A fully distributed multi-parameter acoustic sensing technology is proposed. Current fully distributed sensing techniques are exclusively based on intrinsic scatterings in optical fibers. They demonstrate long sensing span, but their limited applicable parameters (temperature and strain) and costly interrogation systems have prevented their widespread applications.
A novel concept of acoustic fiber Bragg grating (AFBG) is conceived with inspiration from optical fiber Bragg grating (FBG). This AFBG structure exploits periodic spatial perturbations on an elongated waveguide to sense variations in the spectrum of an acoustic wave. It achieves ten times higher sensitivity than the traditional time-of-flight measurement system using acoustic pulses. A fast interrogation method is developed to avoid frequency scan, reducing both the system response time (from 3min to <1ms) and total cost.
Since acoustic wave propagates with low attenuation along varieties of solid materials (metal, silica, sapphire, etc.), AFBG can be fabricated on a number of waveguides and to sense multiple parameters. Sub-millimeter metal wire and optical fiber based AFBGs have been demonstrated experimentally for effective temperature (25~700 degC) and corrosion sensing. A hollow borosilicate tube is demonstrated for simultaneous temperature (25~200 degC) and pressure (15~75 psi) sensing using two types of acoustic modes. Furthermore, a continuous 0.6 m AFBG is employed for distributed temperature sensing up to 500 degC and to accurately locate the 0.18 m long heated section.
Sensing parameters, sensitivity and range of an AFBG can be tuned to fit a specific application by selecting acoustic waveguides with different materials and/or geometries. Therefore, AFBG is a fully distributed sensing technology with tremendous potentiality. / Ph. D. / Fully distributed sensing techniques are part of the growing ”Internet-of-Things” trend, as they improve on traditional point sensors by providing spatially distributed measurements. Current techniques for fully distributed sensing are based on fiber optics, and while these techniques are capable of measuring parameters along a lengthy sensing distance, their wider application is constrained by limited applicable parameters and costly interrogation systems.
In this research, an innovative, fully distributed, multi-parameter acoustic sensing technology based on acoustic fiber Bragg grating (AFBG) is proposed. AFBG takes advantage of the interaction between an acoustic wave and the periodic structure on the measured material, and uses the spectrum property of an acoustic wave to achieve ten times higher sensitivity than traditional time-of-flight methods. In addition, a fast interrogation method is developed to avoid frequency scan, reducing both the system response time (from 3 min. to <1 ms) and system cost (from $5, 000 to < $500).
AFBG can be fabricated using different elongated materials (i.e. waveguides) as acoustic waves propagate along a variety of materials without extensive power loss. In this research, AFBG is deployed on a sub-millimeter metal wire and silica fiber to demonstrate effective corrosion and temperature sensing (25 ∼ 700 ◦C). In addition, hollow tubes are shown to be feasible waveguides for simultaneous temperature (25 ∼ 200 ◦C) and pressure (15 ∼ 75 psi) sensing. Finally a long AFBG is employed for distributed temperature sensing up to 500 ◦C.
Wide applicability and low cost suggest that this sensing technology may be a viable approach for fully distributed sensing, contributing to the growing Internet-of-Things movement.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/85112 |
| Date | 31 March 2017 |
| Creators | Hu, Di |
| Contributors | Electrical and Computer Engineering, Wang, Anbo, Pickrell, Gary R., Zhu, Yizheng, Safaai-Jazi, Ahmad, Li, Qiang |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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