Effects of coating and diametric load on fiber Bragg gratings as cryogenic temperature sensors

Wu, Meng-Chou; Pater, Ruth H.; DeHaven, Stanton L.

doi:10.1117/12.775895

Cited by 14 publications

(6 citation statements)

References 15 publications

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“…Not only at highly elevated temperatures FBG fails to operate but also at cryogenic temperature operation of FBG becomes challenging due to low thermal rate of expansion, but this problem can be overcome by using suitable coating. [123][124][125] It was shown in Ref. 126, to measure temperature at multiple places of the high-temperature superconducting magnets efficiently, instead of using conventional multipoint measurement systems like thermocouples and Cernox (Zirconium Oxy-Nitride), which can intrude heat in superconducting magnets, multiple fiber Bragg gratings can be embedded in a single fiber as they have low heat invasions.…”

Section: Fbg-based Strain Sensorsmentioning

confidence: 99%

Fiber Bragg grating sensors for monitoring of physical parameters: a comprehensive review

2020

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Fiber Bragg grating has embraced the area of fiber optics since the early days of its discovery, and most fiber optic sensor systems today make use of fiber Bragg grating technology. Researchers have gained enormous attention in the field of fiber Bragg grating (FBG)-based sensing due to its inherent advantages, such as small size, fast response, distributed sensing, and immunity to the electromagnetic field. Fiber Bragg grating technology is popularly used in measurements of various physical parameters, such as pressure, temperature, and strain for civil engineering, industrial engineering, military, maritime, and aerospace applications. Nowadays, strong emphasis is given to structure health monitoring of various engineering and civil structures, which can be easily achieved with FBG-based sensors. Depending on the type of grating, FBG can be uniform, long, chirped, tilted or phase shifted having periodic perturbation of refractive index inside core of the optical fiber. Basic fundamentals of FBG and recent progress of fiber Bragg grating-based sensors used in various applications for temperature, pressure, liquid level, strain, and refractive index sensing have been reviewed. A major problem of temperature cross sensitivity that occurs in FBG-based sensing requires temperature compensation technique that has also been discussed in this paper.

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Section: Fbg-based Strain Sensorsmentioning

confidence: 99%

Fiber Bragg grating sensors for monitoring of physical parameters: a comprehensive review

2020

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“…When the CTE of substrate materials M α is different from the CTE of the FBG F α , the FBG embedded onto the substrate is subjected to the stress which is caused by the temperature variations of subtracting materials. As described in [30], this force is due to different coefficients of thermal expansion and can be approximated as the axial force, where the axial strain of the FBG is ( )…”

Section: Effect Of Temperature On the Fiber Bragg Grating Embedded On...mentioning

confidence: 99%

Investigation of Strain-Temperature Cross-Sensitivity of FBG Strain Sensors Embedded Onto Different Substrates

et al. 2022

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The strain-temperature cross-sensitivity problem easily occurs in the engineering strain monitoring of the self-sensing embedded with fiber Bragg grating (FBG) sensors. In this work, a theoretical investigation of the strain-temperature cross-sensitivity has been performed using the temperature reference grating method. To experimentally observe and theoretically verify the problem, the substrate materials, the preloading technique, and the FBG initial central wavelength were taken as main parameters. And a series of sensitivity coefficients calibration tests and temperature compensation tests have been designed and carried out. It was found that when the FBG sensors were embedded on different substrates, their coefficients of the temperature sensitivity were significantly changed. Besides, the larger the coefficients of thermal expansion (CTE) of substrates were, the higher the temperature sensitivity coefficients would be. On the other hand, the effect of the preloading technique and FBG initial wavelength was negligible on both the strain monitoring and temperature compensation. In the case of similar substrates, we did not observe any difference between temperature sensitivity coefficients of the temperature compensation FBG with one free end or two free ends. The curves of the force along with temperature were almost overlapped with minor differences (less than 1%) gained by FBG sensors and pressure sensors, which verified the accuracy of the temperature compensation method. We suggest that this work can provide efficient solutions to the strain-temperature cross-sensitivity for engineering strain monitoring with the self-sensing element embedded with FBG sensors.

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“…At t 4 , the heating cycle begins again. t 4 and t 2 correspond to the setting of the function generator turning on and off the quartz lamps. t 1 and t 3 -t 2 are the times required for the quartz lamps to come to full power and cool respectively.…”

Section: Simulation Of Thermal Response Of Composite With Delaminationmentioning

confidence: 99%

“…1 The other one uses low reflectivity FBGs written at the same nominal wavelength and read with a frequency domain demodulation system. 4,5 This technique allows a single fiber to contain hundreds of FBGs, potentially employed as temperature sensors.…”

Section: Introductionmentioning

confidence: 99%

Fiber optic thermal detection of composite delaminations

Winfree

2011

SPIE Proceedings

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A recently developed technique is presented for thermographic detection of delaminations in composites by performing temperature measurements with fiber optic Bragg gratings. A single optical fiber with multiple Bragg gratings employed as surface temperature sensors was bonded to the surface of a composite with subsurface defects. The investigated structure was a 10-ply composite specimen with prefabricated delaminations of various sizes and depths. Both during and following the application of a thermal heat flux to the surface, the individual Bragg grating sensors measured the temporal and spatial temperature variations. The data obtained from grating sensors were analyzed with thermal modeling techniques of conventional thermography to reveal particular characteristics of the interested areas. Results were compared and found to be consistent with the calculations using numerical simulation techniques. Also discussed are methods including various heating sources and patterns, and their limitations for performing in-situ structural health monitoring.

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Effects of coating and diametric load on fiber Bragg gratings as cryogenic temperature sensors

Cited by 14 publications

References 15 publications

Fiber Bragg grating sensors for monitoring of physical parameters: a comprehensive review

Fiber Bragg grating sensors for monitoring of physical parameters: a comprehensive review

Investigation of Strain-Temperature Cross-Sensitivity of FBG Strain Sensors Embedded Onto Different Substrates

Fiber optic thermal detection of composite delaminations

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