Research On Transmission Performance Of Free Space Optical Communications Based On Vortex Beam

In recent years, vortex beam carrying orbital angular momentum (OAM) has aroused great interest of scholars all over the world, it has a spiral phase structure, which contains a phase factorexp(iιθ), and its intensity distribution is cyclic and vortex beam has a small dark spot in its center, These special characteristics make vortex beam be widely used in the field of optical micro control, information transmission, biomedicine, quantum coding, especially in the field of optical communication, application prospect is extremely important and hugely potential, it can be encoded independently or as a carrier to carry information, making communication system spectrum efficiency and channel capacity be great improved, in addition, it can be used together with existing technology such as WDM, in this paper, we establish atmospheric channel turbulence model based on Zernike polynomial method, research performance changes of vortex beams in a turbulent atmosphere transmission and I put forward a new wave-front repair scheme, the main work and achievements are as follows:Firstly, introduce and analyze in detail the generation principle as well as intensity and phase characteristics of vortex beam carrying OAM, and expound the basic mechanism of improving communication system channel capacity.Secondly, introduce two kinds of numerical simulation methods, power spectrum inversion method and Zernike polynomial method, establish phase screen to emulate atmospheric turbulence based on these two kinds of methods, and analyze and compare the difference.Thirdly, based on Zernike polynomial method, establish phase screen to emulate the atmospheric turbulence, research the variation trend of intensity and phase profile of vortex beam, analyze the topological charge spread of OAM and OAM purity variation trend with transmission distance and turbulence intensity when suffering atmospheric turbulence.Fourthly, propose an adaptive optical vortex beam wave-front repair scheme, and verify its validity by simulation and analysis.This paper researches and analyzes above four aspects, after deeply understanding the OAM technology principle, establish phase screen to emulate atmosphere turbulence, research and probe the characteristics variation of OAM affected by atmospheric turbulence, propose an adaptive optical vortex beam wave-front repair scheme, provide reference and clue for further study and application of OAM technology in optical communication field...