Dynamic strain sensing using Doppler-shift-immune phase-sensitive OFDR with ultra-weak reflection array and frequency-tracking

TL;DR

This paper introduces a novel phase-sensitive OFDR technique that employs frequency-tracking and spectrum-zooming to achieve accurate dynamic strain sensing over 1000 meters, immune to Doppler shifts and with high spatial resolution.

Contribution

The paper presents a Doppler-shift-immune phase-sensitive OFDR method using frequency-tracking and spectrum-zooming, enabling high-precision dynamic strain sensing over long distances.

Findings

Doppler shifts cause demodulation errors in OFDR-based sensing.

The proposed method maintains precision regardless of Doppler-induced mismatch.

Successful experimental demonstration over 1000 meters with 2.5 cm resolution.

Abstract

In distributed fiber-optic sensing based on optical frequency domain reflectometry (OFDR), Doppler frequency shifts due to the changes of disturbances during one sweep period introduce demodulation errors that accumulate along both the distance and time, impairing the sensing performance. Here, we report distributed dynamic strain sensing using Doppler-shift-immune phase-sensitive OFDR based on frequency-tracking and spectrum-zooming with ultra-weak reflection array. Theoretical study has been carried out with the introduction of mismatch coefficient, unveiling quantitatively the impact of Doppler shift. Following a numerical analysis of the proposed method, a retained precision has been experimentally verified regardless of the position mismatch due to the Doppler effect. Doppler-shift-immune sensing for dynamic strains covering continuous spatial resolution over a distance of 1000 m with a 2.5 cm sensing spatial resolution has been demonstrated, verifying the high fidelity promised by the proposed method.