A simultaneous dual-parameter optical fibre single sensor embedded in a glass fibre/epoxy composite

Fazzi, Luigi; Valvano, Stefano; Alaimo, Andrea; Groves, Roger M.

doi:10.1016/j.compstruct.2021.114087

Cited by 15 publications

(14 citation statements)

References 19 publications

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“…At the same time, the cladding resonances undergo a wavelength shift and amplitude change when the external RI is varying. Hence, by performing a preliminary calibration, both the Bragg and the Ghost peaks can be used to measure simultaneously and separately the temperature and the strain variation of the material where the sensor is embedded [8]. At the same time, the envelope area of the upper and lower cladding resonance peaks can be used to detect independently the RI variation of the medium surrounding the TFBG sensor [7,[14][15][16].…”

Section: Tfbg Sensing Theorymentioning

confidence: 99%

“…Each single TFBG sensor has been theoretically demonstrated to be able to measure simultaneously and separately strain, temperature and refractive index (RI) of the surrounding material [7]. While, in a real application, it was proven that this single sensor may be used to determine the thermomechanical state of a glass-fibre/epoxy composite when embedded inside [8].…”

Section: Introductionmentioning

confidence: 99%

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Monitoring of silicone adhesive in space solar cells with an embedded multi-parameter TFBG sensor in a simulated space environment

Fazzi

Dias

Hołyńska

et al. 2022

Meas. Sci. Technol.

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In this research the ageing of a silicone adhesive in a simulated space environment is monitored through an embedded three parameter tilted Fibre Bragg Grating (TFBG) sensor. Here, the silicone is used as an adhesive between two thin cover glasses, and the space environmental ageing is simulated by thermal cycles in high vacuum conditions (better than 10-5 mbar). These operational conditions can induce variations in the silicone adhesive with respect to its original properties such as dimensional stability, chemical composition, generated contaminants, discoloration and, mechanical or optical degradation. Therefore, surrounded by the adhesive, in the centre of the cover glass sandwich, a weakly tilted FBG sensor was placed to obtain information from its spectra on the state of the polymer during the test. Specifically, the temperature, strain and refractive index (RI) of the silicone can be, simultaneously and separately, measured from the spectrum of a single TFBG from selected resonance peaks. These parameters can be used to evaluate the “health” state of the silicone during the vacuum thermal cycles. The simultaneous TFBG thermomechanical measurements gave a solution to the non-localized measuring issues when using classical fibre optic or electrical strain-gauges and a thermocouple (TC) to compensate the temperature and to better understand the material behaviour. The trends of the measured parameters are reported during the entire testing time, and at the end of the test, the optical fibre sensor measured a negative strain of ~100 με and a positive RI variation of ~0.002.

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Section: Tfbg Sensing Theorymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Monitoring of silicone adhesive in space solar cells with an embedded multi-parameter TFBG sensor in a simulated space environment

Fazzi

Dias

Hołyńska

et al. 2022

Meas. Sci. Technol.

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“…Specifically n eff,core and n eff,clad,i are respectively referred to as the core and cladding modes. The wavelengths of the Bragg (λ Bragg ) and cladding (λ clad,i ) resonance peaks can be then obtained using the following fundamental equations [15]:…”

Section: Tfbg Theory and Influence Of The Surrounding Rimentioning

confidence: 99%

“…Figure 2 shows the internal structure of a weak where the tilt angle θ, the grating period ΛG along the OF axis and the no period Λ = ΛGcosθ are defined. By considering the effective refractive inde mode, the nominal wavelength can be calculated for each peak in the spec cally neff,core and neff,clad,i are respectively referred to as the core and claddin wavelengths of the Bragg ( Bragg) and cladding ( clad,i) resonance peaks can be using the following fundamental equations [15]: Once the Bragg structure is defined, if no mechanical perturbations are appli OF, then the grating period and the tilt angle are constant, then neff,core is also fixed the RI of the core and cladding OF layers are defined. As neff,clad,i is sensitive to rounding RI variations, each cladding mode has to fit with a new propagating c so that the phase-matching condition (represented by Equation ( 2)) is satisfied nominal wavelength changes for each external RI.…”

Section: Tfbg Theory and Influence Of The Surrounding Rimentioning

confidence: 99%

“…The degeneration of the single peak into multiple peaks is due to the splitting of the vector modes as their electrical propagation field is less confined in the cladding layer, to the point that the linearly polarized mode approximations are no longer valid to describe the coupling mode theory [15]. The sensing characteristic of these higher cladding modes to the strain and RI variations is such that they have a large irregular wavelength shift and sensitivity coefficients [23].…”

Section: Stability Of the α-Shape Modified Delaunay Demodulation Techniquementioning

confidence: 99%

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Refractometric Properties of a TFBG Sensor Demodulated Using α-Shape Modified Delaunay Triangulation

Fazzi

Groves

2021

Optics

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In our previous research, a novel demodulation technique based on α-shape Delaunay triangulation (D-T) was developed to obtain the refractive index of the medium surrounding the optical fibre using the envelope of the cladding peaks from the spectrum of the tilted fibre Bragg grating (TFBG) sensor. This technique was demonstrated to be efficient, easy to implement, powerful, faster than the previous ones and applicable for real-time measurements. In this paper, a deep parametric analysis of the resolution, repeatability and accuracy of the D-T demodulation technique for a TFBG refractometer sensor is performed and presented. The spectral properties of the TFBG sensor as a refractometer are explored using the same demodulation technique. Specifically, supposing the use of the TFBG as a two-parameter optical sensor, the influence of the strain on the envelope area is analysed, and the measurement stability regarding the external RI is reported. Then, the cladding resonance peaks in the spectrum are observed experimentally as the TFBG undergoes partial immersion in a defined refractive index liquid. This last experiment allowed a better understanding the evolution of the TFBG transmission spectrum when the Bragg gratings were partially surrounded by a medium with a different RI.

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An embedded non-intrusive graphene/epoxy broadband nanocomposite sensor co-cured with GFRP for in situ structural health monitoring

Wang

Tian

Duongthipthewa

et al. 2023

Composites Science and Technology

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A simultaneous dual-parameter optical fibre single sensor embedded in a glass fibre/epoxy composite

Cited by 15 publications

References 19 publications

Monitoring of silicone adhesive in space solar cells with an embedded multi-parameter TFBG sensor in a simulated space environment

Monitoring of silicone adhesive in space solar cells with an embedded multi-parameter TFBG sensor in a simulated space environment

Refractometric Properties of a TFBG Sensor Demodulated Using α-Shape Modified Delaunay Triangulation

An embedded non-intrusive graphene/epoxy broadband nanocomposite sensor co-cured with GFRP for in situ structural health monitoring

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