At 25 seconds into that short EPIC video, if you pause on the very busy slide there, near the bottom it shows, 

Integrated Photonics: Challenge: Fast Modulation, Polymer Photonics, Indium Phosphide, Silicon Photonics, VCSEL's, Packaging at Wafer Level 

https://www.linkedin.com/posts/josepozoepic_on-wednesday-april-21st-2021-at-1600cest-activity-6788043522932011008-sXwT 

This EPIC meeting of beyond 400Gbs is primarily focused on next gen modulators at 70GHz, but notice it also mentions what Poet's Optical Interposer (OI) Platform has successfully developed, that being a Wafer Level Packaging solution which dramatically lowers cost of Transceivers 

The meeting is on April 21, 2021 and available to view for all on YouTube