大气激光通信中的光斑特性模拟和验证

根据空-地大气激光通信信道的特性,基于惠更斯-菲涅耳原理,应用夫琅禾费圆孔衍射的算法,对光波强度和光斑图像在光束截面内的分布进行分析及计算,研究了传输距离、发射孔径、激光波长以及湍流结构常数等对光斑形状及光强分布的影响。利用对数正态分布建立了大气湍流信道模型,通过对不同传输距离条件下光斑上不同点的光强分布进行计算统计和仿真分析,实验和仿真结果表明：光斑的光强分布图样服从贝塞尔分布。因此,在相同的大气湍流条件下,选择较长波长激光和较大孔径的发射器,可以有效降低光强闪烁引起的衰减,从而提高大气激光的通信质量。     

International comparison of the SIAR measurement and the WRR standard

We experimentally compare the solar irradiance absolute radiometer (SIAR) measurement with the world radiometric reference (WRR) standard to improve the accuracy of instrument. The SIAR joined in the international pyrheliometer comparison (IPC) in 2000. The comparison results show that the calibration factors for SIAR to WRR are 0.999 220, 1.001 694, 0.998 334 and 0.997 439 in the 9th IPC, the 10th IPC, the 11th IPC and the 12th IPC, respectively. These results are added to the measurement uncertainty budget of SIAR. The repeatability of the SIAR-type absolute radiometers is also investigated. The relative error introduced by two SIAR-type absolute radiometers is within 0.25%.