Exploring the Potential of Multicore Fibers for Submarine SDM Systems: Experimental Validation and Powering Constraints

This paper examines the feasibility of using 2-core multicore fibers (MCF) for transoceanic submarine systems in the near future. Initially, we investigated system penalties through a 6,154 km experiment in repeated scenarios, isolated the impact of core-to-core crosstalk induced penalties, and compared with existing models. Two propagation schemes were tested: co-propagation and counter-propagation. As expected, crosstalk in counter-propagation was almost negligible, while in co-propagation, system penalties aligned with predictions based on individual span crosstalk power measurements. Subsequently, we characterized the system impact of core crosstalk in an unrepeated scenario, experimentally demonstrating that long span performance can be significantly impacted in counter-propagation. Next, a record 20,512 km counter-propagation setup confirmed that our model could predict system performance with an error margin of less than 4%, verifying the absence of unexpected penalties with this novel fiber. We also quantified the impact of commercially available Fan-in Fan-Out (FIFO) devices with a 1 dB insertion loss, observing an 8-10% degradation in achievable distance and capacity. Finally, we extrapolate on the viability of 2-core MCF, 4-core MCF, and hollow-core fibers (HCF) for next generation transpacific submarine systems based on those experimentally validated modes and realistic assumptions. We can confirm that such advanced technologies with high degree of spatial / wavelength parallelism may fail to reach their full potential due to electrical power constraints and limitations in repeater size, integration or component spacing, thereby hindering their deployment in long-haul submarine networks unless these issues are addressed beforehand.