Research On Turbulent Propagation Characteristics Of High-frequency Laser Pulse Based On Spectrum Analysis

Laser communication is an emerging communication technology,it can meet the practical needs such as high transmission rates,large communication capacity and strong antiinterference ability,in the future of the communications field has great potential development.The high-frequency laser pulse are subject to absorption,scattering and atmospheric turbulence during atmospheric channel propagation,resulting in beam expansion,pulse broadening,angle-of-arrival and other phenomena,leading to sharp decline in the performance of laser communication systems.In this paper,the transmission characteristics of the highfrequency laser pulse in atmospheric channels are studied.In this paper,the transmission characteristics of the high-frequency laser pulse in atmospheric channel as a research object,and the influence characteristics and rules of atmospheric turbulence on high frequency laser pulse propagation are studied.In this paper,firstly,the influence mechanism of atmosphere on laser transmission is studied theoretically,and the attenuation effect caused by atmospheric absorption and scattering is briefly introduced.And the statistical characteristics of atmospheric turbulence and the influence of intensity fluctuation,angle-of-arrival fluctuation and beam drift on the performance of laser communication system are discussed.Secondly,the spectrum analysis method is analyzed,including the basic theory and advantages of Fourier transform and Wavelet transform,at the same time the two are compared.Then,the signal waveform of laser pulse propagation in atmospheric turbulence and the frequency variation rules of intensity fluctuation are studied by numerical analysis.Finally,the Fourier transform and wavelet transform are used to analyze the signal waveform variation and scintillation spectrum characteristics of high frequency laser pulse propagation,as well as the characteristics of the signal waveform and intensity fluctuation trend of the corresponding spectrum analysis.The results show that the slope of the low-frequency and high-frequency parts of the laser pulse signal power spectral density is consistent with the Kolmogorov model.The existence of high frequency bumps seriously interferes with the original signal quality,and the convex intensity is related to the spectral width;when the rectangular pulse sequence with repetition frequency of 100 MHz is transmitted,the side lobes peak of the transmitted pulse time domain waveform spectrum is equal to or larger than 0.48 GHz,and then disappears to the receiver end.The pulse intensity peak appears at the falling edge of the transmitting rectangular pulse,and the pulse intensity time distribution is expanded obviously.The high frequency power exponent of light intensity is no longer a fixed result,and the wind speed has certain influence on the spectrum of intensity fluctuation.