Experimental demonstration of flexible information rate PON beyond 100 Gb/s with probabilistic and geometric shaping

The application of pairwise probabilistic shaping combined with geometric shaping is investigated for a pulse-amplitude-modulation-based intensity modulated and direct detection (IMDD) system. With probabilistically shaped signals, we experimentally demonstrate the flexible information rate beyond 100 Gb/s in a practical passive optical network (PON) link. Similar to the G.hsp 50 Gb/s PON standard, the PON link assumes the existence of a semiconductor optical amplifier (SOA), which boosts the transmitter power to achieve a high link budget. While the optimal signal distributions for the IMDD link with a SOA tend to be unipolar distributions, we consider a practical methodology of accommodating forward error correction (FEC) parity bits using pairwise probabilistic distribution. Since pairwise signaling causes performance degradation when the optimal signal would be strongly shaped, we propose to combine geometric shaping (GS) with probabilistic shaping (PS) to overcome the shortcomings of the pairwise signaling. We present experimental demonstrations of the various achievable rate measurements using PS $+$+ GS modulations with flexible FEC assumption. We also propose a novel descrambling-based decoding technique to evaluate the post-FEC performance based on transmission data that is agnostic of the FEC code. The post-FEC performances are then presented using a fixed and practical low-density parity check code.