TY - CONF A1 - Steffen, Milan A1 - Liehr, Sascha A1 - Basedau, Frank A1 - Krebber, Katerina ED - López-Higuera, J.M. ED - Jones, J. ED - López-Amo, M. ED - Santos, J.L. T1 - Simultaneous vibration and quasi-distributed strain measurement using incoherent OFDR and extrinsic Fabry-Perot interferometers N2 - We present a measurement setup for combined quasi-distributed strain and dynamic point-wise vibration measurement using an incoherent optical frequency domain reflectometry (I-OFDR) setup in combination with extrinsic Fabry-Perot interferometers (EFPIs). Several EFPIs can be multiplexed and at the same time the strain along their supply fibres can be measured in a quasi-distributed manner. The setup is characterised and a demonstration of its general performance is given. T2 - OFS2014 - 23rd International conference on optical fibre sensors CY - Santander, Spain DA - 02.06.2014 KW - Optical fibre sensor KW - EFPI KW - I-OFDR KW - Quasi-distributed KW - Strain KW - Dynamic length and power management PY - 2014 DO - https://doi.org/10.1117/12.2059616 SN - 0277-786X SN - 1996-756X N1 - Serientitel: Proceedings of SPIE – Series title: Proceedings of SPIE VL - 9157 SP - 91576S-1 EP - 91576S-4 AN - OPUS4-31039 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sporea, D. A1 - Mihai, L. A1 - Negut, Daniel A1 - Stajanca, Pavol A1 - Krebber, Katerina ED - Kalli, K. ED - Mendez, A. T1 - On-line monitoring of gamma irradiated perfluorinated polymer optical fiber N2 - In this paper, we present the first results regarding the on-line monitoring of gamma-ray exposure effects on a commercial multi-mode perfluorinated polymer optical fiber (PF-POF), type GigaPOF-50SR from Chromis Fiberoptics. Our focus was to evaluate on-line the radiation induced attenuation (RIA) over a wide spectral range (320 nm – 1700 nm), in order to assess the fiber’s radiation hardness and its possible use in radiation detection. An Ocean Optics QE65000 high sensitivity spectrometer and a StellarNet near-IR spectrometer were used to cover the spectral ranges 200 nm – 1μm and 900 nm – 1.6 μm, respectively. Electron paramagnetic resonance was used to monitor the recovery of the irradiation induced centers at room temperature. The study indicated that the optical fiber can be used as radiation monitor at low dose rates by measuring the attenuation in the UV, while higher dose rates irradiation can be observed by RIA monitoring at specific wavelengths in the visible spectral range. T2 - Photonics Europe 2016, Micro-Structured and Specialty Optical Fibers IV CY - Brussels, Belgium DA - 03.04.2016 KW - electron paramagnetic resonance spectroscopy KW - Perfluorinated polymer optical fiber KW - radiation effects KW - gamma irradiation KW - radiation hardness KW - radiation induced attenuation KW - radiation dosimetry PY - 2016 DO - https://doi.org/10.1117/12.2230688 VL - 9886 SP - 98861Q-1 EP - 98861Q-6 PB - SPIE CY - Bellingham, USA AN - OPUS4-35927 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Fasano, A. A1 - Woyessa, G. A1 - Stajanca, Pavol A1 - Markos, C. A1 - Stefani, A. A1 - Nielsen, K. A1 - Rasmussen, H. K. A1 - Krebber, Katerina A1 - Bang, O. ED - Kalli, K. ED - Mendez, A. T1 - Creation of a microstructured polymer optical fiber with UV Bragg grating inscription for the detection of extensions at temperatures up to 125°C N2 - We describe the fabrication of a polycarbonate (PC) micro-structured polymer optical fiber (mPOF) and the writing of fiber Bragg gratings (FBGs) in it to enable strain and temperature measurements. We demonstrate the photosensitivity of a dopant-free PC fiber by grating inscription using a UV laser. We further show that PC Bragg gratings can be extended up to at least 3% without affecting the initial functionality of the micro-structured fiber. The response of PC FBGs to temperature up to 125°C is also investigated. Polycarbonate has good mechanical properties and its high temperatureresistance might extend the range of application of polymeric FBGs. T2 - Photonics Europe 2016, Micro-Structured and Specialty Optical Fibres IV CY - Brussels, Belgium DA - 03.04.2016 KW - fiber Bragg gratings KW - Polycarbonate KW - polymers KW - micro-structured polymer optical fibers KW - UV laser inscription KW - optical fiber sensors PY - 2016 DO - https://doi.org/10.1117/12.2227843 VL - 9886 SP - 988619-1 EP - 988619-6 PB - SPIE AN - OPUS4-35928 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rohwetter, Philipp A1 - Eisermann, René A1 - Krebber, Katerina T1 - Random quadrature demodulation for direct detection single-pulse rayleigh C-OTDR N2 - We present a demodulation method that partially compensates for the nonlinear and random transfer function of fiber-optic direct detection coherent Rayleigh optical time-domain reflectometry (C-OTDR). Specifically, the proposed method is shown to improve the detection of small amplitude, high frequency dynamic optical fiber strain as it occurs in acoustic emission sensing. The method is applicable provided that the dynamic fiber strain to be sensed is known to affect a longer section of sensing fiber in a spatially homogeneous way. It is shown that this knowledge can be used to extract more quantitative information from the measured C-OTDR signal by averaging signal components from the affected fiber section in a suitable and efficient way. The theoretical basis of the method is developed and supporting experimental results are presented. KW - Optical fiber sensors KW - Coherent optical time-domain reflectometry (C-OTDR) KW - Fiber-optic speckle interferometry KW - Remote acoustic emission sensing PY - 2016 DO - https://doi.org/10.1109/JLT.2016.2557586 SN - 0733-8724 VL - 34 IS - 19 SP - 4437 EP - 4444 PB - IEEE CY - Piscataway, NJ, USA AN - OPUS4-35948 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Stajanca, Pavol A1 - Mihai, L. A1 - Sporea, D. A1 - Negut, D. A1 - Krebber, Katerina ED - Lewis, E. T1 - Perfluorinated polymer optical fiber for gamma radiation monitoring N2 - The sensitivity of low-loss perfluorinated polymer optical fiber (PF-POF) to gamma radiation is investigated for on-line radiation monitoring purposes. The radiation-induced attenuation (RIA) of a commercial PF-POF based on Cytop material is measured in the visible spectral region. The fiber RIA shows strong wavelength dependence with rapid increase towards the blue side of the spectrum. The wide range of radiation sensitivities is available via careful selection of appropriate monitoring wavelength. The accessible sensitivities span from 1.6 ± 0.2 dBm-1/kGy measured at 750 nm to 18.3 ± 0.7 dBm-1/kGy measured at 420 nm. The fairly high radiation sensitivity as well as its wide tunability makes the fiber a promising candidate for a broad range of applications. T2 - Sixth European Workshop on Optical Fibre Sensors CY - Limerick, Ireland DA - 31.05.2016 KW - Perfluorinated polymer optical fiber KW - Cytop KW - gamma radiation KW - optical fiber sensors KW - radiation dosimetry PY - 2016 UR - http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=2525047&resultClick=1 DO - https://doi.org/10.1117/12.2235528 VL - 9916 SP - 99160H-1 EP - 99160H-4 PB - SPIE CY - Bellingham, WA, USA AN - OPUS4-36461 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Lu, Xin A1 - Krebber, Katerina T1 - Direct detection based φOTDR using the Kramers-Kronig receiver N2 - A Kramers-Kronig (KK) receiver is applied to a phase-sensitive optical time domain reflectometry based on direct detection. An imbalanced Mach-Zehnder interferometer with a 2× 2 coupler is used in sensing system to encode the phase information into optical intensity. The directly obtained signal is treated as the in-phase component, and the KK receiver provides the quadrature component by Hilbert transform of the obtained signal, so that the optical phase can be retrieved by IQ demodulation. The working principle is well explained, and the obtained phase variance is theoretically analyzed. The experiment demonstrates the functionality of the sensor and validates the theoretical analysis. KW - Kramers-Kronig detector KW - Distributed fiber sensing KW - Acoustic sensing PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-516803 UR - https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-28-24-37058&id=442839 DO - https://doi.org/10.1364/OE.405723 VL - 28 IS - 24 SP - 37058 EP - 37068 PB - Optical Society of America AN - OPUS4-51680 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Lu, Xin A1 - Krebber, Katerina T1 - Characterizing detection noise in phase-sensitive optical time domain reflectometry N2 - Phase-sensitive optical time domain reflectometry (φOTDR) is an excellent distributed fiber sensing technique and has been applied in various areas. Its noise is however never been comprehensively studied to the best of our knowledge. The different detection noise sources in such a sensing system are thoroughly investigated. The impacts of thermal noise, shot noise and the beat between signal and the amplified spontaneous emission from a pre-amplifier have been theoretically and experimentally demonstrated. Due to the random nature of the φOTDR signal, the detection noise demonstrates distinct features at different fiber positions in a single measurement. The theoretical analysis and the experimental result explicitly affirm most of the fiber sections, and the difference at some positions may be explained by ambient noise. KW - Noise analysis KW - Acoustic sensing KW - Distributed fiber sensing PY - 2021 DO - https://doi.org/https://doi.org/10.1364/OE.424410 SN - 1094-4087 VL - 29 IS - 12 SP - 18791 EP - 18806 PB - Optical Society of America CY - Washington, DC AN - OPUS4-52757 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Lu, Xin A1 - Krebber, Katerina T1 - Phase error analysis and unwrapping error suppression in phase-sensitive optical time domain reflectometry N2 - Phase-sensitive optical time domain reflectometry becomes an effective tool to realize distributed sensing, and the optical phase of the received light is usually used to quantify the strain for both dynamic and static measurement. The analysis on the overall phase error has been improved by considering the proportionality of the detection noise to the local optical power. The estimation accuracy is greatly improved by using the proposed theory, the probability density of the estimation accuracy over 99% is > 0.6, ∼39 times larger than the previously reported method. The phase unwrapping may malfunction due to the noisy signal, causing large phase errors. Point break detection algorithms are used to locate the incorrect phase unwrapping points, so the temporal evolution of the phase retrieved at each position can be divided into several sections with different offset. The phase unwrapping error is then suppressed by removing the offset. KW - Phase unwrapping KW - Distributed fiber sensing KW - Acoustic sensing PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-543919 DO - https://doi.org/10.1364/OE.446517 VL - 30 IS - 5 SP - 6934 EP - 6948 PB - Optica Publishing Group AN - OPUS4-54391 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Shaheen, Sabahat A1 - Hicke, Konstantin A1 - Krebber, Katerina T1 - Phase-sensitive optical time domain reflectometry based on geometric phase measurement N2 - A phase-sensitive optical time domain reflectometer based on coherent heterodyne detection of geometric phase in the beat signal of light, is reported for the first time to our knowledge. The use of the geometric phase to extract strain makes it immune to polarisation diversity fading. This is because a polarisation mismatch between the interfering beams is not a hindrance to its measurement. The geometric phase is calculated using the amplitude of the beat signal and individual beam intensities without any need for phase unwrapping. It is measured per beat period and can be equated with the traditionally measured dynamic phase with appropriate scaling. The results show that the system based on the geometric phase successfully measures strain, free from polarisation mismatch fading and phase unwrapping errors, providing a completely novel solution to these problems. KW - Fiber optic sensing KW - Distributed acoustic sensing KW - DAS KW - Geometric phase KW - Pancharatnam–Berry phase KW - Berry phase PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-570307 DO - https://doi.org/10.1038/s41598-023-29972-4 VL - 13 SP - 1 EP - 11 PB - Nature Portfolio CY - London AN - OPUS4-57030 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Shaheen, Sabahat A1 - Hicke, Konstantin A1 - Krebber, Katerina T1 - Blast-Assisted Subsurface Characterisation Using a Novel Distributed Acoustic Sensing Setup Based on Geometric Phases N2 - A novel DAS setup based on geometric phases in coherent heterodyne detection is applied for the first time to the characterisation of the Earth’s subsurface. In addition, an optimisation of the proposed setup in terms of its spatial resolution is also presented for the first time. The surface waves are generated by strong blasts of 25 kg of explosives at a dedicated test site. A 10 km dark fiber link in the vicinity of the test site connected to the test setup records the resulting strain signals. The spike-free and low-noise strain data thus obtained minimize post-processing requirements, making the setup a candidate for real-time seismic monitoring. An analysis of the dispersion characteristics of the generated surface waves is performed using a recently reported optimised seismic interferometric technique. Based on the dispersion characteristics, the shear wave velocities of the surface waves as a function of the depth profile of the Earth’s crust are determined using an optimised evolutionary algorithm. KW - Geophysics KW - Geometric Phase KW - Distributed Fiber Optic Sensor KW - Distributed Acoustic Sensing KW - Earthquake Monitoring KW - Seismology PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-591913 DO - https://doi.org/10.3390/s24010030 VL - 24 IS - 1 SP - 1 EP - 12 PB - MDPI AN - OPUS4-59191 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Lu, Xin A1 - Hicke, Konstantin A1 - Krebber, Katerina T1 - Distributed acoustic sensing to monitor ground motion/movement at multi-frequency bands N2 - A novel distributed acoustic sensing technique is proposed that exploits both phase and amplitude of the Rayleigh backscattered light to quantify the environmental variation. The system employs a wavelength-scanning laser and an imbalanced Mach-Zehnder interferometer to acquire the reflection spectra and the phase of the detected light, respectively. Fading-free and low-frequency measurements are realized via the crosscorrelation of the reflection spectra. The discrete crosscorrelation is used to circumvent the nonlinear frequency sweeping of the laser. Based on the phase of the backscattered light, it is possible to quantify fast environmental variations. The whole system requires no hardware modification of the existing system and its functionality is experimentally validated. The proposed system has the potential to monitor ground motion/movement at very low frequency band like subsidence around mining areas and at high frequency band like earthquakes and vibrations induced by avalanches. KW - Distributed acoustic sensing KW - DAS KW - Distributed fiber optic sensing KW - Ground motion detection KW - Subsidence monitoring PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-596129 DO - https://doi.org/10.1109/JLT.2024.3358495 VL - 42 IS - 18 SP - 1 EP - 8 PB - Optical Society und IEEE Photonics Society AN - OPUS4-59612 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zabihi, Mohammadmasoud A1 - Krebber, Katerina T1 - Approach for Faster Signal Processing in Փ-OTDR Systems Based on Directional Measurement of Fiber Slices Interaction N2 - In this study, a signal processing approach for heterodyne Փ-OTDR and C-OTDR systems that can obtain external perturbation and its frequency content in a faster way is proposed. We can detect vibrations with the same or better SNR using this processing approach, only with a single step and fast calculation. Fig. 12 shows the comparison of the normalized measurement time for the gamma matrix method and the conventional method throughout the three experiments. The speed of processing using a gamma matrix is ~35%–50% faster compared to a conventional method in high frequency test (PZT), low frequency test (walking) and street monitoring test. The processing speed in low frequency test is normally a bit lower than the similar high frequency one, since we must use higher number of time frames. Also, in street test we have higher speed because we can select wider gauges. KW - Փ-OTDR PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-560492 DO - https://doi.org/10.1364/OPTCON.456421 VL - 1 IS - 8 SP - 1837 EP - 1847 PB - Optica Publishing Group CY - Washington, DC AN - OPUS4-56049 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zabihi, Mohammadmasoud A1 - Krebber, Katerina T1 - Laser source frequency drift compensation in Φ-OTDR systems using multiple probe frequencies N2 - In this study, an approach for mitigation of LSFD in Φ-OTDR systems was proposed. By using one probe pulse as a reference in a system with two or more probe frequencies, we can remove unwanted low frequency noise that is originally caused by the laser source. Although LSFD is problematic issue, it is not the only source of low frequency noise. Change in temperature, humidity, physical surroundings, environment, etc., can result in such noises. The proposed method; however, is expected to highly suppresses all of these effects, regardless of their source, either in the time or frequency domain. For comparing reference and probe signals, there are sophisticated methods, rather than normal differentiation, available for use. Some of these methods have a close relationship with CPD methods and can further enhance the results. These methods can be further discussed in an independent research or future work. The proposed method is very helpful for increasing accuracy in passive and active seismic monitoring, reservoir monitoring, underwater monitoring, etc. It also helps using relatively simpler laser sources and make the whole system price-efficient, as well as processing data without lengthy compensation algorithms. KW - Frequency Drift KW - Փ-OTDR KW - LSFD PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-560517 DO - https://doi.org/10.1364/oe.460302 SN - 1094-4087 VL - 30 IS - 11 SP - 19990 EP - 19998 PB - Optica CY - Washington, DC AN - OPUS4-56051 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -