Abstract: The paper studies the characteristics of EDFA and RFA in detail on the base of emulation experiments using PTDS, which is a simulation platform for optical transmission system emulation. A 1dB-gain-flatness-bandwidth reaching 3.75 THz, 3dB-bandwidth reaching 4.25 THz and OSNR at 193.1 THz reaching 38.5 dB hybrid amplifier comprised of a distributed Raman amplifier and an EDFA has been achieved and is applied in a 4-channel DWDM communications system. After 230 km transmission, the output signals are excellent. The output OSNR reaches 33.14 dB, the output power reaches 4 μW and the BER reaches 3.8×10-10.