Optimal Solutions On Laser Source Configuration For Multiple Transmitters Based On The Spot Image

In atmospheric laser communication, the technology of multi-beam transmission isan important way to reduce effectively atmospheric turbulent. It is especially importantand the key to configure the laser source in order to produce the best possible results.Therefore，the ralationship between laser configuration and atmospheric turbulent has tobe set up to find the configuration law.In this thesis, we adopt turbulent phase screen theory to analyze the impact ofatmospheric turbulence on the multi-beam far field spot, and analyze the impact of thegeometry distribution of the multi-beam laser source, the spacing and the number of themulti-beam laser source on far field beam image quality. In order to ensure a reliableaccuracy of the follow-up positioning methods，we discuss the optimal laser sourceconfiguration required for achieving the best image quality of the far field spot.Firstly, this thesis introduces the basic concepts of atmospheric turbulence, and thebasic theory of laser through atmospheric turbulence. Then we make the simulationanalysis on the fundamental-mode Gaussian laser propagation in the atmosphere usingthe phase screen method.Then, this thesis uses multi-layer phase screen method to establish a multi-beamatmospheric turbulence model. To simplify the problem, the laser source configurationadopts the typical structure of plane geometry distribution in this model. Then weanalyze the effects of geometry distribution of the multi-beam light sources, the spacingand the number of beams on the far field image quality. With the changes of the beamspacing, the centroid error of the spot image will have a minimum point, and we have areasonable explanation for the minimum point. The theoretical analysis shows that, inthe case of moderate or strong intensity turbulence, when the transmission distance ofnot more than5km, the fundamental-mode Gaussian laser source is uniformlydistributed in the plane and its initial spacing of60cm, its number is four can ensure thefar field beam image quality.Finally, through the establishment of the experimental system of multi-beampropagation in the atmosphere, this thesis verifies the theoretical calculation results ofthe optimal laser source configuration. By the experiment, we analyze the influence ofthe laser source configuration on the far-field spot image quality of the vertical surfaceon the inspecting location. The experimental results show that the experiment and simulation are in good agreement.In summary, the theoretical and experimental studies show that there is probabilityof optimizing the laser source configuration. And under certain conditions, there is acertain correspondence between the optimized laser source configuration and the bestspot image quality. Through numerical analysis method validated by experiment, wecan also summarize the law of optimized laser source configuration in other conditions,so as to provide theoretical guidance for application of multi-beam transmission indifferent areas to overcome atmospheric turbulence influence.