Optimization of an erbium-doped fiber amplifier with radial effects

Applying an inversing method and a genetic algorithm, two radial distributions, i.e., a core graded-index and erbium-doped concentration, are optimized for an erbium-doped fiber amplifier (EDFA) in a two-level model under single-mode condition and weakly guided approximations. There is evidence to show that the core graded-index has obvious influence on the gain bandwidth of the EDFA, and similarly, the radial distribution of the erbium concentration has effect on the bandwidth, while no effect on the gain. As an example, we provide an optimized single-fiber EDFA with the graded-index and the erbium concentration distribution, which is characterized with a 33.5 dB gain, a 30 nm bandwidth, and a noise figure of 3.55 dB. The broader bandwidth is one of the outstanding advantages over current single-fiber EDFAs with uniform radial distributions.