O-Band Silicon-Organic Hybrid (SOH) Mach-Zehnder Modulator Operating at a PAM4 Line Rate of 384 Gbit/s with Sub-Volt Drive Voltage

Optical transceivers for exa-scale datacenters and artificial intelligence (AI) clusters need to be compact, efficient, and amenable to low-cost mass production. In this context, the silicon-organic hybrid (SOH) platform is a particularly attractive option for implementing the underlying electro-optic modulators, combining the inherent scalability of silicon photonics with ultra-strong Pockels-type nonlinearities offered by advanced organic electro-optic materials. However, while SOH Mach-Zehnder modulators (MZM) have shown outstanding performance for high-speed transmission in the telecommunication C-band around 1550 nm, the O-band around 1310 nm is much less explored, even though it is much better suited for technically simple but dispersion-sensitive intensity modulation and direct detection (IMDD) schemes. In this paper, we demonstrate SOH MZM that have been specifically designed for high-speed IMDD transmission in the O-band, offering π-voltage-length products of UπL = 0.46 Vmm. Using a 500 μm-long MZM and a drive signal with a 950 mVpp peak-to-peak swing, we demonstrate 192 GBd PAM4 transmission at a line rate of 384 Gbit/s. This corresponds to both a record-high line rate and a record-low drive voltage for O-band MZM on the silicon photonic platform.