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- Dike monitoring (5)
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- Brillouin sensing (2)
- Distributed strain measurement (2)
- Fiber optic sensor (2)
- Fibre optic sensors (2)
We report on the development of distributed fiber sensors and their integration into
geosynthetics as they are commonly used in the construction of dikes and dams for flood protection.
The sensing system uses Stimulated Brillouin Scattering (SBS) in silica optical fibers.
Using the Brillouin frequency analysis, the system is capable of detecting changes in both strain
and temperature along the optical fibers. The strain experienced by the optical fibers corresponds
to the deformation of the geosynthetics in case of a critical soil displacement. To satisfy
requirements of dike structures, the system will be optimized to detect soil displacement with a
spatial resolution of 5 m or less over a length in the range of 10 km. These rather modest requirements
leave space for optimization on resolution of the measurement values, measurement
time and cost efficiency.
To our knowledge, this is the first distributed fiber sensor using SBS that is especially designed
for the monitoring of soil displacement in dikes which is made possible by a novel method
for the integration of optical fibers into different types of geosynthetics.
We report on the development of a complete system for spatially resolved detection of critical soil displacement in river embankments. The system uses Brillouin frequency domain analysis (BOFDA) for distributed measurement of strain in silica optical fibers. Our development consists of the measurement unit, an adequate coating for the optical fibers and a technique to integrate the coated optical fibers into geotextiles as they are commonly used in dike construction. We present several laboratory and field tests that prove the capability of the system to detect areas of soil displacement as small as 2 meters. These are the first tests of truly distributed strain measurements on optical fibers embedded into geosynthetics.
We present, to our knowledge for the first time, the possibility of measuring the backscatter signal of perfluorinated polymer optical fibers (POF) using an incoherent optical frequency domain reflectometry (OFDR) technique. The OFDR setup is described and it is shown that the dynamic range and measurement speed are superior to standard OTDR systems. It is shown for the first time that distributed detection of strain in POF is possible using the OFDR technique.
Protection of critical infrastructure using fiber optic sensors embedded in technical textiles
(2010)
Terrorists and criminals more and more attack and destroy important infrastructures like routes, railways, bridges, tunnels, dikes and dams, important buildings. Therefore, reliable on-line and long-term monitoring systems are required to protect such critical infrastructures. Fiber optic sensors are well-suited for that. They can be installed over many kilometers and are able to measure continuously distributed strain, pressure, temperature and further mechanical and physical quantities. The very tiny optical fibers can be integrated into structures and materials and can provide information about any significant changes or damages of the structures. These so-called smart materials and smart structures are able to monitor itself or its environment. Particularly smart technical textiles with embedded fiber optic sensors have become very attractive because of their high importance for the structural health monitoring of geotechnical and masonry infrastructures. Such textiles are usually used for reinforcement of the structures; the embedded fiber optic sensors provide information about the condition of the structures and detect the presence of any damages and destructions in real time. Thus, critical infrastructures can be preventively protected. The paper will introduce this innovative field and will present the results achieved within several German and European projects.