Wideband and flat-gain optical amplification from 1460 to 1510 nm by serial combination of a thulium-doped fluoride fibre amplifier and fibre Raman amplifier

A wideband and flat-gain optical amplifier is realised for the wavelength band under the gain band of erbium-doped fibre amplifiers by serially connecting a thulium-doped fluoride fibre amplifier and a fibre Raman amplifier. A high gain of > 25 dB is obtained in the range 1460 – 1510 nm.