Hole distortion and drift in extruded microstructured optical fiber glass preforms: Part I – Sensitivity analysis

Abstract Computational simulation of the extrusion of a glass preform for drawing microstructured optical fibers was used to study processing induced distortion and drift of the holes within the preform. Such distortion is the primary weakness of the extrusion approach. The validated model from a previous study for a preform with 36 holes is used herein for a sensitivity analysis. Symmetry of the cross section allows analysis of a thirty-degree subdomain, which contains five holes. Scalar variables are introduced to quantify preform deformation, hole distortion and hole drift. The manuscript describes and compares data sets and normalizing procedures for these variables, in order to choose a suitable set that facilitates the interpretation of the deformation, as well as the comparison between the outputs of different die designs. For two related die inserts, the sensitivity of these variables with respect to the level of friction ranging from no friction to no-slip, was studied in detail for the five holes. Such a study is required to identify ways to optimize the die insert geometry that creates the lattice of holes in the preform. Optimization is addressed in Part II, which is a companion study.