Journal articles: 'Distributed fibre optic strain sensors'

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DeMerchant, Michael, Anthony Brown, Jeff Smith, Xiaoyi Bao, and Theodore Bremner. "Distributed strain sensing for structural monitoring applications." Canadian Journal of Civil Engineering 27, no. 5 (October 1, 2000): 873–79. http://dx.doi.org/10.1139/l00-006.

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Strain sensors are a valuable tool for assessing the health of structures. The University of New Brunswick, in conjunction with ISIS Canada, is developing a distributed fibre optic strain sensor based on Brillouin scattering. This sensor can provide a virtually unlimited number of measurement points using a single optical fibre. A description of the operating principles of the system is given, along with a summary of laboratory test results. Strain measurement accuracy as high as approximately ±11 µε has been demonstrated at 1 m spatial resolution. Spatial resolutions as short as 100 mm can be used, although with decreased strain measurement accuracy. Future development of the technology will include an enhancement allowing both strain and temperature to be measured simultaneously.Key words: strain sensor, fibre optics, distributed sensing, structural monitoring, Brillouin scattering.

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Tennyson, R. C., T. Coroy, G. Duck, G. Manuelpillai, P. Mulvihill, David JF Cooper, PW E. Smith, A. A. Mufti, and S. J. Jalali. "Fibre optic sensors in civil engineering structures." Canadian Journal of Civil Engineering 27, no. 5 (October 1, 2000): 880–89. http://dx.doi.org/10.1139/l00-010.

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This paper presents an overview of the development and application of ISIS fibre optic sensor (FOS) technology by the University of Toronto Institute for Aerospace Studies and Department of Electrical and Computer Engineering. The primary focus of this technology has involved the use of fibre Bragg gratings (FBGs) to measure strain and temperature in concrete structures and fibre reinforced plastic (FRP) overwraps applied to concrete structures. A brief review of existing fibre optic sensor configurations and the advantages of using FOS compared to other strain sensors is first presented. Subsequently, the development of new sensor concepts such as a long gauge of arbitrary length, a distributed gauge for measuring local strain gradients, and multiple FBGs on a single fibre optic cable are discussed, with examples of their application to civil engineering structures. In addition, the specialized instruments under development that are essential for obtaining strain information from these sensors are also described. Finally, the issue of wireless remote monitoring of FOS systems is addressed.Key words: fibre optic sensors, Bragg gratings, civil engineering structures, instrumentation.

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Sieńko, Rafał, Mariusz Zych, Łukasz Bednarski, and Tomasz Howiacki. "Strain and crack analysis within concrete members using distributed fibre optic sensors." Structural Health Monitoring 18, no. 5-6 (October 8, 2018): 1510–26. http://dx.doi.org/10.1177/1475921718804466.

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This article presents laboratory tests, with the purpose being to verify the suitability of standard optical fibres in a tight jacket for advanced strain analysis within concrete members. An optical reflectometer was used to enable the optical signal to be processed on the basis of the Rayleigh scattering phenomenon, so that strains and/or temperature changes were determined along the length of the measuring fibre. The measurements were carried out continuously in a geometrical sense (distributed measurements), with a spatial resolution starting from as fine as 5 mm. The arrangement of optical fibres inside the heterogeneous concrete medium and on its surface allowed for the identification and detailed analysis of local phenomena such as cracks. Remote and early location of structural damage with an estimation of its scale provides new opportunities for the monitoring of the structural health of reinforced concrete structures, facilitating the interpretation of its behaviour as well as failure risk management based on comprehensive and reliable measurement data. If traditional spot techniques are used, this approach is not possible. The aim of the initial studies was to analyse the strain distributions over compressed and tensioned measurement sections located on the surface of a cylindrical specimen of concrete. In the tests which followed, the reinforced concrete rod was eccentrically tensioned with fibre optics installed inside. Qualitative and quantitative verification of crack widths was made, with a narrow range up to 0.05 mm and a wider one to 0.30 mm. The results of the studies show very good accuracy of optical fibre sensor technology as a reference technique during the analysis of microcracks and narrow cracks, and moderate accuracy in the case of wider cracks. Despite using optical fibres in a tight jacket which mediates in strain transfer, the results obtained can be very suitable for the assessment of the structural condition of the member under consideration. It is also worth noting that the tests conducted indicate the effectiveness of distributed optical fibre technology for the analysis of concrete homogeneity and its structural behaviour within compressed areas, as it is possible to calculate strains over measuring bases that start from lengths as short as 5 mm.

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Nagulapally, Prashanth, Md Shamsuddoha, Ginu Rajan, Luke Djukic, and Gangadhara B. Prusty. "Distributed Fibre Optic Sensor-Based Continuous Strain Measurement along Semicircular Paths Using Strain Transformation Approach." Sensors 21, no. 3 (January 25, 2021): 782. http://dx.doi.org/10.3390/s21030782.

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Distributed fibre optic sensors (DFOS) are popular for structural health monitoring applications in large engineering infrastructure because of their ability to provide spatial strain measurements continuously along their lengths. Curved paths, particularly semicircular paths, are quite common for optical fibre placement in large structures in addition to straight paths. Optical fibre sensors embedded in a curved path configuration typically measure a component of strain, which often cannot be validated using traditional approaches. Thus, for most applications, strain measured along curved paths is ignored as there is no proper validation tool to ensure the accuracy of the measured strains. To overcome this, an analytical strain transformation equation has been developed and is presented here. This equation transforms the horizontal and vertical strain components obtained along a curved semicircular path into a strain component, which acts tangentially as it travels along the curved fibre path. This approach is validated numerically and experimentally for a DFOS installed on a steel specimen with straight and curved paths. Under tensile and flexural loading scenarios, the horizontal and vertical strain components were obtained numerically using finite element analysis and experimentally using strain rosettes and then, substituted into the proposed strain transformation equation for deriving the transformed strain values. Subsequently, the derived strain values obtained from the proposed transformation equation were validated by comparing them with the experimentally measured DFOS strains in the curved region. Additionally, this study has also shown that a localised damage to the DFOS coating will not impact the functionality of the sensor at the remaining locations along its length. In summary, this paper presents a valid strain transformation equation, which can be used for transforming the numerical simulation results into the DFOS measurements along a semicircular path. This would allow for a larger scope of spatial strains measurements, which would otherwise be ignored in practice.

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Bai, Hedan, Shuo Li, Jose Barreiros, Yaqi Tu, Clifford R. Pollock, and Robert F. Shepherd. "Stretchable distributed fiber-optic sensors." Science 370, no. 6518 (November 12, 2020): 848–52. http://dx.doi.org/10.1126/science.aba5504.

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Silica-based distributed fiber-optic sensor (DFOS) systems have been a powerful tool for sensing strain, pressure, vibration, acceleration, temperature, and humidity in inextensible structures. DFOS systems, however, are incompatible with the large strains associated with soft robotics and stretchable electronics. We develop a sensor composed of parallel assemblies of elastomeric lightguides that incorporate continuum or discrete chromatic patterns. By exploiting a combination of frustrated total internal reflection and absorption, stretchable DFOSs can distinguish and measure the locations, magnitudes, and modes (stretch, bend, or press) of mechanical deformation. We further demonstrate multilocation decoupling and multimodal deformation decoupling through a stretchable DFOS–integrated wireless glove that can reconfigure all types of finger joint movements and external presses simultaneously, with only a single sensor in real time.

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Martín-Pérez, Beatriz, Amre Deif, Bruno Cousin, Chunshu Zhang, Xiaoyi Bao, and Wenhai Li. "Strain monitoring in a reinforced concrete slab sustaining service loads by distributed Brillouin fibre optic sensors." Canadian Journal of Civil Engineering 37, no. 10 (October 2010): 1341–49. http://dx.doi.org/10.1139/l10-080.

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Reinforced concrete (RC) structures deteriorate and as a result crack due to extreme loading and (or) environmental conditions. Damage accumulation as such adversely affects the structure’s durability properties, impairing its service life. The intensity of cracking in an RC structure is usually regarded as the key criterion toward damage assessment and repair intervention. This paper presents the results of an experimental program in which the concrete strains of a small-scale RC slab sustaining in-service loads were monitored by traditional electrical strain gauges and distributed Brillouin fibre optic sensors in an attempt to detect damage due to crack formation. A comparison of these measurements with classical bending theory is also presented. The results show that distributed Brillouin fibre optic sensors can capture both tensile and compressive strains in concrete; however, the accuracy of their measurements is dependent on the proper installation of the sensors and the fibre length over which the strains are to be measured.

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Rajeev, Pathmanathan, Jayantha Kodikara, Wing Kong Chiu, and Thomas Kuen. "Distributed Optical Fibre Sensors and their Applications in Pipeline Monitoring." Key Engineering Materials 558 (June 2013): 424–34. http://dx.doi.org/10.4028/www.scientific.net/kem.558.424.

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Health monitoring of civil infrastructure systems has recently emerged as a powerful tool for condition assessment of infrastructure performance. With the widespread use of modern telecommunication technologies, structures could be monitored periodically from a central station located several kilometres away from the field. This remote capability allows immediate damage detection, so that necessary actions are taken to reduce the risk. Optical fiber sensors offer a relatively new technology for monitoring the performance of spatially distributed structures such as pipelines. In this regards, several commercially available strain and temperature sensing equipment such as discrete FBGs (Fibre Bragg Gratings) and fully distributed sensing techniques such as Raman DTS (distributed temperature sensor) and Brillouin Optical Time Domain Reflectometry (BOTDR) typically offer sensing lengths of the order of 100 km's. Distributed fiber optic sensing offers the ability to measure temperatures and/or strains at thousands of points along a single fiber. In this paper, the authors will give a brief overview of these optical fiber technologies, outline potential applications of these technologies for geotechnical engineering applications and experience in utilising BOTDR in water pipeline monitoring application.

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Xu, Cheng, and Zahra Sharif Khodaei. "Shape Sensing with Rayleigh Backscattering Fibre Optic Sensor." Sensors 20, no. 14 (July 21, 2020): 4040. http://dx.doi.org/10.3390/s20144040.

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In this paper, Rayleigh backscattering sensors (RBS) are used to realize shape sensing of beam-like structures. Compared to conventional shape sensing systems based on fibre Bragg grating (FBG) sensors, RBS are capable of continuous lateral sensing. Compared to other types of distributed fibre optic sensors (FOS), RBS have a higher spatial resolution. First, the RBS’s strain sensing accuracy is validated by an experiment comparing it with strain gauge response. After that, two shape sensing algorithms (the coordinate transformation method (CTM) and the strain-deflection equation method (SDEM)) based on the distributed FOS’ input strain data are derived. The algorithms are then optimized according to the distributed FOS’ features, to make it applicable to complex and/or combine loading situations while maintaining high reliability in case of sensing part malfunction. Numerical simulations are carried out to validate the algorithms’ accuracy and compare their accuracy. The simulation shows that compared to the FBG-based system, the RBS system has a better performance in configuring the shape when the structure is under complex loading. Finally, a validation experiment is conducted in which the RBS-based shape sensing system is used to configure the shape of a composite cantilever-beam-like specimen under concentrated loading. The result is then compared with the optical camera-measured shape. The experimental results show that both shape sensing algorithms predict the shape with high accuracy comparable with the optical camera result.

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Fenta, Mulugeta C., David K. Potter, and János Szanyi. "Fibre Optic Methods of Prospecting: A Comprehensive and Modern Branch of Geophysics." Surveys in Geophysics 42, no. 3 (March 9, 2021): 551–84. http://dx.doi.org/10.1007/s10712-021-09634-8.

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AbstractOver the past decades, the development of fibre optic cables, which pass light waves carrying data guided by total internal reflection, has led to advances in high-speed and long-distance communication, large data transmission, optical imaging, and sensing applications. Thus far, fibre optic sensors (FOSs) have primarily been employed in engineering, biomedicine, and basic sciences, with few reports of their usage in geophysics as point and distributed sensors. This work aimed at reviewing the studies on the use of FOSs in geophysical applications with their fundamental principles and technological improvements. FOSs based on Rayleigh, Brillouin, and Raman scatterings and fibre Bragg grating sensors are reviewed based on their sensing performance comprising sensing range, spatial resolution, and measurement parameters. The recent progress in applying distributed FOSs to detect acoustic, temperature, pressure, and strain changes, as either single or multiple parameters simultaneously on surface and borehole survey environments with their cable deployment techniques, has been systematically reviewed. Despite the development of fibre optic sensor technology and corresponding experimental reports of applications in geophysics, there have not been attempts to summarise and synthesise fibre optic methods for prospecting as a comprehensive and modern branch of geophysics. Therefore, this paper outlines the fibre optic prospecting methods, with an emphasis on their advantages, as a guide for the geophysical community. The potential of the new outlined fibre optic prospecting methods to revolutionise conventional geophysical approaches is discussed. Finally, the future challenges and limitations of the new prospecting methods for geophysical applications are elucidated.

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Stevens, Kevin J., Grant V. M. Williams, I. Monfils, D. Hirst, P. Wagner, S. G. Raymond, J. W. Quilty, and My T. T. Do. "Optics-Based Strain Sensing System." Materials Science Forum 700 (September 2011): 178–81. http://dx.doi.org/10.4028/www.scientific.net/msf.700.178.

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An optics-based strain sensing system is being developed for quazi-distributed strain sensing in locations and environments that are not accessible to conventional strain sensors. The system comprises an Optical Interrogator that has been designed and constructed by Southern Photonics [1], and optical fibre coupled Bragg grating strain sensors. It has been tested using commercial fibre Bragg gratings [2] that were attached to 2 samples of 316 grade stainless steel and cycled in strain and temperature using an Instron mechanical testing machine and temperature controlled cabinet. The results have been compared to the performance of conventional electrical resistance strain gauges. Pairs of fibre Bragg gratings were simultaneously interrogated at 1540 and 1550 nm centre wavelengths to demonstrate the ability of the system to use multiple sensors for quazi-distributed sensing and temperature compensation. The Optical Interrogator resolution is approximately 4 microstrains, accounting for longer term temperature drift, and it is capable of resolving dynamic strains at rates of up to 90 Hz.

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Xu, Zhigang, Xin Feng, Sheng Zhong, and Wenjing Wu. "Surface Crack Detection in Prestressed Concrete Cylinder Pipes Using BOTDA Strain Sensors." Mathematical Problems in Engineering 2017 (2017): 1–12. http://dx.doi.org/10.1155/2017/9259062.

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Structural deterioration after a period of service can induce the failure of prestressed concrete cylinder pipes (PCCPs), with microcracks in the coating leading to the corrosion of the prestressed wires. In this paper, we propose the use of Brillouin optical time-domain analysis (BOTDA) strain sensors for detecting the onset of microcracking in PCCP coating: the BOTDA strain sensors are mounted on the surface of the PCCP, and distributed strain measurements are employed to assess the cracks in the mortar coating and the structural state of the pipe. To validate the feasibility of the proposed approach, experimental investigations were conducted on a prototype PCCP segment, wherein the inner pressure was gradually increased to 1.6 MPa. Two types of BOTDA strain sensors—the steel wire packaged fiber optic sensor and the polyelastic packaged fiber optic sensor—were employed in the experiments. The experimental distributed measurements agreed well with the finite element computations, evidencing that the investigated strain sensors are sensitive to localized deterioration behaviors such as PCCP microcracking.

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Bao, Yi, Ying Huang, Matthew Hoehler, and Genda Chen. "Review of Fiber Optic Sensors for Structural Fire Engineering." Sensors 19, no. 4 (February 20, 2019): 877. http://dx.doi.org/10.3390/s19040877.

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Reliable and accurate measurements of temperature and strain in structures subjected to fire can be difficult to obtain using traditional sensing technologies based on electrical signals. Fiber optic sensors, which are based on light signals, solve many of the problems of monitoring structures in high temperature environments; however, they present their own challenges. This paper, which is intended for structural engineers new to fiber optic sensors, reviews various fiber optic sensors that have been used to make measurements in structure fires, including the sensing principles, fabrication, key characteristics, and recently-reported applications. Three categories of fiber optic sensors are reviewed: Grating-based sensors, interferometer sensors, and distributed sensors.

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Sherman, Christopher, Robert Mellors, Joseph Morris, and Frederick Ryerson. "Geomechanical modeling of distributed fiber-optic sensor measurements." Interpretation 7, no. 1 (February 1, 2019): SA21—SA27. http://dx.doi.org/10.1190/int-2018-0063.1.

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Fiber-optic-based distributed acoustic sensors (DAS) are a new technology that can be deployed in a well and are continuously interrogated during operations. These sensors measure the strain (or strain rate) at all points along the fiber and have been used extensively to monitor hydraulic stimulations. The data from these sensors indicate that they are sensitive to high-frequency signals associated with microseismicity and low-frequency signals associated with fracture growth. We have developed a set of idealized models to simulate these signals and to identify interpretation methods that may be used to estimate fracture location, geometry, and extent. We use a multiphysics code that includes rock physics, fluid flow, and elastic-wave propagation to generate synthetic DAS measurements from a set of simple models that mimic hydraulic fracturing. We then relate the signals observed in the synthetic DAS to specific features in the model such as fracture height, width, and aperture. Our results demonstrate that the synthetic DAS measurements may be used to interpret field DAS measurements and to optimize the design of future sensor deployments for sensitivity to fracture attributes.

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Bednarz, Bartosz, Paweł Popielski, Rafał Sieńko, Tomasz Howiacki, and Łukasz Bednarski. "Distributed Fibre Optic Sensing (DFOS) for Deformation Assessment of Composite Collectors and Pipelines." Sensors 21, no. 17 (September 2, 2021): 5904. http://dx.doi.org/10.3390/s21175904.

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Due to the low costs of distributed optical fibre sensors (DFOS) and the possibility of their direct integration within layered composite members, DFOS technology has considerable potential in structural health monitoring of linear underground infrastructures. Often, it is challenging to truly simulate the actual ground conditions at all construction stages. Thus, reliable measurements are required to adjust the model and verify theoretical calculations. The article presents a new approach to monitor displacements and strains in Glass Fiber Reinforced Polymer (GFRP) collectors and pipelines using DFOS. The research verifies the effectiveness of the proposed monitoring solution for health monitoring of composite pipelines. Optical fibres were installed over the circumference of a composite tubular pipe, both on the internal and external surfaces, while loaded externally. Analysis of strain profiles allowed for calculating the actual displacements (shape) of the pipe within its cross-section plane using the Trapezoidal method. The accuracy of proposed approach was positively verified both with reference spot displacement transducer as well as numerical simulations using finite element method (FEM). DFOS could obtain a comprehensive view of structural deformations, including both strains and displacements under externally applied load. The knowledge gained during research will be ultimately used for renovating existing collectors.

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Grzymski, Filip, Tomasz Trapko, and Michał Musiał. "Practical use of distributed fibre optic sensors in research on FRCM composites." E3S Web of Conferences 97 (2019): 02019. http://dx.doi.org/10.1051/e3sconf/20199702019.

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This article describes research on FRCM (Fabric Reinforced Cementitious Matrix) composites, which unlike commonly used FRP (Fibre Reinforced Polymers) composites make use of a mineral matrix instead of epoxy resin, which allows to achieve much higher resistance to elevated temperatures. In the described studies, experimental measurement of deformations with the use of the DFOS (Distributed Fibre Optic Sensors) method was applied. This method allows for geometrically continuous measurement of deformations, which is its significant advantage compared to traditional electric resistance wire strain gauge, as it reduces the possibility of measuring deformations in a place where they are not representative. The tests were carried out using two reinforced concrete slab elements loaded to failure in the 4-point bending scheme. Fibre optic sensors were installed on an unstrengthened control element and on an element strengthened with FRCM composite. During the tests, deformations of the concrete under tension and the external surface of the FRCM reinforcing composite were determined. Measurements were carried out simultaneously in two manners: using the DFOS method, and strain gauges placed at the characteristic points of the element. The test results based on both methods were compared and analysed. The comparative analysis confirmed the usefulness and effectiveness of the DFOS method while measuring deformations in strengthening composites, and showed its significant advantages such as precise indication of the place of elements cracking as well as the possibility of conducting a global analysis of deformations.

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Sirat, Qurratu Aini, Dayangku Salma Awang Ismail, Azman Kassim, and Ahmad Safuan A. Rashid. "Application of distributed optical fibre for shallow foundation." MATEC Web of Conferences 250 (2018): 01019. http://dx.doi.org/10.1051/matecconf/201825001019.

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Soil deformation is one of the major interests with regard to the stability analysis of the foundations. The deformations are signified for both vertical and lateral soil deformation; which the former plays vital role in designing a good foundation. As the stability of the foundation affect the stability of the entire structure, instrumentation and monitoring play an important roles in order to monitor the performances of the geotechnical structures. Until now the design of a foundation soil system is relied on the quantification of soil bearing capacity and foundation structural capacity and then followed by conventional monitoring system to observe the settlement so that within the allowable values. Therefore, this study focuses on the newly usage of distributed optical fibre sensing application to monitor strain distribution within a soil mass due to surcharge loading. It is expected to observe the strain distribution goes proportionally to vertical stress distribution concept; where higher strain measurement right below the loading position and decreases with depth. The advantage of distributed optical fibre sensing rather than conventional strain gauge is the sensor able to collect so-called average strain along the optical fibre compare to discrete measurement of strain gauge. This paper describes the experimental work conducted with the use of a distributed sensing technology named Brillouin Optical Time-Domain Analysis (BOTDA). A small scale of 1G model of a shallow foundation which represented by a load plate under incremental surcharge loading was stimulated to assess the soil mass deformation. The optical fibre were embedded in soil mass by layering in a horizontal direction which laid perpendicular to load direction. A comparison of numerical modeling using PLAXIS 2D and experimental works as part of this study. As a results, fibre optic is a good approach for instrumentations and monitoring for geotechnical structures as fibre optics is sensitive to the movement of the soil and fibre optic with anchorage system gave better strain measurement reading compare to without anchorage system.

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Minardo, Aldo, Ester Catalano, Agnese Coscetta, Giovanni Zeni, Lei Zhang, Caterina Di Maio, Roberto Vassallo, et al. "Distributed Fiber Optic Sensors for the Monitoring of a Tunnel Crossing a Landslide." Remote Sensing 10, no. 8 (August 15, 2018): 1291. http://dx.doi.org/10.3390/rs10081291.

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This work reports on the application of a distributed fiber-optic strain sensor for long-term monitoring of a railway tunnel affected by an active earthflow. The sensor has been applied to detect the strain distribution along an optical fiber attached along the two walls of the tunnel. The experimental results, relative to a two-year monitoring campaign, demonstrate that the sensor is able to detect localized strains, identify their location along the tunnel walls, and follow their temporal evolution.

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Feng, Xin, Wenjing Wu, Dewei Meng, Farhad Ansari, and Jing Zhou. "Distributed monitoring method for upheaval buckling in subsea pipelines with Brillouin optical time-domain analysis sensors." Advances in Structural Engineering 20, no. 2 (July 28, 2016): 180–90. http://dx.doi.org/10.1177/1369433216659990.

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A method for monitoring the upheaval buckling of subsea buried pipelines by distributed optical fiber sensors is introduced. The proposed method originates from the fact that the bucked pipe has the deterministic patterns of the bending-induced and axial force–induced strains, which can be used to identify the pre- and post-buckling states of the pipe. The challenge for utilizing these features is that the distributed fiber optic sensor can only measure the compound strain created by both bending and axial compression. A monitoring scheme by placing three sensors with [Formula: see text] space around the circumference of the pipeline was proposed in this article. An approach was presented to extract the bending-induced and axial force–induced strains from the longitudinal strains measured by the distributed fiber optic sensors. The experimental programs were then designed to investigate the feasibility of the proposed method. It is demonstrated that the proposed method is possible to detect the occurrence of buckling in the pipe. However, further research is necessary in order to examine the efficiency of the proposed approach under the complex loading patterns at subsea levels.

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Monsberger, Christoph M., Werner Lienhart, and Bernd Moritz. "In-situ assessment of strain behaviour inside tunnel linings using distributed fibre optic sensors." Geomechanics and Tunnelling 11, no. 6 (December 2018): 701–9. http://dx.doi.org/10.1002/geot.201800050.

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Bersan, Silvia, Otello Bergamo, Luca Palmieri, Luca Schenato, and Paolo Simonini. "Distributed strain measurements in a CFA pile using high spatial resolution fibre optic sensors." Engineering Structures 160 (April 2018): 554–65. http://dx.doi.org/10.1016/j.engstruct.2018.01.046.

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Boujia, Nissrine, Franziska Schmidt, Christophe Chevalier, Dominique Siegert, and Damien Pham Van Bang. "Distributed Optical Fiber-Based Approach for Soil–Structure Interaction." Sensors 20, no. 1 (January 6, 2020): 321. http://dx.doi.org/10.3390/s20010321.

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Scour is a hydraulic risk threatening the stability of bridges in fluvial and coastal areas. Therefore, developing permanent and real-time monitoring techniques is crucial. Recent advances in strain measurements using fiber optic sensors allow new opportunities for scour monitoring. In this study, the innovative optical frequency domain reflectometry (OFDR) was used to evaluate the effect of scour by performing distributed strain measurements along a rod under static lateral loads. An analytical analysis based on the Winkler model of the soil was carefully established and used to evaluate the accuracy of the fiber optic sensors and helped interpret the measurements results. Dynamic tests were also performed and results from static and dynamic tests were compared using an equivalent cantilever model.

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Coscetta, Agnese, Aldo Minardo, Lucio Olivares, Maurizio Mirabile, Mario Longo, Michele Damiano, and Luigi Zeni. "Wind Turbine Blade Monitoring with Brillouin-Based Fiber-Optic Sensors." Journal of Sensors 2017 (2017): 1–5. http://dx.doi.org/10.1155/2017/9175342.

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Wind turbine (WT) blade is one of the most important components in WTs, as it is the key component for receiving wind energy and has direct influence on WT operation stability. As the size of modern turbine blade increases, condition monitoring and maintenance of blades become more important. Strain detection is one of the most effective methods to monitor blade conditions. In this paper, a distributed fiber-optic strain sensor is used for blade monitoring. Preliminary experimental tests have been carried out over a 14 m long WT composite blade, demonstrating the possibility of performing distributed strain and vibration measurements.

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Fan, Xinyu, Bin Wang, Guangyao Yang, and Zuyuan He. "Slope-Assisted Brillouin-Based Distributed Fiber-Optic Sensing Techniques." Advanced Devices & Instrumentation 2021 (July 14, 2021): 1–16. http://dx.doi.org/10.34133/2021/9756875.

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Brillouin-based fiber-optic sensing has been regarded as a powerful distributed measurement tool for monitoring the conditions of modern large civil and geotechnical structures, since it provides continuous environmental information (e.g., temperature and strain) along the whole fiber used for sensing applications. In the past few decades, great research efforts were devoted to improve its performance in terms of measurement range, spatial resolution, measurement speed, sensitivity, and cost-effectiveness, of which the slope-assisted measurement scheme, achieved by exploiting the linear slope of the Brillouin gain spectrum (BGS), have paved the way for dynamic distributed fiber-optic sensing. In this article, slope-assisted Brillouin-based distributed fiber-optic sensing techniques demonstrated in the past few years will be reviewed, including the slope-assisted Brillouin optical time-domain analysis/reflectometry (SA-BOTDA/SA-BOTDR), the slope-assisted Brillouin dynamic grating (BDG) sensor, and the slope-assisted Brillouin optical correlation domain analysis/reflectometry (SA-BOCDA/SA-BOCDR). Avenues for future research and development of slope-assisted Brillouin-based fiber-optic sensors are also prospected.

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Bassil, Antoine, Xavier Chapeleau, Dominique Leduc, and Odile Abraham. "Concrete Crack Monitoring Using a Novel Strain Transfer Model for Distributed Fiber Optics Sensors." Sensors 20, no. 8 (April 15, 2020): 2220. http://dx.doi.org/10.3390/s20082220.

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In this paper, we study the strain transfer mechanism between a host material and an optical fiber. A new analytical model handling imperfect bonding between layers is proposed. A general expression of the crack-induced strain transfer from fractured concrete material to optical fiber is established in the case of a multilayer system. This new strain transfer model is examined through performing wedge splitting tests on concrete specimens instrumented with embedded and surface-mounted fiber optic cables. The experimental results showed the validity of the crack-induced strain expression fitted to the distributed strains measured using an Optical Backscattering Reflectometry (OBR) system. As a result, precise estimations of the crack openings next to the optical cable location were achieved, as well as the monitoring of the optical cable response through following the strain lag parameter.

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Kageyama, Kazuro, Toshio Suzuki, Hideaki Murayama, Isao Kimpara, Isamu Ohsawa, and Jun Takahashi. "Strain Measurement with Multi-Locational, Regional and Distributed Fiber-Optic Sensors." Journal of the Society of Naval Architects of Japan 1997, no. 182 (1997): 579–87. http://dx.doi.org/10.2534/jjasnaoe1968.1997.182_579.

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MURAYAMA, Hideaki, Kazuro KAGEYAMA, and Hirotaka IGAWA. "J044021 Strain Measurements inside Bonded Layer by Distributed Fiber-Optic Sensors." Proceedings of Mechanical Engineering Congress, Japan 2011 (2011): _J044021–1—_J044021–3. http://dx.doi.org/10.1299/jsmemecj.2011._j044021-1.

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Liu, Yunpeng, Yuan Tian, Xiaozhou Fan, Yanan Bu, Peng He, Huan Li, Junyi Yin, and Xiaojiang Zheng. "A Feasibility Study of Transformer Winding Temperature and Strain Detection Based on Distributed Optical Fibre Sensors." Sensors 18, no. 11 (November 14, 2018): 3932. http://dx.doi.org/10.3390/s18113932.

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The temperature distribution and deformation of the transformer windings cannot be measured in a distributed manner by the traditional method and failure location cannot be performed. To solve these problems, we present a transformer winding temperature and strain based on a distributed optical fibre sensing detection method. The design of the optical fibre winding composite model is developed and simulated winding temperature rise test and local deformation test distinguish between measuring the winding temperature and the strain curve. The test results show that the distributed optical fibre can transmit wire strain efficiently. Optical fibres, in the process of winding, have a certain pre-stress. Using the Brillouin–Raman joint measuring method, one can effectively extract the optical fibre temperature and strain information and measure the length of the winding direction of the temperature and strain distribution curve to a temperature measurement precision of ±2 °C and strain detection accuracy of ±50 με. The system can carry out local hot spot and deformation localisation, providing new ideas for the transformer winding state monitoring technology.

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Guillen Bonilla, Guillen Bonilla, Rodríguez Betancourtt, Casillas Zamora, Sánchez Morales, Gildo Ortiz, and Guillen Bonilla. "Signal Analysis, Signal Demodulation and Numerical Simulation of a Quasi-Distributed Optical Fiber Sensor Based on FDM/WDM Techniques and Fabry-Pérot Interferometers." Sensors 19, no. 8 (April 12, 2019): 1759. http://dx.doi.org/10.3390/s19081759.

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In civil engineering quasi-distributed optical fiber sensors are used for reinforced concrete monitoring, precast concrete monitoring, temperature monitoring, strain monitoring and temperature/strain monitoring. These quasi-distributed sensors necessarily apply some multiplexing technique. However, on many occasions, two or more multiplexing techniques are combined to increase the number of local sensors and then the cost of each sensing point is reduced. In this work, a signal analysis and a new signal demodulation algorithm are reported for a quasi-distributed optic fiber sensor system based on Frequency Division Multiplexing/Wavelength Division Multiplexing (FDM/WDM) and low-precision Fabry-Pérot interferometers. The mathematical analysis and the new algorithm optimize its design, its implementation, improve its functionality and reduce the cost per sensing point. The analysis was corroborated by simulating a quasi-distributed sensor in operation. Theoretical analysis and numerical simulation are in concordance. The optimization considers multiplexing techniques, signal demodulation, physical parameters, system noise, instrumentation, and detection technique. Based on our analysis and previous results reported, the optical sensing system can have more than 4000 local sensors and it has practical applications in civil engineering.

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Coricciati, Angela, Ilaria Ingrosso, Antonio Paolo Sergi, and Alessandro Largo. "Application of Smart FRP Devices for the Structural Health Monitoring of Heritage Buildings - A Case Study: The Monastery of Sant’Angelo d’Ocre." Key Engineering Materials 747 (July 2017): 448–55. http://dx.doi.org/10.4028/www.scientific.net/kem.747.448.

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The preservation of heritage buildings requires multidisciplinary skills ranging from materials and seismic design up to structural monitoring.One of the most interesting innovative solution that is being developing in the last years is based on smart FRP (FRP – Fibre Reinforced Polymer) devices, which can combine contemporary reinforcing and monitoring purposes. The use of composite materials has many advantages in comparison with traditional retrofitting techniques, such as low weight, high strength-to-weight ratio, ease of handling, drapability, speed of installation, low thickness and visual impact. At the same time, monitoring the structure during its lifetime (strain, cracks, temperature, etc.) and evaluating its in-service integrity, in order to predict possible anomalous situations, can be achieved by the combination of FRP materials and embedded fibre optic sensors into a smart FRP device, suitable for both reinforcing and monitoring purposes. Optical fibres can provide reliable measurement even in harsh environment, as they are chemically durable, corrosion resistant, stable and insensitive to external electromagnetic and environmental perturbations, allowing long distances signal transmission and several measures in different points along the same optical fibre (multiplexing). Furthermore, the embedding into composite material will preserve them from rupture during handling and installation.In the present work, the application of smart FRP devices for the structural health monitoring of the Monastery in Sant’Angelo d’Ocre, L’Aquila, performed in the framework of the national project PROVACI, is reported.Six Smart Patches, consisting of FRP reinforcing sheet with point FBG (Fibre Bragg Grating) sensors embedded were applied on the extrados of two different vaults, while four Smart Rebars, consisting in FRP pultruded bars with distributed optical fibres sensors embedded, were installed in four buttress of one same vault. All the smart FRP devices, after being cabled, have been connected to the relative control units (BraggMETER from Fibersensing for FBG sensors and OBR4600 control unit of Luna Technologies for the distributed optical sensors) connected with a remote server for on-line remote monitoring.Before the installation, the Smart FRP devices have been preliminary calibrated and tested in the laboratory in terms of mechanical properties, strain sensitivity and accelerated aging.The monitoring on the Monastery has been conducted for five months, showing the reliability of entire system and of the signal transmitted by each sensor over the time.

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Ding, Ke Qin, Li Qi Yi, and Cai Fu Qian. "The Deformation Detection Method for the Buried Pipeline Based on Distributed Fiber Optic Sensor." Applied Mechanics and Materials 330 (June 2013): 444–49. http://dx.doi.org/10.4028/www.scientific.net/amm.330.444.

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The deformation of the long-distance pipeline often happen due to the Soil collapse, gulch and the settlement of the foundation etc. The large deformation is easy to cause the fracture of the long-distance pipeline. Hence, the deformation detection is of very important to the pipeline safety. In this paper, a method for deformation calculation of the long-distance pipeline is presented based on the relation expression brtween the deformation and the strain of the long-distance pipelien. Through the measured strain, the deformation is easy to be calculated. The strains can be obtained through the FBG sensors or distributed fiber optic sensors. The deformation detection method proposed in the papaer provides the basis of the long-distance pipeline risk management.

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Weisbrich, Martin, Klaus Holschemacher, and Thomas Bier. "Comparison of different fiber coatings for distributed strain measurement in cementitious matrices." Journal of Sensors and Sensor Systems 9, no. 2 (July 8, 2020): 189–97. http://dx.doi.org/10.5194/jsss-9-189-2020.

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Abstract. Distributed fiber optic strain measurement based on Rayleigh scattering has recently become increasingly popular in automotive and mechanical engineering for strain monitoring and in the construction industry, especially structural health monitoring. This technology enables the monitoring of strain along the entire fiber length. This article addresses integrating optical fibers of different coatings into the concrete matrix to measure the shrinkage deformations. However, previous studies do not give a clear statement about the strain transfer losses of fiber optic sensors in this application. In this context, three different coating types were investigated regarding their strain transfer. The fibers were integrated into fine-grained concrete prisms, and the shrinkage strain was compared with a precise dial gauge. The analysis shows a high correlation between the reference method and the fiber measurement, especially with the ORMOCER® coating. The acrylate coating used is also consistent in the middle area of the specimen but requires a certain strain introduction length to indicate the actual strain. The main result of this study is a recommendation for fiber coatings for shrinkage measurement in fine-grain concretes using the distributed fiber optic strain measurement. In addition, the advantages and disadvantages of the measurement method are presented.

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Grefe, Hinrich, Dennis Weiser, Maja Wanda Kandula, and Klaus Dilger. "Deformation measurement within adhesive bonds of aluminium and CFRP using advanced fibre optic sensors." Manufacturing Review 7 (2020): 14. http://dx.doi.org/10.1051/mfreview/2020011.

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Monitoring the deformation within an adhesive joint during the curing cycle provides valuable information regarding the build-up of thermal strain and stress. Distributed fibre optic sensors are very useful for spatial continuous measurements of deformation or temperature. Integrated into a hybrid joint, the thermal curing process of the adhesive can be monitored. This detailed insight into the joint helps to understand the deformation and thereby also the resulting stress. Analysing the deformation process establishes the foundation to adapt techniques to reduce the thermally induced deformation and thereby the resulting stress.

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Fernandez, Ignasi, Carlos G. Berrocal, and Rasmus Rempling. "Long-Term Performance of Distributed Optical Fiber Sensors Embedded in Reinforced Concrete Beams under Sustained Deflection and Cyclic Loading." Sensors 21, no. 19 (September 22, 2021): 6338. http://dx.doi.org/10.3390/s21196338.

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This paper explores the performance of distributed optical fiber sensors based on Rayleigh backscattering for the monitoring of strains in reinforced concrete elements subjected to different types of long-term external loading. In particular, the reliability and accuracy of robust fiber optic cables with an inner steel tube and an external protective polymeric cladding were investigated through a series of laboratory experiments involving large-scale reinforced concrete beams subjected to either sustained deflection or cyclic loading for 96 days. The unmatched spatial resolution of the strain measurements provided by the sensors allows for a level of detail that leads to new insights in the understanding of the structural behavior of reinforced concrete specimens. Moreover, the accuracy and stability of the sensors enabled the monitoring of subtle strain variations, both in the short-term due to changes of the external load and in the long-term due to time-dependent effects such as creep. Moreover, a comparison with Digital Image Correlation measurements revealed that the strain measurements and the calculation of deflection and crack widths derived thereof remain accurate over time. Therefore, the study concluded that this type of fiber optic has great potential to be used in real long-term monitoring applications in reinforced concrete structures.

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Murayama, Hideaki, Kazuro Kageyama, Isamu Ohsawa, Makoto Kanai, Kiyhoshi Uzawa, and Tsuyoshi Matsuo. "Development of Smart Composite Panel with Optical Fiber Sensors." Key Engineering Materials 297-300 (November 2005): 659–64. http://dx.doi.org/10.4028/www.scientific.net/kem.297-300.659.

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We have developed a novel fiber-optic vibration sensors and applied commercially available strain and temperature sensors to health monitoring of composite structures. In this study, we constructed an optical fiber network integrating four types of optical fiber sensor into a carbon reinforced plastic (CFRP) panel. These four sensors were the vibration sensor developed by our laboratory, two distributed sensors based on Brillouin and Raman backscattering and Fiber Bragg Grating (FBG) sensors. By dealing the data obtained from the measurement systems corresponding to these four sensors, strain/stress and temperature distributions throughout the panel can be monitored. Vibration and elastic waves transmitting on the panel are also detected at several sensing points. Furthermore, we will be able to determine damage locations and modes by processing the wave signals. To make the panel with the optical fiber sensor network more sensitive and smarter, we are developing some techniques that can improve the performance of the sensors and can assess the structural integrity by analyzing measurement results. In this paper, the development of the first generation of our smart composite panel with the optical fiber sensors is described and the techniques making the panel more sensitive and smarter are also described.

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Enckell, Merit, Branko Glisic, Frank Myrvoll, and Benny Bergstrand. "Evaluation of a large-scale bridge strain, temperature and crack monitoring with distributed fibre optic sensors." Journal of Civil Structural Health Monitoring 1, no. 1-2 (March 3, 2011): 37–46. http://dx.doi.org/10.1007/s13349-011-0004-x.

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Hoult, Neil A., Omurden Ekim, and Ryan Regier. "Damage/Deterioration Detection for Steel Structures Using Distributed Fiber Optic Strain Sensors." Journal of Engineering Mechanics 140, no. 12 (December 2014): 04014097. http://dx.doi.org/10.1061/(asce)em.1943-7889.0000812.

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Tan, Xiao, Yi Bao, Qinghua Zhang, Hani Nassif, and Genda Chen. "Strain transfer effect in distributed fiber optic sensors under an arbitrary field." Automation in Construction 124 (April 2021): 103597. http://dx.doi.org/10.1016/j.autcon.2021.103597.

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Currenti, Gilda, Philippe Jousset, Rosalba Napoli, Charlotte Krawczyk, and Michael Weber. "On the comparison of strain measurements from fibre optics with a dense seismometer array at Etna volcano (Italy)." Solid Earth 12, no. 4 (April 28, 2021): 993–1003. http://dx.doi.org/10.5194/se-12-993-2021.

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Abstract. We demonstrate the capability of distributed acoustic sensing (DAS) to record volcano-related dynamic strain at Etna (Italy). In summer 2019, we gathered DAS measurements from a 1.5 km long fibre in a shallow trench and seismic records from a conventional dense array comprised of 26 broadband sensors that was deployed in Piano delle Concazze close to the summit area. Etna activity during the acquisition period gives the extraordinary opportunity to record dynamic strain changes (∼ 10−8 strain) in correspondence with volcanic events. To validate the DAS strain measurements, we explore array-derived methods to estimate strain changes from the seismic signals and to compare with strain DAS signals. A general good agreement is found between array-derived strain and DAS measurements along the fibre optic cable. Short wavelength discrepancies correspond with fault zones, showing the potential of DAS for mapping local perturbations of the strain field and thus site effect due to small-scale heterogeneities in volcanic settings.

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Chapeleau, Xavier, and Antoine Bassil. "A General Solution to Determine Strain Profile in the Core of Distributed Fiber Optic Sensors under Any Arbitrary Strain Fields." Sensors 21, no. 16 (August 11, 2021): 5423. http://dx.doi.org/10.3390/s21165423.

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Despite recent publications, the strain transfer in distributed optical fiber sensors is still often overlooked and poorly understood. In the first part of this paper, strain transfer is shown to be driven by a second-order differential equation, whether the optical fiber is embedded into the host material or surface-mounted. In this governing equation, only the value of a key parameter, called strain lag parameter, varies according to the attachment configuration and the type of optical fiber used as a sensor. Then, a general solution of the governing equation is proposed. It is an analytical expression established from new boundary conditions that are more adequate than those used previously in the literature and allows the determination of the strain profile in the core of a distributed optical fiber sensor under any arbitrary strain fields. This general solution has been validated by two experiments presented in the third part of the paper. A very good agreement between the analytical solutions and measured strain profiles using a high spatial resolution optical interrogator for both uniform and non-uniform strain fields has been obtained. These results highlight the importance of the strain lag parameter which must be taken into account for a correct interpretation of measurements, especially in the case of important strain gradients.

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Mizutani, Tadahito, Takafumi Nishi, and Nobuo Takeda. "Distributed Fiber Optic Strain Sensing with Embedded Small-Diameter Optical Fibers in CFRP Laminate." Key Engineering Materials 334-335 (March 2007): 1013–16. http://dx.doi.org/10.4028/www.scientific.net/kem.334-335.1013.

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Although demand for composite structures rapidly increase due to the advantages in weight, there are few effective assessment techniques to enable the quality control and guarantee the durability. In particular, an invisible microscopic damage detection technology is highly required because damages such as transverse cracks, debondings, or delaminations can lead to the critical failure of the structures. Among many non-destructive evaluation (NDE) methods for composite structures, fiber optic sensors are especially attractive due to the high sensitivity, the lightweight, and the small size. In the current trend of the structural health monitoring technology, fiber Bragg gratings (FBG) sensors are frequently used as strain or temperature sensors, and Brillouin scattering sensors are also often used for a long distance distributed measurement. The Brillouin distributed sensors can measure strain over a distance of 10km while a spatial resolution was limited to 1m. Some novel sensing method is proposed to improve the spatial resolution. The pulse-prepump Brillouin optical time domain analysis (PPP-BOTDA) is one of the latest distributed sensing applications with a cm-order high spatial resolution. The PPP-BOTDA commercial product has the spatial resolution of 10cm, and can measure the strain with a precision of ±25og. This precision, however, can be achieved by using conventional single-mode optical fibers. In our research, small-diameter optical fibers with a cladding diameter of 40om were embedded in the CFRP laminate to avoid the deterioration of the CFRP mechanical properties. Thus, in order to verify the performance of PPP-BOTDA, the distributed strain measurement was conducted with the small-diameter optical fibers embedded in the CFRP laminate.

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SHIBAYAMA, Atsushi. "QUASI-CONTINUOUS STRAIN MEASUREMENT METHOD OF REINFORCED CONCRETE MEMBER USING DISTRIBUTED FIBER-OPTIC STRAIN SENSORS." AIJ Journal of Technology and Design 26, no. 63 (June 20, 2020): 543–48. http://dx.doi.org/10.3130/aijt.26.543.

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Hu, Leijun, Liwen Sheng, Jisong Yan, Ligong Li, Ming Yuan, Fude Sun, Fushun Nian, et al. "Simultaneous Measurement of Distributed Temperature and Strain through Brillouin Frequency Shift Using a Common Communication Optical Fiber." International Journal of Optics 2021 (April 29, 2021): 1–6. http://dx.doi.org/10.1155/2021/6610674.

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A multiparameter Brillouin fiber-optic sensor for distributed strain and temperature information measuring based on spontaneous scattering in a common communication optical fiber (the G. 652. D commercial fiber) is presented and experimentally demonstrated. Benefiting from the difference of the temperature and strain sensitivity from different Brillouin peaks with different acoustic modes, our proposed sensing configuration can be used to distinguish ambient temperature and applied strain at the same time, which is an excellent candidate to address the problem of cross-sensitivity in the classical Brillouin system. In the experimental section, using a 21.8 km sensing length of communication optical fiber, a temperature accuracy of 1.13°C and a strain accuracy of 21.46 με are obtained simultaneously. Considering the performance we achieved now, the proposed innovation and experimental setup will have some potential applications in the field of fiber sensors.

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Jothibasu, Sasi, Yang Du, Sudharshan Anandan, Gurjot S. Dhaliwal, Rex E. Gerald, Steve E. Watkins, K. Chandrashekhara, and Jie Huang. "Spatially continuous strain monitoring using distributed fiber optic sensors embedded in carbon fiber composites." Optical Engineering 58, no. 07 (February 5, 2019): 1. http://dx.doi.org/10.1117/1.oe.58.7.072004.

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Suzhen Li and Zhishen Wu. "Modal Analysis on Macro-strain Measurements from Distributed Long-gage Fiber Optic Sensors." Journal of Intelligent Material Systems and Structures 19, no. 8 (October 17, 2007): 937–46. http://dx.doi.org/10.1177/1045389x07082477.

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Murayama, Hideaki, Kazuro Kageyama, Kiyoshi Uzawa, Kohei Ohara, and Hirotaka Igawa. "Strain monitoring of a single-lap joint with embedded fiber-optic distributed sensors." Structural Health Monitoring: An International Journal 11, no. 3 (September 12, 2011): 325–44. http://dx.doi.org/10.1177/1475921711419994.

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Cocking, Sam, Haris Alexakis, and Matthew DeJong. "Distributed dynamic fibre-optic strain monitoring of the behaviour of a skewed masonry arch railway bridge." Journal of Civil Structural Health Monitoring 11, no. 4 (June 1, 2021): 989–1012. http://dx.doi.org/10.1007/s13349-021-00493-w.

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AbstractSkewed masonry arch railway bridges are common, yet their structural behaviour under typical working loads, along with gradual changes in behaviour due to degradation, can be difficult to determine. This paper aims to address this problem through detailed monitoring of a damaged, skewed masonry arch railway bridge in the UK, which was recently repaired. A comprehensive Structural Health Monitoring system was installed, including an array of fibre-optic Fibre Bragg Grating (FBG) sensors to provide distributed sensing data across a large portion of the bridge. This FBG monitoring data is used, in this paper, to investigate the typical dynamic structural response of the skewed bridge in detail, and to quantify the sensitivity of this response to a range of variables. It is observed that the dynamic bridge response is sensitive to the time of day, which is a proxy for passenger loading, to the train speed, and to temperature. It is also observed that the sensitivity of the response to these variables can be local, in that the response can differ throughout the bridge and be affected by existing local damage. Identifying these trends is important to distinguish additional damage from other effects. The results are also used to evaluate some typical assumptions regarding bridge behaviour, which may be of interest to asset engineers working with skewed masonry arch bridges.

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Monsberger, Christoph M., and Werner Lienhart. "Distributed Fiber Optic Shape Sensing of Concrete Structures." Sensors 21, no. 18 (September 11, 2021): 6098. http://dx.doi.org/10.3390/s21186098.

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Civil structural health monitoring (CSHM) has become significantly more important within the last decades due to rapidly growing construction volume worldwide as well as aging infrastructure and longer service lifetimes of the structures. The utilization of distributed fiber optic sensing (DFOS) allows the assessment of strain and temperature distributions continuously along the installed sensing fiber and is widely used for testing of concrete structures to detect and quantify local deficiencies like cracks. Relations to the curvature and bending behavior are however mostly excluded. This paper presents a comprehensive study of different approaches for distributed fiber optic shape sensing of concrete structures. Different DFOS sensors and installation techniques were tested within load tests of concrete beams as well as real-scale tunnel lining segments, where the installations were interrogated using fully-distributed sensing units as well as by fiber Bragg grating interrogators. The results point out significant deviations between the capabilities of the different sensing systems, but demonstrate that DFOS can enable highly reliable shape sensing of concrete structures, if the system is appropriately designed depending on the CSHM application.

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Pevzner, Roman, Boris Gurevich, Anastasia Pirogova, Konstantin Tertyshnikov, and Stanislav Glubokovskikh. "Repeat well logging using earthquake wave amplitudes measured by distributed acoustic sensors." Leading Edge 39, no. 7 (July 2020): 513–17. http://dx.doi.org/10.1190/tle39070513.1.

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Well-based technologies for seismic subsurface monitoring increasingly utilize fiber-optic cables installed in boreholes as distributed acoustic sensing (DAS) systems. A DAS cable allows measuring linear strain of the fiber and can serve as an array of densely spaced seismic receivers. The strain amplitudes recorded by the DAS cable depend on the near-well formation properties (the softer the medium, the larger the strain). Thus, these properties can be estimated by measuring relative variations of the amplitudes of seismic waves propagating along the well. An advantage of such an approach to subsurface characterization and monitoring is that no active seismic source is required. Passive sources such as earthquakes can be utilized. A synthetic data example demonstrates viability of the approach for monitoring of small-scale CO2 injection into an aquifer. Two field DAS data examples based on signal recordings from several distant earthquakes show that the relevant properties of the near-well formation can be estimated with an accuracy of approximately 5%.

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Pan’kov, A. A. "Diagnostics of impregnation defects of reinforcing filaments of polymer composite with built-in fibre-optic sensor with distributed Bragg grating." PNRPU Mechanics Bulletin, no. 3 (December 15, 2020): 60–72. http://dx.doi.org/10.15593/perm.mech/2020.3.07.

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Mathematical model of unidirectional fibrous polymer composite material with optical fiber sensor built into reinforcing fiber (filament of elementary fibers) with distributed Bragg grating is developed in order to diagnoste defects of filament impregnation - finding probability of impregnation defect as relative length of local sections of filament without impregnation, i.e. without filling binder of space between its elementary fibers. The technique of digital processing of reflection spectrum according to the solution of the integral Fredholm equation of the 1st kind is used in order to find the desired informative function of density of distribution of axial strains along the length of the sensitive section of the fibre-optic sensor. The approach assumes that the optical fiber sensor is embedded in the composite material at the stage of its manufacture, wherein the low-reflective nature of the sensitive portion of the optical fiber allows linear summation of reflection coefficients from its various local portions regardless of their mutual positions. Algorithm of numerical processing of strain distribution density function is developed for finding of sought probability of presence of impregnation defects along filament length. It has been revealed that the distribution density function has pronounced informative pulses, from the location and value of which the sought-after values of probability of presence of impregnation defects along the length of the filament can be found. The results of diagnostics of different values of the sought probability of the filament impregnation defect are presented based on the results of numerical simulation of the measured reflection spectra and the sought function of strain distribution density along the length of the sensitive section of the optical fiber sensor at different values of the volume fraction of the filaments, combinations of transverse and longitudinal loads of the representative domain of the unidirectional fibrous composite material in comparison with graphs for the case without load.

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Murayama, Hideaki, Daichi Wada, and Hirotaka Igawa. "Structural health monitoring by using fiber-optic distributed strain sensors with high spatial resolution." Photonic Sensors 3, no. 4 (October 8, 2013): 355–76. http://dx.doi.org/10.1007/s13320-013-0140-5.

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Journal articles on the topic 'Distributed fibre optic strain sensors'

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