The paper study on the optimization of the symmetrically split-step Fourier method (S-SSFM) to solve the nonlinear Schrodinger equation for modeling optical transmission systems. With two versions of the method, the trapezoidal S-SSFM and the mid-point S-SSFM, our proposition can reduce by a factor 30 percent (for the trapezoidal S-SSFM) and by a factor 50 percent (for the mid-point S-SSFM) the computational time in comparison with the original methods while preserving the same accuracy. Several cases of transmission have been taken into account including strongly nonlinear transmission, nonlinear transmission and quasi-linear transmission. Simulations using the optimized version of the trapezoidal S-SSFM have also been compared to experimental data in a nonlinear pulse propagation experiment.