Single-mode sapphire fiber optic distributed sensing for extreme environments

Ohanian, Osgar John; Boulanger, Andrew J.; Rountree, S. D.; Jones, Joshua T.; Birri, Anthony; Blue, Thomas E.

doi:10.1117/12.2518521

Cited by 12 publications

(4 citation statements)

References 10 publications

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“…We assume that, using the average of

over several spectra, the temperature uncertainty could be reduced by an order of magnitude toward the performance of the best high-temperature thermocouples. Another way to reduce the measurement uncertainty would be by reducing the number of modes (see Table 1 ) of the sapphire fiber as described in [ 12 , 19 , 20 ].…”

Section: Discussionmentioning

confidence: 99%

“…The upper temperature limit is around 1000 °C [ 10 ], where fused silica starts to devitrify, rendering the fiber unusable for optical applications. However, in vivo sensing in harsh environments, such as gas turbines [ 5 ] and furnaces [ 11 ], gasifiers [ 12 ], or testing the fire resistance of fuel tank materials [ 13 ], can easily reach significantly higher temperatures and pressures. Sapphire fibers are a promising alternative as they remain optically and mechanically stable at very high temperatures.…”

Section: Introductionmentioning

confidence: 99%

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Metrological Characterization of a High-Temperature Hybrid Sensor Using Thermal Radiation and Calibrated Sapphire Fiber Bragg Grating for Process Monitoring in Harsh Environments

Eisermann

Krenek

Habisreuther

et al. 2022

Sensors

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Fiber Bragg gratings inscribed in single crystalline multimode sapphire fibers (S-FBG) are suitable for monitoring applications in harsh environments up to 1900 ∘C. Despite many approaches to optimize the S-FBG sensor, a metrological investigation of the achievable temperature uncertainties is still missing. In this paper, we developed a hybrid optical temperature sensor using S-FBG and thermal radiation signals. In addition, the sensor also includes a thermocouple for reference and process control during a field test. We analyzed the influence of the thermal gradient and hotspot position along the sensor for all three detection methods using an industrial draw tower and fixed point cells. Moreover, the signal processing of the reflected S-FBG spectrum was investigated and enhanced to determine the reachable measurement repeatability and uncertainty. For that purpose, we developed an analytical expression for the long-wavelength edge of the peak. Our findings show a higher stability against mechanical-caused mode variations for this method to measure the wavelength shift compared to established methods. Additionally, our approach offers a high robustness against aging effects caused by high-temperature processes (above 1700 ∘C) or harsh environments. Using temperature-fixed points, directly traceable to the International System of Units, we calibrated the S-FBG and thermocouple of the hybrid sensor, including the corresponding uncertainty budgets. Within the scope of an over 3-weeks-long field trial, 25 production cycles of an industrial silicon manufacturing process with temperatures up to 1600 ∘C were monitored with over 100,000 single measurements. The absolute calibrated thermocouple (Uk=2≈1K…4K) and S-FBG (Uk=2≈10K…14K) measurements agreed within their combined uncertainty. We also discuss possible strategies to significantly reduce the uncertainty of the S-FBG calibration. A follow-up measurement of the sensor after the long-term operation at high temperatures and the transport of the measuring system together with the sensor resulted in a change of less than 0.5 K. Thus, both the presented hybrid sensor and the measuring principle are very robust for applications in harsh environments.

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“…We assume that, using the average of

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Metrological Characterization of a High-Temperature Hybrid Sensor Using Thermal Radiation and Calibrated Sapphire Fiber Bragg Grating for Process Monitoring in Harsh Environments

Eisermann

Krenek

Habisreuther

et al. 2022

Sensors

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show abstract

“…In 2019, Ohanian achieved distributed measurement of temperature inside a furnace using a 0.55 m long SMSF containing 50 type II FBGs with OFDR interrogation [ 203 ]. The system has a spatial resolution of 11mm and is capable of temperature measurements above 1000 °C with an accuracy of 5 °C.…”

Section: Distributed Sensingmentioning

confidence: 99%

Optical Fiber Sensors for High-Temperature Monitoring: A Review

Pang

et al. 2022

Sensors

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High-temperature measurements above 1000 °C are critical in harsh environments such as aerospace, metallurgy, fossil fuel, and power production. Fiber-optic high-temperature sensors are gradually replacing traditional electronic sensors due to their small size, resistance to electromagnetic interference, remote detection, multiplexing, and distributed measurement advantages. This paper reviews the sensing principle, structural design, and temperature measurement performance of fiber-optic high-temperature sensors, as well as recent significant progress in the transition of sensing solutions from glass to crystal fiber. Finally, future prospects and challenges in developing fiber-optic high-temperature sensors are also discussed.

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“…Superlative material characteristics of single crystal sapphire optical fiber α-Al 2 O 3 (SCF) offers various advantages, such as high resolution, superior rigidity, high laser power transfer, flexible strength, chemical unresponsiveness, optical spectroscopy, thermal shock resistance, and high melting point [1][2][3][4]. It is more sustainable and resistant than the ordinary silica fibers and can work under harsh environments [5][6][7][8]. An unclad SCF of a large core structure possesses large value of numerical aperture and effective refractive index, which turn the optical waveguide unrealistic in terms of reliability and compatibility.…”

Section: Introductionmentioning

confidence: 99%

A Star-Wheel Design of Single Crystal Sapphire Optical Fiber Promoting Single Mode Operation in the Infrared Regime

Mumtaz¹,

Dai²,

Ashraf³

et al. 2021

PIER C

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In this study, a star-wheel design of single crystal sapphire optical fiber is proposed to achieve single mode operation in the infrared regime. In the azimuthal direction the structure retains a reduced core of higher refractive index. It is connected to the outer boundary via star-wheel configuration of segments. The region of alternating symmetrical truncated cavities of lower refractive index is air. The enclosed alternating layers of sapphire and air cavities around the reduced core function as cladding. Fiber structure in the azimuthal direction is uniformly distributed in the radial direction. Finite element method is employed to analyze the modal characteristics of fundamental and higher order modes. Under strongly guided approximation, the structure can effectively eliminate the large modal interference. The proposed waveguides, at operating wavelength of ∼ 1.55 µm, with the diameters of ∼ 50 µm, 75 µm, 100 µm, and 125 µm diameter, exhibit confinement loss of ∼ 0.0314 dB/m, 0.0072 dB/m, 0.0023 dB/m, and 0.0009 dB/m, respectively. It is anticipated that such a fiber can be a potential candidate in addressing a wide range of optical sensors and communication systems, which unable to sustain in extremely harsh environments. COMSOL multi-physics R is used to perform numerical investigations.

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Single-mode sapphire fiber optic distributed sensing for extreme environments

Cited by 12 publications

References 10 publications

Metrological Characterization of a High-Temperature Hybrid Sensor Using Thermal Radiation and Calibrated Sapphire Fiber Bragg Grating for Process Monitoring in Harsh Environments

Metrological Characterization of a High-Temperature Hybrid Sensor Using Thermal Radiation and Calibrated Sapphire Fiber Bragg Grating for Process Monitoring in Harsh Environments

Optical Fiber Sensors for High-Temperature Monitoring: A Review

A Star-Wheel Design of Single Crystal Sapphire Optical Fiber Promoting Single Mode Operation in the Infrared Regime

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