Filtern
Dokumenttyp
- Beitrag zu einem Tagungsband (15)
- Vortrag (9)
- Beitrag zu einem Sammelband (6)
- Zeitschriftenartikel (3)
- Posterpräsentation (1)
Schlagworte
- OTDR (7)
- Optical fiber sensor (6)
- POF sensors (6)
- Polymer optical fibers (POF) (6)
- Strain sensor (6)
- Distributed sensor (5)
- Distributed strain sensor (5)
- Fiber optic sensors (5)
- Structural health monitoring (5)
- Geotextiles (4)
Eingeladener Vortrag
- nein (9)
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.
We investigate the suitability of silica graded index multimode fibers (MMF) for distributed Brillouin sensing in structural health monitoring, where the measurement range is limited by small bendings that appear during the integration process of the sensing fibers into the structures. For the investigation of stimulated Brillouin scattering (SBS) in MMF, we use an MMF connected on both ends to the SMF measurement setup by fusion splices to ensure that only the fundamental mode is transmitted. The SBS spectra in MMF are recorded using a 1319 nm single frequency (line width 5 kHz) laser. Results found for standard singlemode fibers and the fundamental mode in multimode silica optical fibers are compared. We present the gain spectra showing the dependence of frequency shift, attenuation and modal noise to both temperature and strain. The dependence of the attenuation due to bending is shown. Finally, the perspective of the excitation of SBS in polymer optical fibers is discussed against the background of our research on SBS in MMF.
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.
Fiber optic sensors based on polymer optical fibers (POF) take advantage of the high elasticity and high break-down strain of POF. Because of their outstanding elastic properties, POF are well suited for integration into technical textiles like geotextiles and medical textiles. Smart textiles with incorporated POF sensors, able to sense various mechanical and physical quantities, can be realized. The integration of POF as a sensor into geotextiles for monitoring of displacement of soil is very attractive since POF can be used for distributed strain measurement of strain values of more than 40 %. An online monitoring of critical mechanical deformations of geotechnical structures like dikes, dams, slopes, embankments as well as of masonry structures can be ensured. Medical textiles that incorporate POF sensors can control vital physiological parameters like respiratory movement and can be used for wearable health monitoring of patients requiring a continuous medical assistance and treatment. The biocompatibility of POF is an important criterion for selecting POF as a medical sensor. The paper shows selected examples of using POF sensors for the mentioned monitoring purposes.
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.
Sensing characteristics of standard polymer
optical fibers (POF) are further studied using the optical time
domain reflectometry (OTDR) technique. The level of the
backscattering inside POF, which highly increases at locations
where strain is applied to the fiber, is further investigated with
respect to spectral behavior, strain rate and span of time from
the stretching event. An algorithem to overcome the problem of
the decrease of spatial resolution as a result of pulse
broadening due to modal disperion, is proposed. The research
is carried out on the background of the development of a new
strain sensor that is integrated in technical textiles.
Distributed polymer optical fiber sensors in geotextiles for monitoring of earthwork structures
(2009)
This paper presents new methods to calculate and interpret Rayleigh scattering profiles in polymer optical fibers (POF) recorded by optical time domain reflectometry (OTDR). In contrast to Silica glass optical fibers (GOF), POF experience inhomogeneous stress when being strained, resulting in small scattering centers which allow for a new distributed sensor based on POF. New methods to overcome issues like blurring due to modal dispersion, uncertainties due to inhomogenious losses in the fiber and signal degradation due to viscoelastic creep in the polymer, are presented, for the first time to our knowledge.