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- Dike monitoring (4)
- Fiber optic sensors (3)
- Structural health monitoring (3)
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- OTDR (2)
- POF sensors (2)
- Strain sensor (2)
- BOFDA (1)
Eingeladener Vortrag
- nein (1)
Fiber optic sensors based on polymer optical fibers (POF) have the advantage of being very elastic and robust at the same time. Unlike silica fibers, standard PMMA POF fibers can be strained to more than 40% while fully maintaining their light guiding properties. We investigated POF as a distributed strain sensor by analysing the backscatter increase at the strained section using the optical time domain reflectometry (OTDR) technique. This sensing ability together with its high robustness and break-down strain makes POF well-suited for integration into technical textiles for structural health monitoring purposes. Within the European research project POLYTECT (Polyfunctional textiles against natural hazards) technical textiles with integrated POF sensors, among others sensors are being developed for online structural health monitoring of geotechnical structures. Mechanical deformation in slopes, dams, dikes, embankments and retrofitted masonry structures is to be detected before critical damage occurs. In this paper we present the POF strain sensor properties, reactions to disturbing influences as temperature and bends as well as the results of the different model tests we conducted within POLYTECT. We further show the potential of perfluorinated graded-index POF for distributed strain sensing with increased spatial resolution and measurement lengths.
The presented research is carried out on the background of the development of a new strain sensor, integrated in technical textiles using the optical time domain reflectometry (OTDR) technique. We investigated the effect of increased scattering in POF due to applied strain as a distributed sensor including research on long-term stability and reliability of this sensor.
Sensing characteristics of polymer optical fibers (POF) are studied using the optical
time-domain reflectometry technique. For the first time to our knowledge, investigations are
carried out with respect to integration of POF in technical textiles for distributed measurement
of mechanical deformation. The research on this new sensor type focuses on its application in
monitoring of geotechnical structures such as railway embankments, dikes, slopes and dams.
We report on a distributed sensor system using POF integrated in technical textiles as sensing
elements for measurement of displacement of soil. This sensor system is very robust it
withstands the integration under rough condition at a construction site and can detect strain
of more than 40 % over distances of more than 100 meters.
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.
DIKE MONITORING
(2008)