透射式微分干涉显微镜测量光纤折射率分布

Measurement of refractive index profile of optical fiber by a transmitted-light DIC microscope

提出一种由两组偏光棱镜组成的透射式微分干涉系统,用来测量光纤的折射率分布。系统利用旋转检偏器对测量光束进行调制,从相位分布和光程分布中计算出折射率分布。介绍了测量原理、测量公式、系统组成及典型应用。用该系统对光纤折射率进行实际测量,给出渐变折射率光纤的二维分布,及折射率沿轴向的分布图,同时还在NR 9200光纤测试仪上进行了测试。结果表明,系统原理正确,结构简捷,具有足够分辨率和测量精度,抗干扰能力强,不破坏光纤,还可测量包层和芯层的直径,发现光纤加工过程中的缺陷,特别适合加工、焊接等工艺过程中的检测。

A novel transmitted-light differential interference contrast (DIC) system is used to nondestructively measure the refractive index profile (RIP) of an optical fiber. By means of the new system the phase of the measured light beam can be modulated using an analyzer, and the phase distribution of a fiber is obtained by calculating the different interference pictures. The measurement theory, structure and some typical application of this system are demonstrated. The measurement results of RIP in multi-mode fiber are presented. Both the experimental results and theoretical analysis show that the system takes the advantages of high resolution, strong anti-disturbing ability and sufficient measurement accuracy for measuring refractive index. The system is feasible to measure the RIP along the fiber axis and acquire the image of the three-dimensional RIP of the fiber.