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Fiber-Optic sensor Applications in Civil and Geotechnical Engineering

Photonic sensors 2011年第3期1卷 268-280页

作者： Wolfgang R. HABEL and Katerina KREBBER Federal Institute for Materials Research and Testing Division VIII. 1: Measurement and Testing Technology sensors D-12205 Berlin Germany

Different types of fiber-optic sensors based on glass or polymeric fibers are used to evaluate material behavior or to monitor the integrity and long-term stability of load-bearing structure components. Fiber-optic sensors have been established as a new and innovative measurement technology in very different fields, such as material science, civil engineering, light-weight structures, geotechnical areas as well as chemical and high-voltage substations. Very often, mechanical quantities such as deformation, strain or vibration are requested. However, measurement of chemical quantities in materials and structure components, such as pH value in steel reinforced concrete members also provides information about the integrity of concrete structures. A special fiber-optic chemical sensor for monitoring the alkaline state （pH value） of the cementitious matrix in steel-reinforced concrete structures with the purpose of early detection of corrosion-initiating factors is described. The paper presents the use of several fiber-optic sensor technologies in engineering. One example concerns the use of highly resolving concrete-embeddable fiber Fabry-Perot acoustic emission （AE） sensors for the assessment of the bearing behaviour of large concrete piles in existing foundations or during and after its installation. Another example concerns fiber Bragg grating （FBG） sensors attached to anchor steels （micro piles） to measure the strain distribution in loaded soil anchors. Polymer optical fibers （POF） can be -- because of their high elasticity and high ultimate strain - well integrated into textiles to monitor their deformation behaviour. Such ＂intelligent＂ textiles are capable of monitoring displacement of soil or slopes, critical mechanical deformation in geotechnical structures （dikes, dams, and embankments） as well as in masonry structures during and after earthquakes.

关键词： Fiber-optic sensor monitoring earthquake damage assessment steel-reinforced structures pH sensor geotextiles distributed sensor

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Recent Progress in Optical Fiber sensors Based on Brillouin Scattering at University of Ottawa

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Photonic sensors 2011年第2期1卷 102-117页

作者： Xiaoyi BAO Liang CHEN Fiber Optics Group Physics Department University of Ottawa Ottawa ON KIN 6N5 Canada

The distributed sensor is proven to be a powerful tool for civil structural and material process monitoring. Brillouin scattering in fiber can be used as point sensors or distributed sensors for measurement of temperature, strain, birefringence and vibration over centimeters （Brillouin grating length） for point sensor or the pulse length for the distributed sensor. Simultaneous strain and temperature measurement with a spatial resolution of 20 cm is demonstrated in a Panda fiber using Brillouin grating technique with the temperature accuracy and strain accuracy of 0.4 ℃ and 9 με. This technique can also be used for distributed birefringence measurement. For Brillouin optical time domain analysis （BOTDA）, we have developed a new technique to measure differential Brillouin gain instead of Brillouin gain itself. This technique allows high precision temperature and strain measurement over long sensing length with sub-meter spatial resolution： 50-cm spatial resolution for 50-km length, using return-to-zero coded optical pulses of BOTDA with the temperature resolution of 0.7 ℃, which is equivalent to strain accuracy of 12 με. For over 50-km sensing length, we proposed and demonstrated frequency-division-multiplexing （FDM） and time-division-multiplexing （TDM） based BOTDA technique for 75-km and 100-km sensing length without inline amplification within the sensing length. The spatial resolution of 2m （100km） and Brillouin frequency shift accuracy of 1.5 MHz have been obtained for TDM based BOTDA and 1-m resolution （75 km） with Brillouin frequency shift accuracy of 1 MHz using FDM based BOTDA. The civil structural health monitoring with BOTDA technique has been demonstrated.

关键词： Brillouin scattering distributed sensor Brillouin grating temperature strain birefringence

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Signal Processing for Fibre-optic distributed Sensing Techniques Employing Brillouin Scattering

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Semiconductor Photonics and Technology 2009年第1期15卷 10-15页

作者： XIAO Shang-hui LI Li School of Communication and Information Engineering University of Electronics Science & Technology of China Chengdu 610054 CHN Institute of Optoelectronic Information Yibin University Yibin 644007 CHN

As fibre optic distributed scattering sensing systems are providing innovative solutions for the monitoring of large structures,Brillouin-based distributed scattering sensing techniques represent a new physical approach for structures health monitoring,which seems extremely promising and is receiving most *** paper comprehensively presents some methods of signal interrogation for fibre optic Brillouin-based distributed scattering sensing technology,especially establishes an accurate Pseudo-Voigt model of Brillouin gain spectrum and gives some results on spectrum analysis and data processing.

关键词： fibre optic sensor distributed sensor Brillouin scattering Brillouin-OTDR

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SIGNAL ANALYSIS OF FLEXOELECTRIC TRANSDUCERS ON RINGS

SIGNAL ANALYSIS OF FLEXOELECTRIC TRANSDUCERS ON RINGS

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2010全国压电和声波理论及器件技术研讨会

作者： Horn-sen(H.S.) TZOU School of Aeronautics and Astronautics Institute of Applied MechanicsStrucTronic Systems and Control LabZhejiang University

In this study,a flexoelectric layer is laminated on ring shells to monitor the modal signal *** to the strain gradient,only the bending strain component contributes to the output *** total signal contains two bending strain gradient components respectively induced by the transverse modal oscillation and the circumferential modal *** analysis suggests that the bending component signal induced by the transverse modal oscillation is dominant and its magnitude shows nearly the same as the total *** signals are evaluated in case studies with different ring modes and sensor segment sizes. Results indicate that the total signal increases with the mode number,decreases with the sensor segment size. These results serve as design guideline to select proper segment patches for practical engineering applications using flexoelectric transducers.

关键词： distributed sensor direct flexoelectric effect strain gradient signal average

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