As optical fibre reaches deeper into passive optical network (PON) in fibre-to-the-x (FTTx) networks, maintaining the integrity of these networks is indeed imperative. Essentially, best practices have been established throughout the installation and verification of the fibre access network. Equally significant is monitoring the optical fibre performance degradation in-service to ascertain efficient service delivery, as well as to guarantee service level agreement. Nevertheless, a minor failure in PON may lead to massive loss of data stemming from inherent passivity of network elements in optical distribution network, thus resulting in customer dissatisfaction and escalated operational expenses borne by network operators. Unfortunately, testing and monitoring optical layer have become rather intricate due to the rapid evolution of PON technology. Hence, an efficient optical layer monitoring system equipped with complete monitoring capabilities may substantially enhance the quality of service. Having that said, this study presents a review pertaining to the progress on the performance of available approaches for optical link monitoring system in PON. Recent advances in improving the performance of the optical link monitoring system, such as measurement accuracy, measurement speed, signal-to-noise (SNR) ratio, spatial resolution, and dynamic range, were investigated. Additionally, the performances of the existing approaches based on optical monitoring specifications were compared to identify an ideal monitoring framework. Finally, this paper discusses several challenges and prospects for future endeavours in formulating an effective optical link monitoring system in PON.

随着光纤深入到FTX网络中的无源光网络（PON）中，维护这些网络的完整性确实是必不可少的。本质上，在整个光纤接入网络的安装和验证过程中已经建立了最佳实践。同样重要的是，监视服务中的光纤性能下降，以确保有效的服务交付，并确保服务水平协议。然而，PON中的小故障可能会由于光分布网络中网络元素固有的无源性而导致大量数据丢失，从而导致客户不满意和网络运营商承担的运营费用不断上升。不幸的是，由于PON技术的快速发展，对光学层的测试和监视变得相当复杂。因此，配备有完整监视功能的高效光学层监视系统可以大大提高服务质量。话虽如此，本研究提出了有关PON中光链路监控系统可用方法性能的进展的综述。研究了提高光链路监视系统性能的最新进展，例如测量精度，测量速度，信噪比（SNR），空间分辨率和动态范围。此外，还比较了基于光学监视规范的现有方法的性能，以确定理想的监视框架。最后，本文讨论了在PON中建立有效的光链路监控系统的若干挑战和未来的努力。配备有完整监视功能的高效光学层监视系统可以大大提高服务质量。话虽如此，本研究提出了有关PON中光链路监控系统可用方法性能的进展的综述。研究了提高光链路监视系统性能的最新进展，例如测量精度，测量速度，信噪比（SNR），空间分辨率和动态范围。此外，还比较了基于光学监视规范的现有方法的性能，以确定理想的监视框架。最后，本文讨论了在PON中建立有效的光链路监控系统的若干挑战和未来的努力。配备有完整监视功能的高效光学层监视系统可以大大提高服务质量。话虽如此，本研究提出了有关PON中光链路监控系统可用方法性能的进展的综述。研究了提高光链路监视系统性能的最新进展，例如测量精度，测量速度，信噪比（SNR），空间分辨率和动态范围。此外，还比较了基于光学监视规范的现有方法的性能，以确定理想的监视框架。最后，本文讨论了在PON中建立有效的光链路监控系统的若干挑战和未来的努力。