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A Method for Determining the Length of FBG Sensors Accurately
摘要： In this study we propose a method for estimating the length of single mode fibre Bragg grating type sensors with high accuracy. Our method is based on calculating the maximum oscillation frequency of the side-lobes of the FBG reflection spectrum. We show that this frequency is independent of the stress field to which the sensor is subjected, and is dependent on the length of the sensor. This method can be used to characterise the gauge length of already installed FBG sensors so that they can provide useful data for engineering models of structural integrity. All the analyses are based on the approximated transfer matrix model, which is a newly developed numerical method for analysis of the FBG reflection spectrum under various stress fields.
关键词： Fiber Bragg grating,structural integrity,reflection spectrum,FBG,length determination
更新于2025-09-23 15:22:29
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Temperature Measurement of Electromagnetic Launcher Rails Based on FBG
摘要： Rails worked under a harsh environment in the electromagnetic launching. Measurement of temperature at or close to the rail-and-armature interface of an electromagnetic launch (EML) is capability that would provide a significant insight into the EML performance. This interface is difficult to access and requires any sensor to tolerate sliding contacts, high electrical currents, and extreme temperatures. As a result, the existing temperature sensor technology has not been successful in providing data at that location. The development of the fiber Bragg grating (FBG) may provide a potential solution for this requirement. By designing and building a temperature measurement system based on FBG, we can collect dynamic temperature data of the rail during the launch. This paper establishes a model of transient thermal field of EML, calculates the variation of rail temperature under the effect of the Joule heat, and compares with the measurement result. After adding the model in the case of the protection package of FBG temperature sensor, the simulation data agrees well with the test data, and the sensors do not been destroyed even disturbed. All of the above prove that this method is feasible, and the sensors can be used in the following tests.
关键词： fiber Bragg grating (FBG),thermal field,Joule heat,temperature measurement,Electromagnetic launch (EML),rails
更新于2025-09-23 15:22:29
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Evaluating the Effect on Demodulation With a Comprehensive Model of Distortions of Fiber Bragg Grating Sensing Signals
摘要： Spectral distortions are complex and unpredictable in fiber Bragg grating (FBG) sensing applications. An inappropriate choice of FBG demodulation algorithm will lead to unacceptable results in practice. Although many demodulation algorithms have been developed for distorted spectra, they may be limited for some types of spectral distortion. Until now, no model of FBG spectral distortion has been proposed to test different demodulation algorithms. Here, we fulfill this aim by introducing a comprehensive model with asymmetrical distortion, multi-peaks distortion, interferometric noise, background noise, and random noise. Using numerical simulations, we evaluate the performance of eight most typical demodulation algorithms with this model. We show that different algorithms should be used within specific ranges of spectral distortions. Altogether, this study provides a guide map as useful reference for selecting an appropriate FBG demodulation algorithm for practical applications. Furthermore, our proposed model paves the way for developing more reliable FBG demodulation algorithms for different spectral distortions.
关键词： spectral distortion,fiber Bragg grating,Demodulation
更新于2025-09-23 15:22:29
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[IEEE 2018 IEEE 3rd Optoelectronics Global Conference (OGC) - Shenzhen (2018.9.4-2018.9.7)] 2018 IEEE 3rd Optoelectronics Global Conference (OGC) - Rapid Response of High Precision Fiber Bragg Grating Based Temperature Sensor
摘要： A new walk-in high precision fiber Bragg grating temperature sensor encapsulated with ultra-fine stainless steel tube was designed. The temperature resolution of the fiber sensor is 0.01 ℃ and the Bragg wavelength of the grating responses linearly with the temperature in the range of room temperature to 175 ℃, meanwhile, the response time is less than 108 ms, which can satisfy the rapid response need of oil temperature profile. In addition, the resistance of the temperature sensor to pressure can be high up to 100 MPa.
关键词： fiber bragg grating,rapid response,temperature sensor
更新于2025-09-23 15:22:29
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Response Time of a Fiber Bragg Grating Based Hydrogen Sensor for Transformer Monitoring
摘要： We developed and optimized a new fiber optic sensor using palladium foils attached to optical fiber Bragg gratings (FBG) for hydrogen measurements. Fifteen in parallel processed sensors were characterized and qualified in two custom tailored experimental set ups and their response to a 5% hydrogen/nitrogen gas mixture and the same gas bubbled trough transformer oil was measured. The hydrogen response is similar for both medium and close to the theoretical maximum sensitivity, but the response time was found to be very different, much slower in oil than in gas. A theoretical comparison of hydrogen diffusion trough palladium and hydrogen absorption on the palladium surface as well as a measurement of the hydrogen uptake and diffusion trough the oil to the sensor have been done to investigate the origin of the different response time. They indicate that the response time determining step is the absorption of hydrogen on the palladium surface and that this process is slowed down in oil compared to a pure gas environment.
关键词： hydrogen sensor,fibre Bragg grating (FBG),fiber sensor,palladium based sensors,hydrogen diffusion and absorption in oil
更新于2025-09-23 15:22:29
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[IEEE 2018 IEEE 13th Annual International Conference on Nano/Micro Engineered and Molecular Systems (NEMS) - Singapore, Singapore (2018.4.22-2018.4.26)] 2018 IEEE 13th Annual International Conference on Nano/Micro Engineered and Molecular Systems (NEMS) - Temperature Sensor Based on Multimode Fiber Bragg Grating
摘要： A multi-layer film fiber Bragg grating (FBG) is used for high temperature measurement. In order to realize the temperature measurement in a wide dynamic range, a multi-layer film fiber Bragg grating (MFBG) is fabricated. Due to its multi-layer structure, the MFBG has been widely studied extensively for temperature measurement. Most of its operation principle is based on the variation analysis of the spectrum caused by temperature change. For measuring temperature, fiber Bragg grating (FBG) temperature sensor has been widely used due to its advantages of good insulation, light weight, low cost, compact structure, chemical property and ability to sense in harsh environment. However, the FBG has been widely studied extensively for temperature measurement. Most of its operation principle is based on the variation analysis of the spectrum caused by temperature change. For measuring temperature, fiber Bragg grating (FBG) temperature sensor has been widely used due to its advantages of good insulation, light weight, low cost, compact structure, chemical property and ability to sense in harsh environment. However, the FBG is difficult to couple with other optical devices, the MFBG has been used to measure the ambient temperature. In order to realize the temperature measurement in a wide dynamic range, a multi-layer film fiber Bragg grating (MFBG) is fabricated. Due to its multi-layer structure, the MFBG has been widely studied extensively for temperature measurement. The working principle is discussed and different reflection peaks are separated from the transmission spectrum. The experimental results show that the temperature response at different peaks is similar, and the optical fiber sensor has a great potential for temperature measurement.
关键词： fiber Bragg grating,multi-layer film,optical fiber sensor,temperature sensor
更新于2025-09-23 15:22:29
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A Rotation Independent In-Place Inclinometer/Tilt Sensor Based on Fiber Bragg Grating
摘要： The inclinometer is one of the most important instruments used in geotechnical engineering. The inclinometer is installed into a borehole to monitor the angle of inclination at regular intervals along the borehole to profile the land/soil displacement. In this paper, a novel design of an in-place inclinometer utilizing fiber Bragg grating (FBG) sensor technology is presented. The presented inclinometer is highly sensitive and has an angle measurement resolution of 0.006°. The conventional inclinometers may be twisted involuntarily due to the force that they experience during installation. This twisting may hamper the measurement accuracy of inclinometers. The performance of the proposed FBG-based in-place inclinometer is independent of twisting; hence, its accuracy remains intact even if it is twisted.
关键词： soil displacement/deformation,Borehole inclinometer,tilt sensor,fiber Bragg grating (FBG),land-slide monitoring,fiber optic sensor,in-place inclinometer
更新于2025-09-23 15:22:29
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Simultaneous measurement of temperature and refractive index based on microfiber Bragg Grating in Sagnac loop
摘要： In this paper, a simultaneous measurement system of temperature and refractive index (RI) is proposed and demonstrated. The dips in the output spectrum of the proposed sensor are formed by the micro?ber Bragg Grating (mFBG) and Sagnac loop. Due to di?erent interference mechanisms, the dual-parameter measurement is realized by mFBG and Sagnac loop with di?erent sensitivities to temperature and RI. Compared with the traditional Sagnac loop sensors, the proposed Sagnac loop with mFBG is much sensitive to surrounding RI. The results show that the temperature sensitivity is 0.033 nm/°C and ?0.015 dB/°C. And the RI sensitivity is 39.30 nm/RIU and 41.51 dB/RIU. The proposed sensor has a simple structure and great potential in biological and chemical ?elds.
关键词： Micro?ber Bragg Grating,Sagnac loop,Dual-parameter measurement
更新于2025-09-23 15:22:29
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Strain Monitoring on PHC Pipe Piles Based on Fiber Bragg Grating Sensors
摘要： Fiber Bragg grating (FBG) sensors emerged as a relatively new strain-sensing technology for civil engineering applications. This study presents a field test to assess the feasibility of FBG sensors in monitoring the strain profile of prestressed high-strength concrete (PHC) pipe piles during installation. Two open-ended PHC pipe piles were instrumented with FBG sensors and then driven into the ground using a hydraulic jacking machine. To measure the strain profile along the test piles, nine FBG sensors were arranged in a single optical fiber and then mounted on one pile at the opposite side to monitor the strain at different levels as a function of wavelength shift. The procedure for installing the FBG sensors along the PHC pipe piles is introduced first. Next, the distribution of the axial forces and average side shear stresses that were evaluated from the strain measurements of the FBG sensors are discussed. The field test results indicate that the FBG sensor system was suitable for monitoring the strain state of PHC pipe piles during installation. The axial forces and side shear stresses along the test piles were influenced significantly by the penetration depth and the local soil resistance.
关键词： Fiber Bragg grating (FBG) technology,Jacking method,Strain monitoring,Prestressed high-strength concrete (PHC) pipe pile
更新于2025-09-23 15:22:29
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High sensitivity fiber optic sensor for hydrogen detection in gas and transformer oil
摘要： This paper reports on the characterisation of a palladium (Pd) based fiber optic hydrogen (H2) sensor for health monitoring of distribution and power transformers in the electrical grid. The sensor consists of a Pd foil, which expands due to H2 absorption, and a fiber Bragg grating (FBG) that measures this expansion. Fifteen sensors were manufactured and characterised in gas and oil environments at various H2 concentrations and temperatures. In gas, the sensors were evaluated at 60°C, 75°C, 90°C, 105°C and 120°C and H2 concentrations from 0.01 to 5%. In oil, the same sensors were evaluated at 90°C and dissolved H2 concentrations from 5 to 2700 ppm. Furthermore, the influence of carbon monoxide (CO), which is often present in transformers and can impact H2 response of the sensor, was investigated. At 90°C in gas, the response to 0.01%, and 5% H2 was on average 28 pm, and 719 pm respectively. At 90°C in oil, the response to 5 ppm, and 2700 ppm dissolved H2 was on average 11 pm, and 763 pm respectively. The average, relative accuracy is better than 20% over the whole measurement range in gas and for measurements above 100 ppm in oil. These specifications make the sensor a promising candidate for online monitoring of H2 in transformers.
关键词： transformer monitoring,Hydrogen,fiber Bragg grating,palladium,gas detection
更新于2025-09-23 15:22:29