The wavelength conversion of 2.5 Gbit/s non return-to-zero optical pulse based on cross-gain modulation in semiconductor optical amplifier is demonstrated. The separation for up-convertion is larger than 10 nm, and down-conversion is larger than 20 nm. The relationship between the receiver power and bit error rate is shown. Co-propagation wavelength conversion is used in this experiment. The signal wavelength is fixed, the probe optical signal is extra-cavity laser with the tunable wavelength. No bit error is observed after a measurement of more than one hour, which will be useful in the application of WDM optical networks.