“…However, their model was used to optimize chirped-pulse FA design only considering co-propagating configurations, whereas the model described here includes boundary conditions such that arbitrary pump configurations can be simulated. While this is already of great interest, as counter propagating FA are commonly used 14 15 16 18 26 , the model presented here also includes ASE, gain saturation and uses the inversion at each position to determine the gain for the GNLSE. Furthermore, the impact of the inversion level on the refractive index is also included.…”