Strain calibration of substrate-free FBG sensors at cryogenic temperature

Abstract

Strain calibration measurements are performed for acrylate coated, substrate-free fiber Bragg grating (FBG) sensors at room temperature of 298 K and cryogenic temperature of 77 K. A 1550 nm Bragg wavelength (λB) FBG sensor, with its sensing part not being bonded to any surface, is subjected to axial strain using MTS25 tensile machine available at Cryogenic Material tests Karlsruhe (CryoMaK), KIT. The Bragg wavelength shift (ΔλB) versus induced strain (ε) is regressed with a linear polynomial function and the strain sensitivity obtained is found to be 0.9 pm/με at both the temperatures, verifying that the FBG strain sensitivity is independent of temperature.