Silicon modulators hit an RC bottleneck at 50–60 GHz. Nokia Bell Labs flip-chip integrated a TFLN modulator with a commercial driver IC to build the first CPO transmitter of its kind: Vπ·L 2.3 V·cm, EO bandwidth >45 GHz. Coupling loss and heat are the next hurdles.

POET's technology direction fits 2026: between the EML shortage and CPO volume production, hybrid integration has real demand. But $2M in annualized revenue backing a $500M framework narrative is a big gap, and the Marvell cancellation is a warning. POET is a PIC springboard for Tier 2 module makers, not the next optical giant.

As optics move face-to-face with the ASIC, CPO has become a packaging engineer's game. John Lau's review lays out every PIC/EIC integration approach, from 2D and bridges to 3D stacking and glass substrates, and shows why 51.2T can't be cleared in 2D.