11 $\,\times\,$ 224-Gb/s POLMUX-RZ-16QAM Transmission Over 670 km of SSMF With 50-GHz Channel Spacing

We demonstrate the generation and transmission of 11 channels with 224-Gb/s polarization-multiplexed return-to-zero 16-level quadrature amplitude modulation over 670 km of standard single-mode fiber (SSMF) with 50-GHz channel spacing and a spectral efficiency of 4.2 b/s/Hz. We report a penalty of around 4.3 dB in the performance at back-to-back in comparison to the theoretical limits, and a margin of 1 dB in Q -factor below the forward-error correction limit (assumed to be at a bit-error rate of 3.8 × 10 -3 ) after transmission over 670 km of SSMF.