Gray-Encoded Set-Partition 8QAM for Per-wavelength 200-Gb/s Application

A simple Gray-encoding scheme, using a pair of small-sized tables, to reduce the non-Gray penalty for set-partition 8QAM is demonstrated. The experimental results show that a 42.3-GBd PDM-SP-8QAM signal, for 200-Gb/s per channel use, can exhibit ~0.5-dB OSNR benefit with this encoding method.