Next-generation optical networks: Integrating adaptive FEC rate LDPC and higher order probabilistic constellation shaping

To address the next-generation communication needs, we present a new framework to improve channel capacity. This framework combines forward error correction (FEC) rate Low-Density Parity-Check (LDPC) coding with advanced enhancements like higher-order modulation and Probabilistic Constellation Shaping (PCS). Our method targets the growing demands of 6G and future technologies. We examine LDPC code rates of 5/6, 8/9, and 9/10 for a fixed block length of 64,800 using 64-QAM and 256-QAM signals. The system features approximate 150 Gbaud symbol rate, capable of generating LDPC coded signals for both modulation schemes. Performance analysis over an optical channel shows the system’s resilience, even with phase noise from a laser source with a higher linewidth. We determine an optimized Optical Signal to Noise Ratio (OSNR) to meet Bit Error Rate (BER) targets of 10^-6 in an Additive White Gaussian Noise (AWGN) channel, ensuring strong performance. The study also explores information-theoretic metrics like Mutual Information (MI), Generalized Mutual Information (GMI), and Normalized GMI (NGMI) for both 64-QAM and 256-QAM signals. We compare the performance of PCS with uniformly distributed QAM signals, providing a thorough evaluation. Through detailed experimentation and analysis, this research offers valuable insights into the practicality and performance of the proposed system, marking a significant advancement in sophisticated optical communication systems for future networks.