On-chip integrated mode-division multiplexing (MDM) is an emerging technique for large
capacity data communications. In the past few years, while several con
fifi
gurations have been
developed to realize on-chip MDM circuits, their practical applications are signi
fifi
cantly
hindered by the large footprint and inter-mode cross talk. Most importantly, the high-speed
MDM signal transmission in an arbitrarily routed circuit is still absent. Herein, we demon
strate the MDM circuits based on digitized meta-structures which have extremely compact
footprints. 112 Gbit/s signals encoded on each mode are arbitrarily routed through the cir
cuits consisting of many sharp bends and compact crossings with a bit error rate under
forward error correction limit. This will signi
fifi
cantly improve the integration density and
bene
fifi
t various on-chip multimode optical systems.
