Enhanced cryogenic temperature sensor from 320 to 20 K amplified by Vernier effect

There are urgent needs for cryogenic temperature sensing in the monitoring of liquefied gas energy, spacecraft, and cryobiology, with properties of electromagnetic immunity, chemical corrosion, high sensitivity, and a wide measurement range. In this paper, we proposed an improved cryogenic temperature sensor with high sensitivity and an ultra-wide temperature range based on the Vernier effect (VE) and fiber Bragg grating (FBG). Owing to the sensitivity amplifying effect of VE in cascaded Sagnac interferometers (CSIs), the proposed cryogenic temperature sensor showed a high average sensitivity of 6.73 nm/K. FBG was used to mark the dip wavelength as it exceeded a free spectral range in the output spectra of CSIs. Finally, cryogenic temperature sensing with high sensitivity and an ultra-wide temperature range of 320–20 K was achieved. The proposed cryogenic temperature sensor also demonstrated good hysteresis, repeatability, and stability. To the best of our knowledge, this is the first report on cryogenic temperature sensing utilizing VE in CSIs. The excellent characteristics make the proposed CSIs a competitive candidate for cryogenic temperature monitoring in various fields.