Stable high-power operation of an all-fiber broadband superfluorescent source, based on ytterbium-doped double-cladding fibers, is achieved via a fiber amplifier. It comprises an amplified spontaneous emission (ASE) seed source which is amplified to over one hundred watts in the next stage for a single pass, with no self-pulsing, relaxation oscillation or lasing modes being observed. The center wavelength of ASE seed source is 1050 nm, and the full width half maximum (FWHM) is 21 nm. The maximum superfluorescent output power yielded by the amplifier is 102 W, the slope efficiency with respect to the pump power is 70%, and FWHM of the emission spectrum is 20.5 nm.