16 research outputs found
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Surface-Mounted Tilt Sensor Using Fiber Bragg Grating Technology for Engineered Slope Monitoring With Temperature Compensation
A surface-mounted tilt sensor was designed and fabricated to measure the inclination angle of engineered structures or slopes in two directions. The device utilizes two strain-sensitive fiber Bragg gratings (FBGs) for tilt angle measurement bidirectionally and one strain-free FBG to provide temperature compensation. In this work, a tilt sensor prototype was fabricated using a 3-D printer, with a robust enclosure and a miniature actuator with dimensions of 115×65×30 mm and 45×20× 3 mm, respectively. The device was first calibrated in the laboratory for tilt and temperature parameters. For tilt calibration, the device yields a sensitivity value of 0.0135 and 0.0123 nm/° for + x- and– x -directions. On the other hand, the device delivers a sensitivity value of 0.0105 nm/°C as the response to temperature changes. The tilt sensor was also tested for suitability in a real-field deployment where it was installed on a retaining wall and was left for four weeks. The field test data indicate no vertical displacement of the wall since the device exhibits zero inclination changes during the test period. This compact, robust, and easy-to-install tilt sensor has excellent potential for various geotechnical applications, mainly in landslide detections, ground movement, and engineered slope monitoring
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Optical fiber Bragg grating-based pressure sensor for soil monitoring applications
An optical-based pressure sensor for a 150 × 150 mm surface was designed and fabricated. The sensor utilizes a fiber Bragg grating (FBG) attached to a 30 × 30 × 30 mm actuator as the pressure sensing mechanism. The middle section of the actuator, which is circular, can bend into an elliptical form and, in the process, pull the FBGP via both ends when force or pressure is applied, thus converting the pressure applied to its surface into a wavelength shift. In laboratory testing, a sensitivity of 0.152 nm∕kPa was obtained. Subsequently, the pressure sensor was tested in the field by burying it 20 cm underground to measure soil pressure, while another FBG was spliced in series to the FBGP to compensate for temperature variations. Testing shows that the proposed design can realize a compact optical-based pressure sensor with enhanced soil monitoring applications such as dynamic soil pressure caused by soil movement
Tunable passively Q-switched thulium doped fluoride fibre (TDFF) laser using reduced graphene oxide-silver (rGO-Ag) as saturable absorber
A tunable, passively Q-switched thulium doped fluoride fibre (TDFF) laser using a reduced-graphene
oxide-silver (rGO-Ag) thin film as a saturable absorber (SA) for S band operation is proposed and its
efficacy demonstrated. Over a pump power range of 91.4 mW up to 158.6 mW, passively generated
Q-switched pulses are observed with repetition rates from 20 to 34.5 kHz and pulse widths from 3.1
to 7.1 µs. The highest pulse energy observed is 101.2 nJ with a signal to noise ratio of ∼ 42 dB. The
proposed laser has a tuning range ∼ 52 nm from 1458 to 1510 nm with a tunable bandpass filter
(TBPF) introduced into the cavity
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A Hi h-Precision Extensometer System for Ground Displacement Measurement Using Fiber Bragg Grating
The design and performance of an innovative high-precision extensometer system, fabricated inexpensively using 3D printing technology, are discussed in this paper. In the development of the extensometer, an embedded Fiber Bragg Grating (FBG) strain sensor was 3D printed using a thermoplastic polyurethane (TPU) filament, which was used as the primary sensing element of the extensometer system, taking advantage of its excellent flexibility and high sensitivity to variations in localized strain. In the performance assessment carried out, the results obtained during the experimental test and validation have demonstrated that it could be used very effectively to measure strain variations, with an average wavelength responsivity of 0.0158 nm/cm (for displacement) and very high linearity (up to 99%). Furthermore, the protection integrated into the sensor systems design makes it well-suited for in-the-field applications, such as monitoring ground displacements which can lead to dangerous slippages of sloped earthworks. In addition, a field testing of the extensometer under simulated conditions has shown that a Fiber Bragg Grating (FBG)-based approach could be applied effectively to the measurement of strain, offering a wavelength responsivity of 0.0012 nm/ με (for strain-sensitive FBGs) under both dry and wet soil conditions. Moreover, taking advantage of the high (~99%) linearity, the extensometer is a reliable instrument for use in different underground conditions, creating an easy-to-use ground movement monitoring system which then enables an excellent representation of the displacement profile of the earth to be made
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Optical fiber Bragg grating (FBG)-based strain sensor embedded in different 3D-printed materials: A comparison of performance
A compact fiber Bragg grating (FBG)-based strain sensor has been developed by embedding an FBG inside a 3D-printed structure, allowing the comparison of FBG responses across different filaments such as polylactic acid (PLA), thermoplastic polyurethane (TPU), polycarbonate (PC), acrylonitrile butadiene styrene (ABS), and nylon. Results have shown that FBG embedded in TPU can be effective in the measurements of mechanical strain, giving a responsivity value of 17.70 pm/cm with outstanding linearity of 98 %. Furthermore, small-scale field testing conducted in below-ground environments has shown that strain sensors based on FBG embedded in TPU are the most effective. They offer a responsivity of 13.9 pm/kg with a small standard deviation and high linearity. Additionally, they have the highest temperature sensitivity value of 15.4 pm/°C compared to the other embedded FBGs. Therefore, for most industrial applications, the FBG embedded in TPU can be considered as an alternative to existing embedment methods for strain sensing applications