基于数字全息图的光纤折射率测量研究∗

摘要

A test system including light path system and software system is built for measuring the refractive index of fiber by using the digital holographic tomography technology. Based on the phase distribution curve of object wave the optimal hologram is recorded. The spectral range corresponding to the object wave is selected accurately based on the optimization of the spectrum. The phase distribution information of object wave is extracted with the angular spectrum reconstraction. The accuracy of extracted phase information has been verified through the simulation holograms of optical fiber. Combined with the multilayers model of fiber, the refractive index distribution along the diameter direction of fiber tomogram is recovered from a single hologram. Single-mode and multi-mode optical fiber are tested as samples. The experiment results are consistent with the results of S14 refractive index profiler, the precision is 10−4. The compare result shows that our method is simple, fast and accurate for the measurement of the refractive index of fibers. We have also studied the measurement of the refractive index distribution of the special optical fiber.%利用数字全息显微层析技术构建了光纤折射率测量的测试系统，包括光路系统与软件系统.以物光波的相位分布曲线为依据由CCD记录最优的数字全息图；在优化频谱图的基础之上对全息图做频域滤波，准确选取物光波所对应的频谱范围；使用基于角谱理论的再现算法提取出物光波的相位分布信息，并通过模拟全息图验证相位提取的准确性；由单幅全息图提取的相位分布信息，结合光纤的多层模型，还原出光纤断层面沿直径方向的折射率分布.以单模、多模光纤为实验样品进行了测量，测量结果与S14折射率测量仪的测量结果吻合，精度可达10−4.实验对比结果表明本文方法可简单、快速、准确地测量光纤内部的折射率.本文还对特种光纤的折射率进行了测量研究.