High-Density MDM Silicon Transmitter Based on Two-Dimensional Grating Coupler for Singlefiber $\mathbf{4} \boldsymbol{\times} \mathbf{8 0}$-Gbps Signaling

A four-channel mode division multiplexing (MDM) transmitter is demonstrated with $4 \times 80$ Gbps signaling, assisted with a low-loss two-dimensional grating coupler over $1.85 ~\text{mm}^{2}$ footprint, exhibiting significant potential for future high-density and large-capacity optical interconnects.