With the steadily increasing demand for fiber-optic communications, researches is more and more being placed in the method known as wavelength division multiplexing (WDM), in this book we will study and design Ultra Wideband using Raman Amplifiers, EDFA using C & L Bands, 83-nm 3 dB Gain-Band using Raman Amplifiers for Long Distance Transmission, and study bit rate and losses limitations in single mode fiber, also we will proposed new model for MC-CDMA and clutter map-CFAR and improved nonlinear equalizer for telephone circuit channels also study the performance analysis of optical ring network and design metropolitan area network.