The resonant cross relaxation processes between Yb3+ and Er3+ ions in calcium alumino-silicate glasses have been quantified under selective Er3+ excitation. The infrared emission spectra, measured under steady state conditions (CW excitation to the 4I9/2 erbium level), have allowed to obtain an experimental relationship linking the transfer (Yb3+ → Er3+) and back transfer (Er3+ → Yb3+) parameters. These measurements combined with the dynamics of the main emitting levels, measured under pulsed excitation to the 2H11/2 erbium level, have allowed the fully quantification of the energy transfer parameters. The obtained values, C25=5.5×10−18cm3s−1 (Yb3+ → Er3+), C52=1.5×10−18cm3s−1 (Er3+ → Yb3+) and C27=7.6×10−18cm3s−1 (up-conversion mechanism, estimated from the Judd-Ofelt analysis previously reported), can be used to predict the temporal evolution of the main luminescent emission bands