In recent years, as fiber optical communication is advancing to mixed signals broadcasting IM and PSK formats simultaneous transmission must be investigated for future WDM solutions, since there are neither agreed recommendations nor standards for mixed WDM systems. However, due to IM simplicity, and its historic dominance, it can be used as a good foundation for the purpose of mixed signals transmission. To realize the simultaneous transmission of IM and PSK signals in WDM network, the system’s design and optimization have to take into account all the contributing factors - such as the signal optical power, channel interval and fiber dispersion.