A study of the spectroscopic properties of PbF3+GeO2+WO3 vitroceramics doped with Tm3+ and codoped with Yb3+ and Tm3+ ions upon 680 nm dye laser light excitation is made. The up-conversion emission and excitation spectra have been measured at room temperature. An enhancement of blue emission centered at 478 nm in the codoped sample is observed. We suggest that this result is due to the interaction between Yb3+ and Tm3+ ions. When the excitation power of 680 nm light is increased, a three-photon absorption process happens for another blue (451 nm) emission.