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Open AccessArticle

Wavelet-Based Demodulation of Multimode Etched Fiber Bragg Grating Refractive Index Sensor

1
National Laboratory Astana, Laboratory of Biosensors and Bioinstruments, 010000 Astana, Kazakhstan
2
Nazarbayev University, School of Engineering, 010000 Astana, Kazakhstan
*
Author to whom correspondence should be addressed.
Sensors 2019, 19(1), 39; https://doi.org/10.3390/s19010039
Received: 27 November 2018 / Revised: 10 December 2018 / Accepted: 17 December 2018 / Published: 22 December 2018
(This article belongs to the Special Issue Bragg Grating Sensors)
Etched fiber Bragg grating (EFBG)-based sensors are used as evanescent field sensors for refractive index detection. When the fiber thickness is thin and the refractive index sensitivity increases, the number of propagating modes increases, resulting in a spectral enlargement that complicates the interrogation of the sensor. In this work, we present a method to analyze the spectrum of a multimode etched fiber Bragg grating (MMEFBG) in the wavelet domain, which analyzes the amount of spectral density independently from the peak reflectivity value. The proposed interrogation method permits defining the integral of the spectral density as a novel and unconventional estimator. With respect to the conventional estimators based on wavelength shift, this estimator can better exploit the larger amount of information given by the spectral enlargement typical of multimode behavior. Results were obtained by etching an MMEFBG in hydrofluoric acid and using water/sucrose mixtures to evaluate the refractive index sensitivity, validating the interrogation method. View Full-Text
Keywords: Evanescent field sensors; fiber Bragg grating (FBG); optical fiber sensor (OFS); refractive index sensors; wavelet density estimation Evanescent field sensors; fiber Bragg grating (FBG); optical fiber sensor (OFS); refractive index sensors; wavelet density estimation
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Ayupova, T.; Sypabekova, M.; Molardi, C.; Bekmurzayeva, A.; Shaimerdenova, M.; Dukenbayev, K.; Tosi, D. Wavelet-Based Demodulation of Multimode Etched Fiber Bragg Grating Refractive Index Sensor. Sensors 2019, 19, 39.

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