Pump induced nonlinear refractive index [n/sub 2/] change in erbium and ytterbium doped fibers-theory and experiments

Summary form only given. The increasingly demanding application of erbium-doped fiber amplifiers (EDFA) in fiber optic communication systems (including solitons), requires a deep understanding of the effects of the pump laser on the optical properties of the amplifier at the signal level. Amplification provides by EDFAs is produced by optically pumping an absorption band to provide signal gain in the emission band. Promoting carriers to upper energy levels modifies the optical properties of the amplifier. There has been few studies on the pump induce refractive index change at the signal level in EDFAs-all focused on the pump-induced effects on the linear index of refraction, and none on the nonlinear index of refraction n/sub 2/. The theory for the nonlinear susceptibility in the presence of a pump laser in a quasi-two-state system was developed. We use a previously described technique called induced grating autocorrelation two-beam coupling, IGA-TBC to verify the results.