.The effects of the near-field diffraction center energy,the far field entropy and the imaging accuracy of the corresponding shaping elements of these three models are investigated.Through the comprehensive comparison,the far field encircled energy of flat top hollow beam is the highest bettwen these three models,but it has a high request in parameter matching accuracy;but the double-Gaussian hollow beam has the strongest stability,its far far field encircled energy is also very high,and it has a better fault tolerance,according to all of these aspects of performance,the double-Gaussian hollow beam is more excellent.(2)Considering the special light properties of hollow beam and ring diaphragm,a new analysis program was used to investigate the relationship between optical system parameters and far field encircled energy,so that to obtain the optimal solution of the matching parameters between the double-Gaussian hollow beam and the ring diaphragm to get the highest far field encircled energy.The optimal parameter matching curve which can achieve the highest entropy is obtained through simulation,which has certain guiding significance for engineering design.(3)In order to preserve the advantage about the high speed of GS algorithm operation,while reducing its iteration extreme bottleneck value,a geometric tracing method for initial selection to GS algorithm is proposed for designing an annular beam shaping diffractive optical element.The geometric contours of the obtained initial value are phaseized and was taken into the algorithm,the iterative results show that the mean square error of the image of the initial value obtained by the new method is lower than that of the planar phase and the random phase.(4)In order to understand the effect of the error that may be introduced in the manufacturing process of the ring laser shaping element on the component performance,the relationship between step quantization,longitudinal error,transverse error and diffraction efficiency,peak energy rate and imaging mean square error were analyzed.Simulation results show that appropriate increasing the number of steps of binary optical elements can greatly improve the diffraction efficiency,and according to the adverse effects on imaging results,the influence of the lateral error is more serious than the longitudinal error.