Abstract

Calibration measurements with two different types of fiber Bragg (FBG) temperature sensors are performed in the temperature range form 4.2 K to 300 K. For both types of sensors the nonlinear temperature induced wavelength shift can be described by a fifth order polynomial function. The first type of fiber sensor, a bare fiber with a removed fiber coating at the location of the FBG, shows a wavelength shift of Δλ = 1.15 nm for a temperature change from 273 K to 4.2K. The second type of sensor, a FBG bonded to a poly(methyl methacrylate) (PMMA) substrate, shows a wavelength shift of Δλ = 11.7 nm for the same temperature range. A lower operation limit of T_{lower limit~} 45 K was acieved in this study for the bare fiber and of T_{lower limit} ~ 30 K for the fiber bonded to the PMMA substrate.

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