Least Angle Regression-Based Modified Volterra Nonlinear Equalizer for Optical Interconnection System

Abstract

Advanced digital signal processing (DSP) is viewed as an inevitable technology to deal with nonlinear distortions in cost-sensitive optical interconnection systems. Classic methods such as equalization based on Volterra series turn out to be quite effective solutions to compensate signal impairments. In practical imple-mentations, a great deal of efforts focus on reducing the com-putational complexity. Several model selection and dimensionality reduction approaches have been proposed to simplify the struc-ture, which employ backward strategies. However, the threshold settings for these pruning approaches are environment-sensitive. In this paper, we propose a least angle regression-based nonlinear equalization method (LaNLE). We extend the non-intrusive least angle regression technique to generalized linear models. Through an incremental process by stagewise feature selection and weight fitting, we obtain the low-complexity nonlinear structure with significant feature basis. Experimental verification is performed based on 120 Gbps PAM8-modulated 850 nm VCSEL plus MMF optical link. The results show that, compared to fully-connected Volterra nonlinear equalizer structure (VNLE), up to 60.4% and 70.1% reduction in complexity can be achieved with similar BER performance in back-to-back and 100 m transmission scenarios, respectively. In addition, we experimentally demonstrate 225 Gbps per lane PAM-8 signal transmission over 100 m MMF in a simple and cost-effective implementation manner based on mass-production 850 nm VCSEL and proposed LaNLE method.