Effects of Four Wave Mixing (FWM) on Optical Fiber in Wavelength Division Multiplexing (WDM) Channels Authors

This paper deals with the investigation of Four Wave Mixing (FWM), a non-linearity in WDM system. In a typical commercial 128 channel 10Gbps system FWM is a third order non linearity in silica fibers that is analogous to intermodulation distortion in electrical system. Dense WDM transmission in which individual wavelength channel are modulated at the rates of 10 Gbps offer capacities of NX10 Gbps, where “N ” is the number of wavelengths. To transmit such a high capacity overlong distance requires operation in the 1550nm window of dispersion shifted fiber.Two dispersion shifted fiber of length 100 km were launched and the fiber dispersion values varied from “-16 ps/nm/km to 16ps/nm/km ” through parametric runs. The signal observed were very close to the transmitter end. However, on increasing the dispersion values the system turned noisier. The low average dispersion minimized pulse spreading, whereas the high local dispersion destroyed the carrier frequency phase relationship that give rise to FWM intermodulation products. Thus, FWM product decreases with increase in dispersion values