Photonic microstructures in optical fiber and their sensing applications

Sadri, Behzad (2021) Photonic microstructures in optical fiber and their sensing applications. Masters thesis, Memorial University of Newfoundland.

[English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (7MB)

Abstract

Optical fiber sensors have attracted significant interest in their physical properties and potential applications due to their advantages of compact size, light weight, immunity to electromagnetic interference, and viability in harsh environments. To achieve the potential for applications, it is essential to reveal the underlying physics through both experimentation and simulation, which is an ongoing task now. In this study, microstructures in optical fiber, such as tapers and long-period grating (LPG), are investigated by simulation with COMSOL Multiphysics software, which is also compared with experiments in this study or the experimental results achieved by this group. In the experimentation of this study, the effects of different fabrication parameters on the formation of micro-taper in optical fiber and the transmission spectra of the resulting LPGs are carried out, which indicates that the average diameter of the micro-taper decreases and a blueshift in the transmission spectrum of the LPG occurs by increasing any of the three fabrication parameters such as arc current, arc duration, and tension along the fiber. The sensitivities of LPG to environmental refractive index and temperature are studied computationally, which shows the highest sensitivity of refractive index of 171.82 nm/RIU (Refractive Index Unit) and the temperature sensitivity of 10 pm/℃. Furthermore, tapered fibers in the configurations of either single or in-line Mach-Zehnder interferometer are studied as biosensors for detecting the concentration of Streptavidin (SV) protein computationally and compared with the experimental results previously obtained in our research group. The simulation results show good agreement with the experimental results indicating the effective refractive indices of the coating materials play a significant role in determining the sensitivity. The findings achieved from this study are helpful for designing LPG-based and tapered fiber-based optical fiber sensors and biosensors, which enable the applications of these optical sensors in various fields, such as telecommunication, chemistry, medical and environmental sciences.

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