Christoph Schulien

Measurement of the dispersion tolerance of optical duobinary with an MLSE-receiver at 10.7 Gb/s

We experimentally demonstrate a significant improvement in the dispersion tolerance of optical duobinary modulation when employing an MLSE instead of a standard receiver. We show that the improvement critically depends on the MLSE design.

Impact of Polarisation Dependent Loss on Coherent POLMUX-NRZ-DQPSK

We present simulations and measurements on the effect of PDL on a POLMUX-NRZ- DQPSK signal. We show that the orientation between the POLMUX signal and PDL element has a major impact on the OSNR performance.

Laser Linewidth Estimation by Means of Coherent Detection

In this letter, we present a novel approach to measure the Lorentzian linewidth of a laser source. The approach is based on a heterodyne detection scheme, such as may be implemented in a coherent optical receiver for data communications, using both in-phase and quadrature information of the optical field. In contrast to previously published works, this approach does not suffer from modulation effects on the laser output.

Cycle slip tolerant hybrid turbo differential decoding

We experimentally investigate the cycle slip tolerance of an enhanced Turbo Differential Decoding algorithm in nonlinear transmission. Error-free post-FEC measurements using a 100G QPSK DWDM module show excellent tolerance against cycle slips without a differential encoding penalty.

Optical Performance Monitoring using a 43Gb/s realtime coherent receiver

We present Optical Performance Monitoring from the equalizer filter setting of an FPGA-based Realtime 43Gb/s Polarization Diverse Coherent Receiver. Chromatic Dispersion and Polarization Mode Dispersion of the optical transmission link are independently estimated from the blindly adapted equalizer filter. The accuracy of the estimates is demonstrated based on measurements.

Towards Robust 100G Ethernet Transmission

We discuss transmission requirements for commercially deployable, robust 100 G Ethernet transport. Coherently equalised POLMUX-RZ-DQPSK is shown to be both compatible with 10 G infrastructure and suitable for long-haul transmission.

Maximum likelihood sequence estimation at 10 Gb/s from concept to implementation

Maximum likelihood sequence estimation is seen as the superior algorithm for electronic equalization at the receiver. We report about the first implementation of a 10.7 Gb/s optical receiver using maximum likelihood sequence estimation.

Real-time prototypes for digital coherent receivers

We review real-time and off-line processing techniques for the proto-typing of a digital coherent receiver.

Digital Signal processing — from simulation to silicon

Optical communications systems at 10, 40 and WOG now use digital signal processing to enhance the signal tolerance against channel impairments such as chromatic dispersion and PMD. The power of digital signal processing is driven by developments in CMOS integration, which push the limits of gate count, feature sizes and development budgets. But what steps are involved in developing a full custom ASIC ? What are the pitfalls and challenges ? This tutorial outlines the development of an ASIC for a CP-QPSK transponder.

Simple automatic nonlinear compensation with low complexity for implementation in coherent receivers

We analyze digital nonlinearity compensation. Due to complexity restrictions in real-time applications we propose a simplified compensator with an automatic control scheme and evaluate its performance with simulations on two different dispersion maps.