Document Type

Theses, Ph.D

Disciplines

Electrical and electronic engineering

Abstract

The optical Vernier effect has emerged as a powerful tool to enhance the sensitivity of optical fiber interferometer-based sensors, opening new opportunities for developing highly sensitive fiber sensing systems. Optical fiber interferometric sensors based on the Vernier effect are widely used for various applications due to their ultra-compact size, high sensitivity, immunity to electromagnetic interference, electrical isolation, resistance to harsh environments, flexibility, multiplexing capability, and remote operation. The aim of this doctoral thesis was to gain a deeper fundamental understanding of the Vernier effect in optical fiber structures and to develop and investigate a series of novel Vernier effect optical fiber sensors with higher sensitivity, better robustness, and potentially lower fabrication costs for applications in temperature sensing, force sensing, and flow rate measurements.

An optical fiber force sensor based on the Vernier effect in cascaded Fabry-Perot interferometers (FPIs) formed by a barium tantalate microsphere and a section of PMMA optical fiber is proposed and investigated. Force sensing was achieved through the elastic deformation of the PMMA fiber section. The experimental results indicate a force sensitivity of 9279.66 nm/N. The sensor also exhibits excellent repeatability, making it a promising candidate for high-performance force monitoring in various challenging environments.

A novel fiber Fabry-Perot interferometer (FPI) temperature sensor that leverages the Vernier effect for enhanced sensitivity is proposed and investigated. The sensor comprises a cascade of two FPIs formed by a short polymethyl methacrylate (PMMA) capillary, a barium titanate microsphere, and a cleaved single-mode fiber. The Vernier effect, induced by the dual Fabry-Perot cavities, amplifies the temperature sensitivity. The fabrication process involves precisely aligning and gluing components, resulting in I a simple, cost-effective sensor. The experimental results indicate a temperature sensitivity of 1.90 nm/°C. The sensor also exhibits excellent repeatability, making it suitable for various temperature monitoring applications.

A novel Vernier effect-based cascade Fabry–Pérot interferometer flow sensor. A very thin PDMS film is fabricated in a silica capillary coupled with a no-core fiber and a single mode fiber. Flow measurement was achieved by measuring pressure changes using Bernoulli's principle and an ultra-thin, high-elasticity PDMS film that is sensitive to pressure. The experimental results indicate a flow rate sensitivity of 6.86 nm/(ml/min). This compact, sensitive, non-invasive, low-cost flow-rate sensor has significant potential for applications in medical treatment, biochemistry, and agricultural irrigation research.

DOI

https://doi.org/10.21427/zapn-sy56

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