Johnson Laura J, Green Roger J, Leeson Mark S
Appl Opt. 2014 Nov 1;53(31):7273-7. doi: 10.1364/AO.53.007273.
Global refractive gradients in seawater cause pointing problems for optical wireless communications. A refractive index depth profile of the Pacific Ocean was calculated from measured salinity, temperature, and pressure, determining the end points of a refracted and nonrefracted 200 m communication link. Numerical ray tracing was used with a point source for angles between 10° and 80° and transmission wavelengths of 500-650 nm; the maximum end-point difference found was 0.23 m. A 500 nm laser with a 0.57° full-angle FOV was traced; the nonrefracted receiver location was outside the FOV for all links angled >15° to the vertical. However, most pointing issues underwater are unlikely to be significant with suitable FOV choice and natural scattering of the source.
海水中的全球折射梯度给光无线通信带来了指向问题。根据测量的盐度、温度和压力计算了太平洋的折射率深度剖面，确定了一条200米折射和非折射通信链路的端点。使用数值光线追踪法，以点源为对象，研究10°至80°之间的角度以及500 - 650纳米的传输波长；发现的最大端点差异为0.23米。追踪了一个全角视场为0.57°的500纳米激光器；对于所有与垂直方向夹角大于15°的链路，非折射接收器位置都在视场之外。然而，通过合适的视场选择和光源的自然散射，水下的大多数指向问题不太可能很严重。
