Research On Propagation Characteristics Of Laser Signal In Solar Wind

With the development of Free Space Optical Communication(FSO),optical communication technology is applied in deep space communication due to its advantages of high transmission rate,small divergence angle,and strong confidentiality.However,due to the extremely complex deep space environment,especially during the superior conjunction,the optical communication link is gradually approaching the solar wind generated by the solar corona,and the laser signal,which is an information carrier at this time,will be affected by it.This paper studies the performance of the laser transmitted in the solar wind when the planets run to the superior conjunction.The main works are as follows:1.According to the solar physical structure,the formation reason of solar wind was derived,and the RYE model suitable for subsequent research was obtained by comparing three different solar wind plasma density models and conducting simulation analysis.Using the turbulent freezing theory,the solar wind is regarded as a continuous random medium,and the representation of the continuous random medium and the solution process under weak fluctuations are explained.2.Using the related concepts of planetary convergence,the communication geometric link diagram of the Superior conjunction period is established.Through the definition,classification,introduction of physical modes and the analysis of the dielectric properties of plasma,the effect of solar wind plasma on the attenuation and pulse broadening of laser light waves is studied by simulation.3.The theory and basic properties of turbulence formation are introduced,the distribution of solar wind turbulence spectrum in different regions is analyzed,and it is concluded that the three-dimensional power spectrum of solar wind turbulence satisfies the-11/3 power law.Combined with the turbulence spectrum,the spatial power spectrum model of solar wind turbulence is given.The order statistical moment is used to derive and analyze the analytical expressions of the angle of arrival fluctuation and scintillation index of the laser light wave,and to analyze the bit error rate under the Binary Phase Shift Keying(BPSK)modulation influenced by the scintillation index.The research results show that compared with the attenuation of laser and microwave and the degree of pulse broadening of laser,the effect of solar wind plasma on laser generation is very small;while solar wind turbulence has a great influence on the fluctuation of the angle of arrival and the scintillation index of laser,among which when the density fluctuation When the coefficient is 0.1 and 0.05,the variance of the angle of arrival fluctuation differs by about 60%.With the decrease of numerical aperture and the increase of laser wavelength,the fluctuation of the angle of arrival shows an upward trend like the scintillation index;in addition,the internal scale of solar wind turbulence has a greater impact on the scintillation index.When the signal-tonoise ratio is 30dB,the bit error rates of 1550nm,1060nm,and 880nm are 3.93×10-6,1.12×10-7,and 4.23×10-9 respectively.Therefore,the effect of solar wind on light wave can be suppressed by decreasing laser wavelength and increasing numerical aperture.