High-Sensitivity Bending Sensor Based on Supermode Interference in Coupled Four-Core Sapphire-Derived Fiber

A Mach-Zehnder interferometer (MZI) sensor based on a four-core sapphire-derived fiber (FSDF) for bending sensing is proposed and demonstrated. The MZI is formed by splicing a coupled FSDF between two single-mode fibers, delivering supermode interference among four LP01-like supermodes (LP01s modes) and eight LP11-like supermodes (LP11s modes). Benefiting from the different response of the field distribution of each supermode to curvature changes, MZI sensors with a variety of bending properties can be fabricated based on the interference of different supermodes in the FSDF. The experimental results show that the sensitivity of the FSDF-MZI sensor I based on the interference between the LP01s and the LP11s modes is about 4.5 dB/m(-1) in the curvature range from 0.4 to 2.5 m(-1). The FSDF-MZI sensor II based on the interference of two LP11s modes can realize bending sensing in +/- Y directions. The sensitivity of FSDF-MZI sensor II in the curvature range of -10.0-5.0 m(-1) is about -24.526 nm/m(-1). It suggests that the proposed FSDF-MZI sensor has potential application in the field of structure health detection.

Automated summary

The Mach-Zehnder interferometer sensor based on a four-core sapphire-derived fiber shows promising potential for bending sensing applications, with the ability to fabricate sensors with different bending properties. The experimental results demonstrate high sensitivity and potential for application in structural health monitoring.