Methods of Projecting Mode Amplitude Changes on the Wavelength Axis in Order to Determine the Bending Radius on the Basis of TFBG Grating Spectra

Tilted fibre Bragg grating (TFBG) are used as sensors to determine many quantities such as refractive index, temperature, stress, rotation and bending. The TFBG spectrum contains a lot of information and various algorithms are used for its analysis. However, most of these algorithms are dedicated to...

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Autores principales:	Sławomir Cięszczyk, Damian Harasim, Ainur Ormanbekova, Krzysztof Skorupski, Martyna Wawrzyk
Formato:	article
Lenguaje:	EN
Publicado:	MDPI AG 2021
Materias:	TFBG sensors demodulation algorithm bending signal processing Chemical technology TP1-1185
Acceso en línea:	https://doaj.org/article/c681a85c85994bb6a97ea6141bacd2e3
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id	oai:doaj.org-article:c681a85c85994bb6a97ea6141bacd2e3
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spelling	oai:doaj.org-article:c681a85c85994bb6a97ea6141bacd2e32021-11-25T18:57:10ZMethods of Projecting Mode Amplitude Changes on the Wavelength Axis in Order to Determine the Bending Radius on the Basis of TFBG Grating Spectra10.3390/s212275261424-8220https://doaj.org/article/c681a85c85994bb6a97ea6141bacd2e32021-11-01T00:00:00Zhttps://www.mdpi.com/1424-8220/21/22/7526https://doaj.org/toc/1424-8220Tilted fibre Bragg grating (TFBG) are used as sensors to determine many quantities such as refractive index, temperature, stress, rotation and bending. The TFBG spectrum contains a lot of information and various algorithms are used for its analysis. However, most of these algorithms are dedicated to the analysis of spectral changes under the influence of the refractive index. The most popular algorithm used for this purpose is to calculate the area occupied by cladding modes. Among the remaining algorithms, there are those that use the determination of the cut-off wavelength as a surrounding refractive index (SRI) indicator. Projection on the wavelength axis can also be used to calculate the bending radius of the fibre. However, this is a more difficult task than with SRI, because the mode decay in bending is not so easy to catch. In this article, we propose a multi-step algorithm that allows to determine the impact of bending on mode leakage. At the same time, the place on the wavelength from the side of the Bragg mode and the ghost mode is determined, which represents the cladding mode radiated from the cladding under the influence of bending. The developed algorithm consists of the following operations carried out on the transmission spectrum: Fourier filtering, calculation of the cumulative value of the spectral length, low-pass filtering of the cumulative curve or its corresponding polynomial approximation, determination of the first and second derivative of the approximated curve, and projection of the second derivative of the curve on the wavelength axis. The shift of the wavelength determined in this way indirectly indicates the bending radius of the optical fibre. Based on multiple measurements, we prove that the presented algorithm provides better results when determining the bending radius compared to other algorithms adopted for this purpose and proposed for SRI measurements. Additionally, we analyse the method of determining the shift of a fragment of the spectrum using the phase of the discrete Fourier transform.Sławomir CięszczykDamian HarasimAinur OrmanbekovaKrzysztof SkorupskiMartyna WawrzykMDPI AGarticleTFBG sensorsdemodulation algorithmbendingsignal processingChemical technologyTP1-1185ENSensors, Vol 21, Iss 7526, p 7526 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	TFBG sensors demodulation algorithm bending signal processing Chemical technology TP1-1185
spellingShingle	TFBG sensors demodulation algorithm bending signal processing Chemical technology TP1-1185 Sławomir Cięszczyk Damian Harasim Ainur Ormanbekova Krzysztof Skorupski Martyna Wawrzyk Methods of Projecting Mode Amplitude Changes on the Wavelength Axis in Order to Determine the Bending Radius on the Basis of TFBG Grating Spectra
description	Tilted fibre Bragg grating (TFBG) are used as sensors to determine many quantities such as refractive index, temperature, stress, rotation and bending. The TFBG spectrum contains a lot of information and various algorithms are used for its analysis. However, most of these algorithms are dedicated to the analysis of spectral changes under the influence of the refractive index. The most popular algorithm used for this purpose is to calculate the area occupied by cladding modes. Among the remaining algorithms, there are those that use the determination of the cut-off wavelength as a surrounding refractive index (SRI) indicator. Projection on the wavelength axis can also be used to calculate the bending radius of the fibre. However, this is a more difficult task than with SRI, because the mode decay in bending is not so easy to catch. In this article, we propose a multi-step algorithm that allows to determine the impact of bending on mode leakage. At the same time, the place on the wavelength from the side of the Bragg mode and the ghost mode is determined, which represents the cladding mode radiated from the cladding under the influence of bending. The developed algorithm consists of the following operations carried out on the transmission spectrum: Fourier filtering, calculation of the cumulative value of the spectral length, low-pass filtering of the cumulative curve or its corresponding polynomial approximation, determination of the first and second derivative of the approximated curve, and projection of the second derivative of the curve on the wavelength axis. The shift of the wavelength determined in this way indirectly indicates the bending radius of the optical fibre. Based on multiple measurements, we prove that the presented algorithm provides better results when determining the bending radius compared to other algorithms adopted for this purpose and proposed for SRI measurements. Additionally, we analyse the method of determining the shift of a fragment of the spectrum using the phase of the discrete Fourier transform.
format	article
author	Sławomir Cięszczyk Damian Harasim Ainur Ormanbekova Krzysztof Skorupski Martyna Wawrzyk
author_facet	Sławomir Cięszczyk Damian Harasim Ainur Ormanbekova Krzysztof Skorupski Martyna Wawrzyk
author_sort	Sławomir Cięszczyk
title	Methods of Projecting Mode Amplitude Changes on the Wavelength Axis in Order to Determine the Bending Radius on the Basis of TFBG Grating Spectra
title_short	Methods of Projecting Mode Amplitude Changes on the Wavelength Axis in Order to Determine the Bending Radius on the Basis of TFBG Grating Spectra
title_full	Methods of Projecting Mode Amplitude Changes on the Wavelength Axis in Order to Determine the Bending Radius on the Basis of TFBG Grating Spectra
title_fullStr	Methods of Projecting Mode Amplitude Changes on the Wavelength Axis in Order to Determine the Bending Radius on the Basis of TFBG Grating Spectra
title_full_unstemmed	Methods of Projecting Mode Amplitude Changes on the Wavelength Axis in Order to Determine the Bending Radius on the Basis of TFBG Grating Spectra
title_sort	methods of projecting mode amplitude changes on the wavelength axis in order to determine the bending radius on the basis of tfbg grating spectra
publisher	MDPI AG
publishDate	2021
url	https://doaj.org/article/c681a85c85994bb6a97ea6141bacd2e3
work_keys_str_mv	AT sławomircieszczyk methodsofprojectingmodeamplitudechangesonthewavelengthaxisinordertodeterminethebendingradiusonthebasisoftfbggratingspectra AT damianharasim methodsofprojectingmodeamplitudechangesonthewavelengthaxisinordertodeterminethebendingradiusonthebasisoftfbggratingspectra AT ainurormanbekova methodsofprojectingmodeamplitudechangesonthewavelengthaxisinordertodeterminethebendingradiusonthebasisoftfbggratingspectra AT krzysztofskorupski methodsofprojectingmodeamplitudechangesonthewavelengthaxisinordertodeterminethebendingradiusonthebasisoftfbggratingspectra AT martynawawrzyk methodsofprojectingmodeamplitudechangesonthewavelengthaxisinordertodeterminethebendingradiusonthebasisoftfbggratingspectra
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Methods of Projecting Mode Amplitude Changes on the Wavelength Axis in Order to Determine the Bending Radius on the Basis of TFBG Grating Spectra

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