Theodor Kupfer

Comparison of Modulation Schemes for 10.7 Gb/s Transmission Over Large-Core 1 mm PMMA Polymer Optical Fiber

The authors give an overview of experimental results on 10.7 Gb/s over large-core 1 mm polymethyl-methacrylate (PMMA) polymer optical fiber (POF). The comparison starts with simple non-return-to-zero (NRZ) transmission without equalization. Next, measurement results with feed-forward-, decision -feedback equalization (FFE, DFE) and maximum likelihood sequence estimation (MLSE) are presented. Finally, experimental results with more advanced modulation schemes like pulse amplitude modulation (PAM) and discrete multitone (DMT) modulation are investigated. The experiments were carried out with a Vertical-Cavity Surface-Emitting Laser (VCSEL) at 0 dBm to comply with consumer eye-safety regulation or with a 10 mW laser diode (LD) that could be used in active optical cables.

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.

PMD Compensation using Electronic Equalization particular Maximum Likelihood Sequence Estimation

We review the basic electronic equalization techniques. We report new results of MLSE equalizers for combined chromatic dispersion and PMD. We show first results on the dynamic channel tracking performance of MLSE equalizers for PMD.

Parametric versus Non-Parametric Branch Metrics for MLSE-based Receivers with ADC and Clock Recovery

We compare the performance of MLSE-based receivers with parametric and non- parametric channel estimation methods and characterize their sensitivity against quantization, sampling jitter, and intersymbol interference (ISI) overload.

On the Design of AGC Circuits in IM-DD NRZ Optical Transmission Systems

This paper presents the investigation on the design of automatic gain control (AGC) circuits assumed to be robust against both bias and swing variations in the received unipolar digital signal. We have derived a small signal AGC general model that includes the impact of all relevant AGC components on the AGC transfer function. This model has been used for the calculation of AGC loop parameters of the specified AGC transfer function. The AGC robustness against signal level transients has been improved by introducing the second-order AGC loop. In ac-coupled receivers, the order and corner frequency of high-pass filter (HPF) placed in front of the AGC have been investigated. The HPF has been designed so that the input signal bias variations caused by signal level transients are compressed in acceptable limits, and so that bit-pattern bias variations do not significantly decrease the receiver performance. Signal swing and bias variations become very critical in optical systems using unipolar modulation format. Since the AGC design depends on its application, as an example, we have presented the AGC design concept in dispersion compensating 10.7 Gb/s intensity-modulated direct-detection (IM-DD) nonreturn-to-zero (NRZ) optical receiver using maximum-likelihood sequence estimation (MLSE).

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.

Carrier and Phase Recovery Algorithms for QAM Constellations: Real-time Implementations

We compare carrier phase recovery algorithms with respect to performance and we discuss their feasibility for real-time implementation in coherent transceivers.

Impact of pluggable analog coherent optics modules on line card architecture and DSP functionality

Pluggable analog coherent optics modules will change the architecture of line cards. Associated benefits like lower cost, installation on-demand and higher face-plate densities will come at the price of more complex DSP algorithms.

10.7-Gb/s Real-Time Transmission Over 1-mm Large-Core Polymer Optical Fiber Using Maximum Likelihood Sequence Estimation

We report 10.7-Gb/s nonreturn-to-zero (NRZ) real-time transmission over a 1-mm large-core polymethylmetacrylate polymer optical fiber (POF) using maximum likelihood sequence estimation. A maximum link length of 10 m of a standard step-index POF (SI-POF) and 35-m graded-index POF (GI-POF) was achieved with a fiber coupled power of 0 dBm, in order to comply with consumer eye-safety regulations. In order to show the robustness of this approach, the influence of fiber bends and different launching conditions were investigated. If the optical output power is increased to

Measurement of the Performance of 16-States MLSE Digital Equalizer with Different Optical Modulation Formats

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