Interference-fading-free phase-demodulated OTDR system

Pan, Zhengqing; Liang, Kezhen; Zhou, Jun; Ye, Qing; Cai, Haiwen; Qu, Ronghui

doi:10.1117/12.975656

Cited by 44 publications

(14 citation statements)

References 8 publications

(7 reference statements)

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“…It also raises difficulties in specifying the system performance, particularly SNR. Different techniques were implemented in order to have a reduced interference fading and relatively stable phase sensitivity [10][11][12]. Additionally, many studies were done to overcome the polarization fading such as adoption of polarization diversity scheme [13], interrogation with orthogonal-state of polarization pulse pair [14] and polarization-maintaining configuration [9].…”

Section: Introductionmentioning

confidence: 99%

Field test and fading measurement of a distributed acoustic sensor system over a 50 km-long fiber

Uyar

Kartaloğlu

Özdür

et al. 2018

Fiber Optic Sensors and Applications XV

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In this study, we present a direct detection distributed acoustic sensor based on phase-sensitive optical time domain reflectometer (φ-OTDR) with long sensing range and high signal-to-noise ratio (SNR), which is field-tested over a 50 kmlong fiber. Due to the random nature of Rayleigh backscattered light and fading phenomena, it is hard to characterize the performance of the system. For this reason, the performance of our sensor is specified in a statistical manner in which the mean SNR is determined using the histograms of the SNR. The SNR values are measured for identical acoustic signals in five different days, total of 48 hours and the SNR histograms are obtained for fiber distances of 100 m, 12 km, 21 km, 30 km, 40 km and 50 km. The system is field-tested using external disturbances that are generated from a 50-Hz vibrator. The SNR values are extracted from the power spectral density (psd) of the collected data over the monitored fiber span. Our results show that the φ-OTDR system exhibits a mean SNR of 22.5 dB at 50 km distance.

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Section: Introductionmentioning

confidence: 99%

Field test and fading measurement of a distributed acoustic sensor system over a 50 km-long fiber

Uyar

Kartaloğlu

Özdür

et al. 2018

Fiber Optic Sensors and Applications XV

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“…The optical phase can also be obtained from the beat frequency of coherent detection, but suffers from the phase noise of laser source. Pan et al extracted phase signals from the beat frequency in -OTDR [15], and a more than 360 Hz vibration detection bandwidth was achieved with a 10 kHz interrogation repetition rate in a 4 km measurement range, which was limited by the phase noise. Tu et al used a differential process to prevent signal deterioration caused by the phase noise and realized a measurement range of 25 km with a 10-m spatial resolution [16].…”

Section: Introductionmentioning

confidence: 99%

Long-Range Distributed Vibration Sensing Based on Phase Extraction From Phase-Sensitive OTDR

et al. 2016

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Distributed fiber-optic vibration sensors based on phase-sensitive optical timedomain reflectometry (-OTDR) have found many applications in various fields. In this paper, we analyze the phase noise of -OTDR, which is the main limiting factor of the measurement range. We found that the laser phase noise and phase extraction error caused by the intensity noise in photodetection contribute to the total phase noise. By introducing a series of auxiliary weak reflection points along the fiber, we develop a phase-noise-compensated -OTDR and realize a long-range distributed vibration sensing based on the phase extraction. Furthermore, a statistical analysis was proposed to maintain the vibration measurement sensitivity along the whole fiber. In the experiment, vibrations at 30 km were measured with a linear response, which confirmed the validity of our proposed system.

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“…There are two typical signal detection schemes in the Ф-OTDR system including direct detection [ 7 , 8 , 9 , 10 ] and coherent detection [ 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 ]. In the direct detection scheme, the setup is simple; only the intensity of the optical signal is detected by using a high-sensitivity photodetector.…”

Section: Introductionmentioning

confidence: 99%

“…This greatly reduces the complexity and the cost of the whole system. Up until now, there were three kinds of signal demodulation methods for the system based on coherent detection, including the zero-span function of the electrical spectrum analyzer (ESA) [ 11 , 12 ], heterodyne detection [ 13 , 14 , 15 , 16 , 17 , 18 ] and digital coherent detection [ 19 , 20 ]. In previous reports, the zero-span function of the ESA was used to eliminate all the other unwanted electrical components to obtain a pure signal [ 11 , 12 ].…”

Section: Introductionmentioning

confidence: 99%

Self-Mixing Demodulation for Coherent Phase-Sensitive OTDR System

Shao

et al. 2016

Sensors

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Phase-sensitive optical time domain reflectometry (Ф-OTDR) attracts much attention due to its capability of telling the type and position of an intrusion simultaneously. In recent decades, coherent Ф-OTDR has been demonstrated to realize long-distance detection. For coherent Ф-OTDR, there are three typical demodulation schemes in the reported studies. However, they still cannot realize real-time monitoring to satisfy practical demands. A simple and effective demodulation method based on self-mixing has been put forward to demodulate the beat signal in coherent Ф-OTDR. It not only saves a local electrical oscillator and frequency locked loop, but also demodulates the beat signal without residual frequency. Several vibrations with different frequency were separately applied at the same location of a 42.5 km fiber. The spatial resolution of 10 m and frequency response range from 8 Hz to 980 Hz have been achieved. The precise location with signal-to-noise ratio of 21.4 dB and broadband measurement demonstrate the self-mixing scheme can demodulate the coherent Ф-OTDR signal effectively.

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Interference-fading-free phase-demodulated OTDR system

Cited by 44 publications

References 8 publications

Field test and fading measurement of a distributed acoustic sensor system over a 50 km-long fiber

Field test and fading measurement of a distributed acoustic sensor system over a 50 km-long fiber

Long-Range Distributed Vibration Sensing Based on Phase Extraction From Phase-Sensitive OTDR

Self-Mixing Demodulation for Coherent Phase-Sensitive OTDR System

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