Performance Analysis Of Laser Communication Under Seawater Channel

Blue-green laser underwater communication is one of the research hotspots of underwater communication in recent years.With the rise of underwater sensing and robots,underwater laser radar,underwater image transmission,underwater optical communication,etc.,it is particularly important to study the turbulence effect and communication performance of laser beam under water.The attenuation effect of scattering and absorption of the laser beam during underwater transmission limits the transmission distance of the laser beam under water and reduces the quality of underwater laser communication.Therefore,how to improve the quality of underwater communication and reduce the bit error rate is especially important.In order to reduce the influence of ocean turbulence on the performance of underwater system links,this paper proposes an optical soliton-shaped pulse and Bessel beam in the blue-green band with anti-atmospheric turbulence properties applied to the underwater transmission system.Firstly,the basic theory of ocean attenuation,scattering and turbulence is introduced,and the research methods of laser transmission under water are introduced.Secondly,assuming that the underwater communication system is under key-controlled OOK modulation,the underwater communication process of the optical soliton,rectangular and Gaussian beam is first derived by using the research method of laser underwater transmission process combined with the ocean weak turbulent Lognormal model.The flicker coefficient model and the bit error rate model are used to analyze the relationship between different dynamic energy dissipation rate,temperature variance dissipation rate,Kolmogorov micro-scale,ratio of salinity change and temperature change,signal-to-noise ratio and bit error rate at receiving aperture.The relationship between distance and time domain broadening,compared with Gaussian and rectangular beams,verifies the advantages of optical soliton pulses for underwater communication,providing a theoretical reference for further research;secondly,using Fourier transform and random phase screen The method simulates the spot condition of Bessel beam after ocean turbulence,and derives the Rytov first-order interference term of the Bessel beam underwater communication turbulent disturbance.The Matlab numerical simulation of Bessel center brightness under different ocean parameters is simulated by Matlab numerical simulation.The relationship between the spot and the scintillation coefficient and the relationship between the communication distance and the bit error rate,so that the size of the Bessel beam center spot diameter is obtained.Effects of different turbulence coefficients and coefficients of sparkle error rate.Finally,an underwater communication experiment under different channels of Bessel beam and Gaussian beam with intensity modulation/direct detection and key-controlled OOK modulation format is designed,and the rate of clear water,turbulence,water flow,bubble and scattering agent channel is set to 1-4MHz square wave signal transmission experiment and binary digital communication experiment with clear water,turbulent flow and water flow channel rate of 2.406 Mbps,analyzing the relationship between signal waveform and peak jitter and power and communication error rate under different channels,through Gaussian The beam contrast confirms the advantages of Bessel's underwater communication against turbulence and current.The content of this paper has important theoretical value and guiding significance for solving some computational difficulties and frontier problems in the field of underwater wireless optical communication.