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Flexible-grid elastic optical networks (EONs) have recently been widely deployed to support the growing demand for bandwidth-intensive applications. For cost-efficient scaling of the network capacity, multi-band systems are a promising solution. Optimized utilization of EONs is required to delay cost-extensive network upgrades and to lower cost and power consumption. Next-generation bandwidth-variable transceivers (BVTs) will offer increased adaptivity in symbol rate and modulation through techniques such as probabilistic shaping (PS). In this work, we investigate the impact of increased configuration granularity on optical networks. We account for practical implementation considerations of BVT configurations for estimating the required signal-to-noise ratio. Additionally, an optimization algorithm is presented that selects the most efficient configuration for each considered data rate and bandwidth combination. We utilize advanced quality of transmission estimation modeling to evaluate PS configurations in multi-band systems with optimized launch power distributions. We present results of network planning studies for C-band systems in a national and a continental optical backbone network topology considering different granularities of the configurations. Our analysis confirms that finer modulation-based rate-adaptivity results in substantial resource savings, decreasing the number of necessary lightpaths by at most 13% in C-band EONs. Additional savings are observed in multi-band systems, showing further increased savings in the number of required lightpaths of up to 20%. In contrast, increased symbol rate granularity only results in minor savings.
Müller et al. (Mon,) studied this question.