Eduardo S. Rosa

Enhanced digital polarization demultiplexation via CMA step size adaptation for PM-QPSK coherent receivers

Fixed step size CMA can exhibit serious penalties due to rapid channel variations during coherent receiver polarization demultiplexing. We propose and experimentally demonstrate two CMA gain adaptation methods that improve dynamic equalizer tracking and convergence.

Network survivability field trial over Brazilian legacy optical fiber links through advanced transponder reconfiguration

We propose a method for optical link survivability preservation by acting on the transmitter launch power and bit rate, and on the receiver DSP for linear/nonlinear impairments compensation. We validated the method for a legacy high-loss Brazilian network.

112 Gb/s DP-QPSK coherent optical transmission over 3000 km using an complete set of digital signal processing algorithms

Digital signal processing is a key feature in coherent dual polarization QPSK optical transmission, and plays an essential role to determine system performance. In this paper, we present a set of signal processing algorithms able to recover a single channel 112 Gb/s DP-QPSK signal after 3000 km propagation in a recirculation loop. The OSNR resilience and optical filtering impact over maximum reached distance were also investigated.

Nonlinear effects compensation in Optical Coherent PDM-QPSK Systems

Nonlinear effects has been appointed as the main limitation in coherent optical fiber transmission. Digital Back-Propagation algorithms and Maximum Likelihood Sequence Estimation are two of the current studied methods to cope with such impairment and extend the systems maximum reach. In this article, we analyzed both methods in a 112 Gb/s Dual Polarization Quadrature Phase Shifting Keying (DP-QPSK) optical coherent system through simulations and experimental results. In order to reduce the huge required computational complexity, a modified back-propagation algorithm is also analyzed.

Wide-range frequency offset estimator for DSP-based optical coherent receivers

We propose a hardware-efficient, feed-forward, wide-range frequency offset estimator for DSP-based optical coherent receivers, employed in 112 Gb/s PM-QPSK systems. This estimator is capable to estimate offsets in a range of ±5 GHz, using a simple relationship of signal spectrum. The obtained results show that this estimator is robust to spectrum asymmetry caused by electrical and optical filtering of the signal, even when using return-to-zero signals.

Advanced modulation formats and receiver filtering analysis of optical WDM systems with optimized distributed Raman amplifiers

This paper presents a systemic simulation analysis to find the maximum reach of an optical WDM distributed Raman amplified system evaluated in the following scenario: three different channel loads located at the C-Band, advanced modulation formats for 46 and 112 Gb/s data rates, chromatic dispersion compensation across the span and signal re-amplification carried out through optimized distributed Raman amplifiers (DRAs), in three distinct amplifiers configurations. The 46 Gb/s NRZ/DQPSK and 112 Gb/s NRZ/DPQPSK modulation formats show superior performances as well as insensitiveness to the filtering effects. The worst channel Q-Factor after the band pass filters is 3.09 which corresponds to an uncorrected BER threshold of 10−3 for the 12% overhead FEC used.

Improvement in dynamic equalization performance of a coherent receiver by CMA gain adaptation

The constant modulus algorithm has a relatively slow convergence speed in digital coherent receivers when compared to other algorithms, such as the least mean square. This paper proposes and experimentally demonstrates a simple gain adaptation method that improves the convergence of the dynamic equalizer in an 112 Gb/s PM-QPSK transmission receiver.