Faster-Than-Nyquist Subcarrier Modulation Utilizing Digital Brick-Wall Filter-Based THP for Band-Limited DML-DD Systems

With digital brick-wall filter-based coefficients estimation and Tomlinson-Harashima precoding, we experimentally demonstrate faster-than-Nyquist subcarrier modulation using a 20GHz O-band DML. At the 20% SD-FEC threshold, up to 105%, 45.5%, and 18.2% FTN rates are achieved for QPSK, 16-QAM and 32-QAM formats, respectively.