This paper introduces the non linear optical effect known as four wave mixing (FWM). In wavelength division multiplexing (WDM) systems four wave mixing can strongly affect the transmission performance on an optical link. As a result it is important to investigate the impact of FWM on the design and performance of WDM optical communication systems. The main objective of this paper is to analyze the FWM power and efficiency for different channel spacing of transmitted signals, dispersion and core effective area of fiber by designing and simulating a model in LabVIEW. In this paper, we have simulated the FWM design for three waves. The results obtained show that the FWM power and efficiency decreases with the increase of the channel spacing of transmitted signals, dispersion and core effective area of fiber. © 2006-2014 Asian Research Publishing Network (ARPN).