米氏理论下悬浮粒子对水下激光传输的影响

针对海洋悬浮粒子引起水下激光传输信道的复杂性问题,采用等效球形粒子米氏散射理论和蒙特卡罗数值模拟方法,研究海洋悬浮粒子对水下光通信链路的影响。分析了悬浮粒子特性及入射光波长与光学系数的关系,研究了粒子尺寸和复折射率对接收归一化能量、接收光强、信道传输长度、信道时延的影响。理论分析和仿真结果表明:粒子的光学系数会随着粒子尺寸增大而增大,使相同信道长度的接收归一化能量减小,接收光强减弱,信道时延增大;粒子复折射率虚部越小,接收的归一化能量越强,接收光强峰值越大,但复折射率虚部相同而实部不同时,接收光强峰值的大小取决于反照率,反照率越大,接收光强越大。     

Analysis of the polarization characteristics of scattered light of underwater suspended particles based on Mie theory

Aiming at the problem of underwater polarized laser scattering caused by underwater suspended particles, the equivalent spherical particle Mie scattering theory simulation method is used to study the polarization characteristics of underwater scattered light. The relationship between underwater suspended particle characteristics and optical characteristics is analyzed, and the effects of particle size, polarization characteristics of incident light, and angle of incidence on the degree of polarization of forward and backward scattering light are studied. The results show that:When the incident light is natural light, the degree of polarization of scattered light is very low at the forward-scattering angle, which increases with the increase of the scattering angle, but changes frequently with the increase of the particle size. When the incident light is linearly polarized, the degree of linear polarization of the scattered light is related to the azimuth Angle. The degree of circular polarization is largely unaffected by particle size.     

Study on reflection characteristics of underwater target and laser echo power

For the design of the underwater laser detection system, the echo power equation of underwater target is derived, and the effects of water’s attenuation coefficient and incident angle on target’s echo power are analyzed. The bidirectional reflection distribution function(BRDF) of the single-station model is used to study the reflection characteristics of the target. The influence of the correlation coefficients of specular and diffuse reflection components on the reflected light intensity of special axisymmetric targets is studied. The signal-to-noise ratio(SNR) values of three types of target under different surface BRDF are given. The simulation results show that the larger the attenuation coefficient is, the smaller the echo power received, and the incidence angle is closer to 90°, the echo power is equal to 0. A smaller surface slope or a larger diffuse reflected coefficient will cause a smaller reflected intensity.