光纤布喇格光栅器件应力疲劳评价理论研究

在10℃~230℃温差下,对大气相干长度r₀分别采用夏克-哈特曼的到达角起伏法、差分像运动法、波面法三种测量法和四象限探测器进行了测试和对比;对折射率结构常量C_n²及闪烁功率谱分别采用夏克-哈特曼和光电倍增管进行对比.实验结果表明:对于r₀,在强湍流时四象限探测器比夏克-哈特曼的稳定性明显降低,且对夏克-哈特曼三种方法,差分像运动法可克服设备抖动等问题,但引入了方向上不一致的问题,波面法可有效避免该问题;对于C_n²,夏克-哈特曼比光电倍增管测量更稳定,拟合相关系数高达0.96;对于闪烁功率谱,由于噪音影响,在200℃时夏克-哈特曼比光电倍增管测得的最大频率高15 Hz;最后,通过对夏克-哈特曼子孔径的闪烁功率谱分析得出,若同一子孔径入射光强不在CCD响应的线性区间时无法准确测量闪烁功率谱,否则可通过不同子孔径可完成湍流均匀性的测量.这将为湍流池提供最优的测试方法及理论依据.

Turbulence Characteristics Optical Test Contrast

During the temperature difference of 10℃~230℃, three kinds of Shack-Hartman measuring methods are used to contrast atmospheric coherence length r₀ with quadrant detector(QD), and Shack-Hartman(SH) and photomultiplier tube(PMT) respectively are applied to contrast refractive index structure parameter C_n² with scintillation power spectrum. The experimental results show that: for r₀, the stability of QD decreases more obviously than SH when there is strong turbulence, and for three Shack-Hartman methods, DIMM overcomes problems such as device jitter but brings in problem of inconsistency in direction which wave front method can avoid; for C_n², SH is more precise than PMT which fitting correlation coefficient is up to 0.96; for scintillation power spectrum, the maximum frequency SH tested is 15 Hz higher than that of PMT when it is 200℃ influenced by noise; through the analysis of Shack-Hartman sub-aperture scintillation power spectrum, the scintillation power spectrum is not able to be measured precisely and different sub-apertures accomplish the measurement turbulence uniformity when the same sub-aperture incident intensity is not in the CCD response linear interval. The results will provide an optimal test method and theoretical basis for turbulence cell.