Really? Are you guessing at this? We were told several  times that each of the four applications they identified at the AGM represented a customer. And  exactly why would they have been paid NRE from a someone for 400G if they were not a  customer?

POET READIES OPTICAL INTERPOSER FOR PRODUCTION IN ALIGNMENT WITH PRODUCT ROADMAP

Poet's product road map, presented in its annual general meeting of shareholders conducted in late August, revealed four products under development, each associated with an individual customer or potential groups of customers. The company reported that the 100/200 G CWDM4 Optical Engine, the 400 G LightBar, 400 G FR4 Receiver, and the 400 G FR4/DR Optical Engines all remain on schedule