TY - JOUR A1 - Weiland, J. A1 - Bartholomee, W. A1 - Luber, M. A1 - Schiebahn, A. A1 - Engelbrecht, Rainer A1 - Reisgen, U. T1 - Investigation into the mechanical behavior of a polymer optical fiber embedded in a structural adhesive JF - International Journal of Adhesion and Adhesives N2 - To guaranty a safe load transfer through adhesively bonded joints, Structural Health Monitoring (SHM) methods that allow for permanent monitoring of the structural bond condition, are becoming more and more important. To meet this increasing demand, a novel approach for SHM of adhesively bonded joints by use of integrated Polymer Optical Fibers (POF) has been demonstrated in previous work. The sensor operating principle is based on strain transfer from the structural adhesive to the integrated POF. This strain transfer leads to a deformation of the POF cross-sectional shape and in that way affects the optical light propagation in the POF. In the current work, numerical and experimental results are presented into the mechanical behavior of embedded POF in adhesive bulk specimens subjected to tensile loading. Local deformations of both the POF (Asahi Kasei DB 500) and the structural adhesive (3 M Scotch Weld DP410) are evaluated using Digital Image Correlation (DIC). In the loading direction, a linear correlation is shown between strain inside the POF core and strain of the surrounding adhesive. Tests results, as well as fracture analysis, show a highly ductile behavior and failure of the POF cladding material and the interface between the POF core and annular cladding. KW - Structural health monitoring SHM Polymer optical fibers POF Epoxy Digital image correlation Finite element modelling Y1 - 2022 U6 - https://doi.org/10.1016/j.ijadhadh.2021.103018 SN - 0143-7496 VL - 117 PB - Elsevier BV ER - TY - JOUR A1 - Kruglov, Roman A1 - Saur, Gregor A1 - Engelbrecht, Rainer T1 - Precise characterization of VCSEL in the 1550 nm band having a wavelength tuning range of 12 nm within 10 µs as light sources for fast sensor systems JF - Journal of Sensors and Sensor Systems N2 - Abstract. A wavelength tuning range up to 12 nm has been achieved over 12 µs pump current pulses within a usable time of 10 µs applied to VCSELs operating in the near infrared around 1550 nm. The instantaneous optical frequency shift has been measured with an interferometric setup; the overall tuning range has then been verified with an optical spectrum analyzer. The repetition rate of the current pulses can be as high as 20 kHz with almost no influence on the sweep parameters. These results can be used for fast spectroscopic gas analysis or for rapid interferometric swept-source distance sensors. Y1 - 2022 U6 - https://doi.org/10.5194/jsss-11-161-2022 SN - 2194-878X VL - 11 IS - 1 SP - 161 EP - 169 PB - Copernicus GmbH ER - TY - CHAP A1 - Weiland, Josef A1 - Luber, Michael A1 - Rostan, Katharina A1 - Schiebahn, Alexander A1 - Engelbrecht, Rainer A1 - Reisgen, Uwe T1 - Strain Monitoring of a Structural Adhesive Bond by Embedding a Polymer Optical Fiber T2 - European Workshop on Structural Health Monitoring , Vol I N2 - In recent decades, adhesive bonding technology has become increasingly important in all industrial sectors, for example in the aerospace industry, the automotive industry or the construction industry. This is accompanied by an increased need for monitoring of adhesive bonds, especially for load-bearing, structural joints. In order to detect a possible failure at an early stage, this work is investigating a cost-effective sensor principle based on embedding of a polymer optical fiber (POF) into the adhesive layer. The strain and stress behavior of the adhesive bond are transferred to the POF and change its light-guiding properties. In the presented work, different light coupling conditions into the fiber (full excitation and angle-selective excitation) and different measurable quantities of the transmitted light decoupled from the fiber (photocurrent and far-field) are studied, to find an optimum sensor performance. The combination of a structural polyurethane adhesive with commercially available POF is investigated. The results show a high potential of the method for simple photocurrent measurement (transmission loss of 8% by half of maximum load) and an even more sensitive sensor effect for mode-dependent light power measurement. Y1 - 2022 SN - 9783031072536 U6 - https://doi.org/10.1007/978-3-031-07254-3_75 SN - 2366-2557 SP - 745 EP - 754 PB - Springer International Publishing CY - Cham ER - TY - CHAP A1 - Engelbrecht, Rainer A1 - Dengler, S. A1 - Luber, M. A1 - Fischer, J. A1 - Hangen, H. T1 - SHM at Giant Mine Heaps by OTDR Sensing with Polymer Optical Fibers BT - Chances and Challenges from Field Campaigns T2 - Optical Fiber Sensors Conference 2020 Special Edition N2 - Results from field measurement campaigns for structural health monitoring (SHM) at giant mine heaps by optical time domain reflectometry (OTDR) in polymer optical fibers (POF) are presented. Polymer geogrids built for soil reinforcement are fitted with POF for strain sensing as part of a geosynthetic sealing system designed to protect the heap from infiltration of surface water. Strain is detected by a local increase of backscatter. Measurements on eight sensor lines have been performed over a time period of six months to monitor the system behavior and potential development of or cracks within the underlying base of a sealing system. Results show the usability of this technology for strain sensing and SHM in such a harsh environment. Challenges still exist in the quantitative evaluation of the fiber sensor data due to cross sensitivity to fiber bending and lateral pressure. Y1 - 2021 U6 - https://doi.org/10.1364/ofs.2020.th4.7 PB - Optica Publishing Group CY - Washington, D.C. ER - TY - CHAP A1 - Dengler, Simon Andreas A1 - Vinogradov, Juri A1 - Engelbrecht, Rainer A1 - Schmauß, Bernhard T1 - Recent Progress in POF OTDR Strain Sensing T2 - International Conference on Plastic Optical Fibers Y1 - 2022 VL - Proceedings 2022 ER - TY - CHAP A1 - Engelbrecht, Rainer A1 - Rostan, Katharina A1 - Weiland, Josef A1 - Luber, Michael A1 - Schiebahn, Alexander A1 - Reisgen, Uwe T1 - Modal Distribution in Polymer Optical Fibers as Sensor for Load Monitoring in Semi-Structural Adhesive Bonds T2 - 27th International Conference on Optical Fiber Sensors N2 - PMMA polymer optical fibers embedded in semi-structural polyurethane adhesive bonds serve as economical load sensor for structural health monitoring by evaluating load-dependent optical transmission as well as modal distribution measured by a far-field camera. Scaling of sensor quantities by the sensitive fiber length is shown. KW - Fiber optics KW - Adhesive bonds KW - Sensors Y1 - 2022 SN - 978-1-957171-14-2 U6 - https://doi.org/10.1364/OFS.2022.W2.3 PB - Optica Publishing Group CY - Washington, D.C. ER - TY - CHAP A1 - Kruglov, Roman A1 - Engelbrecht, Rainer T1 - Rapid and High-Resolution Tunable Diode Laser Spectroscopy within 10 µs for Combustion Gas Analysis T2 - Optica Sensing Congress 2023 (AIS, FTS, HISE, Sensors, ES) N2 - We report on a rapid high-resolution absorption spectroscopy with a VCSEL reaching a peak tuning speed of 2.1 nm/µs (8.8 cm-1/µs) near 1.5 µm. An overall tuning range of up to 12 nm can be achieved within a 12 µs injection current pulse. KW - Laser spectroscopy KW - Semiconductor lasers Y1 - 2023 SN - 978-195717124-1 U6 - https://doi.org/10.1364/sensors.2023.stu2d.3 PB - Optica Publishing Group CY - Washington, D.C. ER - TY - CHAP A1 - Saur, Gregor A1 - Kruglov, Roman A1 - Engelbrecht, Rainer T1 - Microsecond Optical Frequency Tuning of DFB Laser Diodes for Coherent Optical Frequency Domain Reflectometry N2 - Optical frequency tuning ranges up to 600 GHz or 4.8 nm have been achieved within microseconds and a standard telecom DFB laser diode operating at 1550 nm. The dynamic optical frequency tuning is induced by electrical current pulse injection and measured using an interferometric setup. Potentially, low-cost sensor systems based on optical coherence tomography (OCT) or coherent optical frequency domain reflectometry (c-OFDR) could be realized, achieving sub-mm two-point range resolution or even better single-point range precision within a few microseconds for a single measurement. KW - Tunable lasers KW - Semiconductor lasers KW - Wavelength shift KW - Fiber sensing Y1 - 2020 SN - 978-3-9819376-2-6 U6 - https://doi.org/10.5162/SMSI2020/C6.2 VL - 2020 SP - 189 EP - 190 PB - AMA Service GmbH CY - Wunstorf, Germany ER - TY - GEN A1 - Engelbrecht, Rainer A1 - Dengler, Simon Andreas A1 - Luber, Michael A1 - Vinogradov, Juri A1 - Ziemann, Olaf T1 - Condition Monitoring with POF: Recent Progress on Geotextiles and Wind Turbines T2 - Proceedings POF2023 Y1 - 2023 ER - TY - CHAP A1 - Stute, Andreas A1 - Kirchbach, Lucas A1 - Giese, Andreas A1 - Bachmann, Alexander A1 - Braun, Bernd A1 - Engelbrecht, Rainer T1 - Optical Enabling Technologies for QT N2 - Overview of the research topics at TH Nuremberg for optical quantumtechnologies. Deterministic generation of NV-Centers, Integrated Spin Qubits, Micro-Optics Designs of Optical Interfaces, Lab Courses and Fabrication Devices KW - Nichtabbildende Optik KW - Stickstoff-Fehlstellenzentrum KW - Diamant KW - Integrierte Optik KW - Optik KW - Quantum KW - NV-center KW - diamond KW - spin KW - solid-state Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:92-opus4-42924 UR - https://indico.munich-quantum-valley.de/event/446/ ER - TY - CHAP A1 - Rostan, Katharina A1 - Kruglov, Roman A1 - Seiß, Volker A1 - Thiel, Susanne A1 - Eichelbaum, Maik A1 - Engelbrecht, Rainer T1 - In-situ Temperature and Humidity Measurement in PEM Fuel Cells with Off-the-shelf FBG T2 - 28th International Conference on Optical Fiber Sensors N2 - We propose a cost efficient fiber Bragg grating (FBG) sensor for measuring temperature and humidity in polymer electrolyte membrane fuel cells (PEMFC). The multiparameter sensor works with two conventional FBG and achieves an RMSE better than 0.45°C and 4.8 %RH. KW - Proton exchange membrane fuel cells KW - Temperature and humidity KW - Fiber Bragg grating Y1 - 2023 SN - 978-1-957171-30-2 U6 - https://doi.org/10.1364/OFS.2023.Tu3.36 VL - 2023 PB - Optica Publishing Group CY - Washington, D.C. ER - TY - CHAP A1 - Engelbrecht, Rainer A1 - Luber, Michael A1 - Vinogradov, Juri A1 - Hemmerlein, Moritz A1 - Pick, Mathias A1 - Ziemann, Olaf T1 - Range Extension of PMMA POF Sensors Beyond 100 M for Monitoring Large Infrastructures T2 - 33rd International Conference on Plastic Optical Fibers N2 - A POF integral length and extension sensor based on phase detection of intensity modulated light with fiber sensor lengths beyond 100 m for monitoring large infrastructures is discussed. A theory for a scaling law of the precision limit over length and modulation frequency is presented. Experimental results using green light for sensor ranges above 100 m are shown. KW - Fiber sensor KW - length sensor KW - structural health monitoring KW - large infrastructures Y1 - 2025 ER -