This paper investigates for rising optical fiber transmission strength, increasing bandwidth, and decreasing communication system weakness by using wavelength division multiplexing (WDM). WDM gives today's distention speed and communication traffic. Systems using WDM faces nonlinearities, which the most intensive nonlinear attack is, four wave mixing (FWM). FWM creates and increases crosstalk between WDM channels as a result slows down and impairs the performance of the communication system. This investigation uses orthogonal frequency division multiplexing (OFDM) for evaluating execution of WDM fiber system by repairing Polarization Mode Dispersion (PMD). We took results in the case of trying PMD-Emulator and without trying PMD-Emulator in the system design. We compared the results got in both cases. Furthermore, we compared the performance of the system with the investigations done using different ways, methods, and techniques for compensating PMD and FWM appears in WDM systems. As PMD-Emulator, helps enhancing the system design performance, and OFDM gives the feature of robustness and useful execution to the system. OFDM examined by appointing interfered orthogonal signal sets, for 16 channels; with equally spaced OFDM channels. Oure results showed that the optical fiber communication system using OFDM technique gives perfect removing FWM signal crosstalk, and accurate data transmission, comparing to other techniques used in other researches. We got a decreased FWM power to -77dBm, and the BER of -0.317. Furthermore, the system quality increased with applying PMD-Emulator and OFDM. In addition, using PMD-Emulator in the system design raised the results effectiveness. The program used in the present work is optisystem-15, and the results obtained in this study coincide with the theoretical and actual results obtained by the previous studies.