A single semiconductor optical amplifier （SOA） assisted by optical filter is exploited to realize high-speed all-optical wavelength conversion, in which, the filter is employed to optimize output spectrum. We propose a spectrum optimizer which contains a band pass filter （BPF） and a delay interferometer （DI）. Based on this configuration, 80 Gbit/s all-optical non-inverted conversion has been numerically simulated. Furthermore, the quality of output signal has been improved greatly using genetic algorithms to optimize the parameters of the spectrum optimizer. Additionally，the effect of ultra-fast carrier dynamics in SOA on the output signal is analyzed theoretically. The dependence of the signal extinction ratio （ER） and pattern effect （PE） on variations of the BPF’s ER and DI’s ER is also studied.