Arockia Bazil Raj A, Arputha Vijaya Selvi J, Durairaj S
Appl Opt. 2015 Feb 1;54(4):802-15. doi: 10.1364/AO.54.000802.
Atmospheric parameters strongly affect the performance of free-space optical communication (FSOC) systems when the optical wave is propagating through the inhomogeneous turbulence transmission medium. Developing a model to get an accurate prediction of the atmospheric turbulence strength (C(n)(2)) according to meteorological parameters (weather data) becomes significant to understand the behavior of the FSOC channel during different seasons. The construction of a dedicated free-space optical link for the range of 0.5 km at an altitude of 15.25 m built at Thanjavur (Tamil Nadu) is described in this paper. The power level and beam centroid information of the received signal are measured continuously with weather data at the same time using an optoelectronic assembly and the developed weather station, respectively, and are recorded in a data-logging computer. Existing models that exhibit relatively fewer prediction errors are briefed and are selected for comparative analysis. Measured weather data (as input factors) and C(n)(2) (as a response factor) of size [177,147×4] are used for linear regression analysis and to design mathematical models more suitable in the test field. Along with the model formulation methodologies, we have presented the contributions of the input factors' individual and combined effects on the response surface and the coefficient of determination (R(2)) estimated using analysis of variance tools. An R(2) value of 98.93% is obtained using the new model, model equation V, from a confirmatory test conducted with a testing data set of size [2000×4]. In addition, the prediction accuracies of the selected and the new models are investigated during different seasons in a one-year period using the statistics of day, week-averaged, month-averaged, and seasonal-averaged diurnal Cn2 profiles, and are verified in terms of the sum of absolute error (SAE). A Cn2 prediction maximum average SAE of 2.3×10(-13) m(-2/3) is achieved using the new model in a longer range of dynamic meteorological parameters during the different local seasons.
当光波在非均匀湍流传输介质中传播时，大气参数会强烈影响自由空间光通信（FSOC）系统的性能。根据气象参数（天气数据）建立一个能准确预测大气湍流强度（C(n)(2)）的模型，对于理解FSOC信道在不同季节的行为具有重要意义。本文描述了在坦贾武尔（泰米尔纳德邦）海拔15.25米处建造的一条0.5公里范围内的专用自由空间光链路。使用一个光电组件和开发的气象站，分别同时测量接收信号的功率电平以及与天气数据相关的光束质心信息，并记录在数据记录计算机中。简要介绍了预测误差相对较小的现有模型，并选择它们进行比较分析。将测量的天气数据（作为输入因素）和大小为[177,147×4]的C(n)(2)（作为响应因素）用于线性回归分析，并设计更适合测试场的数学模型。除了模型公式方法，我们还展示了输入因素对响应面的个体和综合影响以及使用方差分析工具估计的决定系数（R(2)）。使用新模型（模型方程V），通过对大小为[2000×4]的测试数据集进行验证测试，获得了98.93%的R(2)值。此外，在一年期间的不同季节，使用日、周平均、月平均和季节平均的昼夜Cn2剖面统计数据，研究所选模型和新模型的预测准确性，并根据绝对误差总和（SAE）进行验证。在不同当地季节的更长动态气象参数范围内，使用新模型实现了Cn2预测的最大平均SAE为2.3×10(-13) m(-2/3)。
