Walking the AI rack optical stack: InP substrates and silicon photonics as the cleaner bet

demian_ai · x · 2026-09-08

The author dissects the full stack of a working optical lane in an AI rack: InP substrates (AXTI, Sumitomo, IQE, Freiberger), lasers/EML/CW sources (LITE, COHR, AAOI), DSP/retimer fabric (Marvell, Broadcom, Credo, Astera), and soon hybrid-bonded co-packaged optics (BESI). Goldman-style TAM slides oversimplify CPO's rise; the key divergence is that US laser vendors' pluggable books risk cannibalization, making one layer up — silicon photonics SOI and InP substrates — the cleaner positioning.

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