随着各种互联网新兴业务的崛起以及无源光网络（PON）在行业应用场景的延伸，作为第五代固定网络（F5G）代表技术的PON，需要不断演进升级才能满足未来网络的需求。其中，PON的时延是迫切要改善的关键网络性能指标，故文章对PON的低时延技术进行了深入研究。

文章首先总结了当下PON在低时延方面所面临的挑战，分析了导致PON时延较高的主要原因有两个，分别是因光网络单元（ONU）带宽分配机制引入的上行固有时延和因ONU注册/测距机制引入的上行随机时延。因此，文章提出了基于单帧多突发技术和独立注册通道技术的两种超低时延技术方案，并进行实验验证分析。

通过验证分析，对于单帧多突发技术的低时延技术方案，结合时延和带宽利用率两个性能指标综合来看，1/4调度周期表现最优，但会牺牲小部分带宽，比较适合传输对时延敏感而带宽不敏感的业务；对于独立注册通道技术的低时延技术方案，由于引入了额外的波长用于ONU注册/测距通道，可以完全消除正常业务通道因注册/测距的静默窗口引入的额外时延和抖动。

综合而言，文章所探讨的基于PON的超低时延技术方案，可以有效降低PON的时延，有助于促进虚拟现实（VR）类等新兴业务的规模商用和工业互联网的快速发展。

With the advent of new internet services and the broader application of Passive Optical Network (PON) in the industry, PON, as the core technology of the 5th Generation Fixed Networks (F5G), needs to evolve and upgrade continuously to meet the needs of the future network. The latency of PON networks is a key network performance indicator that urgently needs improvement. This article conducts in-depth research on the low latency technologies in the PON networks.

This article first summarizes the challenges faced by current PON networks in terms of low latency. It identifies two main reasons for high latency: the inherent uplink delay introduced by the Optical Network Unit (ONU) bandwidth allocation mechanism and the random uplink delay introduced by the ONU registration/ranging mechanism. To address these issues, this article proposes two ultra-low latency solutions based on single frame multi burst technology and an independent registration channel, followed by experimental verification and analysis.

Analysis shows that the single-frame multi-burst approach optimally balances latency and bandwidth utilization in a quarter scheduling cycle, albeit at the expense of some bandwidth. This method is ideal for latency-sensitive, bandwidth-tolerant services. The independent registration channel solution, by dedicating an extra wavelength for ONU registration/ranging, eliminates the extra delay and jitter from silent periods in standard service channels.

The ultra-low latency solution for PON discussed in this article can effectively reduce network latency, and help promote the large-scale commercialization of emerging applications such as Virtual Reality (VR) and accelerate the growth of industrial internet.