Examining the Case for Multicore Fibers in Submarine Cable Systems Based on Fiber Count Limits

Abstract

The potential role of multicore fibers (MCFs) in submarine cable systems is investigated in the context of electrical power limitations and physical fiber count limitations. We compare the maximum cable capacity theoretically possible for cables using MCFs with 2, 3, and 4 cores to that of cables built with conventional single-core fibers. The comparisons are made based on ideal Shannon-limited capacity, systems with constant output power amplifiers, and individual amplification of MCF cores using fan-in/fan-out devices. MCFs are assumed to have nominally uncoupled cores for which crosstalk between cores is a system impairment. We examine the relative cost/bit of systems built with MCFs and single-core fibers when designed for maximum capacity, and when designed for minimum cost/bit operation. The relative capacity of a cable with MCFs depends strongly on the number of fibers able to be physically accommodated and is greatest when the fiber count number is relatively small. We find only small differences in the relative capacities of MCFs with 2-4 cores and that any advantage over single-core fiber systems can be eroded with minimum signal-to-noise ratio (SNR) requirements above the theoretical level near 0 dB that maximizes cable capacity. The cost/bit of MCF cable systems is determined to be higher than that of single-core fiber systems when maximum cable capacity is the design goal, according to the cost model employed and the specific system and fiber parameters assumed here. Different results may be obtained with cost model refinements and different parameters.