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An Improved Metal-Packaged Strain Sensor Based on A Regenerated Fiber Bragg Grating in Hydrogen-Loaded Boron – Germanium Co-Doped Photosensitive Fiber for High-Temperature Applications

View Article: PubMed Central - PubMed

ABSTRACT

Local strain measurements are considered as an effective method for structural health monitoring of high-temperature components, which require accurate, reliable and durable sensors. To develop strain sensors that can be used in higher temperature environments, an improved metal-packaged strain sensor based on a regenerated fiber Bragg grating (RFBG) fabricated in hydrogen (H2)-loaded boron–germanium (B–Ge) co-doped photosensitive fiber is developed using the process of combining magnetron sputtering and electroplating, addressing the limitation of mechanical strength degradation of silica optical fibers after annealing at a high temperature for regeneration. The regeneration characteristics of the RFBGs and the strain characteristics of the sensor are evaluated. Numerical simulation of the sensor is conducted using a three-dimensional finite element model. Anomalous decay behavior of two regeneration regimes is observed for the FBGs written in H2-loaded B–Ge co-doped fiber. The strain sensor exhibits good linearity, stability and repeatability when exposed to constant high temperatures of up to 540 °C. A satisfactory agreement is obtained between the experimental and numerical results in strain sensitivity. The results demonstrate that the improved metal-packaged strain sensors based on RFBGs in H2-loaded B–Ge co-doped fiber provide great potential for high-temperature applications by addressing the issues of mechanical integrity and packaging.

No MeSH data available.


Evolution of the reflection peak power and the Bragg wavelength shift of the grating shown in Figure 1 during the isothermal annealing at 500 °C.
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sensors-17-00431-f006: Evolution of the reflection peak power and the Bragg wavelength shift of the grating shown in Figure 1 during the isothermal annealing at 500 °C.

Mentions: In addition to the decay of the grating, a shift of the Bragg wavelength has also been observed, as shown in Figure 6. The step of isothermal annealing at a temperature of 500 °C is zoomed. In this step, as the reflection peak power of the seed FBG fast decreases to the inflection point of complete erasure, the Bragg wavelength is abruptly shifted to shorter wavelengths, which indicates a strong decrease in both the refractive index modulation and average index change at this high temperature, and is typical behavior of thermal decay for a normal type-I FBG in PS1250/1500 fiber [36]. As the reflection peak power of the RFBG increases from the inflection point, its Bragg wavelength is much longer than that of its seed grating, consistent with the similar behavior reported in [37], which may be explained by the RFBG formed with changes (such as stress) at the core-cladding interface. After that, a significant negative shift in the Bragg wavelength of RFBG indicating a reduction in the average refractive index change is also observed until the wavelength gradually stabilizes at the end of the isothermal annealing of 500 °C. The trend of a negative shift in the Bragg wavelength for both seed grating and its regenerated grating is similar to that for the grating in H2-loaded SMF-28 fiber reported in our previous work [31] and also similar to that observed for regenerated type-IIA gratings [38]. However, it is inconsistent with other researchers’ observations that have shown a trend of a positive shift in the Bragg wavelength for the gratings in photosensitive fibers with different dopant composition and concentrations [35,37,39].


An Improved Metal-Packaged Strain Sensor Based on A Regenerated Fiber Bragg Grating in Hydrogen-Loaded Boron – Germanium Co-Doped Photosensitive Fiber for High-Temperature Applications
Evolution of the reflection peak power and the Bragg wavelength shift of the grating shown in Figure 1 during the isothermal annealing at 500 °C.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5375717&req=5

sensors-17-00431-f006: Evolution of the reflection peak power and the Bragg wavelength shift of the grating shown in Figure 1 during the isothermal annealing at 500 °C.
Mentions: In addition to the decay of the grating, a shift of the Bragg wavelength has also been observed, as shown in Figure 6. The step of isothermal annealing at a temperature of 500 °C is zoomed. In this step, as the reflection peak power of the seed FBG fast decreases to the inflection point of complete erasure, the Bragg wavelength is abruptly shifted to shorter wavelengths, which indicates a strong decrease in both the refractive index modulation and average index change at this high temperature, and is typical behavior of thermal decay for a normal type-I FBG in PS1250/1500 fiber [36]. As the reflection peak power of the RFBG increases from the inflection point, its Bragg wavelength is much longer than that of its seed grating, consistent with the similar behavior reported in [37], which may be explained by the RFBG formed with changes (such as stress) at the core-cladding interface. After that, a significant negative shift in the Bragg wavelength of RFBG indicating a reduction in the average refractive index change is also observed until the wavelength gradually stabilizes at the end of the isothermal annealing of 500 °C. The trend of a negative shift in the Bragg wavelength for both seed grating and its regenerated grating is similar to that for the grating in H2-loaded SMF-28 fiber reported in our previous work [31] and also similar to that observed for regenerated type-IIA gratings [38]. However, it is inconsistent with other researchers’ observations that have shown a trend of a positive shift in the Bragg wavelength for the gratings in photosensitive fibers with different dopant composition and concentrations [35,37,39].

View Article: PubMed Central - PubMed

ABSTRACT

Local strain measurements are considered as an effective method for structural health monitoring of high-temperature components, which require accurate, reliable and durable sensors. To develop strain sensors that can be used in higher temperature environments, an improved metal-packaged strain sensor based on a regenerated fiber Bragg grating (RFBG) fabricated in hydrogen (H2)-loaded boron–germanium (B–Ge) co-doped photosensitive fiber is developed using the process of combining magnetron sputtering and electroplating, addressing the limitation of mechanical strength degradation of silica optical fibers after annealing at a high temperature for regeneration. The regeneration characteristics of the RFBGs and the strain characteristics of the sensor are evaluated. Numerical simulation of the sensor is conducted using a three-dimensional finite element model. Anomalous decay behavior of two regeneration regimes is observed for the FBGs written in H2-loaded B–Ge co-doped fiber. The strain sensor exhibits good linearity, stability and repeatability when exposed to constant high temperatures of up to 540 °C. A satisfactory agreement is obtained between the experimental and numerical results in strain sensitivity. The results demonstrate that the improved metal-packaged strain sensors based on RFBGs in H2-loaded B–Ge co-doped fiber provide great potential for high-temperature applications by addressing the issues of mechanical integrity and packaging.

No MeSH data available.