Naive question, is the switch in this article packet switching or circuit switching? (I recall Google's TPU clusters have some optical circuit switching)
The problem is what happens when 1 single ethernet port transmit/receive laser out of 128/256 ports on die fails? You replace the whole switch, or move it to a spare port assuming you have one on the switch, and cabling accounts for it.
You're also talking 25/100/400/800 gigabit ethernet (or infiniband) ports here too using silicon photonics.