Design of ultra-long-distance optical transport networks based on high-order remotely pumped amplifier

In order to further increase the span length of the Optical Transport Network (OTN) transmission system, a combination of Raman amplifier and remotely optical pumped amplifier (ROPA) configuration scheme is recommended. Optimal EDF length, optimal ROPA position and OTN span limitation are obtained through simulations. A field-trial with 8*10 Gb/s in 380 km span system is carried out with the amplifier configuration of Raman amplifier plus first-order and second-order remotely pumped amplifier. By adding a second-order remote pump laser, the transmission limit is increased from 77.5 dB to 80.7 dB. Through detailed analysis of the system, it is concluded that the second-order remote pump can effectively transfer the pump power to the first-order remote pump wavelength, which greatly increases the pump power at the gain module, thereby increasing the gain of the RGU and reduce its noise. Moreover, the introduction of the second-order remote pump effectively weakened the self-excited effect and overcomes the shortcomings of the low pump power threshold of the first-order remote pump.