Digital Non-Linear Transmitter Equalization for PAM-N-Based VCSEL Links Enabling Robust Data Transmission of 100 Gbit/s and Beyond

This paper demonstrates why VCSEL-based transmitter systems are not able to capitalize on higher-order PAM modulation formats (such as PAM-4) push the link data rate towards 100 Gbit/s with BER of better than 10−5. First, non-linear and biasing-dependent VCSEL behavior is analyzed in great detail prove state-of-the-art VCSELs linear equalization reach these bandwidth targets. Consequently, based an enhanced model, a digital transmit equalizer proposed overcome voltage-dependent relaxation frequency shifts well data-dependent variations. The compared standard FFE structure using PAM-4 transmission experiments beyond. way, reveals improvement more 30-fold at 80 Gbit/s. Finally, 112 was successfully demonstrated 1.5·10−7.