Abstract
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.
Highlights
Phase-sensitive optical time domain reflectometry (Φ-OTDR) has attracted growing interest as a practical and effective technology for applications of vibration detection, such as the monitoring of underwater acoustic and seismic signals [1], owing to its high sensitivity, fast response and multi-point measurement capability [2]
When spatial resolution (SR) equals the length of vibration region L, the optimum signal-to-noise ratio (SNR) of a sensing systemTherefore, can be achieved
Theoretical analysis and experiments have proven that the optimum value of SNR can be obtained when the SR equals the length of vibration region
Summary
Phase-sensitive optical time domain reflectometry (Φ-OTDR) has attracted growing interest as a practical and effective technology for applications of vibration detection, such as the monitoring of underwater acoustic and seismic signals [1], owing to its high sensitivity, fast response and multi-point measurement capability [2]. The edge detection and two-dimensional processing of RBS traces have been reported to increase the SNR [8] Other than these time-domain signal processing methods mentioned above, the wavelet denoising method has been adopted to reduce the random noises induced by varied polarization states in different positions of the fiber [9]. The SR and the length of vibration region can be matched in a more accurate way, and the performance optimization of a Φ-OTDR sensing system can be obtained without reducing the detection frequency range. In practice, the vibration may be applied to a long section of the sensing fiber that contains many SR cells These reference regions might be modulated by vibration and other background noise, leading to a noisy phase signal. It is clear that the fiber length variation induced by vibration can be obtained by demodulating the phase difference change ∆φ.
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