Enhanced Φ - OTDR system for quantitative strain measurement based on ultra-weak fiber Bragg grating array

Abstract

Phase-sensitive optical time-domain reflectometry (Φ-OTDR) has been widely used in various applications for its distributed measurement capability of dynamic disturbance. However, traditional Φ-OTDR cannot realize quantitative measurement of the strain variation introduced by the external disturbance. Recently, an ultra-weak fiber Bragg grating (UWFBG) array-based Φ-OTDR system has been proposed to realize quantitative measurement. Unfortunately, the spatial resolution in this system is not satisfactory, since spatial resolution is equal to UWFBGs interval and the interval cannot be too small. We have proposed an enhanced system to realize quantitative strain measurement and high spatial resolution monitoring by combining ordinary Φ-OTDR system with the UWFBG array-based Φ-OTDR system. Experimental results showed that quantitative strain measurement at the end of a 5-km long sensing fiber could be realized with a spatial resolution of 4 m while the interval between adjacent UWFGBs was 50 m.