On the Interplay of Nonlinear Interference Generation with Stimulated Raman Scattering for QoT Estimation

To effectively operate multi-vendor disaggregated networks, performance of physical layer needs to be assessed by a quality-of transmission estimator (QoT-E) delivering quick results with a given reliability range. Beside ASE noise accumulation, nonlinear propagation impairments on WDM optical channels based on multilevel modulation formats relying on DSP-operated coherent receivers and propagating on uncompensated and amplified optical links are well summarized by the accumulation of a Gaussian-distributed disturbance: the nonlinear interference (NLI). When exploiting a transmission bandwidth exceeding the C-band, the interaction of NLI generation with the stimulated Raman scattering (SRS) must be properly considered. We present the derivation of the generalized Gaussian noise (GGN) model for NLI generation, including the SRS and, in general, a spectral and spatial variation of gain/loss. We validate its accuracy by comparing performances predicted by a QoT-E based on the GGN-model with measurements on a testbed exploiting commercial equipment, including 100 Gbps transponders. Considering that operational parameters of commercial equipment are known with a large range of uncertainty, an excellent agreement with errors within 0.5 dB on the generalized SNR is shown, demonstrating that the GGN-model can be used for QoT-E in multi-vendor network scenarios. Moreover, the GGN-model has shown the capability to predict the spectral tilting due to SRS in SNR performances, enabling its application to evaluate the impact of linear pre-tilting for SRS pre-compensation and NLI generation. IEE