Thematische Bibliographien / Brillouin optical time domain analysis (BOTDA) / Zeitschriftenartikel

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Zeitschriftenartikel zum Thema „Brillouin optical time domain analysis (BOTDA)“

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Veröffentlicht am 4. Juni 2021

Zuletzt aktualisiert am 1. Februar 2022

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Barkov, Fedor L., Yuri A. Konstantinov, and Anton I. Krivosheev. "A Novel Method of Spectra Processing for Brillouin Optical Time Domain Reflectometry." Fibers 8, no. 9 (2020): 60. http://dx.doi.org/10.3390/fib8090060.

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A new method of Brillouin spectra post-processing, which could be applied in modern distributed optical sensors: Brillouin optical time domain analyzers/reflectometers (BOTDA/BOTDR), has been demonstrated. It operates by means of the correlation analysis performed with special technique («backward-correlation»). It does not need any additional data for time or space averaging and operates with the single spectrum only. We have simulated the method accuracy dependence on signal-to-noise ratio (SNR) and other parameters. It is shown that the new method produces better results at low SNRs than conventional technique, based on finding of Brillouin spectrum maximum, do. These results are in a good agreement with the experiment. Finally, we have estimated the performance of the new method for its application in polarization-BOTDA set-up for a polarization maintaining (PM) fiber modal birefringence distributed study.

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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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Wei, Haoyu, Yongjun Wang, Qiming Wang, et al. "New BFS Retrieval Technique for Brillouin Optical Time Domain Analysis Sensor System." Electronics 10, no. 11 (2021): 1334. http://dx.doi.org/10.3390/electronics10111334.

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In this paper, Gaussian smoothing (GS), non-local means (NLM), and Quaternion Wavelet Transform (QWT) have been described in detail. Furthermore, a Brillouin optical time domain analysis (BOTDA) experimental system was built to verify the denoising algorithms. The principal and experimental analyses show that the QWT algorithm is a more efficient image denoising method. The results indicate that the GS algorithm can obtain the highest signal-to-noise ratio (SNR), frequency uncertainty, and Brillouin frequency shift (BFS) accuracy, and can be executed in an imperceptible time, but the GS algorithm has the lowest spatial resolution. After being denoised by using NLM algorithm, although SNR, frequency uncertainty, BFS accuracy, and spatial resolution significantly improved, it takes 40 min to implement the NLM denoising algorithm for a BGS image with 200 × 100,000 points. Processed by the QWT denoising algorithm, although SNR increases to 17.26 dB and frequency uncertainty decreases to 0.24 MHz, a BFS accuracy of only 0.2 MHz can be achieved. Moreover, the spatial resolution is 3 m, which is not affected by the QWT denoising algorithm. It takes less than 32 s to denoise the same raw BGS data. The QWT image denoising technique is suitable for BGS data processing in the BOTDA sensor system.

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Horiguchi, Tsuneo, Yuki Masui, and Mohd Zan. "Analysis of Phase-Shift Pulse Brillouin Optical Time-Domain Reflectometry." Sensors 19, no. 7 (2019): 1497. http://dx.doi.org/10.3390/s19071497.

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Distributed strain and temperature can be measured by using local Brillouin backscatter in optical fibers based on the strain and temperature dependence of the Brillouin frequency shift. The technique of analyzing the local Brillion backscatter in the time domain is called Brillouin optical time domain reflectometry (BOTDR). Although the best spatial resolution of classic BOTDR remains at around 1 m, some recent BOTDR techniques have attained as high as cm-scale spatial resolution. Our laboratory has proposed and demonstrated a high-spatial-resolution BOTDR called phase-shift pulse BOTDR (PSP-BOTDR), using a pair of probe pulses modulated with binary phase-shift keying. PSP-BOTDR is based on the cross-correlation of Brillouin backscatter and on the subtraction of cross-correlations obtained from the Brillouin scatterings evoked by each phase-modulated probe pulse. Although PSP-BOTDR has attained 20-cm spatial resolution, the spectral analysis method of PSP-BOTDR has not been discussed in detail. This article gives in-depth analysis of the Brillouin backscatter and the correlations of the backscatters of the PSP-BOTDR. Based on the analysis, we propose new spectral analysis methods for PSP-BOTDR. The analysis and experiments show that the proposed methods give better frequency resolution than before.

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Zhang, Hongying, Dengwang Zhou, Benzhang Wang, et al. "Recent Progress in Fast Distributed Brillouin Optical Fiber Sensing." Applied Sciences 8, no. 10 (2018): 1820. http://dx.doi.org/10.3390/app8101820.

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Brillouin-based optical fiber sensing has been regarded as a good distributed measurement tool for the modern large geometrical structure and the industrial facilities because it can demodulate the distributed environment information (e.g., temperature and strain) along the sensing fiber. Brillouin optical time domain analysis (BOTDA), which is an excellent and attractive scheme, has been widely developed thanks to its high performance in a signal-to-noise ratio, a spatial resolution, and sensing distance. However, the sampling rate of the classical BOTDA is severely limited by several factors (especially the serially frequency-sweeping process) so that it cannot be suitable for the quickly distributed measurement. In this work, we summarize some promising breakthroughs about the fast BOTDA, which can be named as an optical frequency comb technique, an optical frequency-agile technique, a slope-assisted technique, and an optical chirp chain technique.

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Azad, Abul Kalam. "Effects of Pump-Pulse Width and Temperature on Experimental Brillouin Gain Spectrum Obtained from Brillouin Optical Time-Domain Analysis Sensors." Bangladesh Journal of Physics 27, no. 1 (2020): 69–80. http://dx.doi.org/10.3329/bjphy.v27i1.49727.

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In this paper, the characteristics of Brillouin gain spectrum (BGS) obtained from a Brillouin optical time-domain analysis (BOTDA) sensor are investigated and analyzed experimentally. The measured BGSs obtained for various pump-pulse widths and temperatures are fitted with different spectrum profiles using nonlinear least-squares curve fitting technique. The fitting performances of used profiles are presented and analyzed. Based on such performances, the proper spectrum profile to be used in the fitting process is determined and used to extract key parameters of the measured BGSs accurately. The variations of such key parameters with pump-pulse widths and temperatures are also investigated and analyzed. The results reveal that pump-pulse widths and temperatures have significant effects on the extracted key parameters of the measured BGSs obtained from BOTDA sensors. Bangladesh Journal of Physics, 27(1), 69-80, June 2020

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Ismail, Awang, Qurratu Aini binti Siat @ Sirat, Azman bin Kassim, and Hisham bin Mohamad. "Strain and temperature calibration of Brillouin Optical Time Domain Analysis (BOTDA) sensing system." IOP Conference Series: Materials Science and Engineering 527 (May 29, 2019): 012028. http://dx.doi.org/10.1088/1757-899x/527/1/012028.

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Nordin, Nur Dalilla, Mohd Saiful Dzulkefly Zan, and Fairuz Abdullah. "Comparative Analysis on the Deployment of Machine Learning Algorithms in the Distributed Brillouin Optical Time Domain Analysis (BOTDA) Fiber Sensor." Photonics 7, no. 4 (2020): 79. http://dx.doi.org/10.3390/photonics7040079.

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This paper demonstrates a comparative analysis of five machine learning (ML) algorithms for improving the signal processing time and temperature prediction accuracy in Brillouin optical time domain analysis (BOTDA) fiber sensor. The algorithms analyzed were generalized linear model (GLM), deep learning (DL), random forest (RF), gradient boosted trees (GBT), and support vector machine (SVM). In this proof-of-concept experiment, the performance of each algorithm was investigated by pairing Brillouin gain spectrum (BGS) with its corresponding temperature reading in the training dataset. It was found that all of the ML algorithms have significantly reduced the signal processing time to be between 3.5 and 655 times faster than the conventional Lorentzian curve fitting (LCF) method. Furthermore, the temperature prediction accuracy and temperature measurement precision made by some algorithms were comparable, and some were even better than the conventional LCF method. The results obtained from the experiments would provide some general idea in deploying ML algorithm for characterizing the Brillouin-based fiber sensor signals.

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Pan, Qiuyi, Xincheng Huang, Rui Min, and Weiping Liu. "Fast Frame Synchronization Design and FPGA Implementation in SF-BOTDA." Photonics 7, no. 1 (2020): 17. http://dx.doi.org/10.3390/photonics7010017.

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To address the issues of high time consumption of frame synchronization involved in a scanning-free Brillouin optical time-domain analysis (SF-BOTDA) system, a fast frame synchronization algorithm based on incremental updating was proposed. In comparison to the standard frame synchronization algorithm, the proposed one significantly reduced the processing time required for the BOTDA system frame synchronization by about 98%. In addition, to further accelerate the real-time performance of frame synchronization, a field programmable gate array (FPGA) hardware implementation architecture based on parallel processing and pipelining mechanisms was also proposed. Compared with the software implementation, it further raised the processing speed by 13.41 times. The proposed approach could lay a foundation for the BOTDA system in the field with the associated high real-time requirements.

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Li, Yi, Ting Wang, Hong Wu Gao, Sheng Yu, Yuan Lin Chen, and Bo Wen An. "Development and Application of Composite Submarine Cable Online Monitoring System." Applied Mechanics and Materials 552 (June 2014): 139–44. http://dx.doi.org/10.4028/www.scientific.net/amm.552.139.

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This paper focuses on the design and application of the composite submarine cable online monitoring system based on Brillouin optical time domain analysis (BOTDA). It introduces two concepts of the system: the BOTDA technology and the finite element modeling method. Using ideas of modular design, the team developed the PC software on LabWindows/CVI. At the end of the paper, it describes the application of the online monitoring system, and then analyzes the data returned from the system.

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Xiong, Ju Hua, Lu Jie Wang, Wen Yong He, and Hao Feng Xing. "Application of BOTDA in Mass Concrete Temperature Monitoring." Applied Mechanics and Materials 238 (November 2012): 346–49. http://dx.doi.org/10.4028/www.scientific.net/amm.238.346.

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In order to study the application of distributed optical fiber in temperature monitoring of mass concrete, monitoring instruments are embedded in pile cap to carry out the field experiment. The results show that the distributed temperature fiber which is based on brillouin optical time-domain analysis (BOTDA) has the superiority of anti-jamming, corrosion resistance, high precision and continuous measurement. It can accurately reflect the temperature change, effectively guide the construction, and play a positive role in preventing the emergence of concrete cracks caused by temperature change. What’s more, optical fiber has small volume and less influence on engineering, which make it have a good application prospect.

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Ding, Yong, Feng Xiao, Weiwei Zhu, and Tao Xia. "Structural Health Monitoring of the Scaffolding Dismantling Process of a Long-Span Steel Box Girder Viaduct Based on BOTDA Technology." Advances in Civil Engineering 2019 (September 4, 2019): 1–7. http://dx.doi.org/10.1155/2019/5942717.

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In this study, a distributed optical fiber sensing technique based on Brillouin optical time-domain analysis (BOTDA) is used to construct a complete bridge health monitoring system by continuously laying distributed sensing fiber lines in a steel box girder. The bridge scaffolding dismantling process is monitored to study the variation of the strain distribution. Additionally, a bridge finite element model is built to simulate the bridge scaffolding removed condition, and the strain distribution of the long-span steel box girder viaduct after scaffolding dismantling is compared with the measured values. This study provides a reference for monitoring the scaffolding dismantling process based on BOTDA technology.

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Wu, Yichang, Chengkun Yang, Jingshun Pan, Qi Sui, and Dawei Wang. "Ultrafast Resolution-Enhanced Digital Optical Frequency Comb-Based BOTDA with Pump Pulse Array Coding." Sensors 20, no. 22 (2020): 6411. http://dx.doi.org/10.3390/s20226411.

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In this letter, a resolution enhancement and signal-to-noise ratio (SNR) improvement scheme for digital optical frequency comb (DOFC)-based Brillouin optical time-domain analysis (BOTDA) ultrafast distributed sensing employing a pump pulse array is proposed. Based on the properties of the time-invariant linear system and the cyclic revolution theorem, experimental results indicate that its spatial resolution reaches 10.24 m while the frequency uncertainty is below 2 MHz over a 9.5 km fiber. Moreover, the response time is only 209.6 μs and the temperature measurement error is less than 0.52 °C.

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Zan, M. S. D., M. M. Elgaud, A. R. Zainuddin, et al. "Simulation Analysis on the Simultaneous Deployment of Brillouin Gain and Loss in Coded Brillouin Optical Time Domain Analysis (BOTDA) Fiber Sensor." Journal of Physics: Conference Series 1892, no. 1 (2021): 012034. http://dx.doi.org/10.1088/1742-6596/1892/1/012034.

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Liu, Jin, Yong Wang, Yi Lu, Jihong Wei, and Debi Prasanna Kanungo. "Application of Distributed Optical Fiber Sensing Technique in Monitoring the Ground Deformation." Journal of Sensors 2017 (2017): 1–11. http://dx.doi.org/10.1155/2017/6310197.

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The monitoring of ground deformation is important for the prevention and control of geological disaster including land subsidence, ground fissure, surface collapse, and landslides. In this study, a distributed optical fiber sensing technique based on Brillouin Optical Time-Domain Analysis (BOTDA) was used to monitor the ground deformation. The principle behind the BOTDA is first introduced, and then laboratory calibration test and physical model test were carried out. Finally, BOTDA-based monitoring of ground fissure was carried out in a test site. Experimental results show that the distributed optical fiber can measure the soil strain during ground deformation process, and the strain curve responded to the soil compression and tension region clearly. During field test in Wuxi City, China, the ground fissures deformation area was monitored accurately and the trend of deformation can also be achieved to forecast and warn against the ground fissure hazards.

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Zornoza, Ander, Aldo Minardo, Romeo Bernini, Alayn Loayssa, and Luigi Zeni. "Pulsing the Probe Wave to Reduce Nonlocal Effects in Brillouin Optical Time-Domain Analysis (BOTDA) Sensors." IEEE Sensors Journal 11, no. 4 (2011): 1067–68. http://dx.doi.org/10.1109/jsen.2010.2078805.

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Karapanagiotis, Christos, Aleksander Wosniok, Konstantin Hicke, and Katerina Krebber. "Time-Efficient Convolutional Neural Network-Assisted Brillouin Optical Frequency Domain Analysis." Sensors 21, no. 8 (2021): 2724. http://dx.doi.org/10.3390/s21082724.

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To our knowledge, this is the first report on a machine-learning-assisted Brillouin optical frequency domain analysis (BOFDA) for time-efficient temperature measurements. We propose a convolutional neural network (CNN)-based signal post-processing method that, compared to the conventional Lorentzian curve fitting approach, facilitates temperature extraction. Due to its robustness against noise, it can enhance the performance of the system. The CNN-assisted BOFDA is expected to shorten the measurement time by more than nine times and open the way for applications, where faster monitoring is essential.

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Zhang, Dongyu, Yang Yang, Jinlong Xu, Li Ni, and Hui Li. "Structural Crack Detection Using DPP-BOTDA and Crack-Induced Features of the Brillouin Gain Spectrum." Sensors 20, no. 23 (2020): 6947. http://dx.doi.org/10.3390/s20236947.

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Structural damage generally initiates in the form of structural cracks. Thus, developing efficient crack detection techniques is of great importance for the structural health monitoring. In this paper, a new crack identification method is proposed, which is based on the differential pulse-width pair Brillouin optical time domain analysis (DPP-BOTDA) technology and the irregular features of Brillouin gain spectrum (BGS) in the fiber due to structural cracks. The proposed method provides a new way to detect and quantify structural cracks without knowing the strain in the structure. First, the working mechanism of DPP-BOTDA is introduced to illustrate the reason that the DPP-BOTDA, compared to traditional BOTDA technique, can significantly improve the spatial resolution of distributed strain sensing, which is critical for structural crack detection. Then, the BGSs in the fiber with the presence of structural cracks, measured by the DPP-BOTDA, are numerically simulated, from which the crack-induced irregular features of the BGS are summarized. Based these irregular features, new structural crack detection and quantification methods are proposed, which are found to be independent of structural stain. Finally, an experiment is conducted on a simple supported reinforced concrete (RC) beam. The results demonstrate that by using the BGS measured by the DPP-BOTDA, the proposed structural crack identification method successfully detects the occurrence of structural cracks and relatively accurately predicts the crack widths.

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Sirat, Qurratu Aini, Dayangku Salma Awang Ismail, Izwan Shah Ahmad, and Azman Kassim. "Strain monitoring for shallow foundation using the application of Brillouin Optical Time Domain Analysis sensing system (BOTDA)." IOP Conference Series: Materials Science and Engineering 932 (December 18, 2020): 012052. http://dx.doi.org/10.1088/1757-899x/932/1/012052.

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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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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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Hotate, Kazuo. "Brillouin Optical Correlation-Domain Technologies Based on Synthesis of Optical Coherence Function as Fiber Optic Nerve Systems for Structural Health Monitoring." Applied Sciences 9, no. 1 (2019): 187. http://dx.doi.org/10.3390/app9010187.

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Brillouin optical correlation-domain technologies are reviewed as “fiber optic nerve systems” for the health monitoring of large structures such as buildings, bridges, and aircraft bodies. The Brillouin scattering property is used as a sensing mechanism for strain and/or temperature. Continuous lightwaves are used in the technologies, and their optical coherence properties are synthesized to realize position-selective measurement. This coherence manipulation technology is called the “synthesis of optical coherence function (SOCF)”. By utilizing SOCF technologies, stimulated Brillouin scattering is generated position-selectively along the fiber, which is named “Brillouin optical correlation domain analysis (BOCDA)”. Spontaneous Brillouin scattering, which takes place at any portion along the fiber, can also be measured position-selectively by the SOCF technology. This is called “Brillouin optical correlation domain reflectometry (BOCDR)”. When we use pulsed lightwaves that have the position information, sensing performances, such as the spatial resolution, are inherently restricted due to the Brillouin scattering nature. However, in the correlation-domain technologies, such difficulties can be reduced. Superior performances have been demonstrated as distribution-sensing mechanisms, such as a 1.6-mm high spatial resolution, a fast measurement speed of 5000 points/s, and a 7000-με strain dynamic range, individually. The total performance of the technologies is also discussed in this paper. A significant feature of the technologies is their random accessibility to discrete multiple points that are selected arbitrarily along the fiber, which is not realized by the time domain pulsed-lightwave technologies. Discriminative and distributed strain/temperature measurements have also been realized using both the BOCDA technology and Brillouin dynamic grating (BDG) phenomenon, which are associated with the stimulated Brillouin scattering process. In this paper, the principles, functions, and applications of the SOCF, BOCDA, BOCDR, and BDG-BOCDA systems are reviewed, and their historical aspects are also discussed.

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Kwon, Il Bum, Chi Yeop Kim, and Dae Cheol Seo. "Application of Fiber Optic BOTDA Sensor for Fire Detection in a Building." Key Engineering Materials 321-323 (October 2006): 212–16. http://dx.doi.org/10.4028/www.scientific.net/kem.321-323.212.

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Smart structures are to be possessed many functions to sense the external effects, such as seismic loads, temperature, and impact by some explosion, influenced on the safety of structures. This work was focused on the development of a sensing function of smart structures to get the temperature distribution on structures to detect fire occurrences. A fiber optic BOTDA (Brillouin Optical Time Domain Analysis) sensor system was developed to detect the fire occurrence by measuring the temperature distribution of a building’s exterior surfaces. This fiber optic sensor system was constructed with a laser diode and two electro-optic modulators, which made this system faster than systems using only one electro-optic modulator. The temperature distributed on an optical fiber can be measured by this fiber optic BOTDA sensor. An optical fiber, 1400 m in length, was installed on the surface of a building. Using real-time processing of the sensor system, we were able to monitor temperature distribution on the building’s surfaces, and changes in temperature distribution were also measured accurately with this fiber optic sensor.

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Zhang, Shaoyi, and Yang Liu. "Damage Detection in Beam Bridges Using Quasi-static Displacement Influence Lines." Applied Sciences 9, no. 9 (2019): 1805. http://dx.doi.org/10.3390/app9091805.

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Quasi-static strain influence lines (ILs) based on the Brillouin optical time domain analysis (BOTDA) technique have been proposed to effectively locate damage in beam bridges. Using measurement points with a high spatial resolution, the BOTDA technique supplies enough strain ILs to help detect damage in bridges. Unlike quasi-static strain ILs based on the BOTDA technique, quasi-static displacement ILs are relatively easy to implement in actual bridges; furthermore, only a few quasi-static displacement ILs are necessary for actual bridges. On this basis, an improved method is proposed to determine the existence of damage in beam bridges by using only a few quasi-static displacement ILs. First, the Hankel matrix of the damage feature, established based on the number of strain ILs, is reconstructed to generate the damage feature using only a few quasi-static displacement ILs. Second, the method used to obtain the metric for evaluating the damage feature is improved, thereby greatly increasing the efficiency of damage detection using quasi-static ILs. Finally, the effectiveness of the proposed method is demonstrated through both numerical analysis and experimentally measured data obtained during a quasi-static load test of a model bridge.

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Shen, Jiahui, Ting Li, Hong Zhu, Caiqian Yang, and Kai Zhang. "Sensing Properties of Fused Silica Single-Mode Optical Fibers Based on PPP-BOTDA in High-Temperature Fields." Sensors 19, no. 22 (2019): 5021. http://dx.doi.org/10.3390/s19225021.

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The strain of fiber-reinforced polymer (FRP) bars at high temperatures is currently difficult to measure. To overcome this difficulty, a method of smart FRP bars embedded with optical fibers was proposed and studied, in which an ordinary single-mode optical fiber was applied as a distributed sensor. In this paper, both the distributed temperature and strain-sensing characteristics of optical fiber were studied based on pulse pre-pump Brillouin optical time-domain analysis (PPP-BOTDA) under high temperature. The temperature and strain coefficients were investigated under a thermomechanical coupling environment with consideration of large strain levels. The experimental results show that the temperature and strain coefficients decreased as the temperature increased, because the properties of silica and coating materials changed with temperature. Then, the formulas for determining the temperature and strain coefficients at high temperatures were introduced and discussed. The excellent sensing performance of the optical fiber indicated that smart FRP bars have the potential for use at high temperatures.

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Chai, Jing, Qi Liu, Jinxuan Liu, Guihua Zhang, Dingding Zhang, and Fengqi Qiu. "Assessing the Difference in Measuring Bolt Stress: A Comparison of Two Optical Fiber Sensing Techniques." Journal of Sensors 2018 (June 12, 2018): 1–11. http://dx.doi.org/10.1155/2018/7582605.

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Monitoring the load level of the rock bolts is of great importance for assessing risk. Based on the mechanical transmission mechanism of grouting bolts, the bolt pull-out test was carried out in lab. The performance of the bolt under pull-out loading was measured using the pulse-pre-pump Brillouin optical time domain analysis (PPP-BOTDA) and fiber Bragg grating (FBG) sensing technologies. The distribution characteristic of axial stress along the bolt was analysed in combination with the measurements obtained by the two sensing technologies. The relative standard deviation for repeatability errors in the determination and the setting time of resin grout was investigated. The results show that the distribution of axial stress is nonuniform along the anchorage section. The maximum value of axial stress on the bolt is closed to the pull-out side. The relative standard deviation for repeatability errors obtained by PPP-BOTDA is less than that obtained by FBG. The comparison of the measurements obtained by the two methods indicates that when the drawing force is greater than 20 kN and the axial stress is more than 10 kN, the two methods have better consistency. In the field application, it is necessary to estimate the deformation of matrix, leaving at least 500 minutes for resin bond to work.

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Liaw, Shien-Kuei, Chi-Wen Liao, Meng-Hsuan Tsai, et al. "Hybrid Fiber-Optic Sensing Integrating Brillouin Optical Time-Domain Analysis and Fiber Bragg Grating for Long-Range Two-Parameter Measurement." Sensors 21, no. 12 (2021): 4224. http://dx.doi.org/10.3390/s21124224.

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Distributed fiber sensing (DFS) can provide real-time signals and warnings. The entire length of fiber optic cable can act as a sensing element, but the accuracy is sometimes limited. On the other hand, point-to-point fiber sensing (PPFS) is usually implemented using one or more fiber Bragg gratings (FBGs) at specific positions along with the fiber for the monitoring of specific parameters (temperature, strain, pressure, and so on). However, the cost becomes expensive when the number of FBGs increases. A hybrid fiber sensing scheme is thus proposed, combining the advantages of DFS and PPFS. It is based on a Brillouin optical time-domain analysis (BOTDA) fiber system with additional FBGs embedded at certain positions where it is necessary to detect specific parameters. The hybrid fiber sensing system has the advantages of full sensing coverage at essential locations that need to be carefully monitored. In our work, the test results showed that the proposed system could achieve a sensing distance of 16 km with the single-mode fiber with a 2 m spatial resolution. For FBG parameter measurements, the temperature variation was 52 °C, from 25 °C to 77 °C, with a temperature sensitivity of 23 pm/°C, and the strain was from 0 to 400 µε, with a strain sensitivity of 0.975 pm/µε, respectively, using two FBGs.

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Liu, Yang, and Shaoyi Zhang. "Damage Localization of Beam Bridges Using Quasi-Static Strain Influence Lines Based on the BOTDA Technique." Sensors 18, no. 12 (2018): 4446. http://dx.doi.org/10.3390/s18124446.

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The diagnosis of damage in a bridge superstructure using quasi-static strain influence lines (ILs) is promising. However, it is challenging to accurately localize the damage in a bridge superstructure due to limited numbers of strain IL measurement points and inconsistencies between the loading conditions before and after damage. To address the above issues, the Brillouin optical time domain analysis (BOTDA) technique is first applied to bridge damage localization using quasi-static strain ILs, and the number of strain IL measurement points is substantially increased. Additionally, a damage localization index based on quasi-static strain ILs that is independent of differences in the loading conditions before and after damage is proposed to localize damage in the superstructure of a beam bridge. Finally, the effectiveness of the proposed method is demonstrated through both numerical analysis and measured data from a quasi-static test of a model bridge.

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Lalam, Nageswara, Wai Pang Ng, Xuewu Dai, Qiang Wu, and Yong Qing Fu. "Performance analysis of Brillouin optical time domain reflectometry (BOTDR) employing wavelength diversity and passive depolarizer techniques." Measurement Science and Technology 29, no. 2 (2018): 025101. http://dx.doi.org/10.1088/1361-6501/aa9c6e.

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Yoon, Hyuk-Jin, Kwang-Yong Song, Chanyong Choi, Hee-Seoung Na, and Jung-Seok Kim. "Real-Time Distributed Strain Monitoring of a Railway Bridge during Train Passage by Using a Distributed Optical Fiber Sensor Based on Brillouin Optical Correlation Domain Analysis." Journal of Sensors 2016 (2016): 1–10. http://dx.doi.org/10.1155/2016/9137531.

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This study demonstrates the monitoring of distributed strain of rail and girder of a railway bridge occurring during train passage over the bridge’s entire section on a real-time basis by applying a developed distributed optical fiber sensor based on Brillouin Optical Correlation Domain Analysis (BOCDA). The distributed optical fiber sensor system and an algorithm to control as well as to analyze Brillouin gain spectrum signals were also developed. A single-mode optical fiber was attached in the longitudinal direction on the rail and the lower flange of the girder to be used as a sensing fiber of the BOCDA system. Changes in the girder’s strain at the center point of the bridge during the passage of a commercial train were measured at 9 Hz, and the accuracy of this measurement was validated by comparing the measured data with the data from strain gauge. In addition, the distributed strain of a girder and the rail with a length of 40.26 m was measured in real time with a spatial resolution of 31.1 cm. Based on the results of the rail’s strain distribution, the study could identify the location where excessive strain occurred due to an influence of unsupported sleepers on girder of the bridge.

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Fajkus, Marcel, Jan Nedoma, Pavel Mec, Eva Hrubesova, Radek Martinek, and Vladimir Vasinek. "Analysis of the highway tunnels monitoring using an optical fiber implemented into primary lining." Journal of Electrical Engineering 68, no. 5 (2017): 364–70. http://dx.doi.org/10.1515/jee-2017-0068.

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Abstract This article is focused on the analysis of the use of distributed fibre-optic technology for security monitoring of road tunnel and motorway tunnel structural load. The authors focused on the measurements of deformation utilizing Brillouin Time Domain Reflectometry (BOTDR). The principle is based on the measurement of stimulated Brillouin scattering. The article describes and analyses real measurements within a period of 5 months, which were carried out during the tunnelling and the whole process of building a new tunnel in Žilina, Slovakia. The performed experimental measurements were carried out using a standard optic telecommunication cable with water-absorbing aramid yarns and a jacket with a diameter of 4.2 mm. The contribution of this article lies in the introductory analysis of the implementation and use of the fibre-optic technology for security monitoring of road tunnel and motorway tunnel structural load.

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LI Yong-qian, 李永倩, 曹翠新 CAO Cui-xin, 李晓娟 LI Xiao-juan, and 安琪 AN Qi. "Modeling Analysis and Calculation of a Brillouin Optical Time Domain Reflectometer System Using Multi Longitudinal Mode FP Laser." ACTA PHOTONICA SINICA 45, no. 5 (2016): 506001. http://dx.doi.org/10.3788/gzxb20164505.0506001.

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Piao, Chunde, Shaogang Lei, Jiakun Yang, and Lihong Sang. "Experimental Study on the Movement and Evolution of Overburden Strata Under Reamer-Pillar Coal Mining Based on Distributed Optical Fiber Monitoring." Energies 12, no. 1 (2018): 77. http://dx.doi.org/10.3390/en12010077.

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Focusing on the deterioration of the surface ecological environment caused by large-scale exploitation of the Jurassic coal field in northern Shaanxi, the three-dimensional similar material test model is made to simulate the extraction of shallow coal seam. Using Brillouin optical time-domain analysis (BOTDA) optical fiber distributed sensing technology, this paper studied the strain distribution rule and movement characteristics of strata under reamer-pillar mining, analyzed the stability of the remaining coal pillars in the mining area, and obtained the strain contour graph of strata through calculations. The research result shows that the deformation of coal pillars in a safety-critical state under reamer-pillar mining experiences three stages. The stratum deformation is distributed in the shape of a pyramid with the mining area as the center. On the basis of the strain distribution of strata, the settlement curve and subsidence curve of strata deformation are determined to obtain the rupture angle and angle of draw. After being compared with the measured data, the angle values are almost the same.

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Awang Ismail, Dayangku Salma, Azman Kassim, Hisham Mohamad, Ahmad Safuan A. Rashid, and Aliff Ridzuan Bunawan. "Application of Brillouin-based distributed optical fibre sensing technology to measure strain development of a slope model." MATEC Web of Conferences 250 (2018): 01020. http://dx.doi.org/10.1051/matecconf/201825001020.

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For almost two decades, distributed optical fibre sensors are well-known for an alternative to conventional instrumentation in geotechnical engineering applications. However, the technology is yet to be fully implemented due to uncertainties of attachment method or the best way to deploy optical fibre for geo-structure health monitoring. Thus, a project of a 1g model of soil slope was intiated and was constructed with three layers of optical fibre that were horizontally embedded in the soil slope mass in order to observe strain development due to a surcharge load. The strain mobilizations were measured by using Brillouin Optical Time-Domain Analysis (BOTDA) sensing system during the incremental loading on the slope crest until a failure feature had been initiated. The aim of study is to evaluate the development of horizontal strains from Brillouin-based optical fibre sensor subjected to soil slope deformation which lead to slope failures. The results showed that the measurands of optical fibre were highly accumulated at the position of 0.3m depth from the slope crest. The development of high strain at this position was because of soil-fibre interaction to the overburden imposed load in perpendicular direction of optical fibre placement. Therefore, it can be concluded that the optical fibre strain in the soil-strain field were well-responded to the particle soil movement. In addition, the significant trend of positive strain curves were illustrated when the soil was under compression due to external load from a surcharge load plus self-weight of the soil material.

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Zhang, Zhaohui, Peng Guan, Jinlong Xu, Benzhang Wang, Hui Li, and Yongkang Dong. "Horizontal Loading Performance of Offshore Wind Turbine Pile Foundation Based on DPP-BOTDA." Applied Sciences 10, no. 2 (2020): 492. http://dx.doi.org/10.3390/app10020492.

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Offshore wind power is becoming attractive in the wind-power field. With the rapid development of wind-power technology, high-power wind turbines have been implemented in practice. However, the increase in the length of the wind turbine blade causes the pile foundation to withstand a prone overturning moment. For overcoming the problems of traditional sensing technology and meeting the monitoring requirements of pile foundations, a 20 cm spatial resolution differential pulse pair Brillouin optical time-domain analysis (DPP-BOTDA) technique is used to measure a 69 m long offshore wind turbine pile under horizontal loading. From the distributed strain data collected in the test, the maximum stress location of the long pile under the horizontal load can be obtained. By analyzing the load and maximum strain (F-εmax) curve, the horizontal bearing capacity of the pile foundation can exceed 900 kN, which is the maximum horizontal load of the design. The distributed displacement calculation method based on distributed strain data is proposed, according to the force characteristics of steel pipe piles. By comparing the calculated displacement data with the measured data by the dial indicators, the mean absolute percentage error (MAPE) value is only 0.03548. Results show that the 20 cm spatial resolution DPP-BOTDA technology is very suitable for the bearing capacity test of offshore wind turbine steel pipe pile foundations.

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Yoon, Hyuk-Jin, Jung-Seok Kim, Kwang-Yong Song, Hyun-Woo Cho, and Ju-Yeong Jung. "Distributed Strain Monitoring of Railway Composite Bogies Using a Brillouin Optical Correlation Domain Analysis System." Applied Sciences 8, no. 10 (2018): 1755. http://dx.doi.org/10.3390/app8101755.

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The structural deformation of a bogie frame manufactured using a composite material was monitored in real time using a distributed optical fiber sensor. The bogie frame contained an internally embedded standard single-mode optical fiber. Performance tests were conducted by applying a vertical load to the middle of the side beams on each side of the composite bogie frame. The strain distribution was monitored using an optical fiber sensor. A distributed optical fiber sensor system based on the Brillouin optical correlation domain analysis (BOCDA) technique with a 3 cm spatial resolution was used. The distributed strain measured using the optical fiber correlated well with the finite element (FE) analysis data, confirming that the composite bogie frame was fabricated as designed. For a vertical load of 182 kN, the maximum strain, which occurred in the middle of the side frame, increased by 1.3 times, as compared with a vertical load of 140 kN. The experiment was able to verify the balance and the structural stability of the left- and right-hand-side beams. Furthermore, it could confirm that there was a concentrated load where the side beam and the crossbeam meet, owing to a mismatch during the assembly of the composite bogie frame.

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Li Yongqian, 李永倩, 王文平 Wang Wenping, 李晓娟 Li Xiaojuan, and 范寒柏 Fan Hanbai. "Modeling analysis and optimization design of a Golay coding Brillouin Optical Time Domain Reflectometer system with APD detector." Infrared and Laser Engineering 46, no. 11 (2017): 1122002. http://dx.doi.org/10.3788/irla201746.1122002.

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Yoon, Huk Jin, Kwang Yong Song, Jung Seok Kim, Kwang Bok Shin, and Seung Chul Kim. "Crack Propagation Monitoring of DCB Composite Specimens Using Distributed Optical Fiber Sensor." Materials Science Forum 654-656 (June 2010): 2592–95. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.2592.

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In the conventional DCB test, test is usually conducted by observing the crack growth with a microscope, in this paper, new technique is tried to monitor the crack propagation in real time using optical fiber attached in the Kevlar/epoxy specimen. Crack tip position was monitored using strain distribution field data from the optical fiber and compared with the microscope data. BOCDA (Brillouin Optical Correlation Domain Analysis) system was used to measure the strain distribution of the optical fiber and spatial resolution, strain accuracy were about 9mm, ±20με each.

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Cao, Ding-Feng, Bin Shi, Hong-Hu Zhu, et al. "Characterization of Soil Moisture Distribution and Movement Under the Influence of Watering-dewatering Using AHFO and BOTDA Technologies." Environmental and Engineering Geoscience 25, no. 3 (2019): 189–202. http://dx.doi.org/10.2113/eeg-2117.

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ABSTRACT The infiltration and distribution of water through unsaturated soil determine its mechanical and hydrological properties. However, there are few methods that can accurately capture the spatial distribution of moisture inside soil. This study aims to demonstrate the use of actively heated fiber optic (AHFO) and Brillouin optical time domain analysis (BOTDA) technologies for monitoring soil moisture distribution as well as strain distribution. In addition to a laboratory model test, finite element analyses were conducted to interpret the measurements. During the experiment, the fine particle migration was also measured to understand its influence on soil hydraulic conductivity. The results of the experiment indicate that (i) for a soil that has never experienced a watering-dewatering cycle, water infiltration can be accurately calculated using the Richards’ equation; (ii) migration of fine soil particles caused by the watering-dewatering cycle significantly increases the hydraulic conductivity; and (iii) two critical zones (drainage and erosion) play significant roles in determining the overall hydraulic conductivity of the entire soil. This study provides a new method for monitoring the changes in soil moisture, soil strain, and hydraulic conductivity. The observations suggest that the effect of fine particles migration should be considered while evaluating soil moisture distribution and water movement.

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Kapa, Thomas, Andy Schreier, and Katerina Krebber. "A 100-km BOFDA Assisted by First-Order Bi-Directional Raman Amplification." Sensors 19, no. 7 (2019): 1527. http://dx.doi.org/10.3390/s19071527.

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We present, to our knowledge for the first time, a 100-km Brillouin Optical Frequency-Domain Analysis (BOFDA) employing a 200-km fiber loop. Compared to our previous publication, enhanced sensor length, sensor accuracy and spatial resolution are presented. The performance improvements are achieved by applying distributed Raman amplification (DRA) and a digital high-pass filter. We report on temperature measurements over sensing distances of 75 km and 100 km both with a 12.5-m spatial resolution. Temperature changes of 5 ° C have been measured along 75 km sensing fiber. A temperature change of 30 ° C has been detected at 99.5 km.

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Zhang, Cheng-Cheng, Hong-Hu Zhu, Su-Ping Liu, Bin Shi, and Gang Cheng. "Quantifying progressive failure of micro-anchored fiber optic cable–sand interface via high-resolution distributed strain sensing." Canadian Geotechnical Journal 57, no. 6 (2020): 871–81. http://dx.doi.org/10.1139/cgj-2018-0651.

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Distributed fiber optic sensing (DFOS) is gaining increasing interest in geotechnical monitoring. By using soil-embedded fiber optic cables, strain profiles as well as deformation patterns of geotechnical infrastructures can be captured. Probing the fiber optic cable–soil interfacial behavior is vital to the advancement of DFOS-based geotechnical monitoring and our understanding of the soil–inclusion interaction mechanism. To this aim, laboratory pullout tests were performed to investigate the progressive failure of the interface between micro-anchored cables and the surrounding sand. High-resolution strain profiles recorded using Brillouin optical time-domain analysis (BOTDA) not only elucidated the influence of anchorage on strain measurements, but also allowed the classical soil–inclusion interaction problem to be studied in detail. Interfacial shear stresses calculated from step-like strain profiles provided clear evidence of the contribution of each micro-anchor to the pullout resistance. The cable–soil contact is a combination of overall bonding and point fixation depending on the level of mobilized interfacial shear stress, and therefore the validity of measured strains is correlated to a three-stage process of interface failure. This study also shows that installing heat-shrink tubes on the fiber optic cable is a rapid, low-cost, effective approach to make an anchored DFOS system for deformation monitoring of earth structures.

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Sun, Yijie, Bin Shi, Dan Zhang, Hengjin Tong, Guangqing Wei, and Hongzhong Xu. "Internal Deformation Monitoring of Slope Based on BOTDR." Journal of Sensors 2016 (2016): 1–8. http://dx.doi.org/10.1155/2016/9496285.

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To overcome the shortcomings of conventional slope monitoring methods, this paper presented an in-place inclinometer based on BOTDR (Brillouin Optical Time Domain Reflectometer) which was used to obtain the long-term internal deformation in the slope. The installation process of optical fiber sensors and its measuring principle were introduced. The result of analysis indicated that the error in the measured displacement was proportional to the square of the inclinometer length and the precision of the BOTDR instrument, while it was inversely proportional to the diameter of the inclinometer tube. An actual field slope deformation monitoring case was also introduced. The results show that the BOTDR based inclinometer has a good consistency with the traditional inclinometer. It can effectively access the internal deformation of the slope and help to find the position of potential sliding surface accurately. This technology shows a high reliability and practicality in engineering application that will promote deeper research of slope in the future.

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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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Hong, Ki-Nam, Won-Bo Shim, Yeong-Mo Yeon, and Kyu-San Jeong. "Strain Response Characteristics of RC Beams Strengthened with CFRP Sheet Using BOTDR." Applied Sciences 10, no. 17 (2020): 6005. http://dx.doi.org/10.3390/app10176005.

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This paper presents the structural behaviors of reinforced concrete (RC) beams that have been strengthened with carbon-fiber-reinforced polymer (CFRP) sheets experimentally and numerically. Test specimens were subjected to four-point bending, and structural behavior was observed using a strain gauge and a Brillouin optical time domain reflectometer (BOTDR) sensor. Non-linear finite element analysis was conducted to examine the applicability and reliability of numerical models using the commercial finite element code, LS-DYNA. In the results, the de-bonded section between the beam substrate and CFRP sheet affected the initial crack in the structure, while the ultimate load, which is related to structural failure, was unaffected. The predicted results correlated well with the experimental observations in terms of the trend of the load-displacement curve, initial crack load, ultimate load and failure mode. Additionally, it is shown that the de-bonding behaviors in the interface were examined using the strain distributions for the CFRP sheets through the experiment and numerical simulations.

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Zhang, Qinghua, and Ziming Xiong. "Crack Detection of Reinforced Concrete Structures Based on BOFDA and FBG Sensors." Shock and Vibration 2018 (September 3, 2018): 1–10. http://dx.doi.org/10.1155/2018/6563537.

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Reinforced concrete structural elements, as an important component of buildings and structures, require inspection for the purposes of crack detection which is an important part of structural health monitoring. Now existing crack detection methods usually use a single technology and can only detect internal or external cracks. In this paper, the authors propose a new sensing system combining BOFDA (Brillouin optical frequency-domain analysis) and FBG (fiber Bragg grating) technology, which are used to detect internal and surface cracks and their development in reinforced concrete structures, and an attempt is made to estimate the width of surface cracks. In these experiments, a special reinforced concrete beam structure was designed by the author for crack detection under load. Four continuous distributed optical fibers are fixed on the steel skeleton, which is located within the reinforced concrete beam. Three FBG sensors are fixed on the lower surface of the beam, near its centre. By analysing the sensor data, it can be found that the BOFDA-distributed fiber can be used to detect internal cracking before surface cracking, and the difference between scans can be used to judge the time of onset of internal cracking, but the relative error in position is about 5%, while the FBG sensor can detect the cracking time of microcracks on the lower surface in near-real-time and can be used to calculate the crack width. Through the experiment, it is found that if the combination of BOFDA and FBG technology is adopted, we can initially use the strain data obtained by multiple groups of BOFDA monitoring to predict the general location of the internal cracks, then to monitor the exact location of the surface cracks by FBG in the medium term, and to estimate the width of the final expansion of the cracks finally.

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Hu, Tao, Gongyu Hou, Su Bu, et al. "A Novel Approach for Predicting the Height of Water-Conducting Fracture Zone under the High Overburden Caving Strength Based on Optimized Processes." Processes 8, no. 8 (2020): 950. http://dx.doi.org/10.3390/pr8080950.

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The height of water-conducting fracture zones (WCFZs) is vital for the prevention of water, gas, and roof accidents in coal mines. However, its dynamic evolution law and maximum height are difficult to be obtained by traditional prediction methods, especially for conditions in which there is high overburden caving strength and a thick coal seam. Therefore, taking the 150,313 fully mechanized caving working face in Yingying Coal Mine as a background, according to the principle of optimized processes, a new predicting approach based on the Brillouin optical time-domain reflectometry (BOTDR) is proposed. Firstly, we estimated the height through empirical formula calculation, theoretical analysis, and similar model simulation tests. Secondly, we studied the optimized layout of optical cables in the overburden in detail for predicting the maximum height of the WCFZ and keeping the cables in good performance during field prediction. Thirdly, we researched and optimized the borehole parameters, optical fiber selection, and the special protection measures. Finally, we applied the aforementioned optimized outcomes in the field experiment to dynamically predict the height of the WCFZ. As a result of the field experiment, the distribution characteristics of optical fiber strain, the maximum height, and the evolution law of the WCFZ were obtained through the regular monitoring of fiber strain using BOTDR. The experiment demonstrated that its maximum height is consistent with the results studied indoors. The validation and feasibility of the approach proposed in this paper were verified via the aforementioned studies. The research in this paper has good reference value and important significance for predicting the height of the WCFZ using BOTDR in coal mines with similar geological and productive conditions.

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Feng, Cheng, and Thomas Schneider. "Benefits of Spectral Property Engineering in Distributed Brillouin Fiber Sensing." Sensors 21, no. 5 (2021): 1881. http://dx.doi.org/10.3390/s21051881.

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As one of the most consolidated distributed fiber sensors based on stimulated Brillouin scattering, the Brillouin optical time-domain analyzer (BOTDA) has been developed for decades. Despite the commercial availability and outstanding progresses which has been achieved, the intrinsic Lorentzian gain spectrum restricts the sensing performance from possible further enhancements and hence limits the field of validity of the technique. In this paper, the novel method of engineering the gain spectral properties of the Brillouin scattering and its application on static and dynamic BOTDA sensors will be reviewed. Such a spectral property engineering has not only provided improvements to BOTDA, but also might open a new way to enhance the performance of all kinds of distributed Brillouin fiber sensors.

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Kadum, Jaffar Emad, Cheng Feng, and Thomas Schneider. "Characterization of the Noise Induced by Stimulated Brillouin Scattering in Distributed Sensing." Sensors 20, no. 15 (2020): 4311. http://dx.doi.org/10.3390/s20154311.

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The excess noise due to stimulated Brillouin scattering (SBS) in gain and loss-based Brillouin optical time-domain analyzers (BOTDA) has been investigated theoretically and experimentally for the first time to the best of our knowledge. This investigation provides a full insight to the SBS-induced noise distribution, which mainly comes from phase-to-intensity conversion noise and the beating noise between the probe wave and spontaneous Brillouin scattering. A complete theoretical model, which is in good agreement with the experimental results, is presented to describe the noise. The results show that a loss-based BOTDA setup gives a better noise performance than a gain-based one in both time and frequency domain. The SBS-induced noise has been characterized in dependence on the pump and probe power and the spatial resolution.

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Fang, Jian, Miao Sun, Di Che, et al. "Complex Brillouin Optical Time-Domain Analysis." Journal of Lightwave Technology 36, no. 10 (2018): 1840–50. http://dx.doi.org/10.1109/jlt.2018.2792440.

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Feng, Cheng, Stefan Preussler, Jaffar Emad Kadum, and Thomas Schneider. "Measurement Accuracy Enhancement via Radio Frequency Filtering in Distributed Brillouin Sensing." Sensors 19, no. 13 (2019): 2878. http://dx.doi.org/10.3390/s19132878.

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In this article, we demonstrate the noise reduction and signal to noise ratio (SNR) enhancement in Brillouin optical time-domain analyzers (BOTDA). The results show that, although the main noise contribution comes from the Brillouin interaction itself, a simple low pass filtering on the detected radio frequency (RF) signal reduces remarkably the noise level of the BOTDA traces. The corresponding SNR enhancement depends on the employed cut-off frequency of the low pass filter. Due to the enhancement of the SNR, a mitigation of the standard deviation error of the Brillouin frequency shift (BFS) has been demonstrated. However, RF filters with low cut-off frequency could lead to distortions on the trace signals and therefore detection errors on a non-uniform BFS. The trade-off between the noise reduction and the signal distortion as well as an optimal cut-off frequency are discussed in detail.

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