DSP-Based Link Tomography for Amplifier Gain Estimation and Anomaly Detection in C+L-Band Systems

Abstract

A successful migration from current C-band based optical networks to a multiband scenario primarily depends on the development of solutions that can reliably measure physical properties of optical links over broad spectral transmission windows. Additionally, these solutions must be capable of delivering wavelength-dependent and spatially-resolved indicators that can empower network operators to identify faults before they lead to severe service disruptions. Recently, the exploitation of receiver based digital signal processing as a tool for optical performance monitoring has gained tremendous popularity. One successful example is the so-called in-situ power profile estimator, which can reconstruct the per-channel longitudinal power profile along the optical fiber link solely processing the received signal samples. In this work, we propose a novel application for the in-situ power profile estimator by harnessing it on multiple wavelengths to accurately estimate the spectral gain profile of C+L-band in-line Erbium-doped fiber amplifiers deployed in a 280-km single mode fiber link. Furthermore, we show how this scheme can be efficiently used to detect amplification-related anomalies, such as gain tilt and narrowband gain compression. In our measurements, we achieved a sub-dB estimation accuracy by comparing the proposed gain extraction approach with the back-to-back characterization obtained from an optical spectrum analyzer.

Advanced DSP-Based Monitoring for Spatially Resolved and Wavelength-Dependent Amplifier Gain Estimation and Fault Location in C+L-Band Systems

“…Second, this single-channel analysis is immune to the interference originated from adjacent carriers, i.e., cross-channel interference. Therefore, we believe that a C+L-band multi-channel analysis is an interesting and more realistic study that would finally complement the discussions present in [16] and [17].…”

“…In [16], it was also shown that the link tomography can directly support the identification of failures such as anomalous gain tilt imposed by malfunctioning amplifiers. Recently, our work published in [17] also successfully demonstrated that another type of amplification fault, i.e., the narrowband gain compression caused by the spectral hole-burning (SHB) effect, can be likewise captured by using the link tomography.…”

“…Caio Santos, Robert Emmerich, Behnam Shariati, Colja Schubert, Johannes K. Fischer and Ronald Freund are with the Fraunhofer receiver (Rx) based digital signal processing (DSP) methods have been extensively explored to estimate properties of optical fiber links [7]- [17], thus relaxing the demanding requirements of deploying multiple and expensive node-level measurement devices. Thanks to their capability in unveiling multi-span link characteristics, such as longitudinal power evolution [7]- [12], frequency response of optical filters [12], chromatic dispersion mapping [13], Raman gain [14], and polarization-dependent loss [15], these Rx-DSP monitoring methods have gained a momentum over the past few years.…”

“…Despite all credits that [16] and [17] deserve, the experimental results presented in these contributions comprise a methodology where a single wavelength-division multiplexing (WDM) channel is swept across the wavelength domain in order to capture the frequency-dependent information of the optical system. This methodology, consequently, is subject to at least two important implications.…”

“…Another important topic discussed in [17] is the development of fault detection schemes that can further improve the identification of anomaly signatures. As efficient anomaly detection schemes are of key importance for network operators, helping them to carry out more assertive maintenance routines, we believe that the proposal of a novel scheme, with improved performance compared to the one shown in [17], is another appropriate subject for extension in this paper.…”