Random Design Variations of Hollow-core Anti-resonant Fibers: A Monte-Carlo Study

Abstract: Hollow-core anti-resonant fibers (HC-ARFs) have earned great attention in the fiber optics community due to their remarkable light-guiding properties and broad application spectrum. Particularly nested HC-ARFs have recently reached competitiveness to standard fibers and even outperform them in certain categories. Key to their success is a precisely fine-tuned geometry, which inherently leaves optical characteristics highly susceptible to minimal structural deviations. When fabricating fibers, these come into play and manifest themselves in various imperfections to the geometry, ultimately worsening the fiber performance. In this article, for the first time to the best of our knowledge, these imperfections have been statistically modeled and analyzed on their impact to the propagation loss in a Monte-Carlo fashioned simulation. We have considered randomly varying outer and nested tube wall thicknesses as well as random tube angle offsets. We found that the loss increase due to perturbed tube angles dominates that of varying tube thicknesses by approximately an order of magnitude for FM and two orders of magnitude for HOM propagation at a wavelength of 1.55 $\mu$m. Moreover, the higher-order-mode-extinction-ratio (HOMER) is proportional to the intensity of structural variations, indicating an increase in the `single-modeness' of a fabricated fiber. Furthermore, a bend condition worsens the loss contribution of both effects applied jointly dramatically to a value of $+50\%$ at a bend radius of 4 cm compared to $+5\%$ for a straight fiber. We believe that our work helps to predict the performance of realistic HC-ARFs after fabrication.