Strain transfer characteristics of fiber Bragg gratings at ultra-low temperature

Abstract

Strain monitoring for components under low-temperature environment is used in a variety of fields, and Fiber Bragg grating (FBG) is ideally suited for cryogenic sensing measurements due to its unique properties. In this paper, a simulation model of surface-adhesive Fiber Bragg grating with the substrate is established for low-temperature strain precise measurement. The strain distribution on the fiber when subjected to thermal strain is explored. Liquid nitrogen impact experiments are conducted with groups of encapsulation parameters, and it is found that the paste length and paste width affect the spectral chirp rate to a different extent. Furthermore, the suitable encapsulation parameters are selected, and temperature compensation experiments are carried out at 77 K to 293 K for surface-adhesive FBG using 304 stainless steel as the substrate material. The temperature compensation curves are derived from the experiments, which provides an accurate temperature compensation scheme for FBG strain measurement.