Fun with Optics#

Patrick Prangl (Arista Networks)

• Why: An excellent state-of-the-union on the optics transition to 800G/1600G — covering merchant silicon roadmaps (51.2T shipping, 102.4T this year, 204.8T in 2027), Linear Pluggable Optics (LPO), and ZR/ZR+ coherent evolution. Core physical DC optics content.
• What: A structured overview of switch silicon evolution (Broadcom Tomahawk/Jericho generations), 800GbE standardization (IEEE 802.3ck/df, 800GBASE-ETC-R), the 100G→200G SerDes transition, LPO vs LRO vs CPO (all are the same linear-interface technology — difference is packaging position: front-panel pluggable, near-package, or co-packaged), 800G LPO performance data (7.5W typical vs 15W DSP, <3e-10 BER, multi-vendor interop proven), and ZR/ZR+ coherent DCI evolution to 800G and 1.6T.
• How: LPO removes the DSP from the optics module (50%+ power reduction at 800G) by relying on the switch ASIC's high-quality SerDes to drive the optical lanes directly. CPO/NPO/LPO share the same <20dB D2D channel-loss requirement. ZR+ uses multi-rate coherent with oFEC for ROADM/metro links; Coherent Lite targets 20km DCI at 800G/1.6T.
• Where applicable: Any DC operator planning 800G/1600G deployments. LPO is immediately relevant for short-reach (in-rack/adjacent-rack) AI clusters where power per port is a constraint. Arista-branded but the data is vendor-neutral (MSA specs, IEEE standards, plug-fest results).