Towards complete characterization of hollow core fiber geometry

Antiresonant hollow core fibers are significantly more complex to fabricate than solid core fiber, in part due to the need to maintain the uniformity of the complex microstructure along the entire fiber and the lack of techniques available to profile its geometry non-destructively. In this Letter, we present results showing accurate non-destructive measurements of a hollow core fiber microstructure. By combining two previously reported methods, we overcome the limitations of using either technique alone to yield accurate measurements of crucial geometrical parameters, including the distance between the two fusing points where the capillary microstructure elements meet the surrounding jacket tube and the capillary diameter itself. For the DNANF tested here, this combined method offers a substantial improvement to the middle and outer capillary diameter measurements, reducing the discrepancies from around 6% for each measurement to 0.6% and below.