B. T. Ninh, N. Q. Tuan, T. V. Hung, N. T. Anh and P. V. Hoi, Influence of ASE Noise on Performance of DWDM Networks Using Low-power Pumped Raman Amplifiers, Comm. Phys. 25 (2015) 147. DOI: https://doi.org/10.15625/0868-3166/25/2/6000.