Calibration of Temperature by Normalized Up-Conversion Fluorescence Spectra of Germanate Glasses and Glass Ceramics Doped with Erbium and Ytterbium Ions

A multivariate model of temperature calibration by the spectra of green up-conversion fluorescence based on the principal component analysis, cluster analysis, and the interval projection to latent structures is developed to select the best erbium- and ytterbium-doped germanate glasses and glass-ceramics for sensitive elements of fluorescent temperature sensors. The calibration model constructed for GeO2–Na2O–Yb2O3–MgO–La2O3–Er2O3 glass ceramics using 95 spectral variables is characterized by the best quality parameters, namely, the root-mean-square error is 0.37 K, the residual predictive deviation for a test sampling is >102, and the relative error does not exceed 0.20%.