Investigation of Pre-Equalization Technique for Pluggable CFP2-ACO Transceivers in Beyond 100 Gb/s Transmissions

Recently, CFP2 pluggable platforms are widely developed and deployed in 100 G optical networks for its flexibility, increased density, and reduced power consumption. For CFP2-ACO modules, they introduce high-speed analog electrical pluggable channels in line cards and generate additional performance degradation. To mitigate the effects of nonlinearity and limited bandwidth in transmitters, receivers, and pluggable channels, the pre-equalization technique is introduced in optical transmission systems. In this paper, the pre-equalization technique in the transmitter for beyond 100 Gb/s system deploying CFP2-ACO pluggable modules and beyond PM-QPSK modulations, including PM-8-QAM, PM-16-QAM, and PM-64-QAM, are investigated and demonstrated. It has been studied by a theoretical analysis, validated by numerical simulations and experimental measurements. The deviations and reflections by design and manufacturing imperfections are investigated. Effective pre-equalization is achieved for improved optical signal-to-noise ratio and received optical power performance, as well as better stability in the presence of deviations and reflections. Two types of CFP2-ACO modules are tested in experiments: modules with limiting drivers and linear drivers. A comparison between different single carrier modulation formats is performed in both simulation and experiment, suggesting that high-speed systems have more stringent requirements on pre-equalization filter design and optimization, and is more sensitive to fluctuations and reflections in the line-card system.