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Title:Determination of thermo-optic coefficient for B2O3 and GeO2 co-doped optical silica fiber
Author(s):Pan, Guanyi
Advisor(s):Dragic, Peter D.
Department / Program:Electrical & Computer Eng
Discipline:Electrical & Computer Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:M.S.
Genre:Thesis
Subject(s):Thermo-optic coefficient
fiber
Abstract:The goal of this work is to better understand the influence of B2O3 and GeO2 on the thermo-optic coefficient (TOC) of silica optical fiber. This is important since understanding the contributions to the TOC by these constituents can provide insight into the way to lower the positive-valued TOC of SiO2, which is a potential method to decrease the influence of transverse mode instability (TMI). Measurements of thermo-optic coefficients (TOC) in five different optical silica based fibers are presented here. One of them is doped with GeO2 in the core and the remaining four fibers are co-doped with B2O3 and GeO2. A revised additivity model is applied to the measurements in order to determine the relative contributions to the TOC for each constituent. Three of the ternary GeO2 and B2O3 co-doped silica core fibers are drawn from the same preform at different temperature, which gives some indication about the relationship between TOC value and the drawing temperature. TOC of B2O3 calculated here possesses a lower magnitude than that previously reported, and so do SiO2 and GeO2. The results indicate that the magnitude of the TOC value increases with drawing temperature. Two methods of measuring the modal TOC were employed here: (1) measuring the LP11 cutoff wavelength as a function of temperature, (2) determining the composition using the Brillouin gain spectrum and calculating the modal TOC by the additivity model. Both methods provide insight into the reliability of the TOC value for fiber constituents. The former method also suggests an interesting application for fiber cores with a lower TOC value than the cladding: fibers whose V number reduces when raising the temperature for high-energy laser applications.
Issue Date:2020-06-23
Type:Thesis
URI:http://hdl.handle.net/2142/108567
Rights Information:Copyright 2020 Guanyi Pan
Date Available in IDEALS:2020-10-07
Date Deposited:2020-08


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