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

Electronics ◽  
2019 ◽  
Vol 8 (6) ◽  
pp. 617 ◽  
Author(s):  
Yanzhu Hu ◽  
Zhen Meng ◽  
Mohammadmasoud Zabihi ◽  
Yuanyuan Shan ◽  
Siyi Fu ◽  
...  
Keyword(s):  
Performance Enhancement ◽  
Signal To Noise Ratio ◽  
Dead Zone ◽  
High Sensitivity ◽  
Time Domain Reflectometry ◽  
System Structure ◽  
Frequency Division Multiplexing ◽  
Frequency Division ◽  
Rayleigh Backscattering ◽  
Sensing System

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.

scholarly journals Performance Enhancement of the Location and Recognition of a Φ-OTDR System Using CEEMDAN-KL and AMNBP

2020 ◽  
Vol 10 (9) ◽  
pp. 3047
Author(s):  
Yanzhu Hu ◽  
Zhen Meng ◽  
Xinbo Ai ◽  
Yu Hu ◽  
Yixin Zhang ◽  
...  
Keyword(s):  
Performance Enhancement ◽  
Signal To Noise Ratio ◽  
Dead Zone ◽  
Recognition Rate ◽  
High Sensitivity ◽  
Ensemble Empirical Mode Decomposition ◽  
Time Domain Reflectometry ◽  
Long Distance ◽  
Practical Applications ◽  
Leibler Divergence

It is commonly known that for characteristics, such as long-distance, high-sensitivity, and full-scale monitoring, phase-sensitive optical time-domain reflectometry (Φ-OTDR) has developed rapidly in many fields, especially with the arrival of 5G. Nevertheless, there are still some problems obstructing the application for practical environments. First, the fading effect leads to some results falling into the dead zone, which cannot be demodulated effectively. Second, because of the high sensitivity, the Φ-OTDR system is easy to be interfered with by strong noise in practical environments. Third, the large volume of data caused by the fast responses require a lot of calculations. All the above problems hinder the performance of Φ-OTDR in practical applications. This paper proposes an integration method based on a complete ensemble empirical mode decomposition with adaptive noise and Kullback–Leibler divergence (CEEMDAN-KL) and an adaptive moving neighbor binary pattern (AMNBP) to enhance the performance of Φ-OTDR. CEEMDAN-KL improved the signal characteristics in low signal-to-noise ratio (SNR) conditions. AMNBP optimized the location and recognition via a high calculation efficiency. Experimental results show that the average recognition rate of four kinds of events reached 94.03% and the calculation efficiency increased by 20.0%, which show the excellent performance of Φ-OTDR regarding location and recognition in practical environments.

scholarly journals Measurement of CO2 by Wavelength Modulated Reinjection Off-Axis Integrated Cavity Output Spectroscopy at 2 μm

Atmosphere ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 1247
Author(s):  
Zihao Yuan ◽  
Yinbo Huang ◽  
Xingji Lu ◽  
Jun Huang ◽  
Qiang Liu ◽  
...  
Keyword(s):  
Signal Intensity ◽  
Performance Enhancement ◽  
Signal To Noise Ratio ◽  
High Sensitivity ◽  
Co2 Concentration ◽  
Trace Gas ◽  
Cavity Output ◽  
Average System ◽  
Long Time ◽  
Gas Measurements

A high sensitivity wavelength modulated reinjection off-axis integrated cavity output spectroscopy (WM-RE-OA-ICOS) experimental setup was built at a 2 μm band. On the basis of an off-axis integrated output spectroscopy (OA-ICOS), combined with an optical reinjection (RE) approach to improve signal intensity, and wavelength modulation spectroscopy (WMS) to improve the signal-to-noise ratio (SNR) of the system, the experimental study of trace CO2 with high sensitivity was carried out using the setup. The performance was compared and evaluated, and the results show that: Compared with the OA-ICOS, the wavelength modulated reinjection OA-ICOS enhanced the signal intensity by 6.3 times, and the SNR increased 7.2 times from 179 to 1288. The Allan variance results showed that the detection limit of the system is 0.35 ppm when the average system time is 230 s. The setup was used to measure the indoor CO2 concentration for a long time (22 h), and the measured results were in line with the actual concentration change. The proposed method shows good performance enhancement for the OA-ICOS system in trace gas measurements.

scholarly journals Performance Optimization for Phase-Sensitive OTDR Sensing System Based on Multi-Spatial Resolution Analysis

Sensors ◽  
2018 ◽  
Vol 19 (1) ◽  
pp. 83 ◽  
Author(s):  
Yuanyuan Shan ◽  
Wenbin Ji ◽  
Qing Wang ◽  
Lu Cao ◽  
Feng Wang ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Performance Optimization ◽  
Signal To Noise Ratio ◽  
Time Domain Reflectometry ◽  
Sensing System ◽  
Optical Time Domain Reflectometry ◽  
Resolution Analysis ◽  
Phase Sensitive ◽  
Optical Time ◽  
Qualitative Relationship

This paper proposes and demonstrates a phase-sensitive optical time domain reflectometry (Φ-OTDR) sensing system with multi-spatial resolution (MSR) analysis property. With both theoretical analysis and an experiment, the qualitative relationship between spatial resolution (SR), signal-to-noise ratio (SNR) and the length of the vibration region has been revealed, which indicates that choosing a suitable SR to analyze the vibration event can effectively enhance the SNR of a sensing system. The proposed MSR sensing scheme offers a promising solution for the performance optimization of Φ-OTDR sensing systems, which can restore vibration events of different disturbance range with optimum SNR in merely a single measurement while maintaining the same detectable frequency range.

scholarly journals Performance on FBMC-OQAM and OFDM Multicarrier Systems

2019 ◽  
Vol 8 (10) ◽  
pp. 1564-1568
Keyword(s):  
Orthogonal Frequency Division Multiplexing ◽  
Filter Bank ◽  
Signal To Noise Ratio ◽  
Cyclic Prefix ◽  
Frequency Division Multiplexing ◽  
Frequency Division ◽  
Signal To Noise ◽  
Multicarrier Systems ◽  
Noise Ratio ◽  
Power Equality

Filter Bank Multi Carrier (FBMC) offers best detestable properties took a gander at over orthogonal frequency division multiplexing (OFDM) to the attack of nonexistent hindrance. FBMC system is a multicarrier structure, particularly sensible for 5G remote correspondences. FBMC beats OFDM as a result of proficient use of the open information move limit and without usage of cyclic prefix (CP). In this paper, we address the issue of remarkable enrollment at the pilot territory and used to audit the channels with pilot picture, in like way consider the fundamental conditions for utilization of the assistant pilot pictures. First and two partner pictures for each pilot plans with power equality uses instead of one picture; it can attainable inspirations driving necessity of OFDM and FBMC depending upon signal to noise ratio (SNR) what's relentlessly possible to improve the introduction of one frivolity pictures by using multiple associate pictures. Finally autonomous the BER execution reenactment results and adornment pilot pictures

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