Analysis to find the best Hybrid modulation technique for suppression of Four Wave Mixing

The latest trend in lightwave communication system is towards huge information transmission capacity by explosive growth in data rate communication. Wavelength division multiplexing is used to achieve this objective. It is a technology of transmitting data from different sources over a single link at same time whereas each data channel is carried on its own unique wavelength. Dense WDM is evolved from WDM where channel spacing is less than or equal to 100 GHz. But, their performance is limited by various Non-Linear effects which are caused by dependence of refractive index on the intensity of the optical power. Four Wave Mixing is a non linear process that generates new frequency components from the existing frequency components. Also, it degrades the system performance, so this has to be minimized. In this paper, three Hybrid modulation techniques have been discussed in 2.5 Gbps 8-channel DWDM system for suppression of four wave mixing. Firstly, the channels are equally spaced at 100 GHz and then the channel spacing has been reduced to 50 GHz. The techniques are based upon the level of FWM suppression. The three schemes: Low level reduction, High Level reduction and Intermediate Level reduction have been analysed at different distances from 50 Km to 150 Km at different input power levels so as to find the best technique based upon the results of eye diagram and Q factor. The simulation results show that the Intermediate technique is comparatively better than the other two.