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Open AccessArticle

Performance Enhancement Methods for the Distributed Acoustic Sensors Based on Frequency Division Multiplexing

1
School of Automation, Beijing University of Posts and Telecommunications, Beijing 100876, China
2
The Key Laboratory of Intelligent Optical Sensing and Manipulation, Ministry of Education, Nanjing 210093, China
3
School of Physics and Optoelectronic Engineering, Nanjing University of Information Science and Technology, Nanjing 210044, China
4
Central Research Institute of Building and Construction Co., Ltd, MCC Group, Beijing 100088, China
*
Authors to whom correspondence should be addressed.
Electronics 2019, 8(6), 617; https://doi.org/10.3390/electronics8060617
Received: 6 May 2019 / Revised: 22 May 2019 / Accepted: 29 May 2019 / Published: 31 May 2019
(This article belongs to the Special Issue Optical Communications and Networks)
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. View Full-Text
Keywords: frequency-division-multiplexing (FDM); distributed acoustic sensing (DAS); signal to noise ratio (SNR); fading effect suppression; phase-sensitive optical time domain reflectometry (Φ-OTDR) frequency-division-multiplexing (FDM); distributed acoustic sensing (DAS); signal to noise ratio (SNR); fading effect suppression; phase-sensitive optical time domain reflectometry (Φ-OTDR)
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Hu, Y.; Meng, Z.; Zabihi, M.; Shan, Y.; Fu, S.; Wang, F.; Zhang, X.; Zhang, Y.; Zeng, B. Performance Enhancement Methods for the Distributed Acoustic Sensors Based on Frequency Division Multiplexing. Electronics 2019, 8, 617.

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