We present an ultra-wideband supercontinuum source using a dispersion-shifted fiber and an amplified diode-laser pulse source. A gain-switched DFB laser operating at 1550-nm wavelength, which provides 30-ps pulses, was used for generating the seeding pulses. And serially cascaded low-cost EDFAs were employed to boost the peak power of the pulses to more than 1 kW. Single-mode supercontinuum spanning nearly the full near-IR band was obtained by passing the amplified pulses through a dispersion-shifted fiber. By investigating the characteristics of the generated supercontinuum pulses, the walk-off between the spectral components was found to limit the effective interaction length of the spectrum-broadening effects. In order to expand further the spectral range of the output, we have examined the time-gating ASE suppression scheme and use of a high-power EDFA. And the resulted outputs have reached wavelengths of 0.8 and 0.9 μm, respectively at the short-wavelength edges. Only the blue-shifted part that can be obtained using a short-wavelength-pass filter can exhibit 3-dB bandwidth more than 500 nm in the vicinity of 1.2 μm. The supercontinuum generation scheme provides a compact and reliable way to generate ultra-wideband flat spectrum that can be useful for high-resolution OCT.