X-Ray Computed Tomography Observations of Multi-Hollowed Fibers Produced by CO₂ Laser-Heated Drawing

Multi-hollowed fibers can be fabricated by laser-heated drawing without using heteromorphic nozzles. However, the continuity of the voids in the fiber has not been ascertained. In this study, tomographic images of multi-hollowed fibers with 14% and 63% void fractions produced by laser-heated drawing were obtained by two types of X-ray computed tomography devices, and the images were compared with the cross-sectional scanning electron microscopy (SEM) images. The low X-ray absorption coefficient region was observed for the fiber cross-section of the tomographic image with 2-µm spatial resolution, while many voids with near-circular-shaped cross-sections were individually observed for the fiber cross-section of the tomographic image with 0.15-µm spatial resolution. From these observations, it was revealed that the voids in the fiber were deformed during fiber cutting before the SEM observation, and that the void in the fiber continued along the fiber axis for at least 20 times the void’s diameter.