Study On The Ocean Turbulence Phase Screen Model And The Transmission Characteristics Of OAM Beam Under This Model

Oceanic turbulence is one of the important factors that restrict the transmission of laser in the sea water.With the rise of underwater radar detection,underwater laser transmission and underwater communication technology,it is very important to study the characteristics of laser transmission under water.In order to facilitate the study,an oceanic turbulence model needs to be established.In this paper,a random phase screens model of oceanic turbulence and the propagation characteristics of orbital angular momentum beam in seawater are studied.The main work are as follow.Firstly,reference to the atmospheric turbulence random phase screen model,the mathematical expression of the random phase screen model of ocean turbulence is given by using the power spectrum inversion method.The validity of the proposed model is testified by the phase structure function and the transmission characteristic(detection possibility)of orbital angular momentum beam in ocean turbulence.Results show that the phase structure function value of the model is coincident with the theoretical value in high frequency part.At The same time,OAM detection probability is also consistent with the theoretical value.On this basis,in view of the problem that low spatial frequency components deviate from theory value,the statistical characteristics of the phase screen are improved by superposition of low frequency subharmonic.Result shows that the phase structure function of the phase screen will be basically consistent with the theoretical value when 4 order low frequency subharmonic are added.Secondly,as a new degree of freedom,the orbit angular momentum of the beam will greatly increase the rate of information transmission in optical communication.Therefore,it is of great significance to study the transmission characteristics of OAM beam in sea water.This paper uses the random phase screen method for numerical simulation of Laguerre Gauss light and Bessel Gauss,the two light drift characteristics of orbital angular momentum beam in seawater scintillation properties and detection probability.Numerical simulation results show that Bessel-Gaussian Beam in the drift is superior to Laguerre-Gaussion Beam.In the aspect of the scintillation characteristics,the two beams are basically consistent.Bessel-Gaussian Beam through the detection probability of ocean turbulence was higher than Laguerre-Gaussion Beam.