PROCEEDINGS ARTICLE | April 7, 2009
Proc. SPIE. 7293, Smart Sensor Phenomena, Technology, Networks, and Systems 2009
KEYWORDS: Optical fibers, Refractive index, FT-IR spectroscopy, Fiber Bragg gratings, Sensors, Capillaries, Spectroscopy, Composites, Fiber optics sensors, Epoxies
Whilst considerable progress continues to be made on the design and deployment of fibre optic sensors for chemical
process monitoring and structural integrity assessment, the majority of these sensor designs can only impart information
on one or two relevant measurands. For example, in the case of chemical process monitoring of advanced fibrereinforced
composites involving thermosetting resins, it is generally appreciated that cross-linking kinetics can be
influenced by a number of factors including the following: the stoichiometry of the reagents, temperature, surface
chemistry of the substrate and presence or absence of contaminants. Thermosetting resins also shrink during the crosslinking
process. When thermosets are used and processed above room temperature during the production of fibrereinforced
composites, upon cooling back to ambient temperature, residual stress can develop due to the mismatch in
thermal expansions between the reinforcing fibres and the matrix.
This paper reports on recent progress on the design and demonstration of a novel multi-functional fibre optic sensor that
can provide data on (i) temperature, (ii) strain, (iii) refractive index, (iv) transmission infrared spectroscopy and (v)
evanescent wave spectroscopy. A unique and attractive feature of this sensor is that a conventional commercially
available Fourier transform infrared spectrometer is used to interrogate the sensor. The sensor design is based on an
extrinsic fibre Fabry-Perot interferometer.
