New WON papers published in JLT
Two WON papers have been published in the Journal of Lightwave Technology. The Journal of Lightwave Technology is a biweekly peer-reviewed scientific journal covering optical guided-wave science, technology, and engineering, which is published jointly by the Optical Society and the IEEE Photonics Society. Both publications are available in open access.
Title: Characterization, Monitoring, and Mitigation of the I/Q Imbalance in Standard C-Band Transceivers in Multi-band Systems
Authors: Gabriele Di Rosa; Robert Emmerich; Matheus Ribeiro Sena; Johannes Karl Fischer; Colja Schubert; Ronald Freund; Andre Richter
Next-generation optical communication networks aim to vastly increase capacity by exploiting a larger optical transmission window covering the S-C-L-band. Simultaneously, the clear market trend is to maximize capacity per wavelength to reduce operational costs. This approach requires an increase in spectral efficiency, resulting in stringent requirements on the transceivers, which may not be satisfied in a multi-band (MB) scenario by current commercial components designed for operation in C-band. Transceiver specifications for MB operation can be relaxed through additional digital signal processing (DSP), at the cost of additional complexity, and by more resource-intensive calibration procedures. In this context, we experimentally characterize the wavelength-dependent frequency-resolved in-phase/quadrature (I/Q) imbalance of a standard C-band IQ-modulator and coherent receiver operating in an S-C-L-band system utilizing receiver-side DSP. This operation allows us to understand the nature of the wavelength-dependency of I/Q imbalance in MB systems. In the considered scenario, we validate the effectiveness of a cost-effective strategy for transceiver impairments mitigation and monitoring based on standard wavelength-independent calibration and reduced-complexity DSP.
Title: DSP-based Link Tomography for Amplifier Gain Estimation and Anomaly Detection in C+L-band Systems
Authors: Matheus Ribeiro Sena, Robert Emmerich, Mohammad Behnam Shariati, Caio Santos, Antonio Napoli, Johannes Karl Fischer, Ronald Freund
A successful migration from todays C-band based optical networks to a multiband (MB) 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 (Rx) based digital signal processing (DSP) as a tool for optical performance monitoring (OPM) has gained tremendous popularity. As main benefits, these Rx-DSP based OPMs can: 1) minimize the costs associated with the deployment of node-level monitors and 2) map multiple characteristics of the network without direct access to infrastructure information. One successful example of such Rx-DSP based OPM is the so-called in-situ power profile estimator (PPE). This method can reconstruct the per-channel longitudinal power profile along the optical fiber link solely processing the received samples. In this work, we propose a novel application for the in-situ PPE by harnessing it on multiple wavelengths to accurately estimate the spectral gain profile of C+L-band in-line Erbium-doped fiber amplifiers (EDFA)s deployed in a 280-km single mode fiber (SMF) link. Furthermore, we show how this scheme can be efficiently used to detect EDFA 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 (OSA). This supports the importance of this Rx-DSP based method as a relevant OPM tool to diagnose the health of MB optical networks without special measurement equipment.