Impacts of residual facet reflection on the performances of wavelength converters based on semiconductor optical amplifiers (SOAs) are theoretically investigated. Residual facet reflection definitely degrades the converter performance. A probe signal feedback scheme is introduced to improve the wavelength conversion characteristics. With the probe signal feedback, the wavelength conversion parameters, including extinction ratio, frequency chirping and modulation response, can be enhanced, and the facet reflection limits are relaxed due to the enhancement of carrier-photon interaction.