Upconversion-induced variations in gain-spectraof 1.48 µm pumped erbium-doped fluoride fibre amplifier

Upconversion-induced variations in gain-spectra as large as ~1.3 dB are observed in a 1.48 µm pumped erbium-doped fluoride fibre amplifier, when gains at 1540 and 1560 nm are kept equal to each other at different multiwavelength input powers. A novel model that takes upconversion into consideration well explains the experimental results.