Benefits of counterpropagating Raman amplification for multiband optical networks

Abstract

Multiband (MB) optical fiber transmission systems can unlock additional capacity in existing optical fiber infrastructures, enabling them to keep up with the increase in traffic demand while postponing costly optical fiber deployments. However, due to the worse transmission characteristics of MB systems than C-band-only transmission, the network’s overall spectral efficiency decreases when increasing the transmission bandwidth. The extent of this performance degradation is paramount to determining the commercial viability of deploying MB systems. By estimating the generalized signal-to-noise ratio using the GNPy library, this work analyzes the impact of using counterpropagating Raman amplification to improve the performance of an S + C + L -band transmission system comprising a total bandwidth of 15.5 THz. Raman amplification is proposed to mitigate the worse system performance resulting from the stimulated Raman scattering effect and the worse noise figure of the S-band optical amplifier. We show that the optimized deployment of a counterpropagating Raman pump makes it possible not only to improve but also to equalize the network-wide optical performance of the S + C + L -band transmission system, which potentially reduces the complexity of routing and wavelength assignment algorithms. The capacity, spectral efficiency, and number of feasible lightpaths of the S + C + L -band system are compared with C- and C + L -band systems with and without Raman amplification on two reference networks. Results show that the spectral efficiency of the S + C + L -band system with Raman amplification is similar to the C-band-only system without Raman amplification. These results provide evidence that this strategy can be effectively used to compensate for the worse transmission characteristics of MB systems, the higher noise figure of the S-band optical amplifier, the SRS effect, and the additional losses from the band demultiplexer and coupler required at every amplification stage to separate the transmission bands. Overall, the simulation results highlight that a single optical fiber can approximately carry the same data when using a 15.5 THz transmission band (and Raman amplification) as three parallel fibers using C-band-only transmission (without Raman amplification).