Performance Of High-speed Links Research Articles

Simulink-Based Modeling and PCA-Based Nonlinearity Evaluation for High-Speed Links

With the data rate of high-speed links increasing, the impact of nonlinear factors becomes more and more prominent that bring great signal integrity challenges to the analysis and design of high-speed links. However, there are two gaps in the study of the nonlinear behaviors of the high-speed links. One is that there is no simulation platform that can flexibly deal with different kinds of nonlinear behaviors. The other is that there is no metric that can quantify the level of the nonlinearity of the links. Aiming at these two problems, this article first models a nonlinear high-speed link based on Simulink, which can flexibly adjust the nonlinear behaviors, and then analyze the impact of nonlinear behaviors on the performance of high-speed links. Lastly, a metric is presented based on the principal component analysis to quantify the level of the nonlinearity of the high-speed links. Simulation results show that the metric can effectively capture the nonlinear severity of the links.

Advanced Modeling and Accurate Characterization of a 16 Gb/s Memory Interface

As the input/output (I/O) data rate increases to several gigabits per second, determining the performance of high-speed interfaces using conventional simulation and measurement techniques is becoming very challenging. The models of the interconnects have to be broadband and accurate to represent high frequency and second-order effects such as frequency dependence of dielectric losses and surface roughness. The large and small signal behaviors of the transmitter and receiver circuitries have to be correctly represented in link analysis. In addition, the system simulation needs to properly capture the interactions between the circuits and interconnect subsystems to optimize the overall system. However, determining the values of the critical link parameters and their correlations can be complicated. Some of the key parameters are not deterministic and some cannot be observed directly. A combined modeling and measurement approach is indispensable to determine the performance of high-speed links. This paper presents the modeling and characterization techniques employed in the design and verification of a 16 Gb/s bidirectional asymmetrical memory interface. Direct frequency and time-domain methods as well as indirect techniques based on bit-error-rate testing are used to model and determine important link parameters. Complex de-embedding procedures are utilized to extract parameters from externally observed data. On-chip measurements are also used to complement off-chip instrumentation and accurately measure the true performance of the link. The modeling and characterization of prototypes are also discussed and model-to-hardware correlations are presented at component and system levels. Based on both simulation and measurement results, the behavioral model of the complete system is constructed and statistical simulation technique is used to predict the yield and performance at low bit error rate.

Cost-Effective Multimode Polymer Waveguides for High-Speed On-Board Optical Interconnects

Cost-effective multimode polymer waveguides, suitable for use in high-speed on-board optical interconnections, are presented. The fundamental light transmission properties of the fabricated waveguides are studied under different launch conditions and in the presence of input misalignments. Low loss (~0.04 dB/cm at 850 nm) and low crosstalk (<-30 dB) performance, relaxed alignment tolerances (plusmn20 mum) and high-speed operation at a 10-Gb/s data rate are achieved. No degradation in the high-speed link performance is observed when offset input launches are employed. Moreover, a range of useful waveguide components that add functionality and enable complex on-board topologies are presented. The optical transmission characteristics of the fabricated components are investigated and it is shown that excellent performance is achieved. Excess losses as low as 0.01 dB per waveguide crossing, the lowest reported value for such components, and bending losses below 1 dB for 90-degree and S-shaped bends are obtained even with multimode fiber launches. Moreover, high-uniformity power splitting and low-loss signal combining are achieved with Y-shaped splitter/combiners while a variable splitting ratio between 30%-75% is demonstrated with the use of multimode couplers. Overall, the devices presented are attractive potential candidates for use in on-board optical links.