测量侧边抛磨光纤(side-polished fiber, SPF)的包层剩余厚度对其应用有重要的指导意义, 现今的测量方法均有所不足, 现提出一种基于数字全息技术的测量方法。利用单模光纤纤芯折射率比包层折射率高的特点, 基于数字全息成像技术, 通过角谱传播法对二维全息图进行相位重构, 并通过精确最小二乘法解相位包裹, 得到侧边抛磨光纤的相位分布图。根据重构的相位分布图, 进一步运用相关的边缘提取算法处理得到侧边抛磨光纤包层剩余厚度。实验测量结果与电子扫描电镜(SEM)测量结果相比, 测量相对误差小于0.5%。这种测量方法是一种直接测量方法, 减小了间接测量法中由于光纤不对称以及SPF轮廓边缘衍射所带来的测量误差, 为侧边抛磨光纤包层剩余厚度的无损、在线测量提供了一种新的途径。同时, 此方法还可应用于测量其他特种光纤, 例如光子晶体光纤、微纳光纤等。

A novel method to measure the cladding thickness of side-polished fiber (SPF) was demonstrated by using the digital holographic imaging technology. Using angular spectrum method and accurate least-squares phase unwrapping method, SPF’s distribution of phase was reconstructed. Based on the reconstructed distribution of phase, the cladding thickness of SPF could be directly measured. Compared to the results measured by scanning electron microscope (SEM), the relative error is less than 0.5%. This is a non-destructive, real-time and direct measurement, it can reduce the errors due to fiber’s asymmetries and edge diffraction. This method could also be used to measure other special optical fibers such as photonic crystal fiber and nano-fiber.