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 corner of the AI trade that sits further down the data-center supply chain. According to one expert cited in the report, investors are looking past the headline chipmakers toward the companies that supply the optical networking gear underpinning AI clusters, searching for confirmation that demand remains intact.

The context matters: concerns about a possible slowdown in AI-related capital spending have pressured parts of the sector, so any sign of durable orders can shift sentiment quickly. Optical names are a useful read-through because their components are tied to how quickly data centers expand and interconnect. That makes them a barometer for spending trends rather than a direct proxy for any single customer.

What to watch is whether the move reflects genuine demand signals or broader rotation within AI infrastructure. Follow-up earnings commentary, order visibility, and hyperscaler capital expenditure guidance will indicate whether the strength is sustained or simply a single-session reaction.