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.
Distributed polymer optical fiber sensors in geotextiles for monitoring of earthwork structures
(2009)
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.
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.
Fibre-optic sensors are more and more used in geotechnical and civil engineering. There are a big number of applications with the purpose of improvement or proof of the structural integrity. This paper, presents two examples where different fibre sensor types.are exploited for safety-relevant task in geotechnique. Technical textiles with embedded distributed fibre-optic sensors based on Brillouin Scattering in silica optical fibres and OTDR (optical time-domain reflectometry) in polymer optical fibres are presented. Such “smart” technical textiles can be used for reinforcement of geotechnical structures and masonry walls, and the embedded fibre-optic sensors can provide information about the condition of the structures as well as detect the presence of any damage and destructions in real time. Highly sensitive fibre-optic geophones based on Fabry-Perot sensors embedded in large concrete pile can be used for precise measurement of Deformation and wave distribution during static and dynamic pile test. Such sensors make the evaluation of the pile’s integrity and load-bearing capacity easier.