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Study on sliding-window length based on Rayleigh backscattering spectrum correlation in distributed optical-fiber strain measurement
摘要： A theoretical model is established for estimating the strain measurement error based on the Rayleigh backscattering spectrum correlation in distributed optical fiber strain measurements. Assuming the signal is much larger than the noise, the theoretical model predicts the strain measurement error using noise variance and the defined quality factor Q of the Rayleigh backscattering spectrum. Furthermore, an algorithm based on the quality factor Q is proposed to select an optimized sliding-window. The sliding-window length can be obtained by calculating the threshold value of the quality factor using a theoretical model corresponding to the required strain measurement accuracy. Compared with the traditional method where the sliding-window length is defined by the user based on spatial resolution requirements or an empirical definition, the sliding-window length determined by the algorithm is more reasonable and can be automatically defined, alleviating the requirement for user inputs. To verify the correctness of the theoretical model, two experiments are set up: a self-correlation experiment, that analyzes the effect of the quality factor on the strain measurement accuracy, and a virtual experiment of the noise influence, which analyzes the effect of different noise variances. The experimental results are in good agreement with those of the model.
关键词： Distributed optical fiber strain measurement,Rayleigh backscattering spectrum correlation,Optical frequency domain reflectometer
更新于2025-09-23 15:23:52
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[IEEE 2018 11th International Symposium on Communication Systems, Networks and Digital Signal Processing (CSNDSP) - Budapest (2018.7.18-2018.7.20)] 2018 11th International Symposium on Communication Systems, Networks & Digital Signal Processing (CSNDSP) - Multi point strain and temperature sensing based on Brillouin optical time domain reflectometry
摘要： In this paper, multiple points of strain and temperature measurement in real-time is investigated using a Brillouin optical time domain reflectometry (BOTDR) system. The Brillouin frequency shift (BFS) is analysed with strain and temperature effects applied at various locations of the sensing fibre. In addition, a passive depolarizer was employed in order to reduce the polarization noise. The strain and temperature coefficients are found to be 0.79 MHz/oC and 0.057 MHz/με.
关键词： Brillouin gain spectrum,strain measurement,temperature measurement
更新于2025-09-23 15:21:21
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Development of low cost packaged fibre optic sensors for use in reinforced concrete structures
摘要： There is an ongoing need to measure strains in reinforced concrete structures more reliably and under a range of circumstances e.g. long term durability (such as effects of cracking and reinforcement corrosion), response to normal working loads and response under abnormal load conditions. Fibre optic sensors have considerable potential for this purpose and have the additional advantages, including of immunity to electromagnetic interference and light weight (Grattan et al, 2000). This is important in railway scenarios and particularly so when the lines are electrified. Their small size allows for easy installation. However, their use as commercial ‘packaged’ devices (traditionally seen as necessary to achieve adequate robustness) is limited by their high cost relative to other sensor devices such as encapsulated electric resistance strain gauges. This paper describes preliminary work to produce a cost-effective and easy-to-use technique for encapsulating fibre optic sensors in resin using 3D printing techniques to produce a robust, inexpensive ‘packaged’ sensor system suitable for use with concrete structures. The work done to date has shown this to be a convenient and economical way of producing multiple sensors which were suitable for both surface mounting and embedment in reinforced concrete structures. The proof-of-concept testing to which the trial packages were subjected is described in the paper and the results indicate that 3D printed packages have considerable potential for further development and use in a variety of civil engineering applications, competing well with more conventional sensor systems.
关键词： encapsulation,reinforced concrete,3D printing,Fibre optic sensor,strain measurement
更新于2025-09-23 15:21:21
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Camera array-based digital image correlation for high-resolution strain measurement
摘要： Digital image correlation (DIC) is a well-known technique for non-contact, non-destructive, full-field deformation measurement in experimental solid mechanics. Although DIC has been widely used in science and engineering, the resolution of strain measurement with DIC is limited by imaging resolution and is much lower than that obtained with a strain gauge. To achieve a breakthrough in strain measurement using DIC, a camera array-based DIC method is proposed herein for high-resolution strain measurement. Twenty-five industrial cameras were assembled into a plane array, with each camera capturing a part of the specimen. A novel calibration-based image stitching method is proposed and was applied to these images and their corresponding displacement fields. The strain field was then calculated based on the stitched displacement fields. The use of the camera array greatly improved the measurement spatial resolution of DIC and made high-resolution strain measurement possible. Both static error analysis and four point-bending experiments were performed to demonstrate the feasibility and effectiveness of the proposed method, and a full-field strain resolution of 10 με was achieved.
关键词： displacement field stitching,camera array,Digital image correlation,image stitching,high-resolution strain measurement
更新于2025-09-23 15:21:01
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[Lecture Notes in Electrical Engineering] Sensors and Microsystems Volume 629 (Proceedings of the 20th AISEM 2019 National Conference) || Relative Humidity Sensor Based on Tip of Multimode Optical Fiber Integrated with Photonic Crystal of Hydrogel Coated Polystyrene Nanoparticles
摘要： A relative humidity (RH) sensing device based on photonic crystal colloids auto-assembled directly on the tip of a multi-mode optical fiber is here described. The core-shell nanospheres are obtained by Polystyrene (PS) nanoporous structures (core) incorporated into a poly(N-isopropylacrylamide) (PNIPAM) hydrogel (shell) and are subsequently deposited via a vertical dip-coating technique on a multimode optical fiber tip. The sensing capability is due to the hydrogel shell that swells depending on the relative humidity that induce wavelength shift and amplitude changes in the photonic bandgap peak. Spectral characterization and sensing analysis are performed, and the obtained results show that spectral characteristics are highly non-linear and strongly manufacturing dependent. A resolution of 1% RH is measured at 30% RH that significantly decreases at higher RH. Hereby, numerical simulations based on the finite element method (FEM) have been performed in order to investigate the sensing mechanism.
关键词： Structural health monitoring,Deflection monitoring,Optical fiber sensors,Strain measurement
更新于2025-09-23 15:19:57
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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) - Strain Sensor Based on Mach-Zehnder Interferometers by Waist-enlarged Structure and Spherical Structure
摘要： Optical fiber sensors based on waist-enlarged structure and spherical structure were proposed for strain measurement. Their fabrication process and experimental results were compared. The strain sensitivities of the sensors based on the waist-enlarged structure and the spherical structure are -0.66pm/με and -1.28pm/με, respectively. It shows that the Mach-Zehnder sensor the waist-enlarged structure has the advantages of good repeatability and easy fabrication, and the Mach-Zehnder sensor based on the strain spherical measurement. structure has higher fabricated by sensitivity for
关键词： Strain measurement,Mach-Zehnder interferometer,Spherical-shape structure,Waist-enlarged structure
更新于2025-09-16 10:30:52
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Long-Sensing-Length Strain Sensor Based on Optical Fiber Fabry-Perot Interferometer with HCF-SMF Structure
摘要： We proposed and demonstrated an optical fiber Fabry-Perot (F-P) sensor with long sensing length for strain measurement. The structure of the sensor was fabricated with a simple process by splicing a long single mode fiber (SMF) with a short section of hollow-core fiber (HCF). The end of the SMF was cleaved with smooth reflective surface which hence allows the sensing length of the proposed sensor can achieve several centimeters with good visibility. Sensors with different sensing lengths were fabricated and experimentally analyzed in this paper. The relationship between the optical path difference (OPD) of the sensor and strain is found to be linear. With the sensing length of ~10mm and ~49 mm, the sensor can achieve the OPD strain sensitivity of 20.42 nm/ and 115.57 nm/ respectively. Besides, with the sensing length of ~10mm, the OPD temperature sensitivity of the sensor was 187.64 nm/°C. With the advantages of easy making, low cost and long sensing length, it is anticipated that the proposed sensor has great potential in measuring the strain with a large distribution.
关键词： strain measurement,optical fiber sensor,Fabry-Perot interferometer
更新于2025-09-11 14:15:04
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Near infrared spectroscopic measurement of strain in rocks
摘要： The measurement of strain is a fundamental and widely studied parameter in engineering, rock mechanics, construction and materials testing. Contact sensors often used in these fields require contact with the target surface throughout the duration of a strain event. Non-contact methods typically require that that the measurement surface is prepared and often coated prior to testing. This paper considers the potential application of near infrared spectroscopy as a non-contact technique for the measurement of strain on natural surfaces. Excellent correlation was found between surface measurements of visible-NIR spectra and longitudinal strain taken during indirect Brazilian Disc Test for samples of sandstone, marble and basalt.
关键词： rock,indirect tensile strength,Strain measurement,near infrared spectroscopy
更新于2025-09-11 14:15:04
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In-fiber integrated sensor array with embedded weakly reflective joint surface
摘要： An integrated sensor array with the embedded weakly reflective joint surface is proposed and demonstrated. The weak reflector is formed of a single mode fiber (SMF) and a double-cladding fiber (DCF), whose cores have different refractive index. A sensor array based on this structure is sensitive to strain and temperature, and it has the ability to achieve quasi-distributed measurements. Therefore, it can be used for structural health monitoring (SHM). Besides that, without any connector, the sensors were integrated in a fiber. Consequently, they are more suitable for a harsh test environment (space limitation or high temperature).
关键词： strain measurement,white light interferometer,distributed strain sensor,Fiber optic sensor
更新于2025-09-10 09:29:36
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High sensitivity strain sensor based on twin hollow microspheres
摘要： A sensor based on 2 hollow core microspheres is proposed. Each microsphere was produced separately through fusion splicing and then joined. The resultant structure is a Fabry-Perot interferometer with multiple interferences that can be approximated to a 4-wave interferometer. Strain characterization was attained for a maximum of 1350 με, achieving a linear response with a sensitivity of 3.39 (cid:1) 0.04 PM/με. The fabrication technique, fast and with no chemical hazards, as opposed to other fabrication techniques, makes the proposed sensor a compelling solution for strain measurements in hash environments.
关键词： strain measurement,fiber optics sensors,Fabry-Perot
更新于2025-09-10 09:29:36