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Proceedings Paper

Simultaneous strain and temperature measurements in composites using a multiplexed fiber Bragg grating sensor and an extrinsic Fabry-Perot sensor
Author(s): Tonguy Liu; Gerard Franklyn Fernando; Yun-Jiang Rao; David A. Jackson; Lin Zhang; Ian Bennion
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Paper Abstract

Optical fiber Bragg grating (FBG) sensors have significant potential for use as embedded devices to monitor the structural integrity of engineering materials. The main drawback of the FBG strain sensor is its cross-sensitivity to temperature. This paper reports a simple scheme for multiplexing a FBG and an extrinsic Fabry-Perot interferometric (EFPI) sensor to enable the decoupling of strain from temperature. The EFPI sensor was constructed using a precision bore quartz capillary tube which housed two cleaved optical fibers. The gap between the fiber end- faces served as the Fabry-Perot cavity. Since the coefficients of thermal expansion between the optical fiber and the capillary tube were similar, the EFPI sensor has a very low sensitivity towards temperature. Therefore, when both sensors are placed close together, the EFPI sensor can act as the strain sensor, and temperature can be determined from the FBG wavelength shift after taking out the strain effect. The signal processing for the EFPI sensor was based on a channelled spectrum method using a CCD spectrometer. The same CCD spectrometer was also used to determine the wavelength shift of the FBG. The cross-talk between the EFPI and FBG sensors was evaluated. The feasibility of conducting simultaneous strain and temperature measurements was demonstrated.

Paper Details

Date Published: 6 June 1997
PDF: 10 pages
Proc. SPIE 3042, Smart Structures and Materials 1997: Smart Sensing, Processing, and Instrumentation, (6 June 1997); doi: 10.1117/12.275737
Show Author Affiliations
Tonguy Liu, Brunel Univ. (United Kingdom)
Gerard Franklyn Fernando, Brunel Univ. (United Kingdom)
Yun-Jiang Rao, Univ. of Kent at Canterbury (United Kingdom)
David A. Jackson, Univ. of Kent at Canterbury (United Kingdom)
Lin Zhang, Aston Univ. (United Kingdom)
Ian Bennion, Aston Univ. (United Kingdom)

Published in SPIE Proceedings Vol. 3042:
Smart Structures and Materials 1997: Smart Sensing, Processing, and Instrumentation
Richard O. Claus, Editor(s)

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