Just to clarify. There are two fundamental paths to POET's high volume optical engine. 

The small form factor pluggable solution that industry wants as soon as they can get it uses directly modulated lasers which requires a high volume supplier of mature lasers. These lasers are modulated directly by turning the power on and off. 

That application does not use continuous wave lasers in which the  light from the laser is modulated by a silicon modulator or a lithium niobate modulator.

At this point in time I would suggest the message POET is providing is that the POET platform is ready and that they have been working with component suppliers to secure a reliable supply of mature components. I think that once that announcement (DML laser supply) is made then it will mean that the 400G transmit is "in the bag".  And as we should all know by now 400G becomes multiplied with a focus on 1.6T which will be POET planting the flag and 800G becomes a big money maker as soon as it is available in high volume supply.