Interference fading suppression in Phi-OTDR using space-division multiplexed probes

TL;DR

This paper introduces a new method for reducing interference fading in Phi-OTDR systems by using space-division multiplexed probes with multiple modes, demonstrating improved performance through experimental validation.

Contribution

The paper presents a novel interference fading suppression technique in Phi-OTDR using spatially multiplexed modes, which is simpler and more reliable than existing methods.

Findings

Fading probability is significantly reduced with multiple SDM probes.

Distinct modes produce different Rayleigh backscattering waveforms.

The method improves fading suppression without complex modulation.

Abstract

We propose and experimentally demonstrate a novel interference fading suppression method for phase-sensitive optical time domain reflectometry (Phi-OTDR) using space-division multiplexed (SDM) pulse probes in few-mode fiber. The SDM probes consist of multiple different modes, and three spatial modes (LP01, LP11a and LP11b) are used in this work for proof of concept. Firstly, the Rayleigh backscattering light of different modes is experimentally characterized, and it turns out that the waveforms of Phi-OTDR traces of distinct modes are all different from each other. Thanks to the spatial difference of fading positions of distinct modes, multiple probes from spatially multiplexed modes can be used to suppress the interference fading in Phi-OTDR. Then, the performances of the Phi-OTDR systems using single probe and multiple probes are evaluated and compared. Specifically, statistical analysis shows that both fading probabilities over fiber length and time are reduced significantly by using multiple SDM probes, which verifies the significant performance improvement on fading suppression. The proposed novel interference fading suppression method does not require complicated frequency or phase modulation, which has the advantages of simplicity, good effectiveness and high reliability.