Earnings pre-announcements are stacking up today, and optical communications is the brightest beam of all. Yangtze Optical guided first-half net profit of 2.4 to 3.0 billion yuan — up 711% to 914% year on year; Dongshan Precision guided up nearly 300%; PCB leaders like Wus and Shengyi locked limit-up in the afternoon. A near-unquestionable narrative flooded in behind it: compute demand is exploding, and optical modules, fiber, and PCB are the most certain shovel-sellers of this AI build-out — the results are already in, and the secular bull is only beginning. The numbers are so staggering, the logic so smooth, that charging in almost feels like the rational move.

But let me say the unwelcome thing: the moment the growth rate is fastest is usually the moment the risk-reward is worst. The more that 711% quickens your pulse, the more you should be wary — what you're chasing isn't growth, it's a position whose upside has already been spent by that very number, and whose downside has only just swung open. This is not a bearish call on the optical business; it's a bearish call on the act of charging in holding the hottest growth rate. Those two things are separated by an entire margin of safety.