Spectroscopic characteristics (spontaneous emission probabilities, radiative lifetimes, oscillator strengths, branching ratios and quantum efficiency) of Er³⁺ in Ga₂S₃-GeS₂-Er₂S₃ glassy system are investigated by use of Judd-Ofelt theory. Lifetime measurements ⁴S_3/2 level of Er³⁺ in Ga₂S₃-GeS₂-Er₂S₃ glasses with various Er³⁺ concentrations and optical gap energy are performed. Estimations of the non-radiative relaxation rate and the multiphonon relaxation rate demonstrate the occurrence of energy transfer from Er³⁺ ion to the electronic states of the glass matrix. The way of the practical application of this non-radiative energy transfer is suggested.