Low-density parity-check code for high-speed fibre-optic communication and its experimental verification

Although low-density parity-check (LDPC) code has been proved as a powerful forward error correction code for fibre optic communication, its soft-decoding requires high quantisation resolution which is difficult to achieve for high-speed fibre-optic communication systems. A modification to LDPC decoding algorithms is proposed to effectively improve the performance at quantisation resolution as low as two-bit or one-bit. The good decoding performance of LDPC code for error correction is confirmed by experiment. Compared with the RS(255, 239) code commonly used in optical fibre communication, a Q-factor improvement of 2-dB is obtained in the experiment for an LDPC code with quasi-cyclic structure at the same redundancy as the RS code. Furthermore, the impacts of sampling phase and channel estimation using real data over the decoding performance are analysed.