Incremental planning with dual-fiber distributed Raman amplification in (C + L + S) networks

Multi-band transmission is gaining traction as a promising solution for coping with the ever-increasing capacity demands of optical networks. In multi-band networks, long-term network planning must take into account the signal-to-noise ratio (SNR) degradations caused by interchannel stimulated Raman scattering arising when multiple lightpaths provisioned in the extended spectrum bands propagate in the same fiber. To avoid these degradations, in this study, we investigate the benefits of selectively upgrading a subset of the fiber spans with an additional fiber, which allows us to separate the spectrum bands and apply dual-fiber distributed Raman amplification (DF-DRA) in a C + L + S system. The deployment of DF-DRA, combined with EDFAs for the C- and L-bands and TDFAs for the S-band, reduces the overall amplification noise figure, thereby improving the SNR of lightpaths. Additionally, the separation of spectrum bands reduces pump-to-pump and signal-to-signal power transfer, further contributing to SNR improvement. We develop a numerical solver for setting the optimal Raman pump configurations, and we propose different placement strategies for hybrid EDFA/TDFA-Raman amplification and 3R regenerators. Our extensive numerical simulations on incremental traffic show that DF-DRA-enabled multi-band networks can yield up to a complete elimination of 3R regenerators by upgrading 30% of the network spans while having up to a 35% throughput increase.