This book explains the construction of a hybrid amplifier consisted of one stage of Erbium doped Fiber Amplifier (EDFA) and two stages of RAMAN amplifiers for achieving gain flattening in long haul Density Wavelength Division Multiplexed (DWDM) systems. Gain Flattening is achieved for the entire C-band and L-band. Two of the RAMAN fibers are cascaded in series to repress the intensity noise which occurs due to double Rayleigh scattering. Backward pumping is applied at all stages in order to increase the gain of EDFA and to decrease the Polarization dependent gain (PDG) of RFA. Simulation...