DAC-less PAM-4 signal generation using a thin-film lithium niobate dual-drive MZI modulator

In this study, we demonstrate DAC-less PAM-4 signal generation using a lithium niobate on insulator (LNOI) dual-drive Mach–Zehnder modulator (DD-MZM). The modulator is driven by two independent binary streams, eliminating the need for power-hungry digital-to-analog converters (DACs). The high electro-optical (EO) bandwidth and excellent linearity of the LNOI modulator make it suitable for generating high-speed, equally spaced PAM-4 signals. Experimentally, PAM-4 signals were generated at rates up to 128 Gbps with an extinction ratio (ER) of 4.2 dB and a ratio of level separation mismatch (RLM) of 0.96. This work offers a novel, to the best of our knowledge, design approach for high-speed, high-linearity PAM-4 signal generation.