On that note Lumentum has won an award for their 200G PAM4 EML (Externally Modulated Laser). Lumentum (@Lumentum) / Twitter 

We have not heard much about POET's 6.4T optical engine but that design takes full advantage of the dual waverguides with the RX circuit at the top level waveguide and TX on the bottom level waveguide. 

Directly Modulated Laser Platform

6.4Tbps

• DML/EML Implementation

• Custom Configurations

• Industry leading form factor with two layer waveguides (optical chiplet : 18mmx18mm

This level of density is pretty spectacular and I recall Suresh saying (during a presentation) something  about interest being shown by the hyperscale data center providers.

Synopsis-Photonics-Symposium-2022.pdf (poet-technologies.com)