Silicon photonics narrative strengthens, but valuation already assumes perfection

What happened

A new article argues that AI clusters are outgrowing copper wiring, accelerating adoption of silicon photonics, with Coherent and Lumentum as key beneficiaries. This reinforces the existing market narrative that Coherent is central to solving optical interconnect bottlenecks, a view already embedded in the stock's 145x P/E and 49.5x EV/EBITDA multiples. The DeepValue report highlights that while demand is real—supported by NVIDIA's $2 billion investment and multi-year commitment—the company's free cash flow remains deeply negative due to inventory and capex absorption. Gross margin must sustain above 39.6% and the 6-inch indium phosphide ramp must deliver cost benefits before the thesis is validated. At a price of $333, near the report's trim-above level of $390, upside is limited and downside risk elevated if execution slips.

Implication

The long-term silicon photonics tailwind supports Coherent’s growth, but investors should require proof of margin expansion and free cash flow conversion before paying current multiples. Monitor Q4 FY26 and following quarters for gross margin above 39.6% and inventory growth slowing relative to datacenter revenue.

Thesis delta

The new article does not alter the core thesis—it only affirms the demand driver already priced into the stock. The risk is that the market has moved from 'validating the opportunity' to 'assuming flawless execution,' leaving the stock vulnerable to any negative surprise on the 6-inch ramp or cash conversion. The thesis delta is therefore a shift from 'supportive demand narrative' to 'valuation dependency on perfect execution.'