Research On Laser Pulse Temporal Broadening Caused By Horizontal Atmospheric Layer

With the coming of the21st century, humanity has entered the informationage, the importance of information increases dramatically, the amount ofinformation increases rapidly, achieving the worldwide real-time high-speed datatransmission becomes extremely urgent and important. Comparing to thetraditional microwave communication system, free space optical (FSO)communication system has many potential advantages, such as high data rate, lowprobability of intercept, less power consumption, less volume, less mass and so on,therefore it is regarded as an effective way to achieve the worldwide real-timehigh-speed data transmission. At present, the United States, Europe and Japan havecarried on the theory and application research of FSO communication system.Atmospheric channel is an important factor which can greatly affect theperformance of FSO communication system, and its influence on laser signal ismainly caused by atmospheric scattering and atmospheric turbulence. With theincreasing rapidly of FSO communication system communication rate, theinfluence of pulse broadening caused by atmospheric channel on the BER of FSOcommunication system increases rapidly, pulse broadening severely restricts theFSO communication system communication rate, therefore it is very important toresearch the pulse broadening caused by atmospheric channel.In this thesis, the research on pulse broadening caused by atmosphericscattering and atmospheric turbulence are respectively carried out by Monte Carlomethod in a horizontal atmospheric channel, and a Monte Carlo simulation modelwhich consider both atmospheric scattering and atmospheric turbulence isestablished, concrete results are as follows:(1) Based on Mie scattering theory, a Monte Carlo simulation model with theconsideration of pulse broadening caused by atmospheric scattering is establishedin a horizontal urban path, taking into account the accuracy of simulation, theasymmetry factor g is updated according to the parameters of scatterersimultaneously. The correlations between pulse broadening caused by atmosphericscattering and FSO communication system parameters of transmission distance,atmospheric visibility, laser wavelength, receiver aperture, initial pulse width andbeam tracking deviation are analyzed, an optimization method that can effectivelydecrease pulse broadening caused by atmospheric scattering is presented.(2) Based on geometrical optics and bubbles model of atmosphere, a Monte Carlo simulation model with the consideration of pulse broadening caused byatmospheric turbulence is established in a horizontal path. The correlationsbetween pulse broadening caused by atmospheric turbulence and FSOcommunication system parameters of transmission distance, atmosphere refractiveindex fluctuating standard deviation, laser wavelength, receiver aperture, initialpulse width and beam tracking deviation are analyzed, an optimization method thatcan effectively decrease pulse broadening caused by atmospheric turbulence ispresented.(3) On the basis of atmospheric scattering model and atmospheric turbulencemodel, a Monte Carlo simulation model with the consideration of pulse broadeningcaused by atmospheric channel is established in a horizontal path. The correlationsbetween atmospheric scattering and atmospheric turbulence are analyzed.(4) Considering both atmospheric scattering and atmospheric turbulence, anoptimization method that can effectively decrease pulse broadening caused byatmospheric channel is presented.This dissertation can provide a reference for the research on pulse broadeningcaused by atmospheric channel and benefit the FSO communication system design.