Use of Fibre Bragg Grating (FBG)technology to enhance axial resolution in Fibre Optic Low Coherence Interferometry (FOLCI)

2006 ◽  
Author(s):  
Enock Jonathan
Keyword(s):  
Bragg Grating ◽  
Fibre Bragg Grating ◽  
Fibre Optic ◽  
Axial Resolution ◽  
Low Coherence ◽  
Low Coherence Interferometry

Leak detection on water pipelines in unsaturated ground by discrete fibre optic sensing

2019 ◽  
Vol 19 (4) ◽  
pp. 1219-1236 ◽  
Author(s):  
Schalk Willem Jacobsz ◽  
Sebastian Ingo Jahnke
Keyword(s):  
Unsaturated Soil ◽  
Ground Deformation ◽  
Bragg Gratings ◽  
Leak Detection ◽  
Bragg Grating ◽  
Fibre Bragg Grating ◽  
Fibre Optic ◽  
Temperature Changes ◽  
Water Leak ◽  
Fibre Bragg Gratings

The article describes a study using discrete fibre optic sensing as a means of leak detection on water distribution pipes installed in unsaturated ground. A short length of pipe fitted with artificial leak points was installed, to which a fibre optic cable with fibre Bragg gratings was attached. An optical fibre with fibre Bragg gratings was also installed in the ground parallel to but separate from the pipe. Thermistors were installed at selected locations to measure temperature changes independent of strain. It was found that a simulated water leak resulted in clearly detectable temperature changes and thermally induced fibre Bragg grating wavelength changes in the ground around the pipe. However, significantly larger deformation-induced fibre Bragg grating wavelength changes were measured on the pipe walls and also in the initially unsaturated ground in response to leaks. A wetting front originating from a water leak propagating through unsaturated soil is associated with significant effective stress changes because the infiltrating water alters the ambient matric suction in the soil. This effective stress change is associated with significant ground deformation resulting in a fibre Bragg grating response which significantly exceeds the thermal response associated with (usually) colder water leaking into unsaturated soil. The study illustrates advantages of measuring ground deformation-induced fibre Bragg grating wavelength changes over pure temperature changes as an efficient means of leak detection in unsaturated ground. However, due to the limited number of fibre Bragg gratings that can be monitored along a single optical fibre, a leak detection system suitable for practical implementation should be based on distributed fibre optic strain sensing, an aspect requiring further research.

Design and testing of fibre Bragg grating force transducers for the measurement of pantograph–catenary contact force

2018 ◽  
Vol 233 (4) ◽  
pp. 396-409 ◽  
Author(s):  
Marco Bocciolone ◽  
Giuseppe Bucca ◽  
Andrea Collina ◽  
Lorenzo Comolli
Keyword(s):  
Contact Force ◽  
Force Measurement ◽  
Force Transducer ◽  
Optical Force ◽  
Bragg Grating ◽  
Fibre Bragg Grating ◽  
Fibre Optic ◽  
Design Development ◽  
Force Transducers ◽  
Set Up

This paper deals with the design, development and testing of a novel force transducer based on fibre-optic technology, for the measurement of contact force between a pantograph and an overhead line. Due to the particular application, in which part of the measurement chain is at high voltage and part is at ground potential, fibre-optic technology has the advantage of making the set-up easier to install and to manage with respect to the adoption of classical electrical-based transducers. Fibre Bragg grating is used as detectors in strain-based force transducers developed for this purpose. Considering that the force transducers become part of the connection between each collector of the pan head and the suspension, a proper design matching many conflicting requirements, such as encumbrance, mass, static and fatigue strength and sensitivity, is necessary. Laboratory tests and in-line tests proved the suitability of the optical force transducers. In particular, tests demonstrated that optical transducers represent an alternative to the classical electrical-based transducers for pantograph–catenary force measurement, reducing the complexity of the complete measurement set-up.

A temperature-independent fibre-optic magnetic-field sensor using thin-core fibre tailored fibre Bragg grating

2017 ◽  
Vol 393 ◽  
pp. 169-172 ◽  
Author(s):  
Qin Tian ◽  
Zhongyao Feng ◽  
Qiangzhou Rong ◽  
Yun Wan ◽  
Xueguang Qiao ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Field Sensor ◽  
Bragg Grating ◽  
Fibre Bragg Grating ◽  
Fibre Optic ◽  
Core Fibre ◽  
Field Sensor

Novel methods for identifying and quantifying hyporheic exchange fluxes using Fibre Bragg Grating sensor arrays

2020 ◽  
Author(s):  
John Arkwright ◽  
Eddie W Banks ◽  
Margaret Shanafield ◽  
Anthony Papageorgiou
Keyword(s):  
Sensor Arrays ◽  
Heat Pulse ◽  
Heat Diffusion ◽  
Hyporheic Exchange ◽  
Bragg Grating ◽  
Fibre Bragg Grating ◽  
Fibre Optic ◽  
Hydraulic Gradients ◽  
Fibre Bragg Grating Sensor ◽  
Bragg Grating Sensor

<p>Most streambed heat tracer studies use vertical, ambient temperature profiles and a 1D analytical solution of the heat diffusion–advection equation to estimate hyporheic exchange fluxes (HEF). This approach has limited capacity in complex flow settings, which has led to the successful development of active heat pulse sensing to investigate the dynamic 3D flow fields in the near subsurface and to quantify HEF. At the scale of the hyporheic zone very small water level fluctuations drive changes in the hydraulic gradients across streambed bedform structures. Generally, hydraulic head gradients are measured with pressure sensors deployed in shallow monitoring wells, but such devices do not have the required vertical spatial resolution and precision to accurately evaluate these processes. New and novel research developed by the biomedical community for in-vivo medical devices can now be used in the geosciences field to measure temperature and pressure at a much higher spatial and temporal resolution to overcome these challenges. As part of this research we have developed a fibre optic, active heat pulse and pressure sensing instrument (formed from Fibre Bragg Grating sensor arrays) to determine small hydraulic gradients in the subsurface and to quantify the exchange fluxes. The instrument was tested in a controlled laboratory environment and in the field. Combining point-scale measurements from this novel instrument with near surface geophysical data and other hydrological observations (i.e. measurements with fibre optic distributed temperature sensing) can be used to upscale some of the key physical exchange processes to the stream reach and river scale.</p>

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