Nonbinary Quasi-Cyclic LDPC-Based Coded Modulation for Beyond 100-Gb/s Transmission

We propose using coded modulation based on nonbinary quasi-cyclic low-density parity-check (LDPC) codes for beyond 100-Gb/s optical transmission. The proposed scheme not only lowers the latency in the system but also offers much higher coding gains than its binary counterpart based on bit-interleaved coded modulation (BICM). We show that using component LDPC codes over high order finite fields and matching bandwidth-efficient modulations, our scheme can provide around 1-dB coding gain improvement at the bit-error ratio of 10
^-6
compared to a corresponding BICM-based scheme.