Christina Hebebrand

Digital clock recovery with adaptive loop gain to overcome channel impairments in 112 Gbit/s CP-QPSK receivers

The effective loop parameters of digital PLL based clock recovery schemes vary with the degree of impairments in the received signal. We present a novel scheme that guarantees stable PLL design parameters independently of input signal distortions.

Signal Processing Algorithms in 100Gb/s Optical Coherent and Non-coherent Receivers with PSK Modulation

The paper addresses multi-level PSK modulation formats with coherent and non-coherent detection and reviews signal processing algorithms like mitigation of phase noise, the clock and carrier recovery algorithms as well as the equalizer structures and their performance.

Performance of Electronic Dispersion Compensation for Multi-Level Modulation Formats using Homodyne Coherent Detection

We investigate numerically the performance of electronic dispersion compensation with linear transversal filters of different filter lengths and tap delays for RZ-DQPSK, RZ-8-DPSK and star RZ-16-DQAM after homodyne coherent detection at 10.7 Gsymbols/s.

Investigations of the dispersion tolerance of the nonlinear optical transmission channel for different modulation formats in a WDM-system

We investigate the dispersion tolerance for nonlinear WDM transmission of the modulation formats ASK, DPSK, DQPSK and duobinary with NRZ as well as RZ pulse shape. We study different dispersion maps and determine for each modulation format an optimized dispersion map to examine the robustness against variations of the dispersion map and against nonlinear effects.

Signal processing algorithms in 100 Gb/s optical coherent and non-coherent receivers with PSK modulation

The paper addresses multi-level PSK modulation formats with coherent and non-coherent detection and reviews signal processing algorithms like mitigation of phase noise, the clock and carrier recovery algorithms as well as the equalizer structures and their performance.

Clock Recovery with DGD-Tolerant Phase Detector for CP-QPSK Receivers

We present three novel phase detector structures for a 112 Gbit/s CP-QPSK system, which provide, even in the presence of DGD, valid tracking information for a fully digital clock recovery.

Digital signal processing in high-speed optical communications

Electronic digital signal processing is currently introduced in various subsystems of modern optical high-speed transceivers. Traditionally, electronic processing was basically limited to tasks like MUX/DEMUX, clock and data recovery and various synchronization loops as well as analog circuitry like modulator drivers or limiting amplifiers. In order to deal with advanced systems and with the need for increased performance at long reach and higher speed, additional signal processing requirements have appeared. Examples are FEC and electronic equalizers (EDC), electronic pre-compensation, differential encoders, clock and carrier recovery, and polarization control. Recent challenges employ pure digital processing, where ADCs and DACs are required, like OFDM (orthogonal frequency division multiplexing) modulation or MLSE (maximum likelihood sequence estimation) equalizers. In this paper some of these signal processing algorithms are considered in detail and their impact on performance and cost in terms of implementation effort is reviewed.

Advanced System Design and Optimization for Mitigation of Optical Channel Impairments

The paper addresses modern design of optical communications links for handling impairments of the optical high-speed long distance channel. Electronic equalizers, advanced modulation formats, and optical OFDM transmission are considered.

Investigation of Electronic Equalization in Coherent Receivers with Complex Modulation Schemes

We propose a post detection equalizer design for complex multilevel modulation and coherent I/Q-detection and investigate the performance in terms of dispersion tolerance for both linear and nonlinear (Kerr effect) fiber effects.