Abstract: The optical transitions intensity parameters of Er³⁺ in MFT glass were calculated by using the J-O theory. The transition
probabilities, branching ratios and lifetimes of Er³⁺ ion were obtained. The excitation spectra were measured monitored at intense
green of ²H_11/2, ⁴S_3/2→⁴I_15/2 transitions and red fluorescence of ⁴F_9/2→⁴I_15/2 transition
of Er³⁺ ion. The fluorescence intensity variation with temperature for ²H_11/2, ⁴S_3/2→⁴I_15/2 transitions was observed.
The fluorescence decay of ²H_11/2, ⁴S_3/2→⁴I_15/2 transitions was measured and the quantum efficiency and non-radiative transition rates were calculated.

Key words: MFT glass, J-O theory, quantum efficiency, non-radiative transition