The relentless demand for high-bandwidth services and applications in the beyond-5G/6G era necessitates optical networks to provide ample spectral resources to accommodate the increasing traffic loads. This requirement is especially pronounced in metro and regional segments, where a projected traffic compound annual growth rate (CAGR) of over 40%, driven by content delivery network (CDN) traffic concentrated near the end users, threatens to push the fiber capacity to its limits on a number of heavily utilized links in the short to medium term. This limitation cannot be circumvented despite the utilization of spectrally efficient modulation formats designed for short-distance transmission. Thus, it is imperative to explore migration strategies to solutions that allow the expansion of spectral resources beyond the current usage of the extended C-band (4.8 THz). In this article, we present a comprehensive evaluation of multi-homed edge-to-core routing, modulation-level selection, and spectrum assignment simulations conducted over reference metropolitan area networks (MANs) by leveraging on a novel network planner called 6D-MAN, which we have developed to adapt to heterogeneous multi-layer networks based on multi-band and multi-fiber transmission. Our simulations consider coherent transmission with flexible modulation format transponders operating at capacities ranging from 100 to 400 Gbps on the 50 GHz grid and explore link-by-link migration strategies restricted to the C+L${\rm C} + {\rm L}$-band, ensuring optimal performance in terms of the generalized signal-to-noise ratio (GSNR). The obtained results demonstrate that deploying L-band equipment on a selected number of links effectively extends the lifespan of existing networks, enabling congestion-free operation with minimal intervention. In their entirety, our findings underscore the importance of contemplating alternative spectral resources beyond the conventional C-band. They unequivocally accentuate the potential of L-band equipment strategic deployment to tackle capacity constraints in MANs, resulting in a 60% reduction in fiber length and a remarkable 45% decrease in new fiber-pair link deployment needs. The profound implications of efficient fiber capacity utilization manifest themselves in substantial OPEX and optical total cost of ownership savings, amounting to approximately 71% and 17%–27%, respectively, over a 10-year period. This research provides valuable insights for MAN operators seeking sustainable strategies to support the growing demands of future beyond-5G/6G services.

中文翻译：

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实现城域光网络向多频段的无缝迁移：推出面向6G时代的尖端6D规划工具

超5G/6G时代对高带宽业务和应用的持续需求，要求光网络提供充足的频谱资源来适应日益增长的流量负载。这一要求在城域和区域性细分市场中尤为明显，在内容交付网络 (CDN) 流量集中在最终用户附近的推动下，预计流量复合年增长率 (CAGR) 将超过 40%，这可能会将光纤容量推至最高水平。在中短期内限制一些频繁使用的链接。尽管采用了专为短距离传输设计的频谱高效调制格式，但仍无法规避这一限制。因此，必须探索解决方案的迁移策略，以允许将频谱资源扩展到扩展 C 频段 (4.8 THz) 的当前使用范围之外。在本文中，我们利用一种名为 6D-MAN 的新型网络规划器，对参考城域网 (MAN) 上进行的多宿主边缘到核心路由、调制级别选择和频谱分配模拟进行了全面评估，我们开发的它是为了适应基于多频段和多光纤传输的异构多层网络。我们的模拟考虑了在 50 GHz 网格上以 100 至 400 Gbps 的容量运行的灵活调制格式转发器的相干传输，并探索仅限于C + L${\rm C} + {\rm L}$频段的逐链路迁移策略，确保广义性能方面的最佳性能信噪比（GSNR）。获得的结果表明，在选定数量的链路上部署 L 波段设备可以有效延长现有网络的使用寿命，从而以最少的干预实现无拥塞运行。总的来说，我们的研究结果强调了考虑传统 C 频段之外的替代频谱资源的重要性。他们明确强调了 L 波段设备战略部署在解决城域网容量限制方面的潜力，从而使光纤长度减少 60%，并将新光纤对链路部署需求显着减少 45%。高效光纤容量利用的深远影响体现在可观的运营成本和光纤总拥有成本节省上，在 10 年内分别达到约 71% 和 17%–27%。这项研究为城域网运营商寻求可持续战略以支持未来超 5G/6G 服务不断增长的需求提供了宝贵的见解。