Experimental demonstration of the performance of net-coupled staircase code in 240-Gbps optical coherent transmission system

We present a net-coupled staircase code (NCSC) architecture, which leverages the multiple multiplexing dimensions to construct parallel forward error correction (FEC) code chains. Spatial coupling between chains is introduced through cyclic sub-block rearrangement. The net-like structure enhances global information exchange and strengthens inter-codeword constraints. Analysis based on graph models and density evolution shows that the NCSC achieves an improvement in the error correction threshold of up to 0.0461 for t = 7. The proposed scheme is experimentally demonstrated by the 240-Gbps transmission system over 20-km standard single-mode fiber (SSMF). The results demonstrate improvements in receiver sensitivity compared to the sub-block rearranged staircase code (SRSC) using an identical component code. At a post-FEC BER of 4.94E-5, gains of 0.89 dB and 0.78 dB are achieved for code block lengths of m = 48 and m = 100, respectively.