Effect of four-wave-mixing on optical frequency-division-multiplexed systems: Comparison of exact numerical analysis and approximation

The nonlinear interference of the channels of an optical Frequency-Division Multiplexed (FDM) transmission system is investigated by numerical solution of the coupled wave equations which exactly describe the nonlinear signal propagation. Using numerical simulations, the average bit error rate of a 11-channel FDM-system using BPSK-modulation and homodyne detection is evaluated as a function of fiber-length and input power. Finally, the results are compared with an approximate calculation of the nonlinear perturbation that is commonly used. It is found that the approximation tends to underestimate the influence of Four Wave Mixing. Therefore, a correction of the approximate result is introduced to fit the results in the interesting range, presetting in this way the validity of the time saving approximation.