Record Low Loss 0.144 dB/km 2-Core Optical Fiber for Submarine Transmission

Space Division Multiplexing using multicore optical fibers (MCF) is emerging as a promising technology for achieving capacity in excess of 1 Pb/s for submarine transmission systems. In this paper, we discuss the key MCF design considerations that result in transmission performance comparable to a single core fiber in submarine transmission systems. Based on these considerations, uncoupled 2-core multicore fibers having two different core-designs were designed with Effective Area of 112 mm2 at 1550 nm. These designs were fabricated and record attenuation of 0.1444 dB/km and 0.1449 dB/km are reported for lowest attenuation core for each design, with attenuation of 0.1457 dB/km and 0.1455 dB/km at 1550nm. This was enabled by using silica-core technology, along with improvements in core-processing and mitigation of attenuation contributors in the fiber manufacturing, including optimization of the draw conditions. Sensitivity of fiber attenuation (including radiation loss to high index coating) and copropagating and counterpropagating crosstalk to inter-core distance is studied and reported. Heterogeneous core MCF designs are evaluated for achieving good crosstalk performance even in cables where the bend radius encountered by the fiber is significantly larger than the bend radius on a shipping spool. Heterogeneous core MCFs where different core radius is used for core identification are also attractive for elimination of marker cores.