Modeling high-concentration L-band EDFA at high optical powers based on inversion function

High-concentration erbium-doped fibers used in L-band erbium-doped fiber amplifier (EDFA) are known to experience additional losses due to effects of energy transfer between Er³⁺ ions and possibly quenchers (e.g., homogeneous and clustering-induced up-conversion, quenching, etc.). These interactions between Er³⁺ ions make modeling of inversion dynamics in L-band EDFA more complicated. We present a modeling approach for high-concentration doped fiber based on lumping of all complex phenomena of energy transfer in EDFA into a function of two variables hereafter referred to as the inversion function. The inversion function is evaluated for high optical powers (which constitutes a typical situation for fiber amplifiers) using a cluster expansion and assuming that upconversion is the leading loss mechanism. The modeling results show a close agreement with the measurement data for various input power conditions and inversion levels