Co-Propagating Dual-Order Distributed Raman Amplifier Utilizing Incoherent Pumping

We propose a distributed Raman amplifier available for dual-order co-propagating configuration with low-relative intensity noise (RIN) transfer. The first-order and second-order pumps are composed of incoherent and coherent light sources, respectively. By using the incoherent light source as a first-order pump, RIN transfer can be reduced. A semiconductor optical amplifier-based first-order incoherent light source for the configuration has been developed. The results of the RIN measurement and 22.5-Gbaud polarization-division multiplexing 16 quadrature amplitude modulation (PDM-16QAM) transmission experiment over 2720 km in a re-circulating loop show that the proposed configuration will be effective for a practical low-noise co-propagating Raman amplifier.