Study On Propagation Properties Of Array Beams In Atmosphere Turbulent In FSO System

With the rapid development of deep space exploration and satellite communication, people put forward higher and higher requirements for optical communication distance, but only by increasing the power of a single laser to meet the communication requirements was very difficult, so in order to obtain high power, high-quality laser beam output, array beams synthesis technology was proposed. In recent years, with the continuous maturation of beam synthesis technology and the improvement of related theory, the transmission distance and beam quality of Free Space Optical Communication (FSO) system had expanded, the people had widely attention to study the propagation characteristics of array beams.In this paper, the propagation characteristics of array beams in the atmospheric turbulence were studied. The main work included:1. Based on the extended Huygens-Fresnel principle and the modified von Karman spectral model, the analytic expressions of intensity distribution, the root mean square beam width and power in the bucket (PIB), mutual independent partially coherent Gaussian-shell model (GSM) array beams in Free Space Optics Communication (FSO) system propagating in the atmospheric turbulence, were derived. And the changes were analyzed under the influence of different factors.2. Based on non-Kolmogorov spectral model, the analytic expressions of the Rayleigh range and the turbulence distance, radial partially coherent Gaussian-Schell Model (GSM) array beams by coherent and incoherent combinations propagating through non-Kolmogorov turbulence, were derived. And the expressions were used to numerical analyze the changes of the Rayleigh range and the turbulence distance with turbulence parameters and beam parameters.3. Based on the generalized Huygens-Fresnel principle and the modified von Karman spectrum model, the analytic expressions for intensity distribution of radial Gaussian array beams after incoherent combination that propagation in the atmospheric turbulence were derived. And the self-coupling characteristics of array beams was studied with the change of propagation distance and the radial radius. In addition, the spots of fully coherent and partially coherent array beams with different parameters in atmospheric turbulence was actual measured.The experimental results showed that when partially coherent and fully coherent array beams propagated a certain distance in the atmospheric turbulence, they would combine a beam.And the self-coupling characteristics of fully coherent array beams was better than that of partially coherent array beams, but the intensity distribution of fully coherent array beams was smaller. Under the same propagation condition, with the decrease of the coherence length and turbulent internal scale or the increase of the structure constant of atmospheric refractive index,self-coupling characteristics of the array beams was better, but the intensity distribution was smaller. The influence of turbulent outer scale on the intensity distribution was little, and it could be ignored. Under the same propagation condition, the smaller radial radius, the better self-coupling characteristics of the array beams.