Advanced layout of a fiber Bragg grating strain gauge rosette

• Published in: Journal of lightwave technology Vol. 24; no. 2; pp. 1019 - 1026
• Main Authors: Betz, D.C., Thursby, G., Culshaw, B., Staszewski, W.J.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.02.2006; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Backing; Bonding; Bragg gratings; Capacitive sensors; Circuit properties; Design engineering; Electric, optical and optoelectronic circuits; Electronics; Exact sciences and technology; Fiber Bragg gratings; Fiber gratings; Fibers; Finite element method; Finite element methods; Integrated optics. Optical fibers and wave guides; Joining processes; Optical and optoelectronic circuits; Reduction; Robustness; rosette; Strain; Strain gauges; strain mapping; Strain measurement; Temperature measurement; Temperature sensors; Resistance strain gauge; Integrated optics; Fiber Bragg gratings; rosette; Temperature effect; Bragg grating; Mapping; Grating in fiber; Deformation measurement; Temperature measurement; Finite element method; Thermal compensation; Optical fiber; strain mapping
• ISSN: 0733-8724; 1558-2213
• DOI: 10.1109/JLT.2005.862442

A temperature-compensated strain-sensing scheme based on fiber Bragg gratings (FBGs) that is suitable for strain mapping applications is described. FBGs are bonded to a backing patch, together with an extra grating that is used for temperature compensation/measurement. The patch provides a simpler and more robust way of attaching the FBGs to a structure than directly mounting a bare fiber, though it was necessary to design it in such a way that there was minimal reduction in the strain transferred from the structure to the sensing fibers. Finite element (FE) analysis was used to help design the patch, which was then constructed accordingly. The authors have demonstrated experimentally that the use of the backing patch produces a reduction in strain sensitivity of only around 4%, which is slightly better than theoretically predicted values. The temperature measuring FBG had to be bonded in such a way that it experienced the changes in temperature, but not the strain, to which the structure was subjected. A design for doing this was developed and proven. The use of a backing patch to develop a rosette configuration of Bragg gratings, each having a different peak reflective wavelength, is described. The rosette configuration is one that is frequently used with electrical strain gauges and allows here to determine both the magnitude and the direction of strain.