Four-Dimensional Nonbinary LDPC-Coded Modulation Schemes for Ultra-High-Speed Optical Fiber Communication

In this letter, we propose a four-dimensional (4-D) nonbinary low-density parity-check-coded modulation (NB-LDPC-CM) scheme suitable for beyond 100-Gb/s optical fiber communication. Incorporating spectrally efficient modulation formats to achieve high aggregate bit rates and nonbinary LDPC codes for forward error correction (FEC), the proposed scheme offers a superior advanced FEC solution for optical fiber communication systems than the prior-art bit-interleaved LDPC-coded modulation (BI-LDPC-CM) scheme. Compared to the previously reported bit error rate (BER) performance results of BI-LDPC-CM, the proposed scheme offers additional net coding gains (NCGs) of 0.29 dB, 1.17 dB, and 2.17 dB at the BER of 10^-7 when 16-, 32-, and 64-point 4-D constellations are used, respectively.