Multistage MP-DRA optimization across C+L and S+C+L MB-WDM transmission systems

This paper introduces an optimized multistage design approach for multipump distributed Raman amplifiers (MP-DRAs) in future multiband wavelength division multiplexing (MB-WDM) systems. Wideband system increases transmission capacity of the transmission but results in extreme nonuniformity of gain and asymmetric noise accumulation. To limit these impairments, three single-stage configurations are systematically explored in the C+L band: copropagating, counterpropagating, and bidirectional. The bidirectional configuration provides the optimum C+L performance. It has a peak gain of 17.57 dB, a minimal gain ripple of 1.97 dB, an average noise figure of 7.077 dB (average), and a transmission reach of 206 km. This was the starting point for the implementation of a dual-stage cascaded bidirectional DRA in the same system of 8 channels C+L. This configuration increased the maximum common transmission reach to 274 km, an extra 68 km. The optimization framework is then extended to 110 nm S+C+L band (1,515–1,625 nm). Two different configurations are assessed; single-stage gain-flatting filter (SS-GFF)- and dual-stage (DS-GFF)-based DRA. The SS-GFF yields a 14.12 dB peak gain, a 4.125 dB ripple, and 188 km reach. Importantly, the DS-GFF architecture extends the range of transmission reach to be 236 km, an improvement of 25.5 %. The results provided a strong, simple path toward optimizing transmissions in broad band optical infrastructure.