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Impact of VCSEL nonlinearity on Discrete MultiTone modulation: Quasi-static approach

Vertical-Cavity Surface-Emitting Lasers (VCSELs) represent many advantages for high data rate and low cost communication systems. However, they have a nonlinear transfer function, which could drastically affect the multicarrier modulations performances. The static characteristic is usually used to estimate the VCSEL nonlinearity impact on the Discrete MultiTone (DMT) modulation performances. In this paper, we demonstrate that the use of the static characteristic to model the VCSEL nonlinearity, overestimates the nonlinearity distortions when a large dynamic signal is modulating the VCSEL. In order to correctly estimate the VCSEL impact on the DMT modulation performances, we use the quasi-static characteristic to model the VCSEL nonlinearity. We show that the proposed modeling provides accurate estimations of the nonlinear distortions. The error vector magnitude (EVM) simulation results are very close to the measured EVM.