Discrete multitone (DMT) modulation, due to its water-filling nature, is proposed to enable flexibility in passive optical networks (PONs), optimizing the PON resource usage. The use of DMT signals to directly modulate long-wavelength vertical-cavity surface-emitting lasers (VCSELs) can provide energy-efficient transmitters for 50G PONs. First, we present preliminary experimental measures employing both single-sideband and dual-sideband DMT modulation with already available short-cavity VCSELs operating in the third window to study the PON performance as a function of the accumulated chromatic dispersion and of the received power. The experimental results are then compared with simulations, demonstrating the effectiveness of the developed simulation tool. Then we study the performance of DMT-modulated transmitters based on next-generation short-cavity VCSELs with higher bandwidth (up to 20 GHz) operating in the O-band, evaluating their chromatic dispersion resilience. Finally, considering the statistics of a commercially deployed PON, we demonstrate that DMT modulation, providing link adaptation, offers a significant increase in the total aggregated capacity compared to a single-carrier-based fixed-rate PON, optimizing the PON resource usage with respect to the available power budget and the dispersion impairments.

中文翻译：

---

基于直接调制VCSEL的灵活发射机，用于下一代50G无源光网络

由于其充水特性，提出了离散多音（DMT）调制以实现无源光网络（PON）的灵活性，从而优化PON资源的使用。使用DMT信号直接调制长波长垂直腔表面发射激光器（VCSEL）可以为50G PON提供节能的发射器。首先，我们介绍了采用单边带和双边带DMT调制以及在第三窗口中运行的已有短腔VCSEL的初步实验措施，以研究PON性能与累积色散和接收功率的关系。然后将实验结果与仿真进行比较，证明了开发的仿真工具的有效性。然后，我们研究了在O波段工作的，具有更高带宽（高达20 GHz）的下一代短腔VCSEL的DMT调制发射机的性能，评估了它们的色散弹性。最后，考虑到商用PON的统计数据，我们证明，与基于单载波的固定速率PON相比，提供链路自适应的DMT调制可显着增加总的总容量，从而优化PON资源的使用可用功率预算和色散减损。