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Journal articles on the topic 'OTDR'

Author: Grafiati

Published: 4 June 2021

Last updated: 12 June 2025

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1

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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2

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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3

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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4

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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5

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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6

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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7

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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8

Wang, Chen, Ying Shang, Wen-An Zhao, Xiao-Hui Liu, Chang Wang, and Gang-Ding Peng. "Investigation and Comparison of $\varphi $ -OTDR and OTDR-Interferometry via Phase Demodulation." IEEE Sensors Journal 18, no. 4 (2018): 1501–5. http://dx.doi.org/10.1109/jsen.2017.2785358.

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9

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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10

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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11

Hu, Yanzhu, Song Wang, Zhaoyang Wang та Yixin Zhang. "The Research on Information Representation of Φ-OTDR Distributed Vibration Signals". Journal of Sensors 2017 (2017): 1–12. http://dx.doi.org/10.1155/2017/6020645.

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This paper mainly focuses on the representable problem of Φ-OTDR distributed vibration signals. The research included a signal extraction part and a signal representation part. Firstly, in order to extract the better Φ-OTDR signal, the time-domain data should be fully preserved. The 2D-TESP method is used to extract data in this paper. There are 29 characters in the traditional TESP method. The characters’ number is reduced from 29 to 13 and the characters’ dimension is expanded from 1 to 2 in the 2D-TESP method. Secondly, in order to represent Φ-OTDR signal better, the characteristics of Φ-OTDR data and damped vibration signals are combined in the paper. The EMD method and the NMF method are combined to form the new method in the paper. Some parameters in the proposed method are optimized and adjusted by GA method. After Φ-OTDR data is represented by the proposed method, there is excellent performance both on the length dimension and on the time dimension. Lastly, some experiments are carried out according to the physical truth in this paper. The experiments are carried out in the semianechoic room. The methods of the paper have better performance. The methods are proved to be effective through these experiments.

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12

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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13

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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14

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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15

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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16

Healey, P. "Complementary code sets for OTDR." Electronics Letters 25, no. 11 (1989): 692–93. http://dx.doi.org/10.1049/el:19890468.

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17

Kimura, T., H. Shimizu, H. Miyagi, and K. Noda. "Time division multiplexed OTDR system." Electronics Letters 21, no. 23 (1985): 1070. http://dx.doi.org/10.1049/el:19850760.

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18

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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19

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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20

Song, Bin, and Wei Dong Gao. "The Design of Electric Power Optical Cable Circuit Automatic Monitoring System Based on PC Computer." Applied Mechanics and Materials 128-129 (October 2011): 1476–79. http://dx.doi.org/10.4028/www.scientific.net/amm.128-129.1476.

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In view of the increasing scale of electric power optical cable and the problem that it is difficult to ensure the quality of the line, combining the actual situation of power system, using OTDR, program-controlled optical switch, PC computer to form a electric power optical cable circuit automatic monitoring system. The design make use of PC computer to control the starting and stopping of OTDR and which channel of program-controlled optical switch is to be guide circuited and receive the data of OTDR to detect the malfunction spot of fiber cable. The system provides an advanced maintenance measure for electric power optical cable, reducing the duration for repair of fiber cable troubles, can be widely used in electric power optical telecommunication network.

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21

FUKURO, ATSUSSHI, TOSHIHIKO TORIGOE, HIROYUKI MIZUGUCHI, and TAKAO UEDA. "APPLICATION OF A NEW MEASURING METHOD USING AN OPTICAL FIBER STRAIN SENSOR TO AN UNDERGROUND TUNNEL." International Journal of Modern Physics B 20, no. 25n27 (2006): 3692–97. http://dx.doi.org/10.1142/s0217979206040210.

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The measuring methods using optical fiber strain sensors are being considered as structural monitoring technologies for concrete structures. B-OTDR method using optical fiber strain sensors can measure continuous strain along an optical fiber over 80km. Because of this advantage, it is expected to measure deformations in large-scale structures. But, this new measuring method, B-OTDR method, is just in development. There is very few case of applying this measuring method to actual structures. This paper describes a new measuring method using optical fiber strain sensors (B-OTDR method) applying to an actual concrete underground tunnel which was expected to deform by new shaft work near this tunnel. As a result, this method using optical fiber strain sensors can measure the deformation of the underground tunnel.

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22

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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23

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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24

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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25

Gong, Yunrui, Anthony D. Stokes, and David Thorncraft. "Noise analysis on a correlation OTDR." Measurement Science and Technology 7, no. 2 (1996): 170–72. http://dx.doi.org/10.1088/0957-0233/7/2/008.

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26

Eraerds, Patric, Matthieu Legre, Jun Zhang, Hugo Zbinden, and Nicolas Gisin. "Photon Counting OTDR: Advantages and Limitations." Journal of Lightwave Technology 28, no. 6 (2010): 952–64. http://dx.doi.org/10.1109/jlt.2009.2039635.

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27

Liao, Ruolin, Ming Tang, Can Zhao, et al. "Harnessing oversampling in correlation-coded OTDR." Optics Express 27, no. 2 (2019): 1693. http://dx.doi.org/10.1364/oe.27.001693.

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28

Xiong, Ji, Jialin Jiang, Yue Wu, et al. "Chirped-pulse coherent-OTDR with predistortion." Journal of Optics 20, no. 3 (2018): 034001. http://dx.doi.org/10.1088/2040-8986/aaa6fe.

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29

Tateda, M., and T. Horiguchi. "Water penetration sensing wavelength tunable OTDR." IEEE Photonics Technology Letters 3, no. 1 (1991): 1–3. http://dx.doi.org/10.1109/68.68028.

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30

Izumita, H., S. i. Furukawa, Y. Koyamada, and I. Sankawa. "Fading noise reduction in coherent OTDR." IEEE Photonics Technology Letters 4, no. 2 (1992): 201–3. http://dx.doi.org/10.1109/68.122361.

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31

Nazarathy, M., S. A. Newton, and W. R. Trutna. "Complementary correlation OTDR with three codewords." Electronics Letters 26, no. 1 (1990): 70–71. http://dx.doi.org/10.1049/el:19900046.

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32

King, J., D. Smith, K. Richards, P. Timson, R. Epworth, and S. Wright. "Development of a coherent OTDR instrument." Journal of Lightwave Technology 5, no. 4 (1987): 616–24. http://dx.doi.org/10.1109/jlt.1987.1075523.

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33

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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Yu, Ling Hong, Chun Mei Jia, and Guan Gen Hou. "A UDWT Technique to Improve the Optical Signal Denoising Effect." Applied Mechanics and Materials 411-414 (September 2013): 1139–42. http://dx.doi.org/10.4028/www.scientific.net/amm.411-414.1139.

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Fiber signal denoising technology is one of the key technologies the OTDR or distributed fiber optic sensors, fiber optic equipment. Actual project application, proposed an improved undecimated discrete wavelet transform (UDWT) denoising technology, relative to traditional wavelet transform denoising technology, has the following characteristics: Denoised curve is more smooth; Better peak detection capability; Better small attenuation maintain capability; Better denoising capability. This technology has achieved very good results in OTDR equipment, beside it can be applied to other optical signal processing.

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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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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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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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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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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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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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WATANABE, Kazuhiro, Shigeaki MATSUBARA, and Yuzuru KUBOTA. "A Hetero-Core Fiber Sensor Using OTDR." Transactions of the Society of Instrument and Control Engineers 35, no. 1 (1999): 32–37. http://dx.doi.org/10.9746/sicetr1965.35.32.

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Nascimento, Jehan F., Marcionilo J. Silva, Isnaldo J. S. Coêlho, Eliel Cipriano, and Joaquim F. Martins-Filho. "Amplified OTDR Systems for Multipoint Corrosion Monitoring." Sensors 12, no. 3 (2012): 3438–48. http://dx.doi.org/10.3390/s120303438.

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Fu, Yun, Zinan Wang, Richeng Zhu та ін. "Ultra-Long-Distance Hybrid BOTDA/Ф-OTDR". Sensors 18, № 4 (2018): 976. http://dx.doi.org/10.3390/s18040976.

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Murray, Matthew J., Allen Davis та Brandon Redding. "Multimode fiber Φ-OTDR with holographic demodulation". Optics Express 26, № 18 (2018): 23019. http://dx.doi.org/10.1364/oe.26.023019.

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Tateda, M., and T. Horiguchi. "Water penetration sensing using wavelength tunable OTDR." IEEE Photonics Technology Letters 2, no. 11 (1990): 844–46. http://dx.doi.org/10.1109/68.63241.

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Jones, M. D. "Using simplex codes to improve OTDR sensitivity." IEEE Photonics Technology Letters 5, no. 7 (1993): 822–24. http://dx.doi.org/10.1109/68.229819.

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Blank, L. C., and D. M. Spirit. "OTDR performance enhancement through erbium fibre amplification." Electronics Letters 25, no. 25 (1989): 1693. http://dx.doi.org/10.1049/el:19891132.

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Martinez-Pinon, F., J. A. Alvarez-Chavez, L. Cruz-May, and G. Martinez-Romero. "Optimum peak pulse investigation for OTDR instrumentation." Laser Physics 18, no. 7 (2008): 907–10. http://dx.doi.org/10.1134/s1054660x08070153.

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Wang, YunCai. "Chaotic laser brings out higher precision OTDR." Chinese Science Bulletin 55, no. 14 (2010): 1461. http://dx.doi.org/10.1007/s11434-010-9997-5.

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Avramović, Marija, Željen Trpovski, and Dejan Nemec. "PRIMOPREDAJNICI ZA PASIVNE OPTIČKE MREŽE." Zbornik radova Fakulteta tehničkih nauka u Novom Sadu 35, no. 03 (2020): 457–60. http://dx.doi.org/10.24867/07be00avramovic.

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