Coherent just reported 20.5% year-over-year revenue growth, hitting $1.81 billion in Q1 CY2026. The stock is up 86.7% year-to-date. Everyone agrees: AI data centers need more optical transceivers, and Coherent makes them. The story seems simple.
But look at the cash flow. Despite that growth, the company burned $536.9 million in free cash flow last quarter. And it trades at 336 times trailing earnings.
The obvious question is whether Coherent can ride the AI wave. The more interesting one is whether growth at this price makes sense.
Most investors see a company growing revenue 20% while expanding operating margins from 4.8% to 11.1%. They see non-GAAP gross margins at 39%. They see the AI optical transceiver market projected to grow from $16.5 billion to $26 billion this year. What's not to like?
The problem is in the numbers you have to ignore to keep liking it. A P/E of 336 means the market expects near-perfect execution for years. Negative free cash flow of half a billion dollars suggests the growth isn't as clean as the revenue number implies.
I suspect the real test here isn't about demand-AI data centers clearly need more bandwidth-but about turning that demand into sustainable shareholder value. When a company grows 20% but burns cash, you have to ask: is this a business compounding or just accumulating revenue?
Coherent's management says the cash burn is temporary. They're doubling internal indium phosphide capacity by Q4 2026 to address supply constraints. The market for 800G and above optical transceivers is tight, with bottlenecks in electro-absorption modulated lasers and continuous-wave lasers. Investing now to capture future growth could be the right move.
But 336 times earnings is a lot to pay for "could be." It's the kind of multiple that assumes not just success, but dominance. And dominance in optical components isn't guaranteed. Coherent competes with Lumentum, Applied Optoelectronics, and a host of Taiwanese suppliers. The AI optical transceiver market's 57% year-over-year growth attracts everyone.
The company is also heavily concentrated. 72% of revenue comes from datacenter and communications. That's good when those markets are hot, but creates sensitivity when they're not. And we don't know how much of that is pure AI versus other communications spending.
Here's what I'd watch instead of just the revenue growth number: free cash flow conversion. If Coherent can grow while generating cash, the story changes. If it keeps burning cash while growing, the valuation becomes harder to justify no matter how good the AI trend looks.
The other test is margin durability. Optical transceivers face pricing pressure as more capacity comes online. Coherent's current 39% non-GAAP gross margin looks strong, but will it hold when competitors ramp production?
There's a version of this where Coherent executes perfectly, converts growth to cash flow, maintains margins, and the stock works even from here. But that version requires everything to go right. At 336 times earnings, everything has to go right.
The way to think about Coherent isn't to ask whether AI data centers need optical components. They do. It's to ask whether paying 336 times earnings for a company burning cash to fund growth is a bet on superlinear returns or just momentum.
I don't know the answer. But I know which question is more useful.