Quality of transmission estimation and power control strategy for multi-band optical system

Abstract

Fiber optic communication systems play an important role in modern society and economic activities. Emerging applications and services, such as 5G, IoT, and cloud computing, drive the demand for scalable and ultra-high-capacity transmission. Consequently, high-spectral efficiency (SE) coherent fiber optic transmission, paired with advanced QOT estimation techniques, has become the leading technical approach to meet these demands. Some methods focus on expanding the frequency bandwidth of existing fibers, known as ultra-bandwidth transmission. Implementing multi-band systems offers a promising way to improve system utilization, and this approach appears to be a more economical and currently feasible solution in the short future. The development of multi-band system demands new optical performance monitoring (OPM) techniques, and one of the key aspects is the general optical signal-to-noise ratio (GSNR) monitoring. To maximize the capacity of optical network, the key is to fully utilize physical-layer and time resources. Critical technologies include dynamic lightpath provisioning and adaptive selection of bandwidth, modulation format, and amplified gain based on QoT estimation, which predicts the GSNR of each channel. However, due to the lack of an efficient and reliable QoT estimator, current optical networks adopt large operating margins to ensure that the planned demand capacity and service level agreements (SLAs) are met. This results in waste of the SE and reduces the network controllability, which goes against the trend of optical communication development. Therefore, accurate QoT estimation is crucial for enabling low-margin optical networking. However, in multi-bandwidth system and heterogeneous dynamic link environments, QoT estimation becomes a complex task. This complexity arises due to parameter uncertainties and fiber nonlinear distortions. Developing a practical and accurate QoT estimator is a major research challenge prior to large-scale use. In view of the above key problems, a comprehensive analysis of the practical networks with normally distributed parameter uncertainty is conducted. The study is critical with the increasing demands for network capacity and the trend of rerouting the network link and frequently updating devices. It is also helpful to foretaste the risk of an aging fiber link. In addition, a novel method to estimate the IL in C + L band optical communication networks is proposed to improve the accuracy of the QoT estimation. Our investigation covers various system parameters and conditions, providing a comprehensive analysis of error and robustness. Our proposed method can be an important and helpful supplement for QoT estimation in practical C + L band fiber optical communication systems. Finally, a novel power control strategy is proposed to achieve a flat OSNR distribution across all channels on the receiver side in C+L band systems. The proposed strategy has the advantage of straightforward computation and is capable of effectively mitigating the impact of SRS. The proposed strategy can be an important and helpful supplement for power control in practical C + L band long-haul fiber optical communication systems.