Ernst-Dieter Schmidt

High spectral efficiency 1.6-b/s/Hz transmission (8 x 40 Gb/s with a 25-GHz grid) over 200-km SSMF using RZ-DQPSK and polarization multiplexing

With relatively simple standard transmission equipment, we achieved a wavelength-division-multiplexing transmission with a record-high spectral efficiency of 1.6 b/s/Hz using return-to-zero differential quadrature phase-shift keying and polarization multiplexing over 200-km standard single-mode fiber with a 40-Gb/s capacity per wavelength but 10-GSymbol/s rate.

Field trial results on statistics of fast polarization changes in long haul WDM transmission systems

Field trials were carried out to determine the statistics of fast polarization changes in optical networks. Important data enabling the definition of speed requirements for PMD compensators and adaptive equalizers could be obtained.

Chromatic dispersion tolerance of coherent optical communications systems with electrical equalization

Coherent demodulation provides linear transfer of distortions from the optical into the electrical domain. We show by use of Monte-Carlo simulations which equalizer structures available today are best suited to equalize chromatic dispersion after coherent demodulation

Correlation-Based Carrier Phase Estimation for WDM DP-QPSK Transmission

A novel algorithm for frequency offset compensation and carrier phase estimation in systems with 40 or 111 Gb/s coherent dual-polarization quadrature phase-shift keying (DP-QPSK) with on-off keying or DP-QPSK neighbors is demonstrated. The algorithm, which applies correlation phase adjustment embedded between digital differential demodulation and nonredundant error correction, leads to a significant performance improvement over standard algorithms.

Iterative Electronic Equalization Utilizing Low Complexity MLSEs for 40 Gbit/s DQPSK Modulation

We present simulations of a novel electronic signal processing technique that allows digital equalization of optical 40 Gbit/s DQPSK signals using iterative equlization with mutual exchange of information between low complexity MLSEs.

State Based OSNR Estimation in Amplitude Sampling Receivers

We present a state based OSNR estimation, which enables electrical receivers to monitor in-channel optical noise. The estimation is independent from the sampling instant as well as from signal distortions.