In this work, we studied the interlock requirements in a seed failure scenario for Er3¸:Yb3¸ doped fiber amplifiers (EYDFAs) pumped with high intensities in the MWcm-2 range at 9XX nm. We fed a time-dependent FEM-tool with the data from backwards directed amplified spontaneous emission (ASE) transients of different commercially available core-pumped singlemode fibers. In the FEM-tool, the Er3¸:Yb3¸ system is defined as a bi-directional energy transfer process and described by the corresponding rate equations. The power evolution of the pump, seed, and ASE signal is computed by differential equations taking into account the transient population densities of the relevant energy levels. With the model, we computed the temporal evolution of the corresponding energy levels after a seeder failure to take place within tens to hundreds of μs and calculated the associated gain. The fibers under test provide a critical total gain of 30 dB after 80 μs within the Yb3¸ band and after 300 μs within the Er3¸ band. This time decreases with increasing pump power and doping concentration. The results can be extrapolated to high-power cladding-pumped EYDFAs to meet the challenging requirements of ngineering-level systems.