Fabio Pittalà

Fast and robust CD and DGD estimation based on data-aided channel estimation

In this paper data-aided (DA) frequency domain (FD) channel estimation in a 2×2 multi-input-multi-output (MIMO) system is investigated. Using orthogonal training sequences, fast and robust CD and DGD estimation is demonstrated for a 112 Gbit/s PDM-QPSK system over a wide range of combined linear channel impairments.

Joint PDL and in-band OSNR monitoring supported by data-aided channel estimation

Employing a known training sequence robust and precise PDL and OSNR monitoring is demonstrated over a wide range of combined distortions. The proposed in-service monitoring technique is insensitive to CD, PMD and SOP rotation.

Cognitive, Heterogeneous and Reconfigurable Optical Networks: The CHRON Project

High degree of heterogeneity of future optical networks, stemming from provisioning of services with different quality-of-transmission requirements, and transmission links employing mixed modulation formats or switching techniques, will pose a challenge for the control and management of the network. The incorporation of cognitive techniques can help to optimize a network by employing mechanisms that can observe, act, learn and improve network performance, taking into account end-to-end goals. The EU project CHRON: Cognitive Heterogeneous Reconfigurable Optical Network proposes a strategy to efficiently control the network by implementing cognition. In this paper we present a survey of different techniques developed throughout the course of the project to apply cognition in future optical networks.

Training-Aided Frequency-Domain Channel Estimation and Equalization for Single-Carrier Coherent Optical Transmission Systems

Frequency-domain equalization supported by training-aided 2 × 2 multi-input multi-output channel estimation (CE) is proposed for coherent optical transmission systems. In particular, novel training sequence (TS) schemes based on a constant amplitude zero auto-correlation code, efficient CE algorithms and equalizer-tap updating solutions are derived from the theoretical linear fiber channel model and investigated through simulations. The robustness of the proposed methods is demonstrated with respect to the main degrading optical propagation effects, such as amplified spontaneous emission noise, chromatic dispersion, polarization-mode dispersion, polarization-dependent loss, time misalignment between received and reference TS, frequency offset between transmitter and receiver lasers, as well as dynamic state of polarization rotation.

Data-aided frequency-domain 2×2 MIMO equalizer for 112 Gbit/s PDM-QPSK coherent transmission systems

Benefits of a low-complexity adaptive 32-tap 2×2 MIMO frequency-domain filter update by data-aided channel estimation over a time-domain filter with DD-LMS are shown. Superior stability and convergence speed is demonstrated with identical impairment tolerance.

Data-aided Frequency-Domain channel estimation for CD and DGD monitoring in coherent transmission systems

CD and DGD monitoring from Frequency-Domain Zero-Forcing and MMSE filter functions adapted with the aid of short CAZAC training sequences is demonstrated.

Applying implicit training to polarization-division-multiplexed coherent optical systems

We report the use of implicit training-aided channel estimation (ITA-CE) for polarization-division-multiplexed (PDM) single-carrier coherent optical systems. With the concept of ITA-CE, where the training sequence (TS) is arithmetically added onto the information symbols rather than appearing in separate time slots, overhead-free transmission can be achieved with minor optical signal to noise ratio (OSNR) penalty. ITA-CE system enables simple digital pilot-tone based frequency-offset compensation, and inherits the benefits from typical training-aided channel acquisition and data recovery. Furthermore, we address the issue of self-interference to channel estimation (CE) of ITA-CE system in this paper. The data-induced interference can be eliminated by removing the cyclic mean of the transmitted signal, which can accelerate the convergence of the CE and allows smaller power to be allocated to the TS, leading to enhanced system performance. Numerical simulations and experiments for both PDM-QPSK and PDM-16-QAM systems have been conducted to verify the proposed scheme. Comparable performance to the conventional blind equalization system can be achieved when employing the transmitter side pre-distortion approach to the ITA-CE system.

Overhead-free channel estimation using implicit training for polarization-multiplexed coherent optical systems

Implicit training is successfully demonstrated for the first time in a 40-Gb/s QPSK experiment and 224-Gb/s 16-QAM simulation. Overhead-free transmission can be achieved with less than 0.5 dB Q-penalty compared to traditional explicit training scheme.

Training-based channel estimation for signal equalization and OPM in 16-QAM optical transmission systems

Efficient channel estimation for signal equalization and OPM based on short CAZAC sequences with QPSK and 8PSK constellation formats is demonstrated in a 224-Gb/s PDM 16-QAM optical linear transmission system.

Experimental demonstration of single-stage frequency domain equalization for single-carrier coherent receivers

Low complexity, single-stage frequency-domain equalization supported by blind CD estimation and training-aided 2×2 MIMO channel estimation is proposed and experimentally demonstrated in a 32 GBaud Nyquist PDM-QPSK transmission system.