| In this paper,the blue-green laser is used as the background for latent communication,and the attenuation characteristics of blue-green laser in seawater are studied by using Mie scattering as a model.The composition of seawater is complex,with suspended particles of different particle sizes,and inorganic salts can cause different degrees of optical scattering.The number of suspended particles per unit volume in seawater,as well as the size of the suspended particles,can cause varying degrees of scattering attenuation for laser transmission.In the calculation of the scattering effect of general seawater,most of the constants estimated by experience are the scattering coefficients.The particle size of the particles of the suspended particles causing Mie scattering in seawater are qualitatively described in a manner comparable to the wavelength of light,and the description is inaccurate.This leads to inaccurate scattering coefficients in solving actual seawater.In view of the above problems,the relative particle size is constructed by comparing the actual particle size of the particle with the wavelength of the blue-green laser.The correlation coefficient of the Mie scattering model is calculated,and the average value of the cosine of the scattering angle,the extinction factor and the absorption factor are obtained.The ratio of the ratio of forward scatter factor,back scatter factor,back scatter factor and forward scatter factor as a function of relative particle size.Quantitatively calculated the particle size range of the scattered land-source suspended particles that caused the Mie scattering when the 532nm blue-green laser was transmitted in seawater.The complex refractive index of seawater suspended particles in the main component is1.34+2.34×10-4i.The influence of Mie scattering on scattering increases with the increase of the particle size of the suspended particles.The characteristic of Mie scattering,that is,the intensity of forward-backscattering,causes the average value of the cosine of the scattering angle to increase when Mie scattering occurs,and the average value of the cosine of the scattering angle tends to be0.9 when the Mie scattering is obvious.It was judged that the initial particle diameter at which the Mie scattering was generated was 508 nm.By analyzing the variation of the backscattering factor in the calculation results of Mie scattering with the relative particle size,it is judged that the particle size of the suspended particles when the Mie scattering model is not applicable is 2010 nm.This calculation provides a method for determining the particle size range of the scattering particles causing Mie scattering for water bodies of different complex refractive indices when other laser wavelengths are transmitted in seawater.The influence of the particle size of the suspended particles and the number of particles per unit volume on the extinction coefficient was compared using the mass data of terrestrial suspended particles per unit volume of the sea area.It was found that the particle size which caused the strongest Mie scattering under the above conditions was about 1200 nm.The influence of the water content of algae suspended particles on the Mie scattering is calculated.Compared with the suspended particle water dominated by the terrestrial particles,it is important to calculate the Mie scattering of the imaginary part of the complex refractive index of the water body.When the imaginary part is large,mainly affects the absorption factor caused by Mie scattering. |
