Laser Propagation In Atmospheric Turbulence, A Preliminary Analysis Of Time Intensity Fluctuation

In recent years, with the maturation of all kinds of apparatus and breakthrough of a great lot of key techniques, space laser communication has become hot again in science research, and its application changed from military to demotic, and now entered into business application. However, the propagation medium of space laser communication system is atmosphere, and atmospheric pressure and temperature in part of the atmosphere vary randomly, these factors make the intensity of the laser field on the accepting plane asymmetry, thus bring atmospheric scintillation, and affect communication quality. Just because of these reasons, intensity fluctuation of laser propagating in the atmosphere becomes a common problem of science researchers. Many scientists in this field have made great efforts on this problem, and got quite achievements.We have researched many kinds of models of atmospheric turbulence reports in the world, and brought forward an item of long distance communication. According to the requests of this item, we analyzed status properties of light intensity on the accepting plane from theory and computer simulation. The main results of this item are as follows.(1) For debasement of turbulence effect, most laser communication products adopt multi-aperture projector. That is to say, they adopt multi –beam to debase effect of turbulence, and to improve communication quality. Theory and experiments both have approved that amplitude fluctuation of every beam on the accepting plane has correlation for turbulence correlation, and in the actual communication system, every channel always has conjunct, so effect of atmospheric turbulence to every channel is independent impossibly. We adopted multi-beam in the system to research the distance of each beam. In this system, the light spot fluctuation on the accepting plane is the smallest, accepted signals are the best.(2) Absolute coherent laser is only ideal, in fact, light beam are all part-coherent. Laser beams have high coherence can satisfy requests of present system. However, because of laser beams' high coherence and pre-wave phase distortion, laser beams produce intervention in part field, thus brings scintillation. We adopted part-coherent laser beam in the system, used multi-beams to compensate in theory, and adopted adaptive optic to correct, declined light intensity fluctuation variance on the accepting plane. (3) On the base of theory deduction, we simulated and analyzed our system by use of MATLAB. Results suggest that proper design of channel distance and adoption of part-coherent laser projectors can decline laser density fluctuation on the accepting plane; this may bring some reference to actual optic communication productions.