Single-Mode Fiber SDM Submarine Systems

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.