Investigation of signal excited-state absorption in bismuth-based erbium-doped fiber amplifier

Signal excited-state absorption (ESA) in a bismuth oxide-based erbium-doped fiber (EDF) amplifier was investigated in numerical and experimental ways. The signal ESA cross-section of the bismuth oxide-based EDF was first measured by using a especially devised numerical-prediction technique that can give an accurate value for an arbitrary EDF length. Using a range of numerical simulations based on the measured signal ESA cross-section as well as experimental measurements, the signal ESAs impact on the gain and noise figure was investigated. The signal ESA reduces the amplification bandwidth by ̃7 nm compared with that of the theoretical gain bandwidth that can be obtained without signal ESA. The longer wavelength limit of the amplification band was estimated to be ̃1632 nm.