Erich Gottwald

Demonstration of a coherent UDWDM-PON with real-time processing

A filterless coherent PON with channel spacing down to 2.8 GHz and real-time processing in an FPGA is demonstrated. 64-channel operation is verified experimentally using SSB generation at the OLT and fully integrated ONU transceivers.

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.

Coherent Ultra Dense WDM Technology for Next Generation Optical Metro and Access Networks

Coherent optical communication has been well established as the technology of choice for long haul and high bit rate communication systems since a decade ago. Recent technology advances and ongoing price erosion further open the window of opportunity for the application of coherent optical transmission technology in other domains. This paper describes in detail the capabilities, design and implementation of a coherent ultra dense WDM technology for optical metro and access networks. Its capabilities enable a number of attractive options, such as variable downstream bit rates from 150 Mbit/s up to 10 Gbit/s per user, embedded OTDR and the coexistence with legacy systems such as GPON, EPON, XGPON or RF-Video in optical distribution networks. Due to its flexibility and capacity, it is also suitable for deployments in metropolitan networks, as well as for mobile front-haul and back-haul applications.

1.6-b/s/Hz Spectrally Efficient Transmission Over 1700 km of SSMF Using 40

We discuss high spectral efficient long-haul transmission using multilevel modulation formats. In particular, we investigate long-haul transmission with a 1.6-b/s/Hz spectral efficiency using polarization-multiplexed return-to-zero differential quadrature phase-shift keying. In an experimental demonstration, we show 40 times 85.6-Gb/s transmission with a 50-GHz channel spacing over 1700 km (18 times 94.5 km) of standard-single-mode fiber

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We discuss coherent equalization to realize robust 111-Gb/s transmission. For 111-Gb/s POLMUX-RZ-DQPSK we experimentally show the advantage of coherent equalization over direction detection for compensation of both chromatic dispersion and differential group delay.

85.6-Gb/s POLMUX-RZ-DQPSK

The feasibility of long-haul transmission using differential quadrature phase shift keying (DQPSK) modulation is discussed. We focus in particular on the trade-off between spectral efficiency and reach in optical transmission systems using DQPSK modulation.

Coherent Equalization versus Direct Detection for 111-Gb/s Ethernet Transport

Generation of multiple individually modulated wavelengths out of a single laser source is one of the key pre-requisites for an economical UDWDM PON. It is implemented using a 65 GS/s DAC and real time DSP.

DQPSK modulation for robust optical transmission

We show the feasibility of more cost-effective long-haul transmission using fiber Bragg gratings (FBG) for in-line dispersion compensation. 32xl0.7-Gbit/s NRZ modulated channels are transmitted over 40x95 km of SSMF using low group delay ripple FBGs.

Digital multi-wavelength generation and real time video transmission in a coherent ultra dense WDM PON

We report our investigations on the impact of transients stemming from channel reconfiguration or network failure. Erbium-doped fiber amplifier (EDFA) gain dynamics are considered by an average-inversion-level model. The simulation model is also verified by laboratory experiments. In extensive simulations, optimal sets of parameters for an electronic EDFA gain controller have been determined. We show that better results can be obtained if the gain controller is optimized for a chain of EDFAs and not a single amplifier only. Additionally, an efficient simulation methodology to calculate the combined bit error ratio (BER) is presented by coupling simulations of transient phenomena with bit-based simulations incorporating nonlinear fiber effects.

Cost-effective 10.7-Gbit/s Long-Haul Transmission using Fiber Bragg Gratings for In-line Dispersion Compensation

We experimentally compare MLSE equalization with OOK and DPSK in the presence of chromatic- and polarization-mode dispersion. We show that the 3-dB OSNR advantage of DPSK is lost in the presence of chromatic dispersion but maintained with polarization-mode dispersion.