scholarly journals High SNR Φ-OTDR with Multi-Transverse Modes Heterodyne Matched-Filtering Technology

Sensors ◽  
2021 ◽  
Vol 21 (22) ◽  
pp. 7460
Author(s):  
Yifan Liu ◽  
Junqi Yang ◽  
Bingyan Wu ◽  
Bin Lu ◽  
Luwei Shuai ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
Incident Light ◽  
Matched Filtering ◽  
Rayleigh Backscattering ◽  
Optical Time Domain Reflectometer ◽  
Transverse Modes ◽  
Seismic Detection ◽  
Phase Sensitive ◽  
Optical Time ◽  
First Time

Phase-sensitive optical time domain reflectometer (Φ-OTDR) has attracted attention in scientific research and industry because of its distributed dynamic linear response to external disturbances. However, the signal-to-noise ratio (SNR) of Φ-OTDR is still a limited factor by the weak Rayleigh Backscattering coefficient. Here, the multi-transverse modes heterodyne matched-filtering technology is proposed to improve the system SNR. The capture efficiency and nonlinear threshold are increased with multiple transverse modes in few-mode fibers; the incident light energy is permitted to be enlarged by a wider probe pulse by using heterodyne matched-filtering without spatial resolution being deteriorated. As far as we know, this is the first time that both multi-transverse modes integration method and digital heterodyne matched filtering method have been used to improve the SNR of Φ-OTDR simultaneously. Experimental results show that the noise floor is reduced by 11.4 dB, while the target signal is kept. We believe that this proposed method will help DAS find important applications in marine acoustic detection and seismic detection.

scholarly journals Pulse-Width Multiplexing ϕ-OTDR for Nuisance-Alarm Rate Reduction

Sensors ◽  
2018 ◽  
Vol 18 (10) ◽  
pp. 3509 ◽  
Author(s):  
Xiang Zhong ◽  
Xicheng Gao ◽  
Huaxia Deng ◽  
Shisong Zhao ◽  
Mengchao Ma ◽  
...  
Keyword(s):  
Pulse Width ◽  
Signal To Noise Ratio ◽  
Fusion Algorithm ◽  
Multisensor Data Fusion ◽  
Optical Time Domain Reflectometer ◽  
Light Pulses ◽  
Phase Sensitive ◽  
Evidential Theory ◽  
Vibrating Table ◽  
Optical Time

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.

scholarly journals The Sensitivity Improvement Characterization of Distributed Strain Sensors Due to Weak Fiber Bragg Gratings

Sensors ◽  
2020 ◽  
Vol 20 (22) ◽  
pp. 6431
Author(s):  
Кonstantin V. Stepanov ◽  
Andrey A. Zhirnov ◽  
Аnton O. Chernutsky ◽  
Kirill I. Koshelev ◽  
Alexey B. Pnev ◽  
...  
Keyword(s):  
Rayleigh Scattering ◽  
Signal To Noise Ratio ◽  
Fiber Bragg Gratings ◽  
Bragg Gratings ◽  
Optical Time Domain Reflectometer ◽  
Sensitivity Improvement ◽  
Phase Sensitive ◽  
Optical Time ◽  
Electrical Components

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.

scholarly journals Recent Advances in Phase-Sensitive Optical Time Domain Reflectometry (Ф-OTDR)

2021 ◽  
Vol 11 (1) ◽  
pp. 1-30
Author(s):  
Yunjiang Rao ◽  
Zinan Wang ◽  
Huijuan Wu ◽  
Zengling Ran ◽  
Bing Han
Keyword(s):  
Fiber Optics ◽  
Time Domain ◽  
Acoustic Waves ◽  
Rapid Development ◽  
Development Stage ◽  
Time Domain Reflectometry ◽  
Rayleigh Backscattering ◽  
Optical Time Domain Reflectometry ◽  
Phase Sensitive ◽  
Optical Time

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.

scholarly journals Sub-Meter Spatial Resolution Phase-Sensitive Optical Time-Domain Reflectometry System Using Double Interferometers

2018 ◽  
Vol 8 (10) ◽  
pp. 1899 ◽  
Author(s):  
Shengwen Feng ◽  
Tuanwei Xu ◽  
Jianfen Huang ◽  
Yang Yang ◽  
Lilong Ma ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Time Domain ◽  
Time Domain Reflectometry ◽  
Bilateral Filtering ◽  
Rayleigh Backscattering ◽  
Detection Frequency ◽  
Optical Time Domain Reflectometry ◽  
Phase Sensitive ◽  
Optical Time ◽  
Phase Generated Carrier

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.

The Performance Analysis of Fiber Distributed Vibration Monitoring Technology Based on φ-OTDR

2013 ◽  
Vol 336-338 ◽  
pp. 192-195
Author(s):  
Ji Qiang Wang ◽  
Yuan Liu ◽  
Mo Yu Hou ◽  
Lin Zhao ◽  
Tong Yu Liu
Keyword(s):  
Spatial Resolution ◽  
Sampling Rate ◽  
Vibration Monitoring ◽  
Monitoring Technology ◽  
Optical Time Domain Reflectometer ◽  
Response Range ◽  
Phase Sensitive ◽  
Point Positioning ◽  
Optical Time ◽  
Time Domain Reflectometer

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.

scholarly journals The Influence of Laser Linewidth on the Brillouin Shift Frequency Accuracy of BOTDR

2018 ◽  
Vol 9 (1) ◽  
pp. 58 ◽  
Author(s):  
Qing Bai ◽  
Min Yan ◽  
Bo Xue ◽  
Yan Gao ◽  
Dong Wang ◽  
...  
Keyword(s):  
Probe Pulse ◽  
Measurement Accuracy ◽  
Signal To Noise Ratio ◽  
Gain Spectrum ◽  
Laser Source ◽  
Laser Linewidth ◽  
Optical Time Domain Reflectometer ◽  
Brillouin Gain ◽  
Optical Time ◽  
Shift Frequency

This paper analyzes the influence of laser linewidth on the measurement accuracy of a frequency-scanning Brillouin optical time domain reflectometer (FS-BOTDR), allowing for both the width of Brillouin gain spectrum and the signal-to-noise ratio (SNR) of the BOTDR system. The measurement accuracy of the Brillouin frequency shift (BFS) is theoretically investigated versus the duration of the probe pulse and the linewidth of the laser source, by numerically simulating how a FS-BOTDR works and evaluating the Brillouin gain spectrum (BGS) width and the system SNR. The simulation results show that the BFS accuracy is improved as the laser linewidth becomes narrower when the probe pulse width is fixed. We utilize five types of lasers with respective linewidths of 1.05 MHz, 101 kHz, 10.2 kHz, 3.1 kHz, and 98 Hz to compare the BFS measurement accuracy over a ~10 km optical sensing fiber. The experimental results demonstrate that the root-mean-square error (RMSE) of BFS decreases with the laser linewidth narrowing from 1.05 MHz to 3.1 kHz, which is in good agreement with the numerical simulation. However, the RMSE of BFS increases when the laser linewidth is less than 3.1 kHz, which may arise from the coherent Rayleigh noise due to a too narrow laser linewidth. The results can provide a theoretical basis and experimental guidance for choosing the appropriate laser linewidth in BOTDR.

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