RFA： Raman fiber amplifier is an optical amplifier that uses the stimulated Raman scattering effect in single-mode fiber to amplify the optical signal. There are usually Counter Raman amplification and Co-Propagating amplification. It can boost the signal optical power, improve the signal quality, extend the span length and the overall transmission distance, to provide an efficient, safe and convenient high-OSNR transmission solution for the optical communication system. Hybrid OA： Hybrid amplifier integrates the advantages of low noise of Raman amplifier and high output power of EDFA. In the meantime, through joint gain control of Raman and EDFA, it optimizes the spectral flatness under different gains and adapts to the optimal OSNR requirements under different spans, which can effectively support the application in high bit rate optical transmission system.