Regenerated Fibre Bragg Gratings: A critical assessment of more than 20 years of investigations

Polz, Leonhard; Dutz, Franz J.; Maier, Robert R. J.; Bartelt, Hartmut; Roths, Johannes

doi:10.1016/j.optlastec.2020.106650

Cited by 41 publications

(12 citation statements)

References 103 publications

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“…Over the years, the mysterious origin of RFBGs has attracted considerable interest and a number of models have been created to explain it only to find a contradiction in the explanation as new experimental results were produced. According to an excellent review on the history of RFBGs [ 38 ], they were initially referred to as Chemical Composition Gratings [ 15 ] because it was thought that the grating structure was created by the elimination of fluorine at high temperature from the sites in the fibers core where OH was produced under the UV radiation. Later, this explanation evolved into a stress model independent of the presence of fluorine [ 39 ] where UV radiation-induced OH groups enhanced tensile stress at the core-cladding interface that would eventually turn into compressive stress at high temperature, with crystallization also playing a role.…”

Section: High Temperature Fbg Structuresmentioning

confidence: 99%

Fiber Bragg Grating Wavelength Drift in Long-Term High Temperature Annealing

Grobnic

Hnatovsky

Dedyulin

et al. 2021

Sensors

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High-temperature-resistant fiber Bragg gratings (FBGs) are the main competitors to thermocouples as sensors in applications for high temperature environments defined as being in the 600–1200°C temperature range. Due to their small size, capacity to be multiplexed into high density distributed sensor arrays and survivability in extreme ambient temperatures, they could provide the essential sensing support that is needed in high temperature processes. While capable of providing reliable sensing information in the short term, their long-term functionality is affected by the drift of the characteristic Bragg wavelength or resonance that is used to derive the temperature. A number of physical processes have been proposed as the cause of the high temperature wavelength drift but there is yet no credible description of this process. In this paper we review the literature related to the long-term wavelength drift of FBGs at high temperature and provide our recent results of more than 4000 h of high temperature testing in the 900 –1000°C range. We identify the major components of the high temperature wavelength drift and we propose mechanisms that could be causing them.

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Section: High Temperature Fbg Structuresmentioning

confidence: 99%

Fiber Bragg Grating Wavelength Drift in Long-Term High Temperature Annealing

Grobnic

Hnatovsky

Dedyulin

et al. 2021

Sensors

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“…At temperatures above 500 °C, the grating optical properties decay, which is normal for most FBG types, except those designed specifically for higher thermal exposition [ 6 , 7 ] or those treated by regeneration [ 8 , 9 ]. Recent studies explicitly aimed at the regeneration of the grating have focused their efforts on the thermal treatments, defining the thermal stabilization as the FBG regeneration process.…”

Section: Introductionmentioning

confidence: 99%

“…In the literature, FBG regeneration has been developed by means of different techniques such as chemical composition grating (CCG), Tetrahedral FBG (TFBG) and thermal regeneration FBG (RFBG) [ 8 ]. The CCG has been characterized by multiplexing and remote interrogation properties at a high thermal stability.…”

Section: Introductionmentioning

confidence: 99%

FBG Spectrum Regeneration by Ni-Coating and High-Temperature Treatment

Lupi

Vendittozzi

Ciro

et al. 2022

Sensors

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FBG sensors are used in many scientific and industrial fields for assessing the structural integrity of mechanical components and in very high (above 600 °C) or very low (cryogenic) temperature applications. The main concerns with the use of such sensors in applications involving extreme temperatures are related partly to the instability of the reflected spectrum, which tends to dissolve into the noise floor, and partly to the degradation of the mechanical properties of the optical fiber, which tends to worsen the inherent brittleness. All of this raises the need for a robust nickel protective coating to ensure the grating’s integrity in high-temperature environments. In addition, the inherent brittleness of fiber-optic gratings leaves one to wonder whether it is possible to recover a broken, seemingly unusable sensor. In this way, a single-peak commercial FBG was intentionally broken in the middle of the grating length and re-spliced, inducing a strongly asymmetric chirped-like spectrum; then, a nickel coating was electrodeposited on its surface. The most important outcome achieved by this work is the regeneration of a highly distorted reflected spectrum through three thermal cycles performed from room temperature up to 500, 750, and 800 °C, respectively. After reaching a temperature of at least 700 °C, the spectrum, which has been drastically altered by splicing, becomes stable and restores its single peak shape. A further stabilization cycle carried out at 800 °C for 80 min led to an estimation of the stabilizing time of the new single-peak reflected spectrum.

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“…The temperature sensors applications using optical fiber-based approaches are generally related to FBG sensors, due to their inherent sensitivity to temperature variations. In general, the FBGs are inscribed using UV lasers with holographic/interferometric/phase mask techniques [ 77 ], which typically result in type I gratings that operate in temperatures below around 450 °C, since higher temperatures lead to the erasing of the grating [ 78 ]. To address this issue in high temperature operations, the direct inscription using fs lasers result in the possibility of using such sensors in temperatures close to the ones of the material processing [ 79 ].…”

Section: Flight Environment Sensingmentioning

confidence: 99%

Multifunctional Integration of Optical Fibers and Nanomaterials for Aircraft Systems

2023

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Smart sensing for aeronautical applications is a multidisciplinary process that involves the development of various sensor elements and advancements in the nanomaterials field. The expansion of research has fueled the development of commercial and military aircrafts in the aeronautical field. Optical technology is one of the supporting pillars for this, as well as the fact that the unique high-tech qualities of aircrafts align with sustainability criteria. In this study, a multidisciplinary investigation of airplane monitoring systems employing optical technologies based on optical fiber and nanomaterials that are incorporated into essential systems is presented. This manuscript reports the multifunctional integration of optical fibers and nanomaterials for aircraft sector discussing topics, such as airframe monitoring, flight environment sensing (from temperature and humidity to pressure sensing), sensors for navigation (such as gyroscopes and displacement or position sensors), pilot vital health monitoring, and novel nanomaterials for aerospace applications. The primary objective of this review is to provide researchers with direction and motivation to design and fabricate the future of the aeronautical industry, based on the actual state of the art of such vital technology, thereby aiding their future research.

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Regenerated Fibre Bragg Gratings: A critical assessment of more than 20 years of investigations

Cited by 41 publications

References 103 publications

Fiber Bragg Grating Wavelength Drift in Long-Term High Temperature Annealing

Fiber Bragg Grating Wavelength Drift in Long-Term High Temperature Annealing

FBG Spectrum Regeneration by Ni-Coating and High-Temperature Treatment

Multifunctional Integration of Optical Fibers and Nanomaterials for Aircraft Systems

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