LAUSR

Newly developed 125-μm-cladding coupled four-core fibers realized the record-low spatial mode dispersion (SMD) of 3.14 ± 0.17 ps/√km over C-band and the ultra-low attenuation of 0.158 dB/km at 1550 nm, both of which are the lowest ever reported among the optical fibers for the space-division multiplexed transmission. The SMD was observed to be proportional to the fiber bend curvature, i.e., inversely proportional to the bend radius, and the SMD of 3.14 ± 0.17 ps/√km was measured at the bending radius of ∼31 cm. By assuming the 3.14-ps/√km SMD accumulation, the tap count of the multiple-input multiple-output digital signal processing for the crosstalk compensation is estimated to be only 63 taps for covering 99.99% power of the impulse response after 10 000-km propagation when the 25-GBaud (50-GHz sampling) is assumed. The present results demonstrate the strong applicability of the coupled multicore fiber to the ultralong-haul submarine transmission system.