really interesting write-up, but for anyone like me who thought "hmm, I've got $20 and a spare SFP slot, maybe I'll play around with this" - the $20 price tag in the headline is a bit misleading:

> The key piece is an Oscilloquartz OSA-5401 ...

> ... New, they cost thousands of dollars. On eBay, a handful of decommissioned units went for $20. Now they’re unavailable. If they do appear (rarely), they’re $300-500.