3D-printed Tilt Sensor based on an embedded Two-mode Fiber Interferometer

A 3D-printed tilt fiber sensor using a two-mode fiber interferometer (TMFI) as the sensing mechanism has been demonstrated. The TMFI was constructed by splicing single-mode fibers (SMF28s) at both ends of a two-mode fiber (TMF) to generate a comb-like interference spectrum that is sensitive to bending. A 3D-printed cantilever with a weight attached to one end was used to induce bending as the structure was tilted and by embedding the TMFI onto the 3D printed cantilever, different tilt angles can be measured, as a result of the bending of the fiber. The TMFI exhibited a linear response towards the tilt angles, θ, with a responsivity of 1 × 10-2 nm/deg at negative θ (0 to -90°) and 5 × 10-3 nm/deg at positive θ (0 to 90°), respectively. The sensor was able to detect small angle changes in increments as small as 1° and it performs better than embedded FBG sensors. The tilt sensor proposed has a small form factor and simple design, as well as being cost-effective and light-weight, thus showing significant potential for a variety of civil engineering applications

Novel 3D-printed biaxial tilt sensor based on fiber Bragg grating sensing approach

In this work, a novel 3D-printed biaxial sensor system for tilt measurement, based primarily on the use of four Fiber Bragg Grating (FBG) devices, has been developed and its performance characterized. The tilt sensor system created is of a compact design and relatively small dimensions, making it ideally suited to a variety of industrial applications. In the system developed, the four FBGs used were spliced in a serial formation and attached to four different sides of the sensor structure designed, to allow biaxial measurements to be made. The wavelengths' shift of the FBGs used were monitored as a function of the tilt of the device, using an Optical Spectrum Analyzer (OSA) for this development work. In the sensor, an average FBG-based responsivity of 0.01 nm/° of tilt was measured for each of the different FBGs used. To provide compensation for temperature changes in the system itself, a further FBG-based approach was used (in which they were configured to be insensitive to the effect of the tilt). They were thus calibrated by being exposed to a range of operational temperatures for the system, showing, as a result, a calibration of 0.011 nm/°C. Prior work on the sensor system had proved it to be highly linear in response, over the tilt range of 0° ± 90°. The experimental results obtained from the performance characterization indicate that the small, compact design of this type yields excellent responsivity, compared to other larger and more complex designs discussed in the literature. The sensor system was also relatively easy to fabricate using the 3D-printing method, creating in that way an inexpensive, temperature-compensated tilt monitoring device that had a wide variety of potential industrial applications

Multi-wavelength Bismuth-doped fiber laser in 1.3 µm based on a compact two-mode fiber filter

In this work, a multi-wavelength Bismuth-doped fiber laser (MWLBDFL) operating in the 1.3 µm wavelength region is presented and experimentally demonstrated. The MWLBDFL leveraged on a 60 m Bismuth-doped fiber as an active gain medium, a compact two-mode fiber filter (TMFF) as a comb filter and a 2 km single-mode fiber section to induce four-wave mixing in the system. By optimising the polarization controller, the MWLBDFL generated 18 stable lasing output channels within 10 dB from the highest lasing line and a reasonably flat spectrum over a range of 11 nm. The stability of the MWLBDFL tested for a 150-minute duration showed a peak power fluctuation of less than 1 dB with a negligible wavelength drift. The extinction ratio of the TMFF was approximately 8.6 dB while the highest and lowest optical-signal-to-noise ratios (OSNRs) of the MWLBDFL were ~ 55 dB and ~ 50 dB, respectively. To the best of the author's knowledge, the proposed MWLBDFL demonstrates the highest number of output channels compared to other MWLs operating in the same wavelength region.</p

Biaxial 3D-printed inclinometer based on Fiber Bragg Grating technology

A Fiber Bragg Grating (FBG)-based inclinometer has been developed for field use, designed to incorporate biaxial 3-dimensional (3D) printed tilt sensors (in which four FBGs were used). The inclinometer was characterized by examining its response to a wide range of tilts, over the range from 0° to 90°, towards the inclination axes. An excellent linear correlation between the wavelength shifts and the inclination angle (up to the 90° used) was obtained, showing an average sensitivity of 0.01 nm per degree of inclination angle, for each of the FBGs used. In addition to the four FBGs that form the basis of the inclination measurement, a further FBG was included in the design to allow compensation for any temperature changes experienced during the measurements. The device was calibrated over the range from -25°C to 80°C (corresponding to the extremes of cold and hot weather conditions likely to be experienced in-the-field), and a sensitivity to temperature change of 0.011nm/°C was achieved, allowing an effective temperature correction to be applied. The data obtained from a full characterization of the performance of the sensor system, carried out in a stable, controlled environment, indicate that this inclinometer yields good sensitivity, making it highly applicable for use in monitoring rapid ground movements and deformations with its compact design allowing its wide use.</p

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.</p