There is a problem that traditional unrepeatered transmission system need to use disturbed Raman amplifier and remote optical pump amplifier, while both of these two amplifiers need to use high power pump laser which will increase the complexity of fiber link in unrepeatered transmission system. In this paper, we propose a new structure of unrepeatered transmission system using Erbium Doped Optical Fiber Amplifier (EDFA) to replace the forward disturbed Raman amplifier.

We analyze and compare the performance of the proposed unrepeatered transmission system, and realize a real-time unrepeatered transmission experiment with the proposed structure.

The results show that the gain effect of forward Raman pump in traditional unrepeatered communication system can be achieved by using high power amplifier to increase the signal launch power, and the new structure of unrepeatered transmission system is more suitable to achieve higher bitrate with the help of Wavelength Division Multiplexing (WDM) technology. We confirm the unrepeatered transmission system can achieve 500 km span distance at 10 Gbit/s bit rate in single channel communication transmission, and 500 km span distance at 4×10 Gbit/s bit rate in the WDM technology.

The proposed unrepeatered transmission system can simplify the traditional unrepeatered transmission system, and increase the bit rate by using multi-channel WDM system with EDFA. It has important practical significance to simplify the structure and improve the bit rate in future unrepeatered transmission system.