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 GeO$_2$–Na$_{2}$O–Yb$_{2}$O$_3$–MgO–La$_{2}$O$_3$–Er$_{2}$O$_{3}$ 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%.