Whispering Gallery Mode Based Optical Fiber Sensor for Measuring Concentration of Salt Solution

Chia-Chin Chiang,Jian-Cin Chao

doi:10.1155/2013/372625

Chia-Chin Chiang, Jian-Cin Chao

Open Access

https://doi.org/10.1155/2013/372625

Copy DOI

Abstract

An optical fiber solution-concentration sensor based on whispering gallery mode (WGM) is proposed in this paper. The WGM solution-concentration sensors were used to measure salt solutions, in which the concentrations ranged from 1% to 25% and the wavelength drifted from the left to the right. The experimental results showed an average sensitivity of approximately 0.372 nm/% and anR2linearity of 0.8835. The proposed WGM sensors are of low cost, feasible for mass production, and durable for solution-concentration sensing.

Highlights

The whispering gallery mode (WGM), known as whispering gallery wave, was first discovered and proposed in 1912 by the British physicist John William Strutt (Raleigh) [1], who studied the propagation of sound along wall curvatures
This study successfully developed a WGM sensor which is of low cost, can be mass-produced, and has the ability to accurately control the bending radius of the optical fiber
The resonant dip spectrum shows a significant interference loss, and the interference curves of the solutions with a concentration of 1–25% drifted toward the right gradually

Summary

Introduction

The whispering gallery mode (WGM), known as whispering gallery wave, was first discovered and proposed in 1912 by the British physicist John William Strutt (Raleigh) [1], who studied the propagation of sound along wall curvatures. The macrobending optical fiber induces a WGM. When light travels via WGMs from the fundamental mode of fibers to bends, the coupling between the core mode and the cladding mode facilitates the propagation. In 1990, Morgan et al [2] introduced a fiber-optic WGM sensor that was applicable to various angles of fiber bends. They discovered that smaller bend diameters and larger bend angles produced more distinct interference curves. This effect results from the different wavelengths that are produced by different fiber bend angles. Variations in wavelengths can be used to create fiber-optic WGM sensors with various wavelengths

Objectives

Methods

Results

Conclusion