Multipoint high temperature sensing with regenerated fiber Bragg gratings

Dutz, Franz J.; Lindner, Markus; Heinrich, Andreas; Seydel, Carl G.; Bosselmann, T.; Koch, Alexander W.; Roths, Johannes

doi:10.1117/12.2305300

Cited by 7 publications

(12 citation statements)

References 14 publications

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“…Besides, the mechanism is mechanically sensitive, and the space required is usually too much to be applicable in industrial facilities. In contrast, fiber-optic multipoint temperature sensing allows measuring the axial temperature distribution with both high spatial and high temporal resolution simultaneously, combined with miniaturized sensor design and high accuracy [12]. This technology is particularly attractive for industrial process control [23].…”

Section: Introductionmentioning

confidence: 99%

“…The disadvantages of type II FBGs arise from their polarization sensitivity [10,11] and strong cladding mode coupling [5,10], which can limit their multiplexing capabilities. Type II-PbP gratings show significant wavelength drift when exposed to high temperatures [12,13]. For type II-PM FBGs, a stabilization of the wavelength drift after an annealing procedure of 100 h at 1000 • C has been reported [14].…”

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confidence: 99%

“…When compared to type II FBGs, RFBGs typically exhibit lower values of grating reflectivity. However, the high-temperature annealing process that is necessary to form RFBGs leads to a reduction of their tensile strength, but it has the advantageous consequence that this type of high-temperature resistant grating shows low drift rates of the Bragg wavelengths when compared to type II-PbP FBGs [12,13]. The issue of the mechanical robustness of the fiber-optic sensor system has to be addressed with appropriate sensor packaging and with specific measures during the annealing process.…”

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confidence: 99%

“…The issue of the mechanical robustness of the fiber-optic sensor system has to be addressed with appropriate sensor packaging and with specific measures during the annealing process. For the application reported in this article, the priority lies in the low drift characteristics and the multiplexing capabilities, and this is why we use regenerated gratings here.So far, industrial employments of regenerated and type II grating-based multipoint sensing have been reported for gas turbines [12,16,17], various combustor systems [5], nuclear reactors [13] and a test facility of the chemical industry [12]. In the chemical industry, catalytic fixed-bed reactors are widely used for the large-scale synthesis of basic chemicals and intermediates such as methanol, phthalic anhydride [18], and maleic anhydride [19].…”

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confidence: 99%

“…So far, industrial employments of regenerated and type II grating-based multipoint sensing have been reported for gas turbines [12,16,17], various combustor systems [5], nuclear reactors [13] and a test facility of the chemical industry [12]. In the chemical industry, catalytic fixed-bed reactors are widely used for the large-scale synthesis of basic chemicals and intermediates such as methanol, phthalic anhydride [18], and maleic anhydride [19].…”

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Fiber-Optic Multipoint Sensor System with Low Drift for the Long-Term Monitoring of High-Temperature Distributions in Chemical Reactors

Dutz

Heinrich²,

Bank³

et al. 2019

Sensors

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A low-drift fiber-optic sensor system, consisting of 24 regenerated fiber Bragg gratings (RFBG), equally distributed over a length of 2.3 m, is presented here. The sensor system can monitor spatially extended temperature profiles with a time resolution of 1 Hz at temperatures of up to 500 • C. The system is intended to be used in chemical reactors for both the control of the production ramp-up, where a fast time response is needed, as well as for production surveillance, where low sensor drifts over several years are required. The fiber-optic sensor system was installed in a pilot test reactor and was exposed to a constant temperature profile, with temperatures in the range of 150-500 • C for more than two years. During this period, the temperature profile was measured every three to five months and the fiber-optic temperature data were compared with data from a three-point thermocouple array and a calibrated single-point thermocouple. A very good agreement between all temperature measurements was found. The drift rates of the 24 RFBG sensor elements were determined by comparing the Bragg wavelengths at a precisely defined reference temperature near room temperature before and after the two-year deployment. They were found to be in the range of 0.0 K/a to 2.3 K/a, with an average value of 1.0 K/a. These low drift rates were achieved by a dedicated temperature treatment of the RFBGs during fabrication. Here, the demonstrated robustness, accuracy, and low drift characteristics show the potential of fiber-optic sensors for future industrial applications. gratings strongly decay at high temperatures [1,2]. Amongst others, type II FBGs inscribed with femtosecond (fs) lasers [3][4][5] and regenerated FBGs (RFBGs) [6][7][8] have been reported to be suitable for temperatures up to 1200 • C. Most often, type II FBGs are inscribed with high-intensity femtosecond laser beams by phase masks (type II-PM) [3,9] or by a point-by-point (type II-PbP) [10] technique, and their main features are a high grating reflectivity, inherent temperature stability, and high initial tensile strength. The disadvantages of type II FBGs arise from their polarization sensitivity [10,11] and strong cladding mode coupling [5,10], which can limit their multiplexing capabilities. Type II-PbP gratings show significant wavelength drift when exposed to high temperatures [12,13]. For type II-PM FBGs, a stabilization of the wavelength drift after an annealing procedure of 100 h at 1000 • C has been reported [14]. Due to temperature treatments, a thermal-induced glass corrosion and thus a reduction of the tensile strength has to be taken into account.Regenerated fiber Bragg gratings (RFBGs) emerge from type I gratings in H 2 -loaded fibers after an annealing process at temperatures in the range of 800 • C to 1100 • C [7,15]. Their uniform spectral line shapes and the lack of cladding mode coupling make RFBGs perfectly suited for multiplexing applications. When compared to type II FBGs, RFBGs typically exhibit lower values of grating reflectivity. However, ...

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Section: Introductionmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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Fiber-Optic Multipoint Sensor System with Low Drift for the Long-Term Monitoring of High-Temperature Distributions in Chemical Reactors

Dutz

Heinrich²,

Bank³

et al. 2019

Sensors

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Review of fabrication and packaging of UV-induced FBGs for high temperature sensing

Jiang,

Duan,

et al. 2024

Optical Fiber Technology

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Transition from purely elastic to viscoelastic behavior of silica optical fibers at high temperatures characterized using regenerated Bragg gratings

Lindner¹,

Bernard²,

Heilmeier³

et al. 2020

Opt. Express

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In this study, the response of regenerated fiber Bragg gratings (RFGBs) to axial forces was investigated in a temperature range from room temperature to 900 °C. For the first time, the transition from pure elastic to viscoelastic behavior around 700 °C of a standard SMF28 optical fiber was measured with an inscribed RFBG. An elastic model with linear temperature dependencies of Young’s modulus and Poisson’s ratio was established, and showed good agreement with the measurements up to temperatures of ∼500 °C. In the temperature range up to 900 °C, the RFBG response could be well described with a simple, single-material approach and a Burgers model that consists of a Kelvin and a Maxwell part. Based on the elastic parameter of the Maxwell part, the temperature-dependent force sensitivity of the RFBG was determined, and it showed a linear decrease in the range from room temperature to ∼500 °C, constant values in the range between ∼500 °C and ∼600 °C, and a strong increase at higher temperatures. While fulfilling the condition to operate in the elastic domain of the silica fiber, the investigations demonstrate that RFBGs can be used as force sensors up to temperatures of ∼600 °C - the range in which temperature-dependent force sensitivities have to be considered. The temperature-dependent parameters of the effective single-material model (elastic and viscoelastic part) are essential to describe the effective mechanical behavior of the optical fiber at high temperatures.

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Multipoint high temperature sensing with regenerated fiber Bragg gratings

Cited by 7 publications

References 14 publications

Fiber-Optic Multipoint Sensor System with Low Drift for the Long-Term Monitoring of High-Temperature Distributions in Chemical Reactors

Fiber-Optic Multipoint Sensor System with Low Drift for the Long-Term Monitoring of High-Temperature Distributions in Chemical Reactors

Review of fabrication and packaging of UV-induced FBGs for high temperature sensing

Transition from purely elastic to viscoelastic behavior of silica optical fibers at high temperatures characterized using regenerated Bragg gratings

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