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 results showed that the hybrid amplifier has the average Gain of more than 24 dB in the wavelength range between 1530-1605 nm, with the Noise Figure (NF) of less than 6 dB. The Gain of the EDFA and RAMAN was optimized to minimize the ripple value as low as 0.7 dB with an output power of 14.076 dBm.