论文标题
高光谱效率系统的均匀和概率形状的QAM信号的激光相位噪声耐受性
Laser Phase Noise Tolerance of Uniform and Probabilistically-shaped QAM Signals for High Spectral Efficiency Systems
论文作者
论文摘要
我们在数值和实验上研究了概率形状（PS）和均匀形状（US）正交振幅调制（QAM）信号的激光相噪声耐受性。在模拟中，我们将PS-64QAM与US-16QAM，PS-256QAM与US-64QAM和PS-1024QAM与US-256QAM与相同信息率（IR）进行比较。我们确认，使用狭窄的线宽激光器观察到足够的形状增益，而当假定大相噪声和高阶调制格式时，清楚地观察到了形状增益的降解。在我们的实验中，我们使用具有0.1-kHz和40-kHz线宽的激光器在同一IR下比较了极化 - 分离 - 多形的（PDM）16-GBD PS-1024QAM和US-256QAM。对于载体相恢复（CPR），我们采用了飞行员辅助的数字相锁定循环。结果表明，PS-1024QAM使用0.1 kHz-laser或> 5％的初步比率实现高性能，而使用40 kHz线宽的激光器和使用<5％的初步比率时，US-256QAM胜过PS-1024QAM PS-1024QAM。我们还评估了在正向误差校正极限和可实现的信息率下所需的光信号噪声比的试点比率依赖性。此外，我们比较了两种类型的CPR更新方案的性能：仅在PILOT符号或所有符号上更新阶段估计。
We numerically and experimentally investigate the laser phase noise tolerance of probabilistically shaped (PS) and uniformly shaped (US) quadrature amplitude modulation (QAM) signals. In the simulations, we compare PS-64QAM to US-16QAM, PS-256QAM to US-64QAM, and PS-1024QAM to US-256QAM under the same information rate (IR). We confirm that a sufficient shaping gain is observed with narrow linewidth lasers, whereas degradation of the shaping gain is clearly observed when large phase noise and high order modulation formats are assumed. In our experiments, we compare polarization-division-multiplexed (PDM) 16-GBd PS-1024QAM and US-256QAM under the same IR using lasers with 0.1-kHz and 40-kHz linewidths. For carrier phase recovery (CPR), we employ a pilot-assisted digital phase locked loop. Results reveal that PS-1024QAM achieves high performance with the 0.1 kHz-laser or > 5% pilot ratio, whereas US-256QAM outperforms PS-1024QAM when lasers with 40-kHz linewidth and < 5% pilot ratio are used. We also evaluate the pilot ratio dependency of the required optical signal-to-noise ratio at the forward error correction limit and the achievable information rate. Additionally, we compare the performance of two types of CPR updating schemes: updating phase estimation at only the pilot symbol or at all symbols.
