Simultaneous strain and temperature sensor based on the numerical reconstruction of polarization maintaining fiber Bragg gratings |
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Authors: | C Caucheteur F Lhomm K Chah M Blondel P Mgret |
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Institution: | Faculté Polytechnique de Mons, Electromagnetism and Telecommunication Unit, 31 Boulevard Dolez, 7000 Mons, Belgium |
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Abstract: | When a short-length fiber Bragg grating is inscribed into a polarization-maintaining fiber, the resonant peaks produced by birefringence can overlap. In this case, the discrimination between strain and temperature effects is only possible by means of polarization control devices, i.e. a linear polarizer and a polarization controller. To avoid this complexity and the measurement errors that it involves, we propose a novel demodulation technique based on the numerical reconstruction of the grating physical parameters. Our technique evaluates the grating parameters from the amplitude spectrum by means of the coupled-mode equations. The convergence tool used to search the solutions is the Nelder–Mead simplex algorithm. The method is tested on uniform and apodized Bragg gratings and a very good accuracy is reported. The method is finally applied to a 2 mm-long uniform polarization-maintaining grating in order to simultaneously measure longitudinal strain and temperature. |
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Keywords: | Bragg gratings Polarization maintaining fibers Sensor Strain Temperature |
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