Cai Junjie, Liu Bo, Ren Jianxin, Mao Yaya, Zhong Qing, Chen Shuaidong, Song Xiumin, Guo Zhiruo, Tang Xue, Chen Weiming, Yu Wenbo, Ullah Rahat
Opt Express. 2025 Jul 14;33(14):30580-30593. doi: 10.1364/OE.562931.
We propose a four-dimensional quadrature phase shift keying (4D-SS-QPSK) modulation transmission scheme based on entropy-coding-aided symbol selection. The proposed scheme integrates Huffman coding with bit-interleaved coded modulation (BICM) to generate non-uniform signals and aggregates three QPSK signals with one BPSK signal, forming a four-dimensional phase unit. We select symbol subsets aided by source entropy (SE) and map signals onto a predefined four-dimensional symbol subset for transmission, thereby overcoming the limitation of traditional QPSK signals in terms of insufficient utilization efficiency in high-dimensional space. We demonstrate the proposed scheme in a 2-km intensity modulation/direct detection (IM/DD) seven-core fiber transmission system with a signal transmission rate of 14.175 Gb/s. Experimental results indicate that at the hard-decision forward error correction (HD-FEC) bit error rate (BER) limit of 3.8 × 10, the receiver optical power of the 4D-SS-QPSK transmission scheme is -10.4 dBm, achieving approximately 0.7 dB receiver sensitivity gain compared with 3D-SS-QPSK signals, and approximately 0.5 dB gain compared with 4D-SS-QPSK signals without BICM.
我们提出了一种基于熵编码辅助符号选择的四维正交相移键控（4D-SS-QPSK）调制传输方案。该方案将霍夫曼编码与比特交织编码调制（BICM）相结合以生成非均匀信号，并将三个QPSK信号与一个BPSK信号聚合，形成一个四维相位单元。我们借助源熵（SE）选择符号子集，并将信号映射到预定义的四维符号子集上进行传输，从而克服了传统QPSK信号在高维空间中利用效率不足的局限性。我们在信号传输速率为14.175 Gb/s的2公里强度调制/直接检测（IM/DD）七芯光纤传输系统中演示了该方案。实验结果表明，在3.8×10的硬判决前向纠错（HD-FEC）误码率（BER）极限下，4D-SS-QPSK传输方案的接收光功率为-10.4 dBm，与3D-SS-QPSK信号相比，实现了约0.7 dB的接收灵敏度增益，与无BICM的4D-SS-QPSK信号相比，实现了约0.5 dB的增益。
