Why optical stocks Lumentum and Coherent were the day’s biggest S&P 500 gainers

Optical component makers Lumentum and Coherent posted the strongest gains in the S&P 500, a move that put a spotlight on a less-obvious corner of the AI trade. Rather than the chip designers and server builders that have led the rally, attention shifted to the companies supplying the optical networking hardware that moves data inside and between data centers.

According to one expert cited in the coverage, the move reflects investors looking further down the AI data-center supply chain for signs of demand, amid concerns that spending could slow. That framing helps explain the market's relevance: optical names can act as a read on whether AI infrastructure buildouts are continuing to translate into orders for components, not just headlines about chip capacity.

What to watch is whether upcoming earnings and guidance from these suppliers confirm that demand trend, and whether the buying broadens to other parts of the supply chain. For now, the session shows how quickly sentiment can rotate within the AI theme when investors hunt for fresh evidence of durable spending.