Non-destructive real-time characterization of anti-resonant hollow-core fibers using Fabry-Pérot interferometry

Reliable industrial manufacturing of anti-resonant hollow-core fibers (AR-HCFs) requires non-destructive, in-line real-time measurements of the fiber structure during drawing. Such a method was recently developed, but it suffered from measurement deviations as the fiber rotated, as well as other disadvantages. Here we demonstrate a greatly improved measurement principle based on Fabry-Pérot interference, which allows for direct measurement of the wall thickness of the AR cladding elements, the gap between capillaries, jacket thickness, and jacket inner diameter. The core diameter can also be inferred from these measurements. The method is therefore more robust, provides more useful information, and enables a significant improvement in the uniformity and length of AR-HCFs.