I don't think Broadcom is using Poet.
There is a company out of Ottawa, Ranovus, with an optical engine and they were in the Broadcom's section of the OFC exhibit (as per the floor plan).
Technically, I don't know how the products compare.
I found this news article as well.
https://finance.yahoo.com/news/globalfoundries-announces-next-generation-silicon-133000925.html