Signal excited-state absorption in the L-band EDFA: Simulation and measurements

Signal excited-state absorption (ESA) influences the performance of erbium-doped fiber amplifier (EDFA) in the L band. The influence is twofold: 1) ESA is responsible for signal absorption, and thus for noise figure increase in the long wavelength range of the L band and 2) ESA decreases inversion of erbium ions, and as a result, amplifier gain is decreased. Two methods of signal ESA measurement are discussed. It is shown that reliable data can be obtained through measurement and later used for accurate simulation of amplifier performance.