Which in my switch? LPO, CPO, XPO optics. What are they, when to use#

Dr Robert Friskney (Arista)

• Why: Optics format choice is now a switch-architecture decision, not a line-item: LPO, CPO, and XPO change power, latency, port density, and the vendor lock-in surface of a fabric. Anyone planning 800G/1.6T generations needs this decision framework.
• What: An explainer and decision guide: what linear-drive pluggable optics (LPO) are versus traditional DSP-based pluggables; how co-packaged optics (CPO) differs; the practical cost/latency/power trade-offs; which switch and routing use-cases LPO wins today and which it loses; how the answer shifts as port rates rise; and the future evolution toward CPO's density versus the alternative "extra-dense pluggable" (XPO) approach (from abstract only — the event page confirms it is a reprise of a well-received community talk at Net.Ldn with the Q&A topics folded in).
• How: LPO removes the DSP for short-reach links (trading reach and interoperability margin for power and latency savings); CPO integrates optics into the switch package; XPO keeps pluggability while pushing density — the talk maps each onto switch/routing use-cases.
• Where applicable: Short-reach in-fabric and backplane-adjacent links are the LPO sweet spot; CPO/XPO are next-generation switch design questions. Arista-led, so expect some roadmap framing from a switch vendor's perspective, but the material is a category primer, not a product pitch.