Scale-up optical interconnect looks like a seven-way melee, but there are really only two strategies, Fast-and-Narrow and Slow-and-Wide, each hitting a symmetric wall. Learn the yardstick first, then see how the seven approaches layer and coexist.

Most of the optical packaging story revolves around CPO, but AR microLED and FMCW LiDAR are the hidden main axes of the non-datacom race. The first counts LED-on-CMOS as packaging; the second pulls automotive-grade requirements into SiPh. This series finale breaks down both and sums up the six-part series.

Today a rack draws 120 kW; the next generation will exceed 0.5 MW. At ECOC 2026, Microsoft asked a true customer's question: if optics were cheap enough, why keep this architecture? The answer came as a five-number spec sheet, plus a declaration that the die, not the package, is now the unit of design, assembly and failure.

The CPO race is no longer about optics—it is about whether packaging can reach volume at the next tier. This Nature Electronics review plots the pJ/bit of 2D, 2.5D, 3D TSV, hybrid bonding and monolithic integration on one chart, two orders of magnitude apart. We walk through all 24 figure panels and 2 tables, and flag where Taiwan's supply chain really fits.