激光在海水界面上的传输特性分析

Behavior analysis of laser beam traversing the sea surface

利用海—空界面的数学模型,对海面激光束的漂移和扩散作用进行分析。水下激光通信系统的光学信道是由大气、空—海界面和海—空界面以及海水组成;激光由海—空界面和空—海界面分别进行上下行传输。由于上下行信道的传输特性并非是简单可逆的,必须从两个不同的方面来分析激光在海水界面上的传输问题。通常海水界面不是平静的水平面,容易受到风力或其他外力的影响,产生随机起伏,降低接收光功率,由此提高了对接收机的要求。光在不同介质中的传播特性不同,大气和海水折射率的差别是影响激光传输的决定性因素。通过激光在空—海界面上的传输情况,建立海水→大气界面的数学模型,着重在理论上分析激光束在上行信道上通过海面的扩散和漂移规律。

Optical channels of underwater laser communication system consist of air, sea, air to sea and sea to air surface. Laser transmission through sea to air surface and air to sea are respectively transmitted to upllnk and downlink channels, Communication between a platform in atmosphere and a underwater target and communication from underwater to above surface platform are two nonreciprocal problems. The study of laser beam transmission thus can be done in two parts. Generally sea surface is fluctuant and influenced easily by wind or other acting force, which reduces received optical power seriously and raises the requirement of receiver performance. Transmission characteristics of light beam in different media are distinctive. Difference of refractive index of air and seawater is a determination factor that affects laser transmission. Laser transmission through air to sea surface is described briefly and a model of sea to air surface is constructed. Finally, laser beam spread and excursion through rand fluctuant sea surface are analyzed.