A review on Erbium doped fiber amplifier (EDFA) system capable of amplifying incoming signal light between 1525-1610 nm. Understand its basic configuration, materials and their effects in transmission channel. Also learn how to handle amplification of high speed incoming light signals entire C+L band wavelengths in single mode fibers as well as multimode fiber. There are two major issues incorporated to EDFA for example to achieve high gain (? 40 dB) & lower noise figure (? 6 dB) at various parameters like input power and ASE to transmit signals longer distances.