Temperature-Insensitive Strain Sensor Based on Microsphere-Embedded Core-Offset Fiber With High Sensitivity

Strain sensor with low temperature crosstalk over large strain range is essential for field monitoring of structural safety. We develop a tension-compression strain sensor with high strain sensitivity, large strain range, low temperature, and polarization crosstalk due to many high-order modes interferences from asymmetric off-core microsphere-waveguide. It is based on BaTiO
₃
(BTO) microsphere embedded on the surface of the silica core-offset fiber via negative thermal coefficient UV glue. Multi-beam reflection and whispering-gallery modes (WGMs) in the microsphere enhance the multi-mode interference, and then improve the strain sensitivity to 17.29 pm/μϵ, which is three times higher than that without microsphere, along with the temperature sensitivity of -0.87 pm/°C, and the strain accuracy of 0.5 μϵ. Thanks to the reduced effective Young's modulus by microsphere and UV glue on an asymmetric core-offset structure, strain range of tension and compression is increased to 153.2 mϵ.