oldgregs posted quote:

Celestial AI’s Photonic Fabric, in contrast, uses a silicon photonic modulation technology that, in Lazovsky’s words, is “about 60 times more thermally stable than a ring.” This, he says, will enable the Photonic Fabric to deliver bandwidth beyond the beachfront, and directly at the “point of compute” or data consumption in the ASIC. (He notes that the thermally stable modulator is already “in volume production for other applications”; Celestial AI is just the first company, he says, to use it in this way.)

A quick comment:

Recall Suresh commenting on the instability of the microrings that traditional silicon photonics relies on. Wavelength drifts under any temperature deviation and requires very precise dimensional control during fabrication.  And since we are talking about monolithic silicon the microring has to be tuned to a specific temperature that the die operates at. 

In the case for example of Ayer Labs this means heaters to control the microring temperature for microring tuning.

POET of course is largely athermal so wide operating temperature tolerances.