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

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

Applied Sciences ◽

10.3390/app8101899 ◽

2018 ◽

Vol 8 (10) ◽

pp. 1899 ◽

Cited By ~ 3

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.

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Recent Advances in Distributed Acoustic Sensing Based on Phase-Sensitive Optical Time Domain Reflectometry

Journal of Sensors ◽

10.1155/2018/3897873 ◽

2018 ◽

Vol 2018 ◽

pp. 1-16 ◽

Cited By ~ 37

Author(s):

Yonas Muanenda

Keyword(s):

Time Domain ◽

Time Domain Reflectometry ◽

Fiber Optic Sensor ◽

Acoustic Sensing ◽

Rayleigh Backscattering ◽

Recent Advances ◽

Optical Time Domain Reflectometry ◽

Phase Sensitive ◽

Distributed Acoustic Sensing ◽

Optical Time

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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A Fading Tolerant Phase-Sensitive Optical Time Domain Reflectometry Based on Phasing-Locking Structure

Electronics ◽

10.3390/electronics10050535 ◽

2021 ◽

Vol 10 (5) ◽

pp. 535

Author(s):

Xuping Zhang ◽

Yunyin Zheng ◽

Chi Zhang ◽

Qiuhao Dong ◽

Shisong Zhao ◽

...

Keyword(s):

Time Domain ◽

External Disturbance ◽

Intermediate Frequency ◽

Time Domain Reflectometry ◽

Optical Modulator ◽

Noise Floor ◽

Rayleigh Backscattering ◽

Optical Time Domain Reflectometry ◽

Phase Sensitive ◽

Optical Time

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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