- 标题
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- 实验方案
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Effect of Different Inorganics on Polyimide-based Bragg Grating Humidity Sensor
摘要： Effect of activated carbon and lithium chloride on polyimide-based fiber Bragg Grating relative humidity sensor has been experimentally investigated. Through dip coating process, organic-inorganic hybrid coatings were deposited on fiber Bragg grating to form different relative humidity sensors. Experimental results show that the addition of activated carbon or lithium chloride alone could increase the humidity sensitivity (1.67 times and 1.61 times, respectively), but the structure which contains both lithium chloride and activated carbon increases the sensitivity most (3.9 times). In the 14-day stability test, the fluctuation of pure polyimide sensor is ± 6.5%, while the ones of activated carbon sensor, lithium chloride sensor, activated carbon and lithium chloride sensor are ± 3%, ± 8%, and ± 1.6%.
关键词： lithium chloride,fiber Bragg grating,activated carbon,polyimide,humidity sensor
更新于2025-09-23 15:22:29
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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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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
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Optical Interferometry || Applications of Fiber-Optic Interferometry Technology in Sensor Fields
摘要： Optical interferometry as a precision metrology has been widely employed in many aspects for accurate measurements of various physical quantities. As an important branch of measurement technology, now the fiber-optic interferometry technology, based on fiber-optic and laser technologies, has been developed and widely applied in sensor fields for detections of various unknown or uncontrolled physical parameters. In this chapter, basic concepts of fiber-optic interferometry are presented and clarified. Also, three novel fiber-optic sensors, based on the optical interferometry technology and mainly used in the power industry for equipment failure monitoring, are demonstrated.
关键词： optical interferometry,fiber-optic sensor,fiber Bragg grating-based interferometer,interference fringe,laser
更新于2025-09-23 15:21:21
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Point-by-Point Femtosecond-Laser Inscription of 2-μm-Wavelength-Band FBG through Fiber Coating
摘要： We propose a point-by-point inscription method for fiber Bragg grating (FBG) fabrication using a femtosecond pulsed laser focused through a fiber polyimide coating, realizing a 2-μm-wavelength-band FBG. A femtosecond laser acts as the inscription laser, focused by a 63× oil lens. A first-order FBG was fabricated with a grating interval of 700 nm. The 15- μW pulsed laser was focused directly on the fiber core through the polyimide coating and cladding. A first-order FBG for 2004.8-nm light with more than 56% reflectances was fabricated. High wavelength sensitivity and linearity of the FBG were demonstrated by temperature and strain-sensing testing. The first-order FBG of 2004.8 and 2000.2 nm resonant wavelengths could be realized simultaneously through parallel inscription method in 3000μm long grating area.
关键词： 2-μm-wavelength-band,Fiber Bragg grating,Erbium-doped fiber laser,Femtosecond pulsed laser
更新于2025-09-23 15:21:21
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Slit beam shaping technique for femtosecond laser inscription of enhanced plane-by-plane FBGs
摘要： In this work, the development of plane-by-plane (Pl-b-Pl) fiber Bragg gratings (FBGs) by using a single pulse is reported. A slit oriented along the longitudinal axis of the fiber is employed for this. The purpose is to shape the beam so that the focal volume is spatially wider in the transverse direction of the fiber. In this way, it is possible to make 2-D modifications of the refractive index whose width and height depends on the slit width and the pulse energy, respectively. Through an analytical mathematical modelling, the relationship between the diameter of the Gaussian laser beam (Dx) and the slit width (s = Dy) is determined in order to obtain a circular cross-section. In the experimental results carried out, it can be observed that Dx/Dy=3 ratio cause positive and uniform refractive index changes, compared to the negative and inhomogeneous refractive index changes corresponding to point-by-point (PbP) FBGs. Likewise, Pl-b-Pl FBGs, presenting a broader modification of the core cross-section, show significantly lower losses in transmission (0.3 dB), as well as better reflectivity and FWHM. It is observed that these three parameters (losses, reflectivity and FWHM) have a monotonous tendency according to the slit width. Polarization-dependence is also evaluated.
关键词： Optical Fiber Sensor,Slit beam technique,Femtosecond laser,Plane-by-Plane,Fiber Bragg grating
更新于2025-09-23 15:21:01