500?km unrepeatered 200?Gbit?s?1 transmission over a G.652-compliant ultra-low loss fiber only

In this work we experimentally demonstrate 200 Gbs−1 (2 × 100 G) unrepeatered transmission over 502.1 km using a 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 100 G DP-QPSK transponders (the required optical signal-to-noise ratio is 12 dB), Corning® SMF-28® ULL fiber (the average attenuation of the spools used in this experiment ~0.160 dB km−1), and optimization of remotely pumped optical amplifiers, bidirectional Raman amplifiers, and dispersion precompensation.