We consider both physical and economic aspects of submarine transmission to identify optimal designs of submarine space division multiplexed (SDM) systems. We focus on single mode-based SDM systems as the first practical step for implementation of high capacity, low cost-per-unit-capacity systems based on SDM principles. We review power efficiency models in EDFA-based long-haul systems and show existence of optimum SNR. We demonstrate relationship between the power efficiency and cost-per-unit-capacity optimizations for submarine links. We also describe a detailed model that combines physical and economic aspects of the submarine links. The model uses “least amount of technological change” approach based on the existing components and simple scaling rules for repeater and cable designs. The model results suggest that 32-fiber SDM systems are a practical spot for near-future systems close to cost-per-unit-capacity limit of the wet-plant. Further increase of the number of fibers in a cable has diminishing returns for current technologies and cost structure. We also discuss requirements for transponders in terms of spectral efficiency and nonlinearity compensation.

中文翻译：

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单模光纤 SDM 海底系统

我们考虑海底传输的物理和经济方面，以确定海底空分复用 (SDM) 系统的最佳设计。我们专注于基于单模的 SDM 系统，作为实施基于 SDM 原则的高容量、低成本单位容量系统的第一个实际步骤。我们回顾了基于 EDFA 的长途系统中的电源效率模型，并展示了最佳 SNR 的存在。我们展示了海底链路的功率效率和单位容量成本优化之间的关系。我们还描述了一个结合海底链路物理和经济方面的详细模型。该模型使用基于现有组件和简单的中继器和电缆设计缩放规则的“最少技术变化”方法。模型结果表明，32 芯 SDM 系统是接近湿法设备单位容量成本限制的近期系统的实用点。光缆中光纤数量的进一步增加对当前技术和成本结构的回报递减。我们还讨论了在频谱效率和非线性补偿方面对转发器的要求。