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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Polarization-fading-free distributed acoustic sensing system
摘要： A fiber-optic distributed acoustic sensing system based on polarization diversity technology is proposed and demonstrated. Without the polarization fading phenomenon, the false alarm rate is considerably reduced, making the system much practicable for real applications. The technology can't eliminate phase noise caused by polarization disturbance of transmission fiber. In order to solve the above problems, this paper adopts the polarization diversity method in the system to eliminate the polarization fading phenomenon, which is experimentally demonstrated to greatly reduce the missing and false alarm rate of the DAS system, and therefore greatly improved the system practicability.
关键词： polarization diversity,polarization fading,distributed acoustic sensing,false alarm
更新于2025-09-16 10:30:52
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Eliminating Phase Drift for Distributed Optical Fiber Acoustic Sensing System with Empirical Mode Decomposition
摘要： Phase-drift elimination is crucial to vibration recovery in the coherent detection phase-sensitive optical time domain re?ectometry system. The phase drift drives the whole phase signal ?uctuation as a baseline, and its negative e?ect is obvious when the detection time is long. In this paper, empirical mode decomposition (EMD) is presented to extract and eliminate the phase drift adaptively. It decomposes the signal by utilizing the characteristic time scale of the data, and the baseline is eventually obtained. It is validated by theory and experiment that the phase drift deteriorates seriously when the length of the vibration region increases. In an experiment, the phase drift was eliminated under the conditions of di?erent vibration frequencies of 1 Hz, 5 Hz, and 10 Hz. The phase drift was also eliminated with di?erent vibration intensities. Furthermore, the linear relationship between phase and vibration intensity is demonstrated with a correlation coe?cient of 99.99%. The vibrations at 0.5 Hz and 0.3 Hz were detected with signal-to-noise ratios (SNRs) of 55.58 dB and 64.44 dB. With this method, when the vibration frequency is at the level of Hz or sub-Hz, the phase drift can be eliminated. This contributes to the detection and recovery of low-frequency perturbation events in practical applications.
关键词： phase drift elimination,phase recovery,phase-sensitive optical time domain re?ectometry,distributed acoustic sensing system,empirical mode decomposition
更新于2025-09-12 10:27:22
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Proceedings [EAGE Publications BV 76th EAGE Conference and Exhibition 2014 - Amsterdam, Netherlands (2014.06.16-2014.06.19)] Proceedings 76th EAGE Conference and Exhibition 2014 - Fundamentals of Vibration Sensing with Distributed Fibre Optic Sensors through Downscaled Experiments
摘要： In the past few years the Distributed Vibration Sensing of fibre optic sensors (also called Distributed Acoustic Sensing) has gained great interest in geophysics, despite the fundamentals of the measurement being poorly understood. The technology offers immense improvement in terms of efficiency when compared with current geophysical methods and also could be preferred for applications such as permanent reservoir monitoring. We present a method for downscaled experimentation that enabled us to define the fundamentals of the optical fibre measurement. We show seismic data that were recorded simultaneously by both the fibre optical interferometer and conventional geophones, thus enabling the comparison of sensor performance. We present results focused on wave-polarity sensitivity and the directionality of fibre measurements. The current interrogation method of optical fibre cables cannot distinguish between wavefields coming from opposite azimuthal directions, which can be an issue in certain applications where the identification of up-going and down-going wavefields is essential. Observations are also presented that describe the relationship between the velocity signal that is measured using a geophone array and the phase difference measurement from the fibre optic sensing system.
关键词： directionality,Distributed Vibration Sensing,Distributed Acoustic Sensing,optical fibre measurement,geophones,wave-polarity sensitivity,seismic data,fibre optic sensors,geophysics
更新于2025-09-11 14:15:04
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Enabling Simultaneous DAS and DTS Through Space-Division Multiplexing Based on Multicore Fiber
摘要： We have proposed and demonstrated a hybrid optical-fiber sensor that enables simultaneous distributed acoustic sensing (DAS) and distributed temperature sensing (DTS). The hybrid fiber sensor is realized through space-division multiplexed (SDM) reflectometers in a multicore fiber (MCF), where Raman optical time-domain reflectometry (ROTDR) for DTS is implemented simultaneously with phase-sensitive optical time-domain reflectometry (Φ-OTDR) for DAS through space-division multiplexing. The SDM reflectometers share an identical pulse source, but use separate interrogation fiber cores, allowing simultaneous measurement of ROTDR and Φ-OTDR. The proposed hybrid sensor based on MCF does not suffer from the incompatible pump power levels issue existing in its counterpart based on single mode fiber thanks to the SDM implementation. Thus it effectively eliminates the restriction imposed by fiber nonlinear effects (e.g., modulation instability). Wavelet transform denoising method is employed to reduce the noise of temporal ROTDR traces; as a result, the worst temperature uncertainty is reduced from 4.1 to 0.5 °C over 5.76 km sensing range. The proposed SDM hybrid fiber sensor can realize simultaneous distributed intrusion detection and temperature monitoring. It offers great potential in long-term real-time pipeline monitoring for oil and gas industry.
关键词： Distributed acoustic sensing,multicore fiber,distributed temperature sensing,space-division multiplexing
更新于2025-09-11 14:15:04
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A field experiment of walkaway distributed acoustic sensing vertical seismic profile in a deep and deviated onshore well in Japan using a fibre optic cable deployed inside coiled tubing
摘要： A 2D walkaway vertical seismic profiling (VSP) survey using distributed acoustic sensing (DAS) was conducted at an onshore site in Japan. The maximum depth and the deviation of the observation well were more than 4,000 m and 81 degrees, respectively. Among the several methods for installing fibre optic cables, we adopted the inside coiled tubing method, in which coiled tubing containing a fibre optic cable is deployed. The signal-to-noise ratio (SNR) of the raw shot gather was low, possibly due to poor coupling between the fibre optic cable and the subsurface formation resulting from the fibre optic cable deployment method and the existence of considerable tubewave noise. Nevertheless, direct P-wave arrivals, P-P reflections and P-S converted waves exhibited acceptable SNRs after careful optimization of gauge length for DAS optical processing and the application of carefully parameterized tubewave noise suppression. One of the challenges in current DAS-VSP data processing is the separation of P- and S-waves using only one-component measurements. Hence, we applied moveout correction using 2D ray tracing. This process effectively highlights only reflected P-waves, which are used in subsequent subsurface imaging. Comparison with synthetic well seismograms and 2D surface seismic data confirms that the final imaging result has a sufficiently high quality for subsurface monitoring. We acquired DAS-VSP data under both flowing conditions and closed conditions, in which the well was shut off and no fluid flow was allowed. The two imaging results are comparable and suggest the possibility of subsurface imaging and time-lapse monitoring using data acquired under flowing conditions. The results of this study suggest that, by adopting the inside coiled tubing method without drilling a new observation well, more affordable DAS-VSP monitoring can be achieved in fields such as CO2 capture and storage (CCS) and unconventional shale projects, where monitoring costs have to be minimized.
关键词： coiled tubing,vertical seismic profiling,Distributed acoustic sensing,walkaway VSP
更新于2025-09-11 14:15:04
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[ASME 2018 12th International Pipeline Conference - Calgary, Alberta, Canada (Monday 24 September 2018)] Volume 3: Operations, Monitoring, and Maintenance; Materials and Joining - Real-Time Continuous Pipeline Integrity Monitoring Utilising Telecommunications Optical Fibre Cables
摘要： A recent trend in the field of pipeline monitoring has been the utilisation of an optical fibre based distributed acoustic sensing (DAS) technology, for the purpose of security monitoring of buried pipelines [1-3]. The technology comprises an interrogator, connected to an optical fibre cable, which is interrogated to acquire coherent Rayleigh backscatter. Localised environmental vibrations may result in a proportional strain of the fibre. This strain results in a localised optical path length variation, resulting in a phase distortion in the measured signals. Application of signal processing techniques infer the characteristic of the originating stimulus, and thus identify and locate the source activity of interest. Activity may arise as a result of ground excavation, vehicular movement, or similar in the vicinity of the pipeline. Researchers are now studying the possibility of utilisng this technology for the purpose of pipeline leak detection monitoring [4]. This paper provides a review of one such programme of work. Results are presented for a permanent installation, where signatures relating to leaks were identified, and located in the resulting DAS data. Results are provided relating to liquid leaks, where product was emitted at a flow rate of 20.0l/minute and operational pressure 20.0bar.
关键词： Distributed Acoustic Sensing,Leak Detection,Optical Fibre sensing
更新于2025-09-09 09:28:46