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Eingeladener Vortrag
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POF sensors integrated in technical textiles for monitoring of earthwork structures and masonry
(2009)
Distributed fiber optic sensors embedded in technical textiles for structural health monitoring
(2010)
Technical textiles with embedded distributed fiber optic sensors have been developed for the purposes of structural health monitoring in geotechnical and civil engineering. The distributed fiber optic sensors are based on Brillouin scattering in silica optical fibers and OTDR in polymer optical fibers. Such "smart" technical textiles can be used for reinforcement of geotechnical and masonry structures and the embedded fiber optic sensors can provide information about the condition of the structures and detect the presence of any damages and destructions in real time. Thus, structural health monitoring of critical geotechnical and civil infrastructures can be realized. The paper highlights the results achieved in this innovative field in the framework of several German and European projects.
We present the latest advances in distributed strain measurement in perfluorinated polymer optical fibres (POFs) using backscatter techniques. Compared to previously introduced poly(methyl methacrylate) POFs, the measurement length can be extended to more than 500 m at improved spatial resolution of a few centimetres. It is shown that strain in a perfluorinated POF can be measured up to 100%. In parallel to these investigations, the incoherent optical frequency domain reflectometry (OFDR) technique is introduced to detect strained fibre sections and to measure distributed length change along the fibre with sub-millimetre resolution by applying a cross-correlation algorithm to the backscatter signal. The overall superior performance of the OFDR technique compared to the optical time domain reflectometry in terms of accuracy, dynamic range, spatial resolution and measurement speed is presented. The proposed sensor system is a promising technique for use in structural health monitoring applications where the precise detection of high strain is required.
Distributed strain and length change measurement in POF using optical frequency domain reflectometry
(2010)
We show that the incoherent optical frequency domain (l-OFDR) technique provides superior performance compared to standard OTDR techniques in terms of spatial resolution and measurement time. The distributed strain measurement capabilities of perfluorinated POF up 100 % strain are shown and distributed length change measurement using correlation techniques and OFDR are presented.
Polymer optical fiber (POF) sensors have the unique ability to measure high strain distributed along the fiber up to 40% using the optical time-domain reflectometry (OTDR) technique. Both, standard PMMA fibers and perfluorinated (PF) graded-index (GI) POF are introduced and evaluated in potential use and applicability. Further, distributed length change measurement based on cross-correlation analysis of the characteristic fiber signature of PF POF is introduced. We conclude the advances in distributed POF strain sensors technology with respect to application in structural health monitoring. Special focus is on the sensor integration into technical textiles for health monitoring of geotechnical structures and masonry structures. Measurement results of sensor-equipped textiles in different model tests are presented, displacement of soil and cracks in retrofitted masonry structures are detected and evaluated.
Technical textiles with embedded fibre optic sensors habe been developed for the purposes of the structural health monitoring in geotechnical and civil engineering as well as for healthcare monitoring in the medical sector. The paper shows selected examples of using such sensor-based smart textiles for different applications.
Recently, we have proposed, to our knowledge for
the first time, to use perfluorinated graded-index polymer
optical fiber (POF) for distributed measurement of strain.
Thanks to their low attenuation and low modal dispersion
compared to standard-POF, this fiber type allows to extend the
measurement length to more than 500 meters at increased
spatial resolution. In this paper, two mechanisms for strain
sensing are introduced. As in standard PMMA POF, strain in the
fiber can be detected by evaluating the local backscatter
increase occurring at strained fiber sections. Further, we
propose, to our knowledge for the first time, a true distributed
length change measurement in POF using cross-correlation
analysis of the fibers characteristic backscatter signature.
Using this technique, it is possible to measure relative
displacement between different fiber sections avoiding signal
fading failures that are inherent in other measurement
principles. Cross-sensitivities to the sensor signal, as fiber
bends and temperature, are investigated and quantified.