We investigate and demonstrate for the first time the benefit of IM-DPSK signals over NRZ signal in wavelength conversion using Four Wave Mixing in Semiconductor Optical Amplifier. Using this method, we experimentally demonstrate the wavelength conversion at 10 Gb/s with distance of 450 Km (5 span of 90 Km) using Non Zero Dispersion Shifted Fiber (NZDSF) Single Mode Fiber (SMF). The result shows the improvement of IM-DPSK signal versus NRZ signal with BER of 10-11 and 10-6. In addition it also shows an improvement in Q factor versus number of span.