Interesting Macnai. I recall last year a comment that hyperscalers were interested in the very high density enabled by the dual waveguide CWDM design where the receive waveguide (top layer) and send waveguide (bottom layer) overlay each other for 6.4T transfer capability in and area 18mm X 18mm. It is a clear demonstration of the optical interposers capability that has their attention. If you look at slide 7 on the presentation linked below you will note 16 mux and 16 de-mux with 4 channels each for 6.4T.  That is at 100G lamba so I guess that  ultimately becomes 12.8T at 200G.

Note how the receive path and send path crossover each other on separate planes. 

POET Technologies - Optical Interposer for Hybrid Photonics Integration Update July 2022.pdf (poet-technologies.com)