Wu Chensheng, Rzasa John R, Ko Jonathan, Paulson Daniel A, Coffaro Joseph, Spychalsky Jonathan, Crabbs Robert F, Davis Christopher C
Appl Opt. 2018 Jan 20;57(3):551-559. doi: 10.1364/AO.57.000551.
We present the theory, design, simulation, and experimental evaluations of a new laser transmissometer system for aerosol extinction rate measurement over long paths. The transmitter emits an ON/OFF modulated Gaussian beam that does not require strict collimation. The receiver uses multiple point detectors to sample the sub-aperture irradiance of the arriving beam. The sparse detector arrangement makes our transmissometer system immune to turbulence-induced beam distortion and beam wander caused by the atmospheric channel. Turbulence effects often cause spatial discrepancies in beam propagation and lead to miscalculation of true power loss when using the conventional approach of measuring the total beam power directly with a large-aperture optical concentrator. Our transmissometer system, on the other hand, combines the readouts from distributed detectors to rule out turbulence-induced temporal power fluctuations. As a result, we show through both simulation and field experiments that our transmissometer system works accurately with turbulence strength Cn2 up to 10 m over a typical 1-km atmospheric channel. In application, our turbulence- and weather-resistant laser transmissometer system has significant advantages for the measurement and study of aerosol concentration, absorption, and scattering properties, which are crucial for directed energy systems, ground-level free-space optical communication systems, environmental monitoring, and weather forecasting.
我们介绍了一种用于长路径气溶胶消光率测量的新型激光透射仪系统的理论、设计、模拟和实验评估。发射器发射开/关调制的高斯光束，无需严格准直。接收器使用多个点探测器对到达光束的子孔径辐照度进行采样。稀疏的探测器布置使我们的透射仪系统不受湍流引起的光束畸变和大气通道导致的光束漂移的影响。湍流效应常常会导致光束传播中的空间差异，并在使用传统方法通过大孔径光学聚光器直接测量总光束功率时导致对真实功率损失的误算。另一方面，我们的透射仪系统将分布式探测器的读数结合起来，以排除湍流引起的时间功率波动。结果，我们通过模拟和现场实验表明，在典型的1公里大气通道上，我们的透射仪系统在湍流强度Cn2高达10 m时仍能准确工作。在应用中，我们的抗湍流和耐天气的激光透射仪系统在气溶胶浓度、吸收和散射特性的测量和研究方面具有显著优势，这些特性对于定向能系统、地面自由空间光通信系统、环境监测和天气预报至关重要。
