IEEE proposal would fold CPO channels into 400G/lane optical specs
jwt0625 · x · 2026-10-14
jwt0625 shares the IEEE Balan2026 proposal to include CPO channels in the 400G/lane optical specifications. CPO's co-packaged silicon drivers/modulators yield lower signal bandwidth at TP2 due to lower-bandwidth silicon photonics and higher engine-to-ASIC loss, so the spec must accommodate these technologies. An accompanying NVIDIA slide details a 212.5 Gbaud PAM4 channel with FFE+DFE. The author notes CPO will always need better lasers regardless of lane-rate direction.
Related event: NVIDIA's 400G per-lane optical spec raises bar for CPO lasers(2 posts)→
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