Optical link monitoring in fibre-to-the-x passive optical network (FTTx PON): A comprehensive survey

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.