| Atmospheric laser communication technology has the characteristics of light structure and strong confidentiality.It has a good performance in the field of national defense technology.It is also very popular in the communication industry because of its high information transmission rate and the scalability of communication networks.It has received great attention from all countries and has made great progress since the 21 st century.Although atmospheric laser communication technology has various advantages,environmental factors may interfere with the channel and restrict its development.The influence of atmospheric turbulence on atmospheric laser communication cannot be ignored.The turbulence effect can often determine whether the performance of the whole system is suitable for communication.The influence of atmospheric turbulence on atmospheric laser communication cannot be ignored.The turbulence effect can often determine whether the performance of the whole system is suitable for communication.Therefore,studying the characteristics of atmospheric turbulence is very meaningful for understanding the atmospheric channel environment and improving the performance of atmospheric laser communication system.The transient characteristic of a pulse in a turbulent atmosphere is the time-domain characteristic of a turbulent atmosphere when the pulse width reaches the order of picoseconds or more than picoseconds.By analyzing the time-first and second-order intensity moment expressions of the light field in the atmospheric turbulent environment,it is found that there is a strong correlation between the fluctuation of the light intensity and the time.Light intensity is an important parameter to study the phenomenon of pulse broadening and pulse time-of-arrival jitter in atmospheric laser communication.Then,in order to grasp the real-time changes of the pulse,it is necessary to study the instantaneous broadening change of the ultrashort laser pulse and the change of the time-of-arrival.In this way,the communication performance of the atmospheric laser communication system can be improved in a targeted manner.It is found through research that the frequency domain response of the Butterworth filter after cascading is similar to the frequency domain response of a laser pulse with a Gaussian envelope passing through the horizontal atmospheric channel.Based on this,a model can be established to study the time domain broadening of Gaussian pulses,and is applicable to both weak and strong fluctuations.This model is used to simulate the pulse broadening under different initial pulse width,communication distance,wavelength and turbulence intensity,and the relationship between pulse broadening and physical factors such as initial pulse width,wavelength and turbulence intensity is obtained.Regarding the study of the pulse time-of-arrival under the horizontal link,the paper combines the unit delay filter and the fractional filter method to establish the model of the pulse instantaneous time-of-arrival.The relationship between normalized frequency and turbulence intensity and pulse time-of-arrival is obtained by simulation.The model is verified by simulation and achieves femtosecond accuracy.After the simulation,this paper establishes the simulation results of the real experimental environment verification.The atmospheric turbulence pool is used to simulate the real atmospheric turbulent environment,and the laser pulse after passing through the atmospheric turbulence pool is processed by an auto-correlator and an oscilloscope.Each pulse obtained was processed separately,and the data on the broadening and arrival time of the pulse was obtained.The simulation results were basically consistent with the experiment. |
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