TY - GEN A1 - Liehr, Sascha A1 - Wendt, Mario A1 - Krebber, Katerina A1 - Münich, J.C. A1 - Stempniewski, L. A1 - Metschies, H. ED - Bernadette Havranek, ED - Masoud Motavalli, ED - Urs Meier, T1 - Distributed polymer optical fiber sensors integrated in technical textiles for monitoring of masonry structures T2 - 4th International conference on structural health monitoring of intelligent infrastructure CY - Zurich, Switzerland DA - 2009-07-22 KW - Structural health monitoring KW - Fiber optic sensors KW - OTDR KW - Polymer optical fibers (POF) KW - POF sensors KW - Distributed sensor KW - Strain sensor KW - Technical textiles KW - Masonry PY - 2009 SN - 978-3-905594-52-2 IS - Paper 521 SP - 1 EP - 7(?) CY - Zurich, Switzerland AN - OPUS4-19788 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Liehr, Sascha A1 - Lenke, Philipp A1 - Wendt, Mario A1 - Krebber, Katerina A1 - Glötzl, R. A1 - Schneider-Glötzl, J. A1 - Gabino, L. A1 - Krywult, L. ED - Bernadette Havranek, ED - Masoud Motavalli, ED - Urs Meier, T1 - Distributed polymer optical fiber sensors in geotextiles for monitoring of earthwork structures T2 - 4th International conference on structural health monitoring of intelligent infrastructure CY - Zurich, Switzerland DA - 2009-07-22 KW - Distributed sensor KW - Optical fiber sensor KW - Geotextile KW - Technical textile KW - POF sensor KW - Structural health monitoring KW - SHM KW - OTDR KW - Fiber optic sensors KW - Polymer optical fibers (POF) KW - Strain sensor PY - 2009 SN - 978-3-905594-52-2 IS - Paper 520 SP - 1 EP - 7(?) CY - Zurich, Switzerland AN - OPUS4-19787 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Liehr, Sascha A1 - Lenke, Philipp A1 - Krebber, Katerina A1 - Seeger, M. A1 - Thiele, E. A1 - Metschies, H. A1 - Gebreselassie, B. A1 - Münich, J.C. A1 - Stempniewski, L. ED - Francis Berghmans, ED - Mignani, Anna Grazia ED - Cutolo, Antonello ED - Patrick P. Meyrueis, ED - Thomas P. Pearsall, T1 - Distributed strain measurement with polymer optical fibers integrated into multifunctional geotextiles N2 - Fiber optic sensors based on polymer optical fibers (POF) have the advantage of being very elastic and robust at the same time. Unlike silica fibers, standard PMMA POF fibers can be strained to more than 40% while fully maintaining their light guiding properties. We investigated POF as a distributed strain sensor by analysing the backscatter increase at the strained section using the optical time domain reflectometry (OTDR) technique. This sensing ability together with its high robustness and break-down strain makes POF well-suited for integration into technical textiles for structural health monitoring purposes. Within the European research project POLYTECT (Polyfunctional textiles against natural hazards) technical textiles with integrated POF sensors, among others sensors are being developed for online structural health monitoring of geotechnical structures. Mechanical deformation in slopes, dams, dikes, embankments and retrofitted masonry structures is to be detected before critical damage occurs. In this paper we present the POF strain sensor properties, reactions to disturbing influences as temperature and bends as well as the results of the different model tests we conducted within POLYTECT. We further show the potential of perfluorinated graded-index POF for distributed strain sensing with increased spatial resolution and measurement lengths. T2 - Optical Sensors 2008 CY - Strasbourg, France DA - 2008-04-07 KW - Fiber optic sensors KW - OTDR KW - Polymer optical fibers (POF) KW - POF sensors KW - Distributed sensor KW - Strain sensor KW - Geotextiles KW - Structural health monitoring PY - 2008 SN - 978-0-8194-7201-4 DO - https://doi.org/10.1117/12.780508 SN - 0277-786X N1 - Serientitel: Proceedings of SPIE – Series title: Proceedings of SPIE VL - 7003 IS - 7003 SP - 700302-1 - 700302-15 PB - SPIE CY - Bellingham AN - OPUS4-17951 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Lenke, Philipp A1 - Nöther, Nils ED - Mario Bertolotti, T1 - Stimulated Brillouin scattering in graded index multimode optical fiber by excitation of the fundamental mode only N2 - 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. T2 - International Congress on Optics and Optoelectronics 2007 CY - Prague, Czech Republic DA - 2007-04-16 KW - Brillouin KW - SMS KW - Structural health monitoring KW - Multimode KW - Fundamental mode KW - SBS KW - POF PY - 2007 DO - https://doi.org/10.1117/12.722954 SN - 0277-786X VL - 6582 IS - 658213 (CD-ROM) SP - 658213-1 - 658213-7 AN - OPUS4-16436 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rücker, Werner A1 - Rohrmann, Rolf A1 - Said, Samir T1 - Offshore wind energy plants- a challenge for integrated structural health monitoring systems T2 - International Workshop on Lifetime Engineering of Civil Infrastructure CY - Ube Yamaguchi, Japan DA - 2005-11-09 KW - Offshore wind energy turbines KW - Structural health monitoring KW - Early damage detection KW - Control of dynamic behavior KW - Structural assessment PY - 2005 SP - 219 EP - 229 PB - Yamaguchi University CY - Ube Yamaguchi AN - OPUS4-12257 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - THES A1 - Nöther, Nils T1 - Distributed Fiber Sensors in River Embankments: Advancing and Implementing the Brillouin Optical Frequency Domain Analysis N2 - Diese Arbeit beschreibt die Entwicklung eines Systems zur verteilten Dehnungsmessung in optischen Glasfasern. Das System wurde zur Überwachung der strukturellen Integrität von Flussdeichen bei einer Messlänge von mindestens 5 km und einer Ortsauflösung von höchstens 5 m entwickelt. Grundlage des Messsystems ist der nichtlineare optische Effekt der stimulierten Brillouinstreuung (SBS), der die Dehnung einer optischen Glasfaser in eine messbare Frequenzverschiebung des Rückstreulichts eines optischen Signals überträgt. Die in dieser Arbeit angewendete und grundlegend weiterentwickelte Messtechnik ist die optische Brillouin-Frequenzbereichsanalyse (BOFDA). Die grundsätzliche Funktionalität dieser Technik war bereits vor Beginn der Untersuchungen zu dieser Arbeit gezeigt worden. Allerdings war ihre Entwicklung der Brillouin-Zeitbereichsanalyse (BOTDA), die den Stand der Technik darstellt, in Bezug auf ihre Sensoreigenschaften, ihre theoretischen Grundlagen, ihre Integrierbarkeit und ihre Robustheit für praktische Anwendungen weit unterlegen. Die Arbeit umfasst den theoretischen Hintergrund des Messsystems, verschiedene Weiterentwicklungen der Implementierung in ein anwendungsorientiertes Messgerät (u. a. neue Konzepte für Signalkorrekturverfahren zur Verbesserung der Sensoreigenschaften) und die Evaluierung des Systems in experimentellen Untersuchungen. Zu Beginn werden die physikalischen Eigenschaften der SBS in optischen Fasern untersucht und die Differentialgleichungen, mit denen der Effekt beschrieben werden kann, hergeleitet. Die Analyse konzentriert sich auf die spektralen Eigenschaften der Brillouin-Wechselwirkung, um die Messung der SBS im Frequenzbereich genau beschreiben zu können. Die BOFDA- Methode wird mit einer Systembeschreibung und Betrachtungen zur praktischen Umsetzung im Labor vorgestellt. Der Laboraufbau wird im Detail beschrieben; die Beschreibung umfasst die Komponenten, verschiedene Aspekte der Weiterentwicklung gegenüber dem Entwicklungsstand vor Beginn der Arbeiten sowie repräsentative Messergebnisse. Als wichtigster Fortschritt auf dem Weg zur kompletten Implementierung des Systems wird ein digitales Verfahren zur Frequenzbereichsanalyse (mit einer Systembeschreibung, einem Demonstratoraufbau und Messergebnissen) vorgestellt. Auf Grundlage der erarbeiteten Analyse der SBS wird die physikalisch bedingte Begrenzung der Ortsauflösung des Systems untersucht. Das Ergebnis ist eine neue Interpretation von Artefakten in hochauflösenden Messungen, von der aus eine Parallele zu ähnlichen Untersuchungen bezüglich der BOTDA-Methode aufgezeigt wird. Schließlich wird die Anwendung des Messsystems im Deichmonitoring vorgestellt. Hierzu wurde eine Technik zur Integration faseroptischer Kabel in Geotextilien sowie ein optisches Sensorkabel entwickelt. In Labor- und Feldversuchen wird die Eignung des Systems für das Deichmonitoring bestätigt. Durch die Weiterentwicklung des BOFDA-Verfahrens hat das Verfahren nicht nur in Genauigkeit und Auflösung zum BOTDA-Verfahren aufgeschlossen, sondern eröffnet neue Perspektiven in Dynamik, Robustheit und Kosteneffizienz. N2 - This thesis reports on the development of a system for distributed strain measurement in silica optical fibers. The system was developed to provide a solution for monitoring the structural health of river embankments with a measurement length > 5 km and a spatial resolution < 5 m. It is based on stimulated Brillouin scattering (SBS), a nonlinear optical effect which converts the mechanical strain of an optical fiber into a frequency shift of the backscattered light of an optical signal. The measurement technique that is employed and significantly advanced within this work is the Brillouin optical frequency domain analysis (BOFDA). Prior to this work, this technique had been presented as a laboratory setup providing its proof of concept; however, at this development stage, the technique had been limited in performance, theoretical foundation, integrability and robustness for real-life applications when compared to the state-of-the-art Brillouin optical time domain analysis (BOTDA). The thesis comprises the theoretical background of the measurement system, advancements regarding its implementation into a practically applicable device – including the proposal of techniques for performance enhancements in signal processing – as well as the evaluation of the system performance in experimental studies. First, the physical nature of SBS in optical fibers is analyzed. Here, special focus is set on the frequency domain properties of the interaction between the optical signals, which provides a deep understanding of the system behaviour in the special case of distributed measurements in the frequency domain. The BOFDA technique is then presented with a thorough analysis from a system point of view and considerations on its implementation in a practical setup. The laboratory setup is presented with all components and different aspects of advancement in accuracy and efficiency over the state of development prior to this work, along with representative measurement results. As the major advancement regarding the system implementation, a digital approach to frequency domain measurements is presented, with a system description, a demonstrator setup and measurement results. A detailed analysis of the physical occurrences within the system that lead to a limitation of its spatial resolution is given, founding on the description of SBS earlier in the thesis. It comprises a novel point of view on the measurement artifacts that degrade frequency domain measurements of SBS; a connection to corresponding studies that apply to the BOTDA technique is made. From here, a novel approach to overcome the limitations by means of signal correction in post-processing is presented. Finally, the application of the measurement system in dike monitoring is presented. A method for integrating optical fibers into geotextiles is introduced, together with considerations on the coating material and handling on construction sites. By presenting several experimental tests in the laboratory and the field, the feasibility of the system for monitoring of the structural health of river embankments is confirmed. With the advancements achieved within this work, the BOFDA technique meets the specifications in accuracy and resolution of state-of-the-art BOTDA devices, while offering new perspectives in terms of dynamic range, robustness and cost efficiency. T3 - BAM Dissertationsreihe - 64 KW - Stimulated Brillouin scattering KW - Frequency domain analysis KW - Dike monitoring KW - Structural health monitoring KW - Distributed Brillouin sensing PY - 2010 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-948 SN - 978-3-9813550-7-9 SN - 1613-4249 VL - 64 SP - 1 EP - 157 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) CY - Berlin AN - OPUS4-94 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -