Measurement error analysis of surface-bonded distributed fiber-optic strain sensor subjected to linear gradient strain: Theory and experimental validation

Strain transfer analysis is an important means of correcting the measurement error of embedded or surface-bonded distributed fiber-optic sensors, but the effect of host strain patterns has not been well elucidated. Here, a theoretical model for strain transfer analysis of surface-bonded multi-layered fiber-optic sensor subjected to a linear gradient strain was established. Closed-form solutions were obtained for both singleand bi-linear strain distributions, and, in particular, a simple method was described for determining the strain transfer coefficient at the turning point of a bi-linear type strain. The presented model was validated through laboratory testing with high-spatial resolution strain profiles acquired by optical frequency-domain reflectometry. Furthermore, parametric analyses were performed to investigate the influences of mechanical and geometrical properties of protective and adhesive layers on the strain transfer performance, shading light on the design, installation, and measurement error correction of fiber-optic sensors after accounting for the effect of host strain distribution.