TY - JOUR A1 - Karapanagiotis, Christos A1 - Hicke, Konstantin A1 - Wosniok, Aleksander A1 - Krebber, Katerina T1 - Distributed humidity fiber-optic sensor based on BOFDA using a simple machine learning approach N2 - We report, to our knowledge for the first time, on distributed relative humidity sensing in silica polyimide-coated optical fibers using Brillouin optical frequency domain analysis (BOFDA). Linear regression, which is a simple and well-interpretable algorithm in machine learning and statistics, is utilized. The algorithm is trained using as features the Brillouin frequency shifts and linewidths of the fiber’s multipeak Brillouin spectrum. To assess and improve the effectiveness of the regression algorithm, we make use of machine learning concepts to estimate the model’s uncertainties and select the features that contribute most to the model’s performance. In addition to relative humidity, the model is also able to simultaneously provide distributed temperature information addressing the well-known cross-sensitivity effects. KW - Fiber optics sensors KW - Machine learning KW - Brillouin distributed sensing KW - Humidity sensing KW - Simultaneous temperature and humidity sensing PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-546294 DO - https://doi.org/10.1364/OE.453906 VL - 30 IS - 8 SP - 12484 EP - 12494 PB - OPTICA AN - OPUS4-54629 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Krebber, Katerina T1 - Multiscale reinforcement of Semi-Crystalline Thermoplastic Sheets and Honeycombs (M-RECT) T2 - ITHEC 2014, 2nd International Conference and Exhibition on Thermoplastic Composites CY - Bremen, Germany DA - 2014-10-27 PY - 2014 AN - OPUS4-32029 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Reiche, T. A1 - Teichmann, H. A1 - Krebber, Katerina A1 - Salomon, O. A1 - Wood, A. T1 - Multiscale reinforcement of semi-crystalline thermoplastic sheets and honeycombs (M-RECT) N2 - M-RECT was a European FP7 funded project investigating multiscale reinforced thermoplastic composites. The project involved the functionalisation of carbon nanotubes (CNT) with a view to: • Improving their performance and ease of dispersion • Improving the damping characteristics of composites • Evaluating the mechanical performance of CNT reinforced laminates • Developing modelling Software for the design of materials and components • Developing sensor Systems to provide feedback on the local strains within such composites This presentation seeks to provide a general overview of the results from the project with particular emphasis T2 - ITHEC 2014 - 2nd International Conference and Exhibition on Thermoplastic Composites CY - Bremen, Germany DA - 27.10.2014 KW - Carbon nanotubes KW - Multiscale thermoplastic-matrix composites KW - Modelling PY - 2014 SN - 978-3933339256 SP - 12 EP - 15 AN - OPUS4-32353 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Krebber, Katerina T1 - Fiber Optic Sensors for SHM - From Laboratory to Industrial Applications (invited lecture) T2 - OSA Conference "Applied Industrial Optics: Spectroscopy, Imaging and Metrology (AIO)" CY - Seattle, WA, USA DA - 2014-07-13 PY - 2014 AN - OPUS4-31131 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Liehr, Sascha A1 - Nöther, N. A1 - Steffen, Milan A1 - Gili, O. A1 - Krebber, Katerina ED - López-Higuera, J.M. ED - Jones, J. ED - López-Amo, M. ED - Santos, J.L. T1 - Performance of digital incoherent OFDR and prospects for optical fiber sensing applications N2 - We propose a digital implementation of the incoherent optical frequency domain reflectometry (I-OFDR) technique for precise backscatter measurement and optical fiber sensing applications. Specific performance parameters of the I-OFDR are discussed and compared to an analog vector network analyzer-based I-OFDR system. Improved sensitivity, dynamic range and signal stability of the digital I-OFDR is presented and demonstrated by means of quasi-distributed length change measurement. T2 - OFS2014 - 23rd International conference on optical fibre sensors CY - Santander, Spain DA - 02.06.2014 KW - Optical fiber sensors KW - Backscatter measurement KW - Strain sensor KW - OFDR KW - OTDR PY - 2014 DO - https://doi.org/10.1117/12.2059639 SN - 0277-786X SN - 1996-756X N1 - Serientitel: Proceedings of SPIE – Series title: Proceedings of SPIE VL - 9157 SP - 915737-1 EP - 915737-4 AN - OPUS4-30899 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Krebber, Katerina T1 - Fiber optic sensors for SHM - from laboratory to industrial applications N2 - The paper highlights the research activities in Germany and Europe in the development of distributed fiber optic sensor for structural health monitoring (SHM) like the monitoring of geotechnical and civil infrastructures and presents selected results achieved within these projects. T2 - OSA Optics & photonics congress - Imaging and applied optics CY - Seattle, Washington, USA DA - 13.07.2014 PY - 2014 SN - 978-1-55752-308-2 DO - https://doi.org/10.1364/AIO.2014.AM4A.1 SP - 1 EP - 2 AN - OPUS4-31195 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Liehr, Sascha A1 - Muanenda, Y. S. A1 - Münzenberger, Sven A1 - Krebber, Katerina T1 - Relative change measurement of physical quantities using dual-wavelength coherent OTDR N2 - We propose the use of alternating pulse wavelengths in a direct-detection coherent optical time domain reflectometry (C-OTDR) setup not only to measure strain and temperature changes but also to determine the correct algebraic sign of the change. The sign information is essential for the intended use in distributed mode shape analysis of civil engineering structures. Correlating relative backscatter signal shifts in the temporal/signal domain allows for measuring with correct magnitude and sign. This novel approach is simulated, experimentally implemented and demonstrated for temperature change measurement at a spatial resolution of 1 m. KW - Fiber optics sensors KW - Backscattering KW - Rayleigh KW - C-OTDR KW - Distributed sensing KW - Temperature measurement KW - Strain measurement PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-389449 DO - https://doi.org/10.1364/OE.25.000720 SN - 1094-4087 VL - 25 IS - 2 SP - 720 EP - 729 PB - Optical Society of America CY - Washington, DC, USA AN - OPUS4-38944 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hicke, Konstantin A1 - Krebber, Katerina ED - Chung, Y. ED - Jin, W. ED - Lee, B. ED - Canning, J. ED - Nakamura, K. ED - Yuan, L. T1 - Towards efficient real-time submarine power cable monitoring using distributed fibre optic acoustic sensors N2 - Online condition monitoring of submarine power cables helps to avert failures and damages produced by mechanical impacts. We report, to our knowledge for the first time, on investigations regarding the feasibility of distributed fiber optic acoustic sensors based on C-OTDR, with the sensor fibres being embedded in the cable, to detect vibrations due to mechanical disturbances along the cable. We present first results of sensing experiments where acoustic signals are transmitted through water to simulate the corresponding submarine conditions. Furthermore, we show results evaluating the usefulness of fibre commonly embedded in existing power cable designs for our sensing purposes. T2 - 25th International Conference on Optical Fiber Sensors CY - Jeju-City, Jeju, Republic of Korea DA - 24.04.2017 KW - Distributed acoustic sensing KW - Power cable monitoring KW - C-OTDR KW - Fibre optic sensors KW - DAS PY - 2017 SN - 978-1-5090-4850-2 DO - https://doi.org/10.1117/12.2267474 SN - 0277-786X SN - 1996-756X VL - 10323 SP - 1032390-1 EP - 1032390-4 PB - SPIE CY - Bellingham, WA, USA AN - OPUS4-40088 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hicke, Konstantin A1 - Hussels, Maria-Teresa A1 - Eisermann, René A1 - Chruscicki, Sebastian A1 - Krebber, Katerina ED - Chung, Y. ED - Jin, W. ED - Lee, B. ED - Canning, J. ED - Nakamura, K. ED - Yuan, L. T1 - Condition monitoring of industrial infrastructures using distributed fibre optic acoustic sensors N2 - Distributed fibre optic acoustic sensing (DAS) can serve as an excellent tool for real-time condition Monitoring of a variety of industrial and civil infrastructures. In this paper, we portray a subset of our current Research activities investigating the usability of DAS based on coherent optical time-domain reflectometry (C-OTDR) for innovative and demanding condition Monitoring applications. Specifically, our application-oriented Research presented here aims at acoustic and vibrational condition monitoring of pipelines and piping systems, of rollers in industrial heavy-duty conveyor belt systems and of extensive submarine power cable installations, respectively. T2 - 25th International Conference on Fiber Optic Sensors CY - Jeju-City, Jeju, Republic of Korea DA - 24.04.2017 KW - Condition monitoring KW - Distributed fibre optic acoustic sensing KW - Fibre optic sensors KW - Industrial monitoring KW - DAS PY - 2017 SN - 978-1-5090-4850-2 DO - https://doi.org/10.1117/12.2272463 SN - 0277-786X SN - 1996-756X VL - 10323 SP - 103230J-1 EP - 103230J-4 PB - SPIE CY - Bellingham, WA, USA AN - OPUS4-40091 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hicke, Konstantin A1 - Hussels, Maria-Teresa A1 - Eisermann, René A1 - Chruscicki, Sebastian A1 - Krebber, Katerina T1 - Distributed Fibre Optic Acoustic and Vibration Sensors for Industrial Monitoring Applications N2 - We investigate the usability of distributed fibre optic acoustic sensing (DAS) for innovative and advanced monitoring applications in industrial and civil infrastructure installations. In this paper, we report on our ongoing application-oriented research activities regarding the utilization of DAS based on coherent optical time-domain reflectometry (C-OTDR) for condition monitoring of a variety of infrastructures. Specifically, our research presented here aims at acoustic condition monitoring of and fault detection in pipelines and industrial piping systems, at acoustic condition monitoring of rollers in industrial conveyor belt installations, and at acoustic condition monitoring of and threat detection in extensive submarine power cables, respectively. Furthermore, we show a method to mitigate the effect of sensitivity fading of C-OTDR based DAS due to unstable environmental conditions via the modification of the sensor fibre. This can help to provide a continuous adequate sensor functionality for a number of different industrial monitoring applications. T2 - SENSOR 2017 - 18th International Conference on Sensors and Measurement Technology CY - Nuremberg, Germany DA - 30.05.2017 KW - distributed acoustic sensing KW - fibre optic sensors KW - condition monitoring KW - industrial monitoring KW - C-OTDR PY - 2017 SN - 978-3-9816876-4-4 DO - https://doi.org/10.5162/sensor2017/B7.3 SP - 274 EP - 279 PB - AMA Service GmbH CY - Wunstorf AN - OPUS4-40473 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Stajanca, Pavol A1 - Krebber, Katerina ED - Webb, D. J. ED - Scully, P. ED - Sugden, K. T1 - Radiation induced attenuation in perfluorinated polymer optical fibres for dosimetry applications N2 - Real-time measurement of radiation-induced attenuation (RIA) in a commercial perfluorinated polymer optical fibre (PF-POF) is performed with regard to on-line Radiation monitoring purposes. Spectral character and dose dependence of fibre’s RIA is measured in 450-900 nm spectral region. Fibre exhibited high radiation sensitivity in the visible region with strong increase towards the UV wavelengths. Good linearity and high sensitivity reaching up to 130 dBm-1/kGy was demonstrated in the VIS region for a low-dose range. This of-the-shelf PF-POF could be therefore interesting for on-line remote dosimetry applications. T2 - POF 2016: 25th International Conference on Plastic Optical Fibres CY - Birmingham, UK DA - 13.09.2016 KW - Perfluorinated polymer optical fibers KW - Gamma radiation monitoring KW - Radiation induced attenuation PY - 2016 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-403221 SN - 978-1-85449-408-5 SP - 167 EP - 170 CY - Birmingham AN - OPUS4-40322 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Stajanca, Pavol A1 - Krebber, Katerina ED - Chung, Y. ED - Jin, W. ED - Lee, B. ED - Canning, J. ED - Nakamura, K. ED - Yuan, L. T1 - Towards on-line radiation monitoring with perfluorinated polymer optical fibers N2 - Sensitivity of two commercial perfluorinated (PF) polymer optical fibers (POFs) to gamma radiation was measured, compared and exploited for dosimetry purposes. Fiber radiation induced attenuation (RIA) was found to be highly wavelength dependent and pronounced towards the UV part of the spectrum. PF-POFs were shown to be highly radiation sensitive and RIA-based on-line radiation monitoring with sensitivity as high as 135 dBm-1/kGy was demonstrated at 460 nm with co-extruded PF-POF. In addition, thanks to low inherent attenuation in the near-infrared region, possibility of distributed radiation detection with PF-POFs was demonstrated for the first time, utilizing optical time domain reflectometry. T2 - 25th International Conference on Optical Fiber Sensors CY - Jeju, Republic of Korea DA - 24.04.2017 KW - Radiation-induced attenuation KW - Perfluorinated polymer optical fibers KW - Cytop KW - Gamma radiation KW - Optical fiber dosimetry KW - Optical fiber sensors KW - Distributed radiation sensing PY - 2017 SN - 978-1-5090-4850-2 DO - https://doi.org/10.1117/12.2256354 SN - 0277-786X SN - 1996-756X VL - 10323 SP - 103231O-1 EP - 103231O-4 PB - SPIE AN - OPUS4-40323 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wosniok, Aleksander A1 - Sporea, D. A1 - Neguţ, D. A1 - Krebber, Katerina T1 - Gamma radiation influence on silica optical fibers measured by optical backscatter reflectometry and Brillouin sensing technique N2 - We have studied the influence of gamma rays on physical properties of different commercially available silica optical fibers stepwise irradiated up to a total dose of 100 kGy. The detection of radiation-induced changes in silica glass offers the possibility of using selected optical fibers as distributed radiation sensors. The measurements performed by us were based on optical backscatter reflectometry and Brillouin distributed sensing. The measurement methods enable an analysis of radiation-induced modification of the group refractive index and density of the optical fibers. The most distinct physical effect observed by us concerns the increase of the optical attenuation with rising total radiation doses. Quantitative measurement results indicate a crucial impact of fiber dopants on radiation-induced physical and sensory characteristics of silica optical fibers affected by differences in fiber fabrication techniques. Based on the obtained results, the suitability of distributed Brillouin sensing for dosimetry applications seems to be improved by modifying the refractive index profile of the fiber core. T2 - Sixth European Workshop on Optical Fibre Sensors CY - Limerick, IRL DA - 31.05.2016 KW - Brillouin frequency shift KW - Lonizing radiation KW - Gamma radiation KW - Radiation dosimetry KW - Optical fiber sensor KW - Brillouin scattering KW - Distributed measurement KW - Backscatter reflectometry PY - 2016 SN - 978-1-5106-0219-9 DO - https://doi.org/10.1117/12.2236678 SN - 0277-786X VL - 9916 SP - Article Number: 99162J PB - Spie-Int Soc Optical Engineering CY - Bellingham, WA, USA AN - OPUS4-37083 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Habel, Wolfgang R. A1 - Krebber, Katerina A1 - Daum, Werner T1 - Results in standardization of FOS to support the use of SHM systems N2 - Measurement and data recording systems are important parts of a holistic Structural Health Monitoring (SHM) system. New sensor technologies such as fiber-optic sensors are often used; however, standards (or at least guidelines) are not yet available or internationally approved. This lack in standardization makes the acceptance of FOS technologies in complex SHM systems substantially difficult. A standard family for different FOS technologies is therefore being developed that should help to design SHM systems in an optimal way. International standardization activities take place in several standardization bodies such as IEC and ASTM, and within SHM societies such as ISHMII. The paper reports on activities in standardization of fiber-optic sensors, on results already achieved, and on newly started projects. Combined activities of fiber sensor experts and SHM experts from Civil Engineering are presented. These contributions should help owners of structures as well as developers of sensors and monitoring systems to select effective and validated sensing technologies. Using these standards, both parties find recommendations how to proceed in development of SHM systems to evaluate the structural behavior based on e.g. standardized fiber optic sensors, and to derive necessary measures, e.g. the optimal maintenance strategy. T2 - Sixth European Workshop on Optical Fibre Sensors CY - Limerick, Ireland DA - 30.05.2016 KW - Fiber-optic sensor KW - Standard KW - Temperature KW - Strain KW - Monitoring KW - Structural health KW - Application PY - 2016 DO - https://doi.org/10.1117/12.2236863 SN - 0277-786X VL - 9916 SP - 991625-1 EP - 991625-4 AN - OPUS4-37053 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Liehr, Sascha A1 - Krebber, Katerina T1 - Phase-OFDR for Distributed Disturbance Measurement N2 - We introduce the optical frequency domain reflectometry (OFDR) technique based on intensity modulation frequency sweep measurement for distributed disturbance measurement in optical fibres. By evaluating interferometric Rayleigh scattering changes along the fibre, strain and temperature changes are detected with 100 nε sensitivity and 10 mK resolution. The vibration frequencies for low frequencies and up to the kHz-range can be obtained from power change Evaluation in the spatial domain. This novel OFDR approach is a low-cost alternative for distributed disturbance measurement up to distances of several kilometres. T2 - Sixth European Workshop on Optical Fibre Sensors CY - Limerick, Ireland DA - 31.05.2016 KW - Temperature sensing KW - OFDR KW - Distributed sensor KW - Rayleigh scattering KW - Strain measurement PY - 2016 UR - http://proceedings.spiedigitallibrary.org/conferenceproceedings.aspx DO - https://doi.org/doi:10.1117/12.2236851 SN - 0277-786X VL - Vol. 9916 SP - Paper 991624, 4 PB - SPIE CY - Bellingham, Washington USA AN - OPUS4-37228 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Liehr, Sascha A1 - Krebber, Katerina T1 - Applications and prospects for distributed sensing using polymer optical fibres N2 - One of the unique advantages of polymer optical fibres (POF) is that they can be used to measure very high strain values up to 100 % and beyond exceeding the strain limits of silica fibre-based sensor principles. In this paper the distributed strain measurement capabilities of POF based on backscatter change evaluation are summarized and distributed backscatter measurement technologies are intro-duced. Application examples in the structural health monitoring (SHM) field are presented: a promising approach is the integration into technical textiles for high-strain measurement in earthwork structures and crack detection in buildings. The potential of POF for future applications in SHM such as distributed relative humidity sensing is discussed. T2 - International Conference on Smart Infrastructure and Construction CY - Cambridge, UK DA - 27.06.2016 KW - Strain measurement KW - Structural health monitoring KW - OTDR KW - Polymer Optical Fibre KW - Distributed sensing PY - 2016 UR - http://www.icevirtuallibrary.com/doi/abs/10.1680/tfitsi.61279.093 SN - 978-0-7277-6127-9 DO - https://doi.org/10.1680/tfi tsi.61279.093 SP - 93 EP - 98 PB - ICE Publishing CY - London, UK AN - OPUS4-37230 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hofmann, Detlef A1 - Krebber, Katerina ED - Lutz, B. ED - Möller, G. ED - Rücker, Werner ED - Schiefelbein, N. T1 - Herausforderungen bei der Nutzung faseroptischer Sensoren für spezielle geotechnische Fragestellungen N2 - Geotechnische Tätigkeitsfelder und Forschungsaufgaben haben sich immer an den modernen Herausforderungen orientiert und umfassen z. B. die Beschreibung und Quantifizierung der Interaktion zwischen Baugrund und Bauwerk, die Untersuchung des Untergrunds besonders hinsichtlich der technischen und sozialen Infrastrukturen und die Beeinflussung der Umwelt. Fragen der zivilen Sicherheit stellen steigende Anforderungen an die Tragfähigkeit und Dauerhaftigkeit von Bauwerken. Zur Lösung dieser Aufgaben entstehen vielfältige interessante Methoden und Verfahren zur Strukturbewertung, die neben der Erfassung des allgemeinen Zustands auch neue Erkenntnisse zum Bauwerksverhalten im Hinblick auf moderne Bautechnologien und auf die Lebensdauer von Bauwerken liefern. Die systematische, zuverlässige und langzeitstabile Erfassung von geotechnischen Messgrößen und Parametern bei der Strukturbewertung sowie die Beobachtung und Bewertung der geologischen Gegebenheiten mit technischen Hilfsmitteln ist dafür unerlässlich und lässt sich mit den Begriffen Zustandsanalyse und Bauwerksmonitoring zusammenfassen. Das Ziel dabei ist, mögliche Schädigungsmechanismen frühzeitig zu erkennen, um rechtzeitig Gegenmaßnahmen ergreifen zu können. T2 - Messen im Bauwesen 2014 - Neue Messtechniken und Anwendungsfälle CY - Berlin, Germany DA - 04.03.2014 KW - Faseroptische Sensorik KW - Optische Messverfahren KW - Fabry-Perot-Interferometer KW - Faser-Bragg-Gitter KW - Applikation KW - Anwendungen KW - Geomatten KW - Raman KW - Brillouin PY - 2014 SN - 978-3-9815944-7-8 SP - 7 EP - 26 AN - OPUS4-33812 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Habel, Wolfgang A1 - Krebber, Katerina A1 - Daum, Werner ED - Peters, K.J. T1 - Standardization in fibre-optic sensing for structural safety - activities in the ISHMII and IEC N2 - Fiber-optic sensors are increasingly established in the sensor market. Their advantages have unquestionably been verified by numerous demonstrations to enhance the operational performance of aged structures or to monitor the structural behavior of safety-relevant structures or their components. However, there are some barriers in use due to a lack of extensive standardization of fiber-optic sensors. This leads very often to restraints in the user’s community. The paper shows the status in international standardization of fiber-optic sensors as well as current activities in leading institutions such as IEC and ISHMII and others with the purpose of providing relevant standards for a broader use of selected fiber-optic sensor technologies. T2 - Smart sensor phenomena, technology, networks, and systems integration 2015 CY - San Diego, CA, USA DA - 08.03.2015 KW - Fibre-optic sensor KW - Standard KW - Temperature KW - Strain KW - Monitoring KW - Reliability KW - Application PY - 2015 DO - https://doi.org/10.1117/12.2185602 SN - 0277-786X VL - 9436 SP - 94360S-1 EP - 94360S-7 AN - OPUS4-33814 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Habel, Wolfgang A1 - Basedau, Frank A1 - Hofmann, Detlef A1 - Krebber, Katerina A1 - Jentsch, H. A1 - Senze, A. ED - Ilki, A. ED - Motavalli, M. ED - Inci, P. ED - Köhli, M. T1 - Online-detection of slipping soil areas by embedded fiber-optic sensing rods N2 - Movements in geological areas are often caused by shear zones deep in the underground or by hardly observable slipping zones. Detection of movements reaching critical values is of crucial importance to avoid losses and harms. Optical sensor fibers with gauge lengths of several meters or even distributed fiber-optic sensors with gauge lengths of hundreds of meters allow detecting deformation of such zones with quite good resolution. The paper presents a new technology of detecting deformations and movements in soil or rock massifs. The core part of the sensing system is a tiny pultruded rod with an outer diameter of 3 mm to 6 mm. It contains two fiber-optic sensor systems. One sensor system is used for permanent online measurement and provides integral strain information along the whole length of the rod; in case of critical deformations, it provides a warning signal. The second sensing system uses fiber-optic Bragg grating (FBG) strain sensors located close to the expected shear zone. This measurement system will be activated after the warning signal has been initiated by the integral strain measurement system. The FBG strain sensor system records then resulting deformations in detail. The sensing rod containing both sensor systems can be installed in a borehole to detect beginning soil movements automatically. The electronic equipment is powered by a solar panel; the amount of deformation in soil or rock formations can be estimated from the strain change measured in the sensor fibers. The effectiveness of this warning system will be shown using the example of a critically sliding slope in an open brown coal pit in Germany. T2 - SMAR 2015 - 3rd Conference on smart monitoring, assessment and rehabilitation of civil structures CY - Antalya, Turkey DA - 07.09.2015 KW - SHM KW - Standardization KW - Reliability KW - Fibre-optic sensor KW - Embedded sensor KW - Monitoring KW - Maintenance PY - 2015 SN - 978-3-905594-65-2 SP - Paper 222, 1 EP - 8 AN - OPUS4-34544 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Stajanca, Pavol A1 - Cetinkaya, O. A1 - Schukar, Marcus A1 - Mergo, P. A1 - Krebber, Katerina T1 - Climatic stability of polymer optical fibers for sensing applications N2 - Systematic investigation of annealing behavior of drawn PMMA fibers was performed. Dynamics of annealing process were measured under different environmental conditions by fiber longitudinal shrinkage monitoring. Process was found to follow stretched exponential decay function indicating heterogeneous nature of underlying molecular dynamics. Consequences of fiber annealing for climatic stability of polymer optical fiber-based sensors are discussed, emphasizing importance of fiber controlled post-fabrication annealing. Dependence of induced fiber shrinkage on annealing time, temperature and fiber drawing conditions is investigated and interpreted. In addition, strong influence of humidity on annealing process was observed, which was not recognized in previous studies. This further highlights role of fiber post-fabrication thermal treatment with respect to intended operating conditions. T2 - POF 2015 - 24th International conference on plastic optical fibers CY - Nuremberg, Germany DA - 22.09.2015 KW - Polymer optical fibers KW - Polymethyl methacrylate KW - Climatic stability KW - Fiber annealing PY - 2015 SP - 209 EP - 212 AN - OPUS4-34422 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rohwetter, Philipp A1 - Eisermann, René A1 - Krebber, Katerina ED - Kalinowski, H.J. ED - Fabris, J.L. ED - Bock, W.J. T1 - Distributed acoustic sensing: Towards partial discharge monitoring N2 - We report on the successful application of distributed acoustic sensing (DAS) to the detection of partial discharge (PD). A detection limit of about 1 nC discharge magnitude was achieved for PD in a real-scale model of a high voltage termination. Dedicated ultrasonic fibre-optic transducers were interrogated using coherent optical time-domain Rayleigh backscatter reflectometry (C-OTDR). Random quadrature demodulation was employed for retrieving relevant acoustic information from the raw C-OTDR backscatter traces. To our knowledge, our results are a first-time demonstration that quasi-distributed fibre-optic acoustic sensing is a candidate technology for the acoustic partial discharge monitoring of power cable joints and terminations. T2 - OFS2015 - 24rd International conference on optical fibre sensors CY - Curitiba, Brazil DA - 28.09.2015 KW - Distributed acoustic sensing KW - Coherent Rayleigh OTDR KW - Partial discharge KW - Acoustic emission KW - Silicone elastomer KW - Stress cone KW - High voltage cable accessories PY - 2015 SN - 9781628418392 DO - https://doi.org/10.1117/12.2194850 SN - 0277-786X N1 - Serientitel: Proceedings of SPIE – Series title: Proceedings of SPIE VL - 2015/9634 SP - 96341C-1 EP - 96341C-4 PB - SPIE CY - Bellingham, WA, USA AN - OPUS4-34407 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - RPRT A1 - Liehr, Sascha A1 - Krebber, Katerina A1 - Steffen, Milan A1 - Wosniok, Aleksander T1 - Fördermaßnahme KMU-innovativ: Informations- und Kommunikationstechnologie (IKT), EMS-261-003 (Digital OFDR - Entwicklung der digitalen Frequenzbereichsanalyse zur verteilten Rückstreumessung in optischen Fasern-Teilvorhaben: Sensorverfahren und Systembetrachtung / Schlussbericht zum Teilvorhaben KW - Digital OFDR KW - Verteilte Rückstreumessung KW - Frequenzbereichsanalyse PY - 2015 IS - BAM Vh 8158 SP - 1 EP - 45 CY - Berlin AN - OPUS4-34170 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wosniok, Aleksander A1 - Krebber, Katerina T1 - Distributed Brillouin fiber optic sensor system for long-term structural health monitoring N2 - We report on the development of a distributed fiber optical sensor system for structural health monitoring of largc-scale geotechnical and civil infrastructures. The system is based on Brillouin frequency domain analysis (BOFDA) for distributed measurement of strain and temperature along Standard silica optical fibers used as sensors. By additional incorporation of the fiber optic sensors in geosynthetics, two-dimensional sensors can be realized. Such smart geosynthetics can be used for reinforeerneut 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. T2 - 16th International conference 'Technical dam control' CY - Wierchomla Mala, Poland DA - 29.09.2015 KW - Distributed fiber optical sensor KW - Brillouin frequency domain analysis KW - Smart geosynthetics KW - Structural health monitoring PY - 2015 SN - 978-83-64979-09-5 SP - 271 EP - 278 AN - OPUS4-34728 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schreier, Andy A1 - Jeschke, T. A1 - Petermann, K. A1 - Wosniok, Aleksander A1 - Krebber, Katerina T1 - Analytical model for mode-based insertion loss in ball-lensed coupling of graded-index silica and polymer fibres N2 - Analytical model for ball-lensed couplers to calculate the insertion loss for each optical mode. The basis for the calculation are commercial perfluorinated polymer optical (PFGI-POFs) and silica based fibres (SOFs). The modal power distribution for given misalignments are presented as well as the reflection-based losses at all optical interfaces. Additionally, the ball-lensed interconnection between PFGI-POF and SOF was theoretically demonstrated. T2 - POF 2017: 26th International Conference on Plastic Optical Fibres CY - Aveiro, Portugal DA - 13.09.2017 KW - Polymer optical fibre KW - Optical connector PY - 2017 VL - 2017 SP - 1 EP - 4 AN - OPUS4-41979 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -