Study of fiber Bragg gratings with TiN-coated for cryogenic temperature measurement

Abstract In this study, single metal-coated Fiber Bragg grating (FBG) sensors and bare FBG sensors were placed in an aluminum alloy mold, which were in turn packaged in a thermal insulation container to monitor the temperature response, and used as cryogenic temperature sensors. Specifically, the performance of titanium nitride (TiN)-coated FBG sensors in cryogenic temperature environments was evaluated. Using an optical spectrum analyzer (OSA), the reflection spectra of the TiN-coated FBG sensors were measured and compared with those of bare FBG for temperatures ranging from 25 to −195 °C. The results showed that the TiN-coated FBG exhibited a temperature sensitivity of 10.713 pm/°C and R-squared value of 0.995. The TiN-coated on the FBG altered the non-linear characteristics of the thermo-optic and thermal expansion coefficients of the FBG. Through this research to get thermo-optic coefficient ( ξ  = 5.12 × 10−6) and thermal expansion coefficient (α = 1.81 × 10−6) and resulted in more precise measurements at cryogenic temperature.