Fiber non-linearity can cause interactions and severe crosstalk among co-propagating wavelength division multiplexing (WDM) channels in high capacity optical fiber communication system. The crosstalk between channels leads to degradation of the bit error performance of the transmission system. This book is for the researchers who are interested to achieve a deep knowledge about fiber optics and its research phenomena. Undergraduate and post-graduate can also get help from this book about the basic area of future research topics.