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Journal articles on the topic 'Optical time domain reflectometry (OTDR)'

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Published: 4 June 2021

Last updated: 1 February 2022

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Rao, Yunjiang, Zinan Wang, Huijuan Wu, Zengling Ran та Bing Han. "Recent Advances in Phase-Sensitive Optical Time Domain Reflectometry (Ф-OTDR)". Photonic Sensors 11, № 1 (2021): 1–30. http://dx.doi.org/10.1007/s13320-021-0619-4.

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AbstractPhase-sensitive optical time domain reflectometry (Ф-OTDR) is an effective way to detect vibrations and acoustic waves with high sensitivity, by interrogating coherent Rayleigh backscattering light in sensing fiber. In particular, fiber-optic distributed acoustic sensing (DAS) based on the Ф-OTDR with phase demodulation has been extensively studied and widely used in intrusion detection, borehole seismic acquisition, structure health monitoring, etc., in recent years, with superior advantages such as long sensing range, fast response speed, wide sensing bandwidth, low operation cost and long service lifetime. Significant advances in research and development (R&D) of Ф-OTDR have been made since 2014. In this review, we present a historical review of Ф-OTDR and then summarize the recent progress of Ф-OTDR in the Fiber Optics Research Center (FORC) at University of Electronic Science and Technology of China (UESTC), which is the first group to carry out R&D of Ф-OTDR and invent ultra-sensitive DAS (uDAS) seismometer in China which is elected as one of the ten most significant technology advances of PetroChina in 2019. It can be seen that the Ф-OTDR/DAS technology is currently under its rapid development stage and would reach its climax in the next 5 years.

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Bao, Xiaoyi, and Yuan Wang. "Recent Advancements in Rayleigh Scattering-Based Distributed Fiber Sensors." Advanced Devices & Instrumentation 2021 (March 11, 2021): 1–17. http://dx.doi.org/10.34133/2021/8696571.

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Recently, Rayleigh scattering-based distributed fiber sensors have been widely used for measurement of static and dynamic phenomena such as temperature change, dynamic strain, and sound waves. In this review paper, several sensing systems including traditional Rayleigh optical time domain reflectometry (OTDR), Φ-OTDR, chirped pulse Φ-OTDR, and optical frequency domain reflectometry (OFDR) are introduced for their working principles and recent progress with different instrumentations for various applications. Beyond the sensing technology and instrumentation, we also discuss new types of fiber sensors, such as ultraweak fiber Bragg gratings and random fiber gratings for distributed sensing and their interrogators. Ultimately, the limitations of Rayleigh-based distributed sensing systems are discussed.

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Muanenda, Yonas. "Recent Advances in Distributed Acoustic Sensing Based on Phase-Sensitive Optical Time Domain Reflectometry." Journal of Sensors 2018 (2018): 1–16. http://dx.doi.org/10.1155/2018/3897873.

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Distributed acoustic sensing (DAS) using coherent Rayleigh backscattering in an optical fiber has become a ubiquitous technique for monitoring multiple dynamic events in real time. It has continued to constitute a steadily increasing share of the fiber-optic sensor market, thanks to its interesting applications in many safety, security, and integrity monitoring systems. In this contribution, an overview of the recent advances of research in DAS based on phase-sensitive optical time domain reflectometry (ϕ-OTDR) is provided. Some advanced techniques used to enhance the performance of ϕ-OTDR sensors for measuring backscattering intensity changes through reduction of measurement noise are presented, in addition to methods used to increase the dynamic measurement capacity of ϕ-OTDR schemes beyond conventional limits set by the sensing distance. Recent ϕ-OTDR configurations which significantly enhance the measurement spatial resolution, including those which decouple it from the probing pulse width, are also discussed. Finally, a review of recent advances in more precise quantitative measurement of an external impact based on frequency shift and phase demodulation methods using simple direct detection ϕ-OTDR schemes is given.

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Zhang, Xuping, Yunyin Zheng, Chi Zhang, et al. "A Fading Tolerant Phase-Sensitive Optical Time Domain Reflectometry Based on Phasing-Locking Structure." Electronics 10, no. 5 (2021): 535. http://dx.doi.org/10.3390/electronics10050535.

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The demand for phase-sensitive optical time domain reflectometry (φ-OTDR), which is capable of reconstructing external disturbance accurately, is increasing. However, φ-OTDR suffers from fading where Rayleigh backscattering traces (RBS) have low amplitude and may be lower than the noise floor. Therefore, signal-to-noise ratio (SNR) is reduced. In conventional coherent φ-OTDR, an acoustic optical modulator (AOM), which consists of an RF driving source and an acousto-optic crystal, is commonly used to generate optical pulses and frequency shifts. Since RF driving and external modulation signals come from an independent oscillation source, every intermediate frequency (IF) trace has a different phase bias. Therefore, it is difficult to average the IF signals directly for noise reduction. In this paper, a coherent φ-OTDR system based on phase-locking structure was proposed. This structure provided a clock homologous carrier signal, a modulation signal and a data acquisition (DAQ) trigger signal. Then, moving average methods were taken on IF signals before phase demodulating to reduce the overall noise floor of the system. This new φ-OTDR is more tolerant to fading, which can provide higher accuracy for vibration reconstruction. The frequency response range of vibration was as low as 1Hz, and a 25dB improvement of SNR was achieved.

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Guo, Lin, Pei Zhang, and Yan Shao. "Use Case and Functional Requirements of Optical Time Domain Reflectometer." Applied Mechanics and Materials 543-547 (March 2014): 3696–99. http://dx.doi.org/10.4028/www.scientific.net/amm.543-547.3696.

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As the scalable deployment of PON network and the maturity of next generation PON technologies, optical link fault management should be well considered. OTDR is now under study in the industry. Based on our study and real network operation experience, we give an analysis on use case and functional requirements of OTDR, which could be used as a guide in OTDR development and implementation.

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Hagemann, H. J., J. Ungelenk, and D. U. Wiechert. "Optical time-domain reflectometry (OTDR) of diameter modulations in single mode fibers." Journal of Lightwave Technology 8, no. 11 (1990): 1641–45. http://dx.doi.org/10.1109/50.60559.

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Жирнов, А. А., К. В. Степанов, А. О. Чернуцкий та ін. "Влияние дрейфа частоты лазера в фазочувствительной рефлектометрии". Журнал технической физики 127, № 10 (2019): 603. http://dx.doi.org/10.21883/os.2019.10.48364.177-19.

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AbstractThe influence of the laser frequency drift on the operation of phase-sensitive optical time domain reflectometry (φ-OTDR) systems is considered. Theoretical results based on a new numerical φ-OTDR model demonstrating the influence of the laser frequency instability on a signal are reported. This model is verified based on experimental data. It has been used to calculate the signal-to-noise ratio (SNR) of the system for different parameters of the laser source stability. As a result, quantitative requirements for lasers used in φ-OTDR systems are formulated.

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Jin, Xiu Mei, Yu Mei Lv, and Li Feng Du. "Research on a New Detection Technique of FBG Using OTDR." Advanced Materials Research 317-319 (August 2011): 2346–50. http://dx.doi.org/10.4028/www.scientific.net/amr.317-319.2346.

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A new technique of using Optical Time Domain Reflectometry (OTDR) to detect the reflected power of FBG sensing array was researched systematically. The theoretical model between the reflected power detected by OTDR and the reflected wavelength of FBG was established by analyzing, and consequently the selection rule of FBG wavelength in OTDR detection system was proposed. Moreover, experiments about multi-combination of FBGs with high reflectivity were carried out. The cause of dummy peak and resonance peak in OTDR test curves were analyzed, and meanwhile the selection basis of FBG reflectivity was also given. Based on time division multiplexing theory, detecting low-reflectivity FBG by OTDR can increase the FBG multiplexing number greatly, which has wide prospect to be applied in FBG array detection.

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Hubbard, Peter G., James Xu, Shenghan Zhang, et al. "Dynamic structural health monitoring of a model wind turbine tower using distributed acoustic sensing (DAS)." Journal of Civil Structural Health Monitoring 11, no. 3 (2021): 833–49. http://dx.doi.org/10.1007/s13349-021-00483-y.

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AbstractMaintenance of wind turbine towers is currently a manual process that requires visual inspection and bolt tightening yearly. This process is costly to energy companies and its necessity is not well-defined. In this study, two Rayleigh-based distributed fiber optic sensing technologies are evaluated and compared for their ability to monitor the dynamic structural behavior of a model wind turbine tower subject to free and forced vibration. They are further tested for their ability to detect structural phenomena associated with loose bolts and material damage within the tower. The two technologies examined are optical frequency domain reflectometry (OFDR) and phase-based optical time domain reflectometry ($$\phi$$ ϕ -OTDR), which is a technology used in distributed acoustic sensing (DAS). OFDR is a tested and proven strain measurement technology commonly used for structural health monitoring but can only make strain measurements over short distances (10 s of meters). OFDR was used to validate the measurements made with $$\phi$$ ϕ -OTDR which can measure over much longer distances (several kilometers). Due to its sensing distance capability, $$\phi$$ ϕ -OTDR is a promising technology for monitoring many wind turbines networked together with a single fiber optic cable. This study presents a first-of-its-kind use of $$\phi$$ ϕ -OTDR for structural health monitoring to demonstrate its capabilities.

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Zinsou, Romain, Xin Liu, Yu Wang, Jianguo Zhang, Yuncai Wang, and Baoquan Jin. "Recent Progress in the Performance Enhancement of Phase-Sensitive OTDR Vibration Sensing Systems." Sensors 19, no. 7 (2019): 1709. http://dx.doi.org/10.3390/s19071709.

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Recently, phase-sensitive Optical Time-Domain Reflectometry (Φ-OTDR)-based vibration sensor systems have gained the interest of many researchers and some efforts have been undertaken to push the performance limitations of Φ-OTDR sensor systems. Thus, progress in different areas of their performance evaluation factors such as improvement of the signal-to-noise ratio (SNR), spatial resolution (SR) in the sub-meter range, enlargement of the sensing range, increased frequency response bandwidth over the conventional limits, phase signal demodulation and chirped-pulse Φ-OTDR for quantitative measurement have been realized. This paper presents an overview of the recent progress in Φ-OTDR-based vibration sensing systems in the different areas mentioned above.

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Cai, Yunpeng, Jihui Ma, Wenfa Yan, Wenyi Zhang, and Yuhang An. "Aircraft Detection Using Phase-Sensitive Optical-Fiber OTDR." Sensors 21, no. 15 (2021): 5094. http://dx.doi.org/10.3390/s21155094.

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Aircraft detection plays a vital role in aviation management and safe operation in the aviation system. Phase-Sensitive Optical Time Domain Reflectometry (Φ-OTDR) technology is a prevailing sensing method in geophysics research, structure inspection, transportation detection, etc. Compared with existing video- or radio-based detection methods, Φ-OTDR is cost-effective, suitable for long-distance detection, and resistant to severe weather conditions. We present a detection system using Φ-OTDR technology and analyze the character of the acoustic signal of aircraft. Instead of runway monitoring in the airport or noise detection in the air, this study focuses on the detection of seismic vibration signal excited by the sound of aircraft. The Chebyshev filter is adopted to eliminate the impact of background noise and random noise from the original vibration signal; the short-time Fourier transform is used for time-frequency analysis. The experimental results showed that the seismic vibration signal excited by the aircraft sound is mainly low-frequency, which is under 5 Hz. Time delay of aircraft vibration signal in different locations of the optic fiber is recorded by the sensing system. The Doppler effect is also revealed by the time-domain analysis: the frequency increases when the aircraft is approaching and decreases when the aircraft moves away.

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Feng, Shengwen, Tuanwei Xu, Jianfen Huang, Yang Yang, Lilong Ma, and Fang Li. "Sub-Meter Spatial Resolution Phase-Sensitive Optical Time-Domain Reflectometry System Using Double Interferometers." Applied Sciences 8, no. 10 (2018): 1899. http://dx.doi.org/10.3390/app8101899.

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An improved phase-sensitive optical time-domain reflectometry (φ-OTDR) system with sub-meter spatial resolution is demonstrated. Two Michelson interferometers (MIs) with different path length differences are used in the proposed system. One is 10 m, the other is 9.2 m. Two Rayleigh backscattering phase traces with different spatial resolution are obtained by a phase generated carrier (PGC) algorithm at adjacent times. After using differencing and adaptive 2-D bilateral filtering algorithms, a 0.8-m spatial resolution over 2 km is achieved. Experimental results indicate that the system shows an extraordinary linearity as high as 99.94% with amplitude-modulation and acquires a detection frequency from 5 to 500 Hz.

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Ratuszek, M., Z. Zakrzewski, and J. Majewski. "Reflectometric measurements of thermally expanded core area." Bulletin of the Polish Academy of Sciences: Technical Sciences 58, no. 4 (2010): 513–17. http://dx.doi.org/10.2478/v10175-010-0051-1.

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Reflectometric measurements of thermally expanded core area In this work an analysis method of one-way optical time domain reflectometer (OTDR) measurements has been presented. This method uniquely confirms mode field radii matching in diffusion transit area of the thermally expanded core (TEC) of thermally connected single mode telecommunication fibers. A comparison of reflectometric measurements with theoretical calculations of losses in TEC areas has been demonstrated.

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Sifta, Radim, Petr Munster, Petr Sysel, et al. "Distributed Fiber-Optic Sensor for Detection and Localization of Acoustic Vibrations." Metrology and Measurement Systems 22, no. 1 (2015): 111–18. http://dx.doi.org/10.1515/mms-2015-0009.

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Abstract A sensing system utilizing a standard optical fiber as a distributed sensor for the detection and localization of mechanical vibrations is presented. Vibrations can be caused by various external factors, like moving people, cars, trains, and other objects producing mechanical vibrations that are sensed by a fiber. In our laboratory we have designed a sensing system based on the Φ-OTDR (phase sensitive Optical Time Domain Reflectometry) using an extremely narrow laser and EDFAs.

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Romanova, Agata, and Vaidotas Barzdenas. "A Review of Modern CMOS Transimpedance Amplifiers for OTDR Applications." Electronics 8, no. 10 (2019): 1073. http://dx.doi.org/10.3390/electronics8101073.

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The work presents a review of modern CMOS transimpedance amplifiers (TIAs) in the context of their application for low-cost optical time-domain reflectometry (OTDR). After introducing the basic principles behind the OTDR, the requirements for a suitable CMOS TIA are presented and discussed. A concise review of several basic TIA topologies is provided with a brief overview of their main properties. A detailed discussion is given on a representative set of approaches reported in the literature and the figure of merit (FOM) is introduced as a unified basis for performance comparison. Limitations of a single FOM as a basis for comparison are pointed out. Based on the provided discussion, some suggestions are made on the suitability of the TIA topologies for OTDR applications.

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Hu, Yanzhu, Song Wang, and Xinbo Ai. "Research of the Vibration Source Tracking in Phase-Sensitive Optical Time-Domain Reflectometry Signals Based by Image Processing Method." Algorithms 11, no. 8 (2018): 117. http://dx.doi.org/10.3390/a11080117.

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This paper aims to improve the source tracking efficiency of distributed vibration signals generated by phase-sensitive optical time-domain reflectometry (Φ-OTDR). Considering the two dimensions (time and length) of Φ-OTDR signals, the authors saved and processed these signals as images after particle filtering. The filtering method could save 0.1% of hard drive space without sacrificing the original features of the signals. Then, an integrated feature extraction method was proposed to further process the generated image. The method combines three individual extraction methods, namely, texture feature extraction, shape feature extraction and intrinsic feature extraction. Subsequently, the signal of each frame image was recognized to track the vibration source. To verify the effect of the proposed method, several experiments were carried out to compare it with popular and traditional approaches. The results show that: Hard drive space is greatly conserved by saving the distributed vibration signals as images; the proposed particle filter is a desirable way to screen the vibration signals for monitoring; the integrated feature extraction outperforms the individual extraction methods for texture features, shape features and intrinsic features; the proposed method has a better effect than other popular integrated feature extraction methods; and, the signal source tracking method has little impact on the positioning accuracy of the vibration source. The research findings provide important insights into the source tracking of Φ-OTDR signals.

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Chen, Zhen, Liang Zhang, Huanhuan Liu, et al. "3D Printing Technique-Improved Phase-Sensitive OTDR for Breakdown Discharge Detection of Gas-Insulated Switchgear." Sensors 20, no. 4 (2020): 1045. http://dx.doi.org/10.3390/s20041045.

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In this paper, we propose and demonstrate a gas-insulated switchgear (GIS) breakdown discharge detection system based on improved phase-sensitive optical time domain reflectometry (φ-OTDR) assisted by 3D-printed sensing elements. The sensing element is manufactured by a material with a high Poisson ratio for enhancement of the sensitivity of φ-OTDR to the acoustic emission detection during the breakdown discharge process. In our experiment, seven 3D-printed sensing elements incorporating with optical fibers are attached tightly onto the shell of the GIS, which are monitored by φ-OTDR to localize and detect the acoustic emission signal resulted from the breakdown discharge. Ultimately, thanks to the phase demodulation, acoustic signals induced by the breakdown discharge process can be captured and recovered. Furthermore, the time delay analysis of detected signals acquired by different sensing elements on the GIS breakdown discharge unit is able to distinguish the location of the insulation failure part in the GIS unit. It suggests that the φ-OTDR incorporated with 3D printing technology shows the advantage of robustness in GIS breakdown discharge monitoring and detection.

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Sheng Qinghua, 盛庆华, 俞钊 Yu Zhao, 卢斌 Lu Bin, 李竹 Li Zhu, 叶青 Ye Qing, and 张泽鑫 Zhang Zexin. "Real-Time Phase-Sensitive Optical Time-Domain Reflectometry Signal Processing System Based on Heterogeneous Accelerated Computing." Chinese Journal of Lasers 47, no. 1 (2020): 0104002. http://dx.doi.org/10.3788/cjl202047.0104002.

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Shan, Yuanyuan, Wenbin Ji, Qing Wang, et al. "Performance Optimization for Phase-Sensitive OTDR Sensing System Based on Multi-Spatial Resolution Analysis." Sensors 19, no. 1 (2018): 83. http://dx.doi.org/10.3390/s19010083.

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This paper proposes and demonstrates a phase-sensitive optical time domain reflectometry (Φ-OTDR) sensing system with multi-spatial resolution (MSR) analysis property. With both theoretical analysis and an experiment, the qualitative relationship between spatial resolution (SR), signal-to-noise ratio (SNR) and the length of the vibration region has been revealed, which indicates that choosing a suitable SR to analyze the vibration event can effectively enhance the SNR of a sensing system. The proposed MSR sensing scheme offers a promising solution for the performance optimization of Φ-OTDR sensing systems, which can restore vibration events of different disturbance range with optimum SNR in merely a single measurement while maintaining the same detectable frequency range.

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Wu, Huijuan, Shunkun Xiao, Xiaoyu Li, Zinan Wang, Jiwei Xu та Yunjiang Rao. "Separation and Determination of the Disturbing Signals in Phase-Sensitive Optical Time Domain Reflectometry (Φ-OTDR)". Journal of Lightwave Technology 33, № 15 (2015): 3156–62. http://dx.doi.org/10.1109/jlt.2015.2421953.

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Pniov, Alexey, Andrey Zhirnov, Dmitriy Shelestov, et al. "Yb,Er:glass Microlaser at 1.5 µm for optical fiber sensing: development, characterization and noise reduction." ACTA IMEKO 5, no. 4 (2016): 24. http://dx.doi.org/10.21014/acta_imeko.v5i4.423.

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A fiber-pumped single-frequency microchip erbium laser was developed and characterized with the aim of using it in coherent Optical Time Domain Reflectometry (OTDR) measurements and sensing. The laser is pumped by a fiber-coupled 976 nm laser diode and provides 8 mW TEM00 single frequency output power at 1.54 µm wavelength, suitable for efficient coupling to optical fibers. The amplitude and phase noise of this 200 THz oscillator were experimentally investigated and a Relative Intensity Noise (RIN) control loop was developed providing 27 dB RIN peak reduction at the relaxation oscillation frequency of 800 kHz

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Tabi Fouda, Bernard Marie, Dezhi Han, Bowen An та Xiangzhi Chen. "Research and Software Design of an Φ-OTDR-Based Optical Fiber Vibration Recognition Algorithm". Journal of Electrical and Computer Engineering 2020 (24 січня 2020): 1–13. http://dx.doi.org/10.1155/2020/5720695.

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Distributed optical fiber vibration signal plays a significant role in the communication and safety of any perimeter security monitoring system. It uses light as an information carrier and optical fiber as a means of signal transmission and communication. Phase-sensitive optical time-domain reflectometry (Φ-OTDR) is used to detect the signals generated during events (intrusions or nonintrusion). This paper proposes the time-frequency characteristic (TFC) method for the recognition of the fiber vibration signal and designs and implements the corresponding software function module. The combination of time-domain features and time-frequency-domain features is called TFC; and it is based on the Hilbert transform and on the empirical mode decomposition (EMD) of time-frequency entropy and center-of-gravity frequency that is described. A feature vector is formed, and multiple types of probabilistic neural networks (PNNs) are performed on it to determine whether intrusion events occur. The experimental simulation results show that the monitoring system software can intelligently display the data collected in real time, which demonstrates that the proposed method is effective and reliable in identifying and classifying accurately the types of events. The data processing time is less than 2 s, and the accuracy of the system identification can reach 99%, which ensures the system’s validity.

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Yanuary, Tio Hanif, and Lita Lidyawati. "Analisis Link Budget Penyambungan Serat Optik Menggunakan Optical Time Domain Reflectometer AQ7275." Jurnal Teknik Elektro 10, no. 1 (2018): 36–40. http://dx.doi.org/10.15294/jte.v10i1.13996.

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An optical fiber is a high-speed telecommunication transmission medium. Principally, an optical fiber is made of a very fine glass fiber material, which is able to transmit light waves using light reflection method on the surface of the fiber optics core. An underground installation of the fiber optics makes this device robust from external interferences. However, the fiber optic cable performance should always be checked to maintain performance during data transmission process. One way to test fiber optics cable performance is by using an Optical Time - Domain Reflectometer (OTDR) device. This device sends a light wave from one point of the fiber optics cable. The light wave then returns when reaching the other point of the fiber optic cable while carrying some measurement parameters especially the physical length and attenuation of a fiber optic cable. The evaluation of the fiber optics cable performance requires the preparation, installation, and configuration of the OTDR. In this paper, we conducted evaluation on the performances of fiber optics cable. The data generated by the performed evaluation indicated an occurring attenuation on the fiber optics cable along 64.402 km of its lengths.

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Jiang, Fei, Zixiao Lu, Feida Cai, et al. "Low Computational Cost Distributed Acoustic Sensing Using Analog I/Q Demodulation." Sensors 19, no. 17 (2019): 3753. http://dx.doi.org/10.3390/s19173753.

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Distributed acoustic sensing based on phase-sensitive optical time-domain reflectometry (Φ-OTDR) has been widely used in many fields. Phase demodulation of the Φ-OTDR signal is essential for undistorted acoustic measurement. Digital coherent detection is a universal method to implement phase demodulation, but it may cause severe computational burden. In this paper, analog I/Q demodulation is introduced into the Φ-OTDR based DAS system to solve this problem, which can directly obtain the I and Q components of the beat signal without any digital processing, meaning that the computational cost can be sharply reduced. Besides, the sampling frequency of the data acquisition card can theoretically be lower than the beat frequency as the spectrum aliasing would not affect the demodulation results, thus further reducing the data volume of the system. Experimental results show that the proposed DAS system can demodulate the phase signal with good linearity and wide frequency response range. It can also adequately recover the sound signal sensed by the optical fiber, indicating that it can be a promising solution for computational-cost-sensitive distributed acoustic sensing applications.

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Filograno, Riziotis, and Kandyla. "A Low-Cost Phase-OTDR System for Structural Health Monitoring: Design and Instrumentation." Instruments 3, no. 3 (2019): 46. http://dx.doi.org/10.3390/instruments3030046.

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The design, development, and testing of a low-cost phase optical time-domain reflectometry (Phase-OTDR) system, intended for use in structural health monitoring (SHM) applications, are presented. Phase-OTDR is a technology that is growing and evolving at an impressive rate. Systems based on this principle are becoming very sensitive and elaborate and can perform very accurate condition monitoring, but at the same time, they are critically alignment-dependent and prohibitively costly to be considered as viable options in real field applications. Certain Phase-OTDR systems have been applied in real field studies, but these examples are mostly a proof-of-concept. The system presented here is the result of a compromise between performance and cost, using commercial components, specifically combined and tuned for SHM applications. The design and implementation of all the electronic and optoelectronic steps are presented, and the operation of the system is demonstrated, achieving a spatial resolution of ~6 m over 5 km. This work provides useful engineering guidelines for the low-cost implementation of Phase-OTDR systems. It is anticipated that the affordable development of such interrogation systems will promote their use in a wide range of SHM applications with moderate monitoring requirements and will assist the penetration of Phase-OTDR technology in the industry.

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Zhang, Yixin, Jingxiao Liu, Fei Xiong та ін. "A Space-Division Multiplexing Method for Fading Noise Suppression in the Φ-OTDR System". Sensors 21, № 5 (2021): 1694. http://dx.doi.org/10.3390/s21051694.

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Phase-sensitive time-domain reflectometry (Φ-OTDR) can be used for fully distributed long-distance vibration monitoring. There is a fading phenolmenon in the Φ-OTDR, which will cause the signal intensity somewhere to be too low to extract the phase of the signal without distortion. In this paper, the Φ-OTDR based on space-division multiplexing (SDM) is proposed to suppress fading and we used multi-core optical fiber (MCF) to realize SDM. While inheriting the previous optimization strategy, we proposed a strategy based on frequency spectral similarity to process multiple independent signals obtained by SDM. And we compared the two methods. Through the experiments, the distortion rate can be reduced from an average level of 9.34% to less than 2% under continuous running of 270 s, which proves that SDM is a reliable technical route to achieve fading suppression. This method can effectively improve the fading suppression capability of the existed commercial systems.

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Coscetta, Agnese, Ester Catalano, Enis Cerri, et al. "Distributed Static and Dynamic Strain Measurements in Polymer Optical Fibers by Rayleigh Scattering." Sensors 21, no. 15 (2021): 5049. http://dx.doi.org/10.3390/s21155049.

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We demonstrate the use of a graded-index perfluorinated optical fiber (GI-POF) for distributed static and dynamic strain measurements based on Rayleigh scattering. The system is based on an amplitude-based phase-sensitive Optical Time-Domain Reflectometry (ϕ-OTDR) configuration, operated at the unconventional wavelength of 850 nm. Static strain measurements have been carried out at a spatial resolution of 4 m and for a strain up to 3.5% by exploiting the increase of the backscatter Rayleigh coefficient consequent to the application of a tensile strain, while vibration/acoustic measurements have been demonstrated for a sampling frequency up to 833 Hz by exploiting the vibration-induced changes in the backscatter Rayleigh intensity time-domain traces arising from coherent interference within the pulse. The reported tests demonstrate that polymer optical fibers can be used for cost-effective multiparameter sensing.

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Soriano-Amat, Miguel, David Fragas-Sánchez, Hugo F. Martins, et al. "Monitoring of a Highly Flexible Aircraft Model Wing Using Time-Expanded Phase-Sensitive OTDR." Sensors 21, no. 11 (2021): 3766. http://dx.doi.org/10.3390/s21113766.

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In recent years, the use of highly flexible wings in aerial vehicles (e.g., aircraft or drones) has been attracting increasing interest, as they are lightweight, which can improve fuel-efficiency and distinct flight performances. Continuous wing monitoring can provide valuable information to prevent fatal failures and optimize aircraft control. In this paper, we demonstrate the capabilities of a distributed optical fiber sensor based on time-expanded phase-sensitive optical time-domain reflectometry (TE-ΦOTDR) technology for structural health monitoring of highly flexible wings, including static (i.e., bend and torsion), and dynamic (e.g., vibration) structural deformation. This distributed sensing technology provides a remarkable spatial resolution of 2 cm, with detection and processing bandwidths well under the MHz, arising as a novel, highly efficient monitoring methodology for this kind of structure. Conventional optical fibers were embedded in two highly flexible specimens that represented an aircraft wing, and different bending and twisting movements were detected and quantified with high sensitivity and minimal intrusiveness.

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Lanticq, V., E. Bourgeois, P. Magnien, et al. "Soil-embedded optical fiber sensing cable interrogated by Brillouin optical time-domain reflectometry (B-OTDR) and optical frequency-domain reflectometry (OFDR) for embedded cavity detection and sinkhole warning system." Measurement Science and Technology 20, no. 3 (2009): 034018. http://dx.doi.org/10.1088/0957-0233/20/3/034018.

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Wang, Ji Qiang, Yuan Liu, Mo Yu Hou, Lin Zhao та Tong Yu Liu. "The Performance Analysis of Fiber Distributed Vibration Monitoring Technology Based on φ-OTDR". Applied Mechanics and Materials 336-338 (липень 2013): 192–95. http://dx.doi.org/10.4028/www.scientific.net/amm.336-338.192.

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The performance of the fiber distributed vibration monitoring technology based on the phase sensitive optical time domain reflectometer (φ-OTDR) is reseached. the principle of fiber distributed vibration monitoring of the φ-OTDR and multi-point positioning are illustrated. And this paper indicates the feasibility of realizing multi-point positioning by the φ-OTDR system, and carry on a further research on the φ-OTDR system ́s frequency response range, measuring distance, spatial resolution and other aspects. The inverse proportion relations between the frequency range and distance of the φ-OTDR system, and the relations among spatial resolution, laser pulse width, refractive index and sampling rate are illustrated.

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Piacentini, Fabrizio, Alice Meda, Paolo Traina, et al. "Measurement facility for the evaluation of the backscattering in fiber: Realization of an OTDR operating at single photon level." International Journal of Quantum Information 12, no. 02 (2014): 1461014. http://dx.doi.org/10.1142/s0219749914610140.

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This paper presents the INRIM effort related to the implementation of an optical time domain reflectometer (OTDR) that exploits backscattered light to test an optical fiber operating at single photon level, using two different avalanche photodetectors: a free-running Id220 and a gated Id201. Our tests show that the use of the Id220-based OTDR could be very helpful for QKD application, since it allows testing much longer portions of an optical link. This represents a great advantage for QKD systems, where single components and connections are often embedded in a non-separable optical system.

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Zhang, Pu, Qiguang Feng, Wei Li, Qiang Zheng, and You Wang. "Simultaneous OTDR Dynamic Range and Spatial Resolution Enhancement by Digital LFM Pulse and Short-Time FrFT." Applied Sciences 9, no. 4 (2019): 668. http://dx.doi.org/10.3390/app9040668.

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This paper proposes a novel optical time domain reflectometry (OTDR) method based on the digital linear frequency modulation (LFM) pulse, which can achieve a tradeoff between maximum measurable distance and spatial resolution. Direct modulation and detection are adopted at the transmitting and receiving ends, respectively, which is simple in construction and does not require additional optics. The short-time fractional Fourier transform (STFrFT) is introduced for the signal processing and noise filtering. The theoretical analysis of the working principle confirmed that the spatial resolution is determined by the sweep frequency range of the digital LFM signal rather than the pulse width. The influence of the STFrFT window on the peak sidelobe ratio of the reflection peak is also studied. By combining STFrFT and sidelobe suppression, the dynamic range and spatial resolution can be appreciably enhanced simultaneously. In the demo experiments testing the proposed method on a conventional OTDR development board for comparison, a 7-dB improvement in the dynamic range and an approximately 10-times improvement in the spatial resolution are simultaneously achieved.

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Babin, Sergey A., Alexey G. Kuznetsov, and Ivan S. Shelemba. "Comparison of Raman and Fiber Bragg Grating-Based Fiber Sensor Systems for Distributed Temperature Measurements." Key Engineering Materials 437 (May 2010): 309–13. http://dx.doi.org/10.4028/www.scientific.net/kem.437.309.

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Two types of distributed fiber sensor systems for temperature measurements have been developed: the first one is multi-point Fiber Bragg Grating based system with interrogation by CW tunable laser and nonlinearity compensation by reference interferometer. The second device is Raman scattering system based on optical time domain reflectometry (OTDR) with a pulsed laser providing spatial resolution of several meters and efficient spectral filtering of the Stokes and anti-Sokes signals by means of WDM couplers. Physical effects important for the systems operation are analyzed and their parameters are compared and optimized for applications in oil-gas industry and turbogenerator temperature monitoring.

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Sensfelder, E., J. Bürck, and H. J. Ache. "Characterization of a Fiber-Optic System for the Distributed Measurement of Leakages in Tanks and Pipelines." Applied Spectroscopy 52, no. 10 (1998): 1283–98. http://dx.doi.org/10.1366/0003702981942799.

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A fiber-optic sensor system for the distributed measurement of organic chemicals is presented in this paper. The system uses the technique of optical time-domain reflectometry (OTDR) and a polymerclad optical fiber that is sensitive to nonpolar substances. The location of the chemicals is attained by measuring the time delay between a short laser light pulse entering the fiber and a discrete change in the backscatter signal caused by the enrichment of the analyte in the fiber cladding. Chemical substances enriched in the cladding of the sensor fiber lead to changes in the OTDR response signal, because the light-guiding properties of the fiber are affected through the evanescent wave. The enrichment of an analyte with a higher refractive index than the fiber cladding, for example, will induce a light loss because of mode stripping. This light loss is followed by a step drop in the OTDR response signal. If the analyte penetrating into the fiber cladding absorbs the emitted laser light pulse, a step drop also occurs in the backscatter signal because of the light loss due to the absorption. A fluorescent substance in the fiber cladding leads to a characteristic peak in the OTDR response signal. The intensity of the different signals is correlated with the refractive index and the concentration of the analyte, the interaction length between analyte and sensing fiber, and the temperature, fiber diameter, and bend radius of the fiber.

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Novotný, Vít, Petr Sysel, Aleš Prokeš, Pavel Hanák, Karel Slavíček, and Jiří Přinosil. "Fiber Optic Based Distributed Mechanical Vibration Sensing." Sensors 21, no. 14 (2021): 4779. http://dx.doi.org/10.3390/s21144779.

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The distributed long-range sensing system, using the standard telecommunication single-mode optical fiber for the distributed sensing of mechanical vibrations, is described. Various events generating vibrations, such as a walking or running person, moving car, train, and many other vibration sources, can be detected, localized, and classified. The sensor is based on phase-sensitive optical time-domain reflectometry (ϕ-OTDR). Related sensing system components were designed and constructed, and the system was tested both in the laboratory and in the real deployment, with an 88 km telecom optical link, and the results are presented in this paper. A two-fiber sensor unit, with a double-sensing range was also designed, and its scheme is described. The unit was constructed and the initial measurement results are presented.

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Hu, Yanzhu, Zhen Meng, Xinbo Ai, Yu Hu, Yixin Zhang та Yanchao Shao. "Performance Enhancement of the Location and Recognition of a Φ-OTDR System Using CEEMDAN-KL and AMNBP". Applied Sciences 10, № 9 (2020): 3047. http://dx.doi.org/10.3390/app10093047.

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It is commonly known that for characteristics, such as long-distance, high-sensitivity, and full-scale monitoring, phase-sensitive optical time-domain reflectometry (Φ-OTDR) has developed rapidly in many fields, especially with the arrival of 5G. Nevertheless, there are still some problems obstructing the application for practical environments. First, the fading effect leads to some results falling into the dead zone, which cannot be demodulated effectively. Second, because of the high sensitivity, the Φ-OTDR system is easy to be interfered with by strong noise in practical environments. Third, the large volume of data caused by the fast responses require a lot of calculations. All the above problems hinder the performance of Φ-OTDR in practical applications. This paper proposes an integration method based on a complete ensemble empirical mode decomposition with adaptive noise and Kullback–Leibler divergence (CEEMDAN-KL) and an adaptive moving neighbor binary pattern (AMNBP) to enhance the performance of Φ-OTDR. CEEMDAN-KL improved the signal characteristics in low signal-to-noise ratio (SNR) conditions. AMNBP optimized the location and recognition via a high calculation efficiency. Experimental results show that the average recognition rate of four kinds of events reached 94.03% and the calculation efficiency increased by 20.0%, which show the excellent performance of Φ-OTDR regarding location and recognition in practical environments.

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Gordelier, Tessa, Phillip Rudolph Thies, Giovanni Rinaldi, and Lars Johanning. "Investigating Polymer Fibre Optics for Condition Monitoring of Synthetic Mooring Lines." Journal of Marine Science and Engineering 8, no. 2 (2020): 103. http://dx.doi.org/10.3390/jmse8020103.

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Synthetic mooring lines are becoming a popular alternative to conventional chain mooring systems. For marine renewable energy devices, they have been considered as an enabling technology for this nascent sector, given their reduced costs and ease of deployment. However, the extreme operating environment has led to an increased interest in the ‘in-situ’ condition monitoring of these mooring lines. This paper considers the use of polymer fibre optic technology and the optical time domain reflectometry (OTDR) technique for the condition monitoring of synthetic mooring lines. To establish the operating envelope of the fibres, Polymethylmethacrylate (PMMA) polymer optical fibres are mechanically tested. Additionally, an OTDR is used to monitor fibres whilst under elongation using a tensile test machine, and the sensitivity of the system in monitoring strain is established. At the lowest strain rate, the average proportional limit and yield points of the fibres are found at 1.16% strain and 5.41% strain, respectively. Fatigue exposure of fibres up to 1.25% strain identifies no measurable effect on fibres’ proportional limit or yield point. The occurrence of significant creep is identified for fibres strained beyond 1.5%. The OTDR system is able to identify strains at and above 4%. The study identifies important criteria that should be considered in the integration of polymer optical fibres for mooring applications. Limitations are discussed and suggestions for progressing this technology are provided.

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Jiang, Fei, Honglang Li, Zhenhai Zhang, Yixin Zhang, and Xuping Zhang. "Localization and Discrimination of the Perturbation Signals in Fiber Distributed Acoustic Sensing Systems Using Spatial Average Kurtosis." Sensors 18, no. 9 (2018): 2839. http://dx.doi.org/10.3390/s18092839.

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Location error and false alarm are noticeable problems in fiber distributed acoustic sensing systems based on phase-sensitive optical time-domain reflectometry (Φ-OTDR). A novel method based on signal kurtosis is proposed to locate and discriminate perturbations in Φ-OTDR systems. The spatial kurtosis (SK) along the fiber is firstly obtained by calculating the kurtosis of acoustic signals at each position of the fiber in a short time period. After the moving average on the spatial dimension, the spatial average kurtosis (SAK) is then obtained, whose peak can accurately locate the center of the vibration segment. By comparing the SAK value with a certain threshold, we may to some degree discriminate the instantaneous destructive perturbations from the system noise and certain ambient environmental interferences. The experimental results show that, comparing with the average of the previous localization methods, the SAK method improves the pencil-break and digging locating signal-to-noise ratio (SNR) by 16.6 dB and 17.3 dB, respectively; and decreases the location standard deviation by 7.3 m and 9.1 m, respectively. For the instantaneous destructive perturbation (pencil-break and digging) detection, the false alarm rate can be as low as 1.02%, while the detection probability is maintained as high as 95.57%. In addition, the time consumption of the SAK method is adequate for a real-time Φ-OTDR system.

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Lipovac, Adriana, Vlatko Lipovac, Mirza Hamza, and Vedran Batoš. "Extending OTDR Distance Span by External Front-End Optical Preamplifier." Electronics 10, no. 18 (2021): 2275. http://dx.doi.org/10.3390/electronics10182275.

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Optical time-domain reflectometer (OTDR) is used to characterize fiber optic links by identifying and localizing various refractive and reflective events such as breaks, splices, and connectors, and measuring insertion/return loss and fiber length. Essentially, OTDR inserts a pulsed signal into the fiber, from which a small portion that is commonly referred to as Rayleigh backscatter, is continuously reflected back with appropriate delays of the reflections expressed as the power loss versus distance, by conveniently scaling the time axis. Specifically, for long-distance events visibility and measurement accuracy, the crucial OTDR attribute is dynamic range, which determines how far downstream the fiber can the strongest transmitted optical pulse reach. As many older-generation but still operable OTDR units have insufficient dynamic range to test the far-end of longer fibers, we propose a simple and cost-effective solution to reactivate such an OTDR by inserting a low-noise high-gain optical preamplifier in front of it to lower the noise figure and thereby the noise floor. Accordingly, we developed an appropriate dynamic range and distance span extension model which provided the exemplar prediction values of 30 dB and 75 km, respectively, for the fiber under test at 1550 nm. These values were found to closely match the dynamic range and distance span extensions obtained for the same values of the relevant parameters of interest by the preliminary practical OTDR measurements conducted with the front-end EDFA optical amplifier, relative to the measurements with the OTDR alone. This preliminary verifies that the proposed concept enables a significantly longer distance span than the OTDR alone. We believe that the preliminary results reported here could serve as a hint and a framework for a more comprehensive test strategy in terms of both test diversification and repeating rate, which can be implemented in a network operator environment or professional lab.

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Li, Gang, Kehong Zeng, Bin Zhou, et al. "Vibration monitoring for the West-East Gas Pipeline Project of China by phase optical time domain reflectometry (phase-OTDR)." Instrumentation Science & Technology 49, no. 1 (2020): 65–80. http://dx.doi.org/10.1080/10739149.2020.1780253.

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Shi, Yi, Yuanye Wang, Lei Zhao та Zhun Fan. "An Event Recognition Method for Φ-OTDR Sensing System Based on Deep Learning". Sensors 19, № 15 (2019): 3421. http://dx.doi.org/10.3390/s19153421.

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Phase-sensitive optical time domain reflectometer (Φ-OTDR) based distributed optical fiber sensing system has been widely used in many fields such as long range pipeline pre-warning, perimeter security and structure health monitoring. However, the lack of event recognition ability is always being the bottleneck of Φ-OTDR in field application. An event recognition method based on deep learning is proposed in this paper. This method directly uses the temporal-spatial data matrix from Φ-OTDR as the input of a convolutional neural network (CNN). Only a simple bandpass filtering and a gray scale transformation are needed as the pre-processing, which achieves real-time. Besides, an optimized network structure with small size, high training speed and high classification accuracy is built. Experiment results based on 5644 events samples show that this network can achieve 96.67% classification accuracy in recognition of 5 kinds of events and the retraining time is only 7 min for a new sensing setup.

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Xu, Shaohua, Zujun Qin, Wentao Zhang та Xianming Xiong. "Monitoring Vehicles on Highway by Dual-Channel φ-OTDR". Applied Sciences 10, № 5 (2020): 1839. http://dx.doi.org/10.3390/app10051839.

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As a fully distributed sensor, the phase-sensitive optical time domain reflectometer (φ-OTDR) has attracted remarkable attention in real-time vibration detection. We present a dual-channel φ-OTDR (DC-φ-OTDR), formed by two single-channel φ-OTDRs (SC-φ-OTDR), to monitor running vehicles on a highway. In the double-channel system, an improved algorithm (will be referred to as the CDM&V) is proposed to alleviate the strong dependence of vibration detection on the differential step as in the widely used conventional differential method (CDM). The DC-φ-OTDR is first tested over campus road before applying it to locate moving vehicles on the highway. For comparison purposes, both the DC-φ-OTDR and SC-φ-OTDR are used to monitor the vehicles with respective signal processing methods of the CDM and CDM&V. The experimental results at campus show that the dual-path scheme can undoubtedly reduce vibration misjudgment relative to the single one due to the very small possibility of false measurements occurred simultaneously at the same location in both channels. In signal demodulation, the CDM&V greatly relaxes the constraints on the differencing interval for identifying the vehicle-caused vibration. With a step size of 5 or lower, the CDM fails to locate the running vehicle at z=~8.5 km, but the CDM&V successfully demonstrates the feasible capability of locating the vibration. With an increase in the differential interval, both the CDM and CDM&V are able to detect the vibration signal, but with the latter showing a much better noise suppression performance and hence a larger SNR. Importantly, in comparison with the SC-φ-OTDR system, the DC-φ-OTDR exhibits a considerable enhanced SNR for the detection signal regardless of which processing algorithm (i.e., CDM, CDM&V) is used. The vehicle locations positioned by the DC-φ-OTDR are confirmed by the monitoring cameras.

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Hicke, Konstantin, René Eisermann, and Sebastian Chruscicki. "Enhanced Distributed Fiber Optic Vibration Sensing and Simultaneous Temperature Gradient Sensing Using Traditional C-OTDR and Structured Fiber with Scattering Dots." Sensors 19, no. 19 (2019): 4114. http://dx.doi.org/10.3390/s19194114.

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We present results demonstrating several beneficial effects on distributed fiber optic vibration sensing (DVS) functionality and performance resulting from utilizing standard single mode optical fiber (SMF) with femtosecond laser-inscribed equally-spaced simple scattering dots. This modification is particularly useful when using traditional single-wavelength amplitude-based coherent optical time domain reflectometry (C-OTDR) as sensing method. Local sensitivity is increased in quasi-distributed interferometric sensing zones which are formed by the fiber segments between subsequent pairs of the scattering dots. The otherwise nonlinear transfer function is overwritten with that of an ordinary two-beam interferometer. This linearizes the phase response to monotonous temperature variations. Furthermore, sensitivity fading is mitigated and the demodulation of low-frequency signals is enabled. The modification also allows for the quantitative determination of local temperature gradients directly from the C-OTDR intensity traces. The dots’ reflectivities and thus the induced attenuation can be tuned via the inscription process parameters. Our approach is a simple, robust and cost-effective way to gain these sensing improvements without the need for more sophisticated interrogator technology or more complex fiber structuring, e.g., based on ultra-weak FBG arrays. Our claims are substantiated by experimental evidence.

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Stepanov, Кonstantin V., Andrey A. Zhirnov, Аnton O. Chernutsky, et al. "The Sensitivity Improvement Characterization of Distributed Strain Sensors Due to Weak Fiber Bragg Gratings." Sensors 20, no. 22 (2020): 6431. http://dx.doi.org/10.3390/s20226431.

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Weak fiber Bragg gratings (WFBGs) in a phase-sensitive optical time-domain reflectometer (phi-OTDR) sensor offer opportunities to significantly improve the signal-to-noise ratio (SNR) and sensitivity of the device. Here, we demonstrate the process of the signal and noise components’ formation in the device reflectograms for a Rayleigh scattering phi-OTDR and a WFBG-based OTDR. We theoretically calculated the increase in SNR when using the same optical and electrical components under the same external impacts for both setups. The obtained values are confirmed on experimental installations, demonstrating an improvement in the SNR by about 19 dB at frequencies of 20, 100, and 400 Hz. In this way, the minimum recorded impact (at the threshold SNR = 10) can be reduced from 100 nm per 20 m of fiber to less than 5 nm per 20 m of fiber sensor.

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Hu, Yanzhu, Zhen Meng, Mohammadmasoud Zabihi, et al. "Performance Enhancement Methods for the Distributed Acoustic Sensors Based on Frequency Division Multiplexing." Electronics 8, no. 6 (2019): 617. http://dx.doi.org/10.3390/electronics8060617.

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The last years have witnessed the wide application of Distributed Acoustic Sensor (DAS) systems in several fields, such as submarine cable monitoring, seismic wave detection, structural health monitoring, etc. Due to their distributed measurement ability and high sensitivity, DAS systems can be employed as a promising tool for the phase sensitive optical time domain reflectometry (Φ-OTDR). However, it is also well-known that the traditional Φ-OTDR system suffers from Rayleigh backscattering (RBS) fading effects, which induce dead zones in the measurement results. Worse still, in practice it is difficult to achieve the optimum matching between spatial resolution (SR) and signal to noise ratio (SNR). Further, the overall frequency response range (FRR) of the traditional Φ-OTDR is commonly limited by the length of the fiber in order to prevent RBS signals from overlapping with each other. Additionally, it is usually difficult to reconstruct high frequency vibration signals accurately for long range monitoring. Aiming at solving these problems, we introduce frequency division multiplexing (FDM) that makes it easier to improve the system performance with less system structure changes. We propose several novel Φ-OTDR schemes based on Frequency Division Multiplexing (FDM) technology to solve the above problems. Experimental results showed that the distortion induced by fading effects could be suppressed to 1.26%; when the SR of Φ-OTDR is consistent with the length of the vibration region, the SNR of the sensing system is improved by 3 dB compared to the average SNR with different SRs; vibration frequencies up to 440 kHz have been detected along 330 m artificial microstructures. Thus, the proposed sensing system offers a promising solution for the performance enhancement of DAS systems that could achieve high SNR, broadband FRR and dead zone-free measurements at the same time.

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Zhan, Yage, Qiao Yu, Kun Wang, Fu Yang, and Borui Zhang. "Optimization of a distributed optical fiber sensor system based on phase sensitive OTDR for disturbance detection." Sensor Review 35, no. 4 (2015): 382–88. http://dx.doi.org/10.1108/sr-12-2014-0764.

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Purpose – The purpose of this paper is to theoretically analyze and experimentally demonstrate the investigation on and optimization of a distributed optical fiber sensor based on phase-sensitive optical time domain reflectometer (F-OTDR) for disturbance detection. Design/methodology/approach – The F-OTDR system is investigated and optimized in two aspects: the hardware parameter and the interrogation scheme. Findings – Based on the optimized hardware and the new interrogation scheme, the performances of the F-OTDR system have been improved greatly, compared with conventional F-OTDR system. A location accuracy of 2 m and a signal-to-noise ratio (SNR) of 16 dB have been achieved under a spatial resolution of 8 m. On the other hand, four disturbances at four different locations have been detected and located simultaneously, which is the most effective detection system with the maximum detection capability reported to date, to the best of the authors’ knowledge. Originality/value – Four disturbances at four different locations have been detected and located simultaneously, which is the most effective detection system with the maximum detection capability reported to date, to the best of the authors’ knowledge. With same hardware conditions, more existing disturbances can be detected by using the new interrogation scheme, which is helpful to reduce the miss report of disturbance.

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Zhong, Xiang, Xicheng Gao, Huaxia Deng та ін. "Pulse-Width Multiplexing ϕ-OTDR for Nuisance-Alarm Rate Reduction". Sensors 18, № 10 (2018): 3509. http://dx.doi.org/10.3390/s18103509.

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A pulse-width multiplexing method for reducing the nuisance-alarm rate of a phase-sensitive optical time-domain reflectometer ( ϕ -OTDR) is described. In this method, light pulses of different pulse-widths are injected into the sensing fiber; the data acquired at different pulse-widths are regarded as the outputs of different sensors; and these data are then processed by a multisensor data fusion algorithm. In laboratory tests with a sensing fiber on a vibrating table, the effects of pulse-width on the signal-to-noise ratio (SNR) of the ϕ -OTDR data are observed. Furthermore, by utilizing the SNR as the feature in a feature-layer algorithm based on Dempster–Shafer evidential theory, a four-pulse-width multiplexing ϕ -OTDR system is constructed, and the nuisance-alarm rate is reduced by about 70%. These experimental results show that the proposed method has great potential for perimeter protection, since the nuisance-alarm rate is significantly reduced by using a simple configuration.

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Naeem, Khurram, Bok Hyeon Kim, Dong-Jin Yoon, and Il-Bum Kwon. "Enhancing Detection Performance of the Phase-Sensitive OTDR Based Distributed Vibration Sensor Using Weighted Singular Value Decomposition." Applied Sciences 11, no. 4 (2021): 1928. http://dx.doi.org/10.3390/app11041928.

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We propose a weighted singular value decomposition (WSVD) to reduce the random noise in the Rayleigh backscattering signal of the phase-sensitive optical time domain reflectometry (Φ-OTDR) to enhance the detection performance of the distributed vibration sensing. A 2D image is formed by assembling the raw Rayleigh backscattering traces into a matrix form, and slowly varying fluctuation and random noise can be removed using the WSVD. Consequently, the location information and the frequency of vibration induced by the external vibration event can be extracted. A vibration event with 9 m spatial resolution is detected along a 2.4 km single mode fiber. The signal-to-noise ratio (SNR) of location information for the 102 Hz physical vibration and the 525 Hz acoustic vibration was found to be 10.7 and 12.2 dB, respectively. The SNR of the vibration events demonstrate an increase of 6–7 dB compared to the conventional method, showing the excellent denoising capability of this new approach.

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Zhao, Jie, Jiang Feng, and Liang Ren. "Inversion Calculation Analysis of Operational Tunnel Structure Based on the Distributed Optical-Fiber Sensing System." Advances in Civil Engineering 2017 (2017): 1–9. http://dx.doi.org/10.1155/2017/6159095.

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In combination of the actual project in Dalian Baiyun Mountain Tunnel, this paper introduces the principle of fiber optic sensor monitoring system based on optical time domain reflectometer. Then, based on the orthogonal design and even design scheme, this paper carries out a numerical experiment on the tunnel surrounding rock and establishes a regression model of the mapping relation between surrounding rock parameters of operation tunnel and the monitored displacement in order to set the difference between the monitored displacement and the calculated displacement as the fitness function. In the end, this paper carries out parameter identification based on the differential evolution algorithm. Achievements of the study proved that real-time safety warning could be realized inside the tunnel by monitoring the deformation parameters of tunnel vault at real time relying on the optical-fiber sensing system of the optical time domain reflectometer (OTDR). Parameters identification was carried out on the structure with differential evolution according to measured data and selected parameters, and great coincidence was obtained between the measured displacement and the identified parameters displacement, which proved the strong adaptability of the method.

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Magalhães, Regina, Susana Silva, and Orlando Frazão. "Curvature Sensor Based on a Long-Period Grating in a Fiber Ring Resonator Interrogated by an OTDR." Photonic Sensors 10, no. 1 (2019): 1–6. http://dx.doi.org/10.1007/s13320-019-0398-3.

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Abstract The proposed technique demonstrates a fiber ring resonator interrogated by an optical time domain reflectometer (OTDR), for intensity sensing. By using this methodology, a cavity round trip time of 2.85 μs was obtained. For a proof of concept, a long-period grating was inserted in the resonant cavity operating as a curvature sensing device. A novel signal processing approach was outlined, regarding to the logarithmic behavior of the OTDR. Through analyzing the experimental results, an increase in the measured sensitivities was obtained by increasing applied bending. With curvatures performed from 1.8 m−1 to 4.5 m−1, the sensitivity values ranged from 2.94 dB·km−1 to 5.15 dB·km−1. In its turn, the sensitivities obtained presented a linear behavior when studied as a function of the applied curvature, following a slope of 0.86×10−3 dB. The advantages of applying this technique were also discussed, demonstrating two similar fiber rings multiplexed in a series of configurations.

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