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 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$4 \times 80$</tex> Gbps signaling, assisted with a low-loss two-dimensional grating coupler over <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$1.85 ~\text{mm}^{2}$</tex> footprint, exhibiting significant potential for future high-density and large-capacity optical interconnects.