Shash: First, the die being used for all this "testing" are produced on small wafers, in the 2 and 4 inch range, that can be made and rejected quickly and maniplulated by the engineers in the extapial stage (building them).
There is no need for wafer size conversion as the Optical Interposer is already being tested at 8” and we know this since the physical evidence was brought to the AGM last year.
https://agoracom.com/ir/POETTechnologies/photos
The InP active die may well be using 2 inch wafers for R&D of future discrete components at DL and other locations but it is OI where we begin to talk about wafer scale production through the use of pick and place tools at high throughput.
Clearly this will require clarification by Suresh and/or Vivek.