Four-wave mixing (FWM) is the intermodulation phenomenon in the optical signal, as a result of which several linearly polarized optical waves interact. An experimental study of the Four-Wave Mixing effect in standard single-mode fiber (SSMF) and nonzero dispersion-shifted fiber (NZDSF) was carried out, with two and three wavelengths. An experimental investigation was carried out with the typical DWDM equipment. It was shown that FWM-effect has the significant influence on the propagation of the symbol pulses in dispersion - shifted optical fiber.