A high sensitivity and wide dynamic range fiber-optic sensor for low-concentration VOC gas detection.

Md Khan,Shin-Won Kang

doi:10.3390/s141223321

Abstract

In this paper, we propose a volatile organic compound (VOC) gas sensing system with high sensitivity and a wide dynamic range that is based on the principle of the heterodyne frequency modulation method. According to this method, the time period of the sensing signal shift when Nile Red containing a VOC-sensitive membrane of a fiber-optic sensing element comes into contact with a VOC. This sensing membrane produces strong, fast and reversible signals when exposed to VOC gases. The response and recovery times of the proposed sensing system were less than 35 s, and good reproducibility and accuracy were obtained.

Highlights

Volatile organic compounds (VOCs) are common air pollutants found as ingredients in many household products
The waveforms of the sensing and reference signals under ideal conditions with no VOC gas in the gas chamber are shown in Figure 4a; there was no phase difference of the sensing signal with respect to the reference signal
On the other hand, when VOC gas flowed into the gas chamber, the sensing signal shift with respect to the reference signal and was measured by an oscilloscope

Summary

Introduction

Volatile organic compounds (VOCs) are common air pollutants found as ingredients in many household products. We propose a low-cost, highly sensitive, easy-to-fabricate, fiber-optic VOC gas sensing system with wide dynamic range that is based on the principle of the optical heterodyne frequency modulation technique. According to this technique, the time period of the received sensing signal shift with respect to the reference signal time period, but the pulse width remains constant when the VOC sensitive optical sensing element comes into contact with the VOC. The proposed fiber-optic VOC gas sensing system has several other advantages, such as real-time monitoring capabilities, good reproducibility, a linear sensing response over a large dynamic range, remote sensing capabilities, compactness, and low cost, as the circuitry is based on available and inexpensive opto-electronic components

Theory and Operation Principle

Fabrication of the Side-Polished Optical Fiber Device

Fabrication of the Sensing Membrane

VOC Detection System

Results and Discussion

Conclusions