Put them all together using optical connections. They have announced the light source from POET. 

I think they may also have multiple uses for optical interposers in these optical networks. Have they announced every instance of their planned purchases from POET? No, why would they? The game is to announce enough to be credible, and tell more when they have something to sell. Of course they will eventually want to have other vendors so that they are not wholly dependent on POET, but they know they can build with what POET has shown them, and won't wait around to solve the single vendor part of the architecture. 

But mainly, there may be more opportunities for POET inside, that are currently under NDA while Celestial gets their products ready.