Date of Award
8-2026
Document Type
Thesis
Degree Name
Master of Science in Engineering (MSE)
Department
Materials Science and Engineering
Committee Chair/Advisor
Dr. John Ballato
Committee Member
Dr. Wade Hawkins
Committee Member
Dr. Phil Brown
Abstract
P₂O₅ is a common dopant core material in silica-based glass optical fibers, in part due to its ability to increase the refractive index of silica, required for the fiber to guide light. However, P₂O₅-doped fibers can show a significant decrease in the refractive index profile compared to that of the parent preform. The question arises as to whether the refractive index decreasing could be a direct result of the fiber draw process and, if so, what is it about the draw process that causing such changes in phosphosilicate fibers. More specifically, this Thesis explores the hypothesis that these draw-induced reductions in refractive index between parent preform and drawn fiber result from one or both of the following effects: draw-induced stresses caused by the mismatch in thermal expansion coefficients between the phosphosilicate core and the pure silica (SiO₂) cladding combined with the sudden quenching these fibers endure during the fiber draw process, and/or a change in core chemistry that is connected to the draw tension before the core glass structure is locked-in when the fiber rapidly cools. These added stresses and this possible chemistry change may alter the glass structure thus impacting the refractive index profile.
The goal of this research is to systematically investigate the current fiber draw parameters, ultimately looking to have more control over this preform verse fiber index change. This research will also look to determine if internal stresses or core chemistry plays a major part in the refractive index profile (RIP) changes, relating back to the fiber draw parameters. Several approaches are investigated, including changing fiber draw speed, furnace temperature, fiber size, and draw tension while the parent preform composition and fabrication are kept as consistent as possible. By identifying how these draw conditions affect the intrinsic stress and core chemistry, the ultimate aim of this Thesis is to understand the post-draw refractive index change and look to establish primary draw conditions for future P₂O₅-doped fibers. On top of specific fiber draw experiments, this research will also explore post processing techniques such as fiber annealing to further investigate the RIP decrease, although the primary goal will remain focused on the fiber draw process and parameters.
Recommended Citation
Baldus, Brandi, "Investigating the Effects of Draw Parameters on the Refractive Index Profiles of Phosphosilicate Fibers" (2026). All Theses. 4821.
https://open.clemson.edu/all_theses/4821