Modulated Pulses Based High Spatial Resolution Distributed Fiber System for Multi-Parameter Sensing

TL;DR

This paper presents a hybrid fiber sensing system that simultaneously detects vibration, temperature, and strain with high spatial resolution and long distance by modulating laser pulses and integrating two optical reflectometry techniques.

Contribution

It introduces a novel modulation approach combining {}-OTDR and B-OTDR for multi-parameter sensing with enhanced signal-to-noise ratio and sub-meter spatial resolution.

Findings

Achieved 4.8 kHz vibration sensing at 3 m resolution over 10 km fiber.

Simultaneous temperature and stress measurements with 80 cm resolution.

Enhanced signal quality through laser pulse modulation and advanced data processing.

Abstract

We demonstrate a hybrid distributed fiber sensing system for multi-parameter detection. The integration of phase-sensitive optical time domain reflectometry ({\Phi}-OTDR) and Brillouin optical time domain reflectometry (B-OTDR) enables measurement of vibration, temperature and strain. Exploiting the fast changing property of vibration and the static property of temperature and strain, the laser pulse width and intensity are modulated and then injected into the single-mode sensing fiber proportionally, so that the three concerned parameters can be extracted simultaneously by only one photo-detector and data acquisition channel. Combining with advanced data processing methods, the modulation of laser pulse brings additional advantages because of trade and balance between the backscattering light power and nonlinear effect noise, which enhances the signal-to-noise ratio, and enables sub-meter level spatial resolution together with long sensing distance. The proposed method realizes up to 4.8 kHz vibration sensing with 3 m spatial resolution at 10 km standard single-mode fiber. And measurements of the distributed temperature and stress profile along the same fiber with 80 cm spatial resolution are also achieved concurrently.