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Organisationseinheit der BAM
Wavelength-scanning distributed acoustic sensing for structural monitoring and seismic applications
(2019)
We introduce wavelength-scanning coherent optical time domain reflectometry (WS-COTDR) for dynamic vibration sensing along optical fibers. The method is based on spectral shift computation from Rayleigh backscatter spectra. Artificial neural networks (ANNs) are used for fast and high-resolution strain computation from raw measurement data. The applicability of the method is demonstrated for vibration monitoring of a reinforced concrete bridge. We demonstrate another application example for quasi-static and dynamic measurement of ground deformation and surface wave propagation along a dark fiber in a telecommunication cable.
In this paper the influence of combined temperature and strain changes as well as changes of moisture content on polymer optical fibers made of polymethyl methacrylat (PMMA) is investigated. The increase of the scattering coefficient with increasing temperature for various strain levels is observed and quantified. The measurement results of influence of humidity on scattering intensity of PMMA-POF encourage to porpose these as a distributed humidity sensor.
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.
We propose to use focused femtosecond laser pulses to create scattering damage in standard singlemode optical fibres as reference points for quasi-distributed sensing applications. Such sensor fibres are interrogated with incoherent optical frequency domain reflectometry (I-OFDR) technique and optical time domain reflectometry (OTDR). A performance comparison of both techniques with the clear advantage of the I-OFDR is presented as well as a quasi-distributed length change measurement application. Also dynamic measurement based on the I-OFDR technique is demonstrated on a femtosecond laser-induced sensor chain.
We propose to use focused femtosecond laser pulses to inscribe Scattering damage in the core of polymer optical fibers for interrogation as quasi-distributed sensor points by optical time domain reflectometry.
Fiber bend measurement is demonstrated on off-center inscribed sensor points and absolute temperature measurement is presented by evaluation of the constant backscatter intensities from the inscribed structures relative to temperature-dependent Rayleigh Scattering. Application possibilities and limitations of this new approach are discussed.
We present a novel technique based on the incoherent optical frequency domain reflectometry (l-OFDR) technique for dynamic (2 kHz) and quasi-distributed length change measurement in polymer optical fibers (POF). The extreme strain sensing capabilities (> 125 %) and cyclic load behaviour of perfluorinated POF are investigated using this technique.