We report, for the first time, a broadband upconversion emission (800–1000 nm) in Bi-doped germano-silicate glass optical fibers with excitation in the range of 1515–1585 nm, which can explain the low laser efficiency at wavelengths longer than 1500 nm. The mechanism responsible for the emission is two-step upconversion process. The origin of this upconversion luminescence is discussed and new energy transition schemes are proposed. • We fabricated bismuth-doped germane-silicate glass optical fibers. • New upconversion emission band was observed by pumping around 1.5 μm. • Both emissions at 837 and 945 nm depend quadratically on the incident power. • Two-step upconversion process and new energy transition scheme was proposed.