Abstract
An evaluation of a novel spectrum features combining the distant longer and shorter wavelengths of a single chirped fiber Bragg grating (CFBG) for temperature and transverse forces discrimination is experimentally demonstrated. The shift of the two distant wavelengths’ pair is compared with the conventional pair combining the bandwidth modulation and center wavelength shift. The CFBG sensor is simply bonded to a cantilever beam and subjected to transverse loading (four times) and a heating-cooling cycle. The transverse forces calibration results show a repeatability of 3.9 pm and 1.7 pm for the bandwidth’s and center wavelength’s responses, respectively, while the distant wavelengths’ show a repeatability of 2.37 pm and 3.01 pm, respectively. The cantilever CFBG sensor exhibits high correlation coefficients of 0.9 between the two heating and cooling data sets, except for the bandwidth, which only had a lower coefficient of 0.75. The linear model of both pairs for calculating temperature and transverse forces can provide an accurate estimate, with the longer-shorter wavelengths’ pair having an advantage over the pair of the bandwidth-centre-wavelength. The study has demonstrated the feasibility of the method proposed by our group in a previous work, by which three physical quantities can be measured with a single custom FBG.
Highlights
CROSS sensitivity of the central resonance wavelength shift of fiber Bragg grating (FBG) between the temperature and the mechanical strain is the main challenge in many applications
This study aims to investigate the response of the two reflection spectra pairs of the chirped fiber Bragg grating (CFBG) to the transverse forces and temperature and perform a feasibility assessment of the proposed spectral pair for simultaneous temperature and transverse forces measurement
The CFBG sensor is illuminated by a superluminescent lightemitting diode (SLED) through a built-in optical circulator, the back-reflected light from the CFBG travel to the FBG interrogator IMON-256USB (Ibsen Photonics, Rytter-Marken 17, Denmark) in which transmission diffraction gratings disperse the incoming light to be eventually focused onto an array of photodiodes
Summary
CROSS sensitivity of the central resonance wavelength shift of fiber Bragg grating (FBG) between the temperature and the mechanical strain is the main challenge in many applications. The situation in which more than one FBG sensor are required to be employing to achieve the elimination tactic. There are several applications where FBGs are surface mounted/embedded on flexible smart structures where loads can be applied axially and transversely, inducing both uniform and non-uniform strains along with the structure containing the FBG sensor [9]- [13]. In such applications, it is desirable to monitor both strains together with temperature simultaneously. The conventional FWHM&CRW pair is not sufficient, but an additional spectrum feature is needed that has a different sensitivity
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