Opt Express. 2023 Mar 27;31(7):11447-11456. doi: 10.1364/OE.480741.
We experimentally demonstrated a low-complexity probabilistic shaping (PS) 16-ary quadrature amplitude modulation (16QAM) scheme based on intra-symbol bit-weighted distribution matching (Intra-SBWDM) for discrete multi-tone (DMT) symbols with field-programmable gate array implementation in an intensity modulation and direct detection (IM-DD) system. Different from the traditional PS scheme such as Gallager many-to-one mapping, hierarchical distribution matching and constant composition distribution matching, the Intra-SBWDM scheme with lower computation and hardware complexity does not need to continuously refine the interval to find the target symbol probability, nor does it need a look-up table, so it does not introduce a large number of extra redundant bits. In our experiment, four PS parameter values (k = 4, 5, 6, and 7) are investigated in a real-time short-reach IM-DD system. 31.87-Gbit/s net bit PS-16QAM-DMT (k = 4) signal transmission is achieved. The results show that the receiver sensitivity in terms of the received optical power of the real-time PS scheme based on Intra-SBWDM (k = 4) over OBTB/20 km standard single-mode fiber can be improved by about 1.8/2.2 dB at the bit error rate (BER) of 3.8 × 10, compared to the uniformly-distributed DMT. In addition, the BER is steadily lower than 3.8 × 10 during a one-hour measurement for PS-DMT transmission system.
我们实验演示了一种基于符号内比特加权分布匹配（Intra-SBWDM）的低复杂度概率成形（PS）16 进制正交幅度调制（16QAM）方案，用于离散多音（DMT）符号，该方案在强度调制和直接检测（IM-DD）系统中采用现场可编程门阵列（FPGA）实现。与传统的 PS 方案（如 Gallager 多对一映射、分层分布匹配和恒组成分布匹配）不同，Intra-SBWDM 方案具有较低的计算和硬件复杂度，不需要不断细化间隔来找到目标符号概率，也不需要查找表，因此不会引入大量额外的冗余位。在我们的实验中，在实时短距离 IM-DD 系统中研究了四种 PS 参数值（k=4、5、6 和 7）。实现了 31.87-Gbit/s 净比特 PS-16QAM-DMT（k=4）信号传输。结果表明，基于 Intra-SBWDM（k=4）的实时 PS 方案的接收灵敏度（以接收光功率表示）在 OBTB/20km 标准单模光纤上可以提高约 1.8/2.2dB，在误码率（BER）为 3.8×10时，与均匀分布的 DMT 相比。此外，在 PS-DMT 传输系统的一小时测量期间，BER 始终低于 3.8×10。
