Are you saying this is done dynamically?
Google has scaled its network capacity from over one petabit per second to beyond six petabits per second since 2015, and some of that growth has come from switches that bounce optical signals off an array of mirrors to redirect traffic. As our sibling site The Next Platform reported in 2015, Google calls its datacenter …
They're components you can buy, they've been on sale for a decade or more. They're like small blocks that you connect fibers to that you switch using a voltage (think "optical relays"). Its likely that the 2022 version is rather more sophisticated -- and dense -- than the 2006 version.
There are situations where physical connectivity rather than logical connectivity is useful, especially if you need to isolate circuits or you're working with optical data and you don't need to switch circuits packet by packet.