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Proceedings Paper

Special optical fiber design to reduce reflection peak distortion of a FBG embedded in inhomogeneous material
Author(s): Lun-Kai Cheng; Peter Toet; Jan de Vreugd; Remco Nieuwland; Ming-Leung Vincent Tse; Hwayaw Tam
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Paper Abstract

During the last decades, the use of optical fiber for sensing applications has gained increasing acceptance because of its unique properties of being intrinsically safe, unsusceptible to EMI, potentially lightweight and having a large operational temperature range. Among the different Fiber Optic sensor types, Fiber Bragg Grating (FBG) is most widely used for its unique multiplexing potential and the possibility of embedding in composite material for Structural Health Monitoring. When the fiber is embedded in an inhomogeneous environment, typically a material composed of filler and base material of different stiffness, local stiff material will generate extra lateral load to the fiber. Via the Poisson effect, this will be converted to a local axial strain. The narrow and sharp peak in the reflection spectrum of an FBG sensor relies on the constant periodicity of the grating. An inhomogeneous axial strain distribution will result in distortion or broadening of the FBG reflection spectrum. For the FBG strain sensitivity of about 1.2pm/με, the spectral distortion can be disastrous for strain measurements. A fiber design to tackle this critical problem is presented. Finite Element Modeling is performed to demonstrate the effectiveness of the solution. Modeling with different configurations has been performed to verify the influence of the design. The deformation of the core in the special fiber depends on the design. For a particular configuration, the core deformation in the axial direction is calculated to be a factor of 10 lower than that of a standard fiber. The first prototype fiber samples were drawn and the manufacturing of FBG in this special fiber using the phase mask method was demonstrated successfully.

Paper Details

Date Published: 10 March 2014
PDF: 6 pages
Proc. SPIE 9059, Industrial and Commercial Applications of Smart Structures Technologies 2014, 90590L (10 March 2014); doi: 10.1117/12.2052872
Show Author Affiliations
Lun-Kai Cheng, TNO (Netherlands)
Peter Toet, TNO (Netherlands)
Jan de Vreugd, TNO (Netherlands)
Remco Nieuwland, TNO (Netherlands)
Ming-Leung Vincent Tse, The Hong Kong Polytechnic Univ. (Hong Kong, China)
Hwayaw Tam, The Hong Kong Polytechnic Univ. (Hong Kong, China)

Published in SPIE Proceedings Vol. 9059:
Industrial and Commercial Applications of Smart Structures Technologies 2014
Kevin M. Farinholt; Steven F. Griffin, Editor(s)

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