Record 500 km unrepeatered 1 Tbit/s (10 x 100 G) transmission over an ultra-low loss fiber.

In this work we experimentally demonstrate 1 Tbit/s (10 x 100 Gbit/s) unrepeatered transmission over 500.5 km using dual polarization quadrature phase shift keyed (DP-QPSK) format and real-time processing. Such ultra-long distance is enabled by the use of high-performance 100G DP-QPSK transponders (the required optical signal-to-noise ratio is 12 dB), ultra-low loss Corning SMF-28 ULL fiber (the average attenuation of the spools used in this experiment <0.