A complete spectroscopic investigation of energy transfer processes in oxyfluoride glass ceramics containing CaF 2 nano-crystals doped with various amounts of Er 3+ and Yb 3+ was reported. An enhancement of the 1.53μm emission and infrared to visible up-conversion fluorescence was confirmed experimentally due to efficient non-radiative energy transfer from Yb 3+ to Er 3+ ions concentrated in CaF 2 nano-crystals. The efficiency of Yb 3+ to Er 3+ energy transfer in excess of 85% was obtained for 0.5mol% Er 3+ /2.0mol% Yb 3+ co-doped glass ceramic. Using rate equation formulism, the coefficient of Yb 3+ to Er 3+ energy transfer was determined to be about 3.5 times higher than that of Er 3+ to Yb 3+ energy back transfer, which is sufficient to provide high 4 I 11/2 population of Er 3+ to improve the fluorescence of the co-doped glass ceramics.