Measurement of CO2 and Ultrasonic Vibration Based on Tunable Fiber Ring Laser

Nageswara Lalam,Tao Hong,Ping Lu,Michael P Buric,Fei Lu

doi:10.1109/access.2020.3032253

Nageswara Lalam, Tao Hong + Show 3 more

Open Access

https://doi.org/10.1109/access.2020.3032253

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Abstract

In this paper, we propose a method to simultaneously measure carbon dioxide (CO 2 ) concentrations and ultrasonic vibration using fiber sensors with a tunable fiber ring laser based on a loop design. The in-line interferometric vibration sensor consists of a single-mode-multimode-single-mode fiber structure and detects continuous dynamic vibrations through intensity demodulation. The evanescent wave absorption based CO 2 sensor is composed of a no-core fiber coated with silica derived from tetraethylorthosilicate. The fiber ring laser output is tuned to the CO 2 absorption wavelength of 1574.6 nm, which also best matches the quadrature bias point of the vibration sensor. The vibration frequency signals from 10 Hz to 50 kHz, and fast detection of CO 2 concentrations from 10% to 100% are experimentally demonstrated. The proposed hybrid sensor system is a promising method for monitoring the gas pipelines operating state, gas turbines, nuclear power plants, and automotive engines, where both vibration and CO 2 concentration measurements are essential.

Highlights

Monitoring and quantifying the vibrations of critical infrastructures is essential for early damage detection, structural safety, and maintenance improvement
Liu et al [10], investigated an ultrasonic vibration sensor using a fiber ring laser with two fiber Bragg grating (FBG) placed at the same sensing location and with different spectral responses to external vibrations
To demonstrate ultrasonic vibration sensing using a tunable fiber ring laser based on SMS fiber structure, a 16 cm MMF wrapped and glued around the piezoelectric transducer (PZT, outer diameter: 32 mm), where the PZT is driven by a waveform amplifier (Accel instruments, TS250) and an arbitrary waveform generator

Summary

INTRODUCTION

Monitoring and quantifying the vibrations of critical infrastructures is essential for early damage detection, structural safety, and maintenance improvement. Current techniques for monitoring vibration and CO2 gas leakage in such critical structures involve expensive and complex sensors Simultaneous monitoring of both vibration and CO2 requires a novel hybrid sensor system that allows highly sensitive and cost-effective evaluation of structural health and gas leakage concentration. The two fiber sensor structures include (i) a simple SMS fiber structure for vibration sensing and (ii) evanescent wave absorption based a no-core fiber coated with silica for CO2 measurement. Both the sensor structures use the narrowlinewidth tunable fiber ring laser, where the lasing wavelength is tuned to the CO2 absorption wavelength of 1574.6 nm by varying the displacement of a tied loop structure into the laser cavity. To the best of our knowledge, this is the first demonstration of monitoring both vibration and CO2 simultaneously, while both the sensors share a single tunable fiber ring laser source

OPERATING PRINCIPLE

30 Hz–40 kHz 42 dB at 500 Hz

CONCLUSION