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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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[IEEE 2018 Asia Communications and Photonics Conference (ACP) - Hangzhou, China (2018.10.26-2018.10.29)] 2018 Asia Communications and Photonics Conference (ACP) - All-fibre acoustic sensor for the sound source localization
摘要： The large size and electromagnetic interference of microphones array are long standing challenges for sound source localization. Here an all-fibre vector acoustic sensor based on crossed microfiber Bragg gratings (micro-FBGs) has been proposed and experimentally demonstrated that enables the two-dimension sound source localization with a size less than 1.5mm. Two micro-FBGs inscribed in the Co2+-doped fibre are fabricated through a hydrofluoric acid solution, which are placed parallel to each other to form a micro-FBG pair. Based on the self-heating and asymmetric temperature distribution of two Co2+-doped fibres, the crossed micro-FBGs provide a direct two-dimensional measurement of the acoustic particle velocity. The experimental results show that an orientation sensitivity of 1.57 mV/deg for the micro-FBGs is achieved with a figure-of-eight response of the acoustic source direction. Meanwhile, the direction responses of two crossed pairs of micro-FBGs are exactly orthogonal to each other, which could detect the sound source localization. The all-fibre vector acoustic sensor is immune to electromagnetic interference, which appears to have a variety of potential applications, including research in acoustic communication, pipeline monitoring and navigation, etc.
关键词： Co2+-doped fibre,sound source localization,micro-FBG
更新于2025-09-23 15:22:29
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Nuclear Power Plant Prestressed Concrete Containment Vessel Structure Monitoring during Integrated Leakage Rate Testing Using Fiber Bragg Grating Sensors
摘要： As the last barrier of nuclear reactor, prestressed concrete containment vessels (PCCVs) play an important role in nuclear power plants (NPPs). To test the mechanical property of PCCV during the integrated leakage rate testing (ILRT), a fiber Bragg grating (FBG) sensor was used to monitor concrete strain. In addition, a finite element method (FEM) model was built to simulate the progress of the ILRT. The results showed that the strain monitored by FBG had the same trend compared to the inner pressure variation. The calculation results showed a similar trend compared with the monitoring results and provided much information about the locations in which the strain sensors should be installed. Therefore, it is confirmed that FBG sensors and FEM simulation are very useful in PCCV structure monitoring.
关键词： structure health monitoring (SHM),finite element method (FEM),integrated leakage rate test (ILRT),fiber Bragg grating (FBG),prestressed concrete containment vessel (PCCV)
更新于2025-09-23 15:21:01
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - All-Fiber 2.07 μm Distributed Feedback Laser Based on π-Phase-Shifted FBG Inscribed in Heavily Doped Holmium Fiber by Femtosecond Laser Pulses
摘要： Distributed-feedback (DFB) fiber laser is a versatile source of low-noise single-frequency radiation that finds applications in spectroscopy, optical communications and sensing devices. Depending on the active medium, different lasing wavelengths can be obtained: 1.03–1.12 μm for Yb, 1.53–1.62 μm for Er, and 1.73–1.93 μm for Tm-doped fibers. Special fiber Bragg grating (FBG) with a length of 20–70 mm and phase shift in the structure, directly written in an active medium, serves as distributed feedback cavity of this type of laser. Commonly, special UV photosensitive fibers and phase masks inscription technique are used for an FBG fabrication. Alternative femtosecond (fs) point-by-point technique [1] has a number of advantages as compared to UV-based ones: 1) wide variety of active fibers can serve as a host material for an FBG, thanks to the nonlinear mechanism of fs pulses absorption, 2) FBG period can be easily tuned by controlling fs pulses frequency and velocity of fiber translation during the inscription process, 3) each fiber grating “pitch” can be written independently, which means that phase shift with an exact value and position along FBG can be introduced. Despite the number of publications dealing with holmium fiber lasers [2], there no publications devoted to DFB ones. At the same time, such type of laser sources has a great potential as a master oscillator in all-fiber coherent beam combination systems [3]. We report on the creation of holmium-doped DFB fiber laser with a wavelength of 2.07 μm operating in single-frequency regime (Fig. 1a). The laser is based on custom-made single-mode holmium-doped fiber having absorption coefficient about 43 dB/m at 1.125 μm, which is the wavelength of pump Yb fiber laser. 42-mm π-phase-shifted FBG was directly inscribed in the active fiber by femtosecond IR laser pulses and served as distributed feedback cavity of the laser. Lasing threshold was reached at 350 mW pump power, and output power exceeded 36 mW at pump power of 4.8 W (Fig. 1b). Single-polarization mode operation was observed with linewidth of ~10 kHz. Additionally to the room-temperature operation regime we will present and discuss the laser operation regimes at cryogenic temperature (77 K), as well as high-temperature (>400 K). To the best of our knowledge, it is the first realization of all-fiber DFB laser based on holmium active medium.
关键词： femtosecond laser pulses,holmium-doped fiber,single-frequency radiation,Distributed-feedback fiber laser,π-phase-shifted FBG
更新于2025-09-23 15:19:57
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Development of Picosecond Laser Writing for Heat Resistant FBG Sensors and Adhesion Technique for High Temperature Industrial Plants; ?????3?§??????????????·￥?????????è????±FBG ?????3??μè￡??????¨é???????￡?￥-??¨????????3???????????￥???;
摘要： Pulse laser processing point by point method is applied for heat resistant Fiber Bragg Grating structure. In order to fabricate fine FBG, a close packaged picosecond laser system is used with a CCD camera microscopy. An optical fiber is mounted on a precision translation stage. The stage speed is controlled by the current position and the corrector output. In order to contact the FBG on a metal surface, nano-size colloidal silver adhesive is used under temperature monitoring. Heat expansion of SUS plate can be successfully monitored by strain gauge of the heat resistant FBG. It can be available for monitoring the structural integrity of high temperature industrial plant. Complex coolant piping systems of liquid sodium and molten salt are facing the risk of coolant leakage, which is the most promising usage.
关键词： Structural Health Integrity,Picosecond Laser Processing,Adhesion,High Temperature,FBG
更新于2025-09-23 15:19:57
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A Novel Fabry-P??rot Optical Sensor for Guided Wave Signal Acquisition
摘要： In this paper, a novel hybrid damage detection system is proposed, which utilizes piezoelectric actuators for guided wave excitation and a new ?bre optic (FO) sensor based on Fabry-Perot (FP) and Fiber Bragg Grating (FBG). By replacing the FBG sensors with FBG-based FP sensors in the hybrid damage detection system, a higher strain resolution is achieved, which results in higher damage sensitivity and higher reliability in diagnosis. To develop the novel sensor, optimum parameters such as re?ectivity, a wavelength spectrum, and a sensor length were chosen carefully through an analytical model of the sensor, which has been validated with experiments. The sensitivity of the new FBG-based FP sensors was compared to FBG sensors to emphasize the superiority of the new sensors in measuring micro-strains. Lastly, the new FBG-based FP sensor was utilized for recording guided waves in a hybrid setup and compared to the conventional FBG hybrid sensor network to demonstrate their improved performance for a structural health monitoring (SHM) application.
关键词： ?ber optic sensors,guided waves,structural,health monitoring,hybrid PZT-FBG,Fabry-Perot
更新于2025-09-23 15:19:57
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Response of FBG sensors embedded in SRM interface of combustor when subjected to tri-axial normal loadings
摘要： In this paper, polymer packaged fiber Bragg grating (FBG) sensors are installed inside of the combustor wall to monitor the health of solid rocket motor. The responses of sensor embedded in adhesive specimen composed of propellant, insulation and case when subjected to axial and unaxial tensile stress are investigated. The strain distribution and spectrum of FBG were simulated when the specimen suffered from different normal loadings by finite element method and computer simulation technology. The result is validated by axis and unaxis tensile test. It is shown that the proposed type of sensing system can measure the bond stress (the radial stress) in SRMs.
关键词： solid rocket motor,optical sensors,interface,FBG
更新于2025-09-19 17:15:36
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Clamp looseness detection using modal strain estimated from FBG based operational modal analysis
摘要： Clamps are widely used to fix and support the pipe in engineering community. Clamps looseness may further lead to the fatigue damage of the pipe, therefore the early detection of clamps looseness is very crucial. The robustness and the accuracy of damages detection have already been the greatest challenges in traditional methods in Structural Health Monitoring (SHM). Due to the higher sensitivity of Strain Mode Shape (SMS) to local damages and more effective performance of fiber Bragg grating (FBG) sensing technology for industrial and mechanical devices, present works focus on a new method to detect clamp looseness based on Strain Mode Shape Differences (SMSD) and FBG sensing technology. In order to estimate the SMSs online, a novel diagram of Operational Strain Modal Analysis (OSMA) with FBG sensing technology is also presented, in which a rational fraction composed by Forsythe Complex Orthogonal Polynomials (FCOP) is employed to fit the 'Positive' Strain Power Spectral Density (PSPSD) of a single output. Traditionally, the fitting of the all the outputs need to be conducted to obtain the SMSs, which increases the calculation cost. To further address this issue, an improved OSMA integrated with strain response transmissibility (SRT) is also proposed to calculate the SMSs by just fitting a single output. Firstly, the identified modal parameters based on the presented method is validated with simulation results. And then, the ability of the SMSD index is further investigated analytically and experimentally for clamp looseness detection under different locations and degrees , the results indicate that the clamp looseness can be detected by the SMSD index.
关键词： modal strain,Operational Strain Modal Analysis,Clamp looseness detection,FBG sensing.
更新于2025-09-19 17:15:36
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Optical fiber relative humidity sensor based on FBG embedded in SMS fiber structure
摘要： A novel optical fiber humidity sensor based on fiber Bragg grating (FBG) embedded in single-mode-multimode-single-mode (SMS) fiber structure is proposed. With relative humidity (RH) changing, the transmission spectrum of the SMS fiber structure shifts while the central wavelength of FBG remains unchanged. Numerical simulations of light distribution of the SMS structure have been carried out, analyzing the effects of different wavelengths of the input light, lengths and core diameters of the multimode fiber (MMF). The cross-sensitive problem of temperature has also been solved.
关键词： relative humidity measurement,FBG,Single-mode-multimode-single-mode fiber structure
更新于2025-09-16 10:30:52
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Theoretical and experimental study on optical fiber microseismic accelerometer based on cantilever beam structure
摘要： According to the characteristics of underground environment and microseismic signal in coal mine, a kind of optical fiber microseismic accelerometer based on cantilever beam structure is put forward in this paper, and its mechanical model is established, its sensitivity is analyzed, and tested by B&K shaking table test system. The experimental results show that the frequency response range of the sensor is 10Hz-100Hz, which meets the requirements of microseismic test.
关键词： FBG,accelerometer,microseismic,cantilever beam,frequency response
更新于2025-09-16 10:30:52