QoT-aware spectral and spatial scaling trade-offs in multi-band space division multiplexing over EONs [Invited]

Abstract

Multi-band space division multiplexed (MB-SDM) elastic optical networks provide a practical path to ultra-high-capacity backbone transport by combining spectral expansion beyond the C-band with spatial multiplexing over weakly coupled multi-core fibers (MCFs). Yet, the benefits of these two scaling dimensions are strongly shaped by physical layer impairments and cannot be assessed independently. This paper presents a quality of transmission (QoT)-aware planning framework for MB-SDM backbone networks that jointly evaluates C, $\text{C} +\text{L}$, $\text{C} +\text{S}$, and $\text{C} +\text{L} +\text{S}$ transmission over 4-, 7-, 13-, and 19-core MCFs. The framework relies on a unified generalized signal-to-noise ratio model including amplified spontaneous emission, nonlinear interference, inter-channel stimulated Raman scattering, inter-core crosstalk (ICXT), transceiver limitations, and filtering and aging penalties. A QoT-aware spectral–spatial resource allocation algorithm is evaluated under dynamic traffic, where modulation formats are precomputed based on precise impairment modeling with launch power optimization, and bandwidth slicing is applied; the ICXT model is further validated through experiments on a commercial 19-core MCF. Results on the U.S. backbone topology show that the preferred band configuration depends strongly on the core count scenario. For 4- and 7-core MCFs, $\text{C} +\text{L}$ provides better throughput and lower blocking than $\text{C} +\text{S}$. For 13-core MCFs, $\text{C} +\text{S}$ becomes more effective because the L-band is more strongly affected by ICXT. For 19-core MCFs, the system becomes ICXT-dominated, causing severe degradation in C and $\text{C} +\text{L}$, while $\text{C} +\text{S}$ achieves the best overall performance. Notably, despite the larger spatial resource pool, the maximum throughput in the $\text{C} +\text{L} +\text{S}$ scenario decreases from 107.94 Pbps in the 13-core case to 44.76 Pbps in the 19-core case, confirming that aggressive spatial densification can reduce usable network capacity.