# Distributed fiber sparse-wideband vibration sensing by sub-Nyquist additive random sampling

## TL;DR

This paper introduces a sub-Nyquist additive random sampling method for phase-sensitive optical time domain reflectometry, enabling wide-band vibration detection over long fibers by randomizing pulse intervals.

## Contribution

It proposes a novel random sampling technique to extend the vibration frequency response range of { extphi}-OTDR systems for sparse-wideband signals.

## Key findings

- Successfully verified wide-band signal reconstruction through experiments.
- The method broadens vibration detection capabilities for long-distance fiber sensing.
- Theoretical analysis and simulations optimize the sampling approach.

## Abstract

The round trip time of the light pulse limits the maximum detectable vibration frequency response range of phase-sensitive optical time domain reflectometry ({\phi}-OTDR). Unlike the uniform laser pulse interval in conventional {\phi}-OTDR, we randomly modulate the pulse interval, so that an equivalent sub-Nyquist additive random sampling (sNARS) is realized for every sensing point of the long interrogation fiber. For an {\phi}-OTDR system with 10 km sensing length, the sNARS method is optimized by theoretical analysis and Monte Carlo simulation, and the experimental results verify that a wide-band spars signal can be identified and reconstructed. Such a method can broaden the vibration frequency response range of {\phi}-OTDR, which is of great significance in sparse-wideband-frequency vibration signal detection, such as rail track monitoring and metal defect detection.

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Source: https://tomesphere.com/paper/1702.08253