1024 QAM, 7-core (60 Gbit/s x 7) fiber transmission over 55 km with an aggregate potential spectral efficiency of 109 bit/s/Hz.

We report the first 1024 QAM polarization-multiplexed transmission at 3 Gsymbol/s over a 55 km 7-core fiber, with a total bit rate of 420 Gbit/s (60 Gbit/s x 7 cores). The potential spectral efficiency per core reached 15.6 bit/s/Hz, which corresponds to an aggregate spectral efficiency as high as 109 bit/s/Hz in a multi-core single-mode fiber.