Performance Analysis For Space-to-ground Optical Communication System With Existence Of Atmospheric Turbulence

At present, atmospheric turbulence is an important concern in free-space optical communication. Addictive effects must be taken into account when the laser is transmitted through the aerosphere, especially the append space ullage and possible beam aberration caused, which will affect beacon orientation and signal detection severely. All of above will produce unpredictable effects on the APT and signal detection system, which in turn has a direct connection with the communication quality of the whole system.The optical communication is not only influenced by atmospheric attenuation, but also turbulence domino. However, the turbulence dominos include beam spreading, scintillation, spot dancing and variance of the angle-of-arrival. Based on the Rytov Method, Markov Theory as well as the Gaussian diffusion equation in atmospheric turbulence, this paper has studied different Gaussian turbulence domino models with consideration of the inner-scale and outer-scale of turbulence. With the background of space-to-ground optical communication, the effects upon the models of different parameters are studied by numerical analysis and computer simulation. Further more, beam intensify distributing models of both up-link and down-link are built in the latter section including all the turbulence dominos above. So, we can work out the error between facular position calculated by CCD barycenter arithmetic and the actual one. And according to the error, we further discussed the problem of whether the CCD barycenter model can still be used in facular positioning in the area of strong turbulence. All the research above can be used as reference in optical communication system design.Due to the unneglectable turbulence effects, this paper will also propose several schemes to improve the system performance from the views of modulation methods and beam parameters. Meanwhile, the relationship model between beam launching power and system BER is also set up. The feasibility and effect are confirmed and demonstrated by detailed theory research and numerical analysis.