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Journal of Electrical and Computer Engineering
Volume 2013, Article ID 240814, 14 pages
http://dx.doi.org/10.1155/2013/240814
Research Article

Efficient Parallel Carrier Recovery for Ultrahigh Speed Coherent QAM Receivers with Application to Optical Channels

Laboratorio de Comunicaciones Digitales, Universidad Nacional de Córdoba (CONICET), Avenida Vélez Sarsfield 1611, X5016GCA Córdoba, Argentina

Received 10 December 2012; Accepted 28 March 2013

Academic Editor: Ashkan Ashrafi

Copyright © 2013 Pablo Gianni et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

This work presents a new efficient parallel carrier recovery architecture suitable for ultrahigh speed intradyne coherent optical receivers (e.g., ≥100 Gb/s) with quadrature amplitude modulation (QAM). The proposed scheme combines a novel low-latency parallel digital phase locked loop (DPLL) with a feedforward carrier phase recovery (CPR) algorithm. The new low-latency parallel DPLL is designed to compensate not only carrier frequency offset but also frequency fluctuations such as those induced by mechanical vibrations or power supply noise. Such carrier frequency fluctuations must be compensated since they lead to higher phase error variance in traditional feedforward CPR techniques, significantly degrading the receiver performance. In order to enable a parallel-processing implementation in multigigabit per second receivers, a new approximation to the DPLL computation is introduced. The proposed technique reduces the latency within the feedback loop of the DPLL introduced by parallel processing, while at the same time it provides a bandwidth and capture range close to those achieved by a serial DPLL. Simulation results demonstrate that the effects caused by frequency deviations can be eliminated with the proposed low latency parallel carrier recovery architecture.