125-μm-Cladding coupled multi-core fiber with ultra-low loss of 0.158 dB/km and record-low spatial mode dispersion of 6.1 ps/km

A 125-μm-cladding coupled four-core fiber realized 0.158-dB/km attenuation at 1550 nm and 6.1-ps/km12 spatial mode dispersion over C-band, both of which are the lowest ever reported among optical fibers for the space-division multiplexed transmission.