In-Band Power Ripple Detection and Localization Using Longitudinal Power Monitoring

Optical performance monitoring has undergone a significant transformation with the advent of longitudinal power profile estimation (PPE), enabling advanced monitoring of signal and transmission link characteristics using only the received signal at the receiver side. As modern optical networks operate with higher symbol-rate signals, they require more extensive and accurate monitoring for effective management and optimized performance through just-enough margin systems. This paper presents the application of PPE for in-band power ripple (IPR) monitoring, demonstrating its effectiveness in detecting and localizing spectral variations. Two PPE-based techniques are introduced: sub-band PPE, which estimates spectral power within digital sub-bands to achieve higher granularity in signal power estimation, and reference-sweeping PPE, which adapts reference waveforms to match distortion patterns. While sub-band PPE allows precise detection of IPR with arbitrary shapes at the expense of spatial resolution, reference-sweeping PPE enhances efficiency by eliminating the need for deconvolution and reducing the number of estimation points when the IPR shape is approximated by a simple form. Simulation and experimental validation confirm the effectiveness of these approaches in high-baud-rate systems. This enables more accurate transmission quality assessment, facilitates rapid fault detection and localization, and further improves PPE performance, contributing to enhanced optical network reliability and efficiency.