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- 2011 (16) (entfernen)
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- Beitrag zu einem Tagungsband (11)
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- Distributed sensor (4)
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- POF OTDR (3)
- Spatial distributed sensor (3)
- Strain sensor (3)
- Technical textiles (3)
- Dynamic sensor (2)
Eingeladener Vortrag
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This paper reports on a fiber optic sensor for heart rate measurements. The sensor will be integrated into personal protective equipment within the framework of the FP7 EU project i-Protect. Two different sensor prototypes were developed. One is based on fiber Bragg gratings in silica fiber and the other one is based on macrobending effects in polymer optical fiber.
We investigated to our knowledge for the first time the capabilities of long period gratings (LPG) in single-mode microstructured polymer optical fibre (mPOF) as real-time gamma dosimeter. The fibre is made from polymethyl methacrylate (PMMA) with a polycarbonate jacket. We measured the radiation-induced wavelength shift of the mPOF LPG loss feature wavelength and the radiation-induced attenuation of a mPOF for
different wavelength between 600 nm and 800 nm for gamma radiation with an energy distribution between 6 keV and 18 keV.
This paper reports on a fibre optic sensor for heart rate measurement which is developed within the framework of the FP7 EU project i-Protect. Goal is integration of the sensor into personal protective equipment Two different sensor prototypes based on polymer optical fibre (POF) were developed. One is based on long period gratings in microstrutured POF and the other one is based on macrobending effects in POF.
We investigated the capabilities of long period gratings (LPG) in single-mode microstructured polymer optical fibre (mPOF) for humidity sensing. For that mPOF LPGs were exposed to different humidity levels
at a constant temperature of 30°C in a climate chamber. During the long term tests, which took up several weeks, the humidity was changed in several steps while mPOF LPG wavelength and fibre attenuation were measured.
We also measured the water uptake of mPOF in environment with different relative humidity.
A novel quasi-distributed long-gauge fiber optic strain sensor system for dynamic measurement
(2011)
We present a novel technique based on incoherent optical frequency domain reflectometry (OFDR) to measure length changes quasi-distributed between reflection points in optical fibres. The technique enables length changes to be measured with a resolution better than 1 µm and allows for static and dynamic measurement capabilities up to 2 kHz. We demonstrate that dynamic measurements of multiple fibre sections can be conducted independently from each other with high precision. Due to the precise and dynamic measurement capabilities, the proposed sensor system is expected to open new fields of application, especially in the structural-health-monitoring sector. Possible applications are discussed in the paper.
For long-range measurements in geotechnical and industrial applications, distributed optical fiber sensors have become a tool of increasing importance throughout the past decade.
Classic deformation monitoring (performed by strain gauges etc.) and temperature monitoring (Pt100 and alike) deliver data from fixed, single spots of a structure; quasidistributed measurements (fiber bragg gratings) provide a Chain of discrete measurement points along a limited sensing length. In contrast, an opticai fiber connected to a device for distributed strain and temperature sensing (DTSS) will provide a continuous profile of strain and temperature - spatially resolved down to less than 1 m - over a ränge of several tens of kilometers.
In DTSS measurements, the nonlinear opticai effect of stimulated Brillouin Scattering (SBS) is employed: two light waves with a stable, tunable frequency offset are injected into opposite ends of the sensing fiber, where they will form a beat pattem, at which parts of the light will be scattered. By matching the frequency offset of the light waves to the propagation of acoustic fluctuation in the opticai fiber, a power transfer from one light wave to the other can be measured; since the acoustic propagation directly shifts with train and temperature of the fiber, these two quantities can be measured by tuning the light waves’ frequency offset.
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.
A dynamic and quasi-distributed sensor principle for simultaneous measurement of length changes and optical power changes between reflection points in an optical fiber is presented. The technique is based on the incoherent optical frequency domain reflectometry (I-OFDR). Length change resolutions < 1 µm and measurement repetition rates up to 2 kHz can be achieved using standard single-mode and multi-mode optical fibers. Simultaneous length change and refractive index measurement as well as field test results showing the deformation of a masonry building under seismic load are presented. Promising fields of application for this technique are the structural health monitoring sector and chemical process control.
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.