Liu Qiaoya, Fu Mengfan, Jiang Hexun, Ren Huiling, Cai Meng, Zeng Xiaobo, Lun Huazhi, Yi Lilin, Hu Weisheng, Zhuge Qunbi
Opt Express. 2021 Aug 30;29(18):28852-28863. doi: 10.1364/OE.434742.
A subcarrier-pairing entropy loading (SubP-EL) scheme with fairly low complexity is proposed for digital subcarrier-multiplexing (SCM) systems with colored signal-to-noise ratio (SNR) distributions. With the constraint of the target entropy, SubP-EL iteratively optimizes the entropy of subcarriers in pair. After convergence, SubP-EL can approach the optimal performance which is evaluated in simulations and experiments by comparison with the brute-force search method. Meanwhile the complexity of SubP-EL is significantly reduced compared with the brute-force search. In particular, in an 8-subcarrier system with five different SNRs, the complexity of SubP-EL is reduced by approximately a factor of 764, 95 and 13 with the entropy granularities of 0.05 bits/2D-symbol, 0.1 bits/2D-symbol and 0.2 bits/2D-symbol, respectively. The performance of SubP-EL is evaluated in simulations and experiments. In the experiments with 345 km fiber transmissions, the average NGMI gain of SubP-EL over the system without entropy loading is 0.0286 for different optical filtering cases.
针对具有有色信噪比（SNR）分布的数字子载波复用（SCM）系统，提出了一种复杂度相当低的子载波配对熵加载（SubP-EL）方案。在目标熵的约束下，SubP-EL迭代优化成对子载波的熵。收敛后，通过与穷举搜索方法比较，SubP-EL在仿真和实验中能接近最优性能。同时，与穷举搜索相比，SubP-EL的复杂度显著降低。特别是在一个具有五种不同SNR的8个子载波系统中，当熵粒度分别为0.05比特/2D符号、0.1比特/2D符号和0.2比特/2D符号时，SubP-EL的复杂度分别降低了约764、95和13倍。通过仿真和实验对子载波配对熵加载（SubP-EL）方案的性能进行了评估。在345公里光纤传输的实验中，对于不同的光滤波情况，SubP-EL相对于无熵加载系统的平均归一化广义互信息（NGMI）增益为0.0286。
