A two-electrode multi-quantum-well semiconductor optical amplifier is designed and fabricated.The amplified spontaneous emission（ASE）spectrum and gain were measured and analyzed.It is shown that the ASE spectrum and gain characteristic are greatly influenced by the distribution of the injection current density.By changing the injection current density of two electrodes,the full width at half maximum,peak wavelength,peak power of the ASE spectrum and the gain characteristic can be easily controlled.
