基于数字全息显微层析技术，采用横向干涉系统，旋转被测的扭转保偏光纤，获得光纤180°视角下各个角度的全息图并由CCD记录, 通过图像处理与再现算法提取物光波的相位分布信息.利用滤波反投影还原出光纤各个断面的二维折射率分布，并由此构建扭转保偏光纤的三维折射率分布，揭示扭转保偏光纤内部的三维信息.测量结果显示，扭转保偏光纤的应力柱随着光纤同时扭转，但包层、应力柱和纤芯的折射率并不改变.采用边缘检测提取了光纤不同断面应力柱的位置，并计算了扭转保偏光纤的扭转角度.

Based on digital holographic tomography and transverse interference system, by means of rotating the spun polarization-maintaining optical fiber within 180°viewing angle, optimal digital holograms of a section of spun polarization-maintaining optical fiber were recorded by CCD, and then the phase information was extracted through digital image process and the angular spectrum algorithm. Using the filtered back-projection algorithm, the 2D refractive index distribution of each cross-section was retrieved in order to constitute the 3D refractive index distribution of a section of spun polarization-maintaining optical fiber, which revealed the 3D inner structure of the fiber. The measurement results show that the stress legs rotate synchronously with the spin of polarization-maintaining optical fiber, and the refractive indices of the fiber core, stress legs and cladding are unchanged. Finally, the position of the stress legs was achieved by edge detection algorithm and then the spun angle was computed.