Fabrinet reported the largest quarter in its history after the close on 17 August. One line undid it. Datacom revenue — the part that carries artificial-intelligence traffic — slipped 1% from the prior quarter because sales to NVIDIA declined.

Fabrinet is a Thailand-based contract manufacturer that assembles optical transceivers, tunable lasers and active optical cables for the equipment makers whose names appear on them. Revenue for the June quarter was $1.316bn, up 45% year on year and above its own guidance; full-year revenue rose 36% to $4.641bn. Telecom grew 70%, and two new datacom customers — Amazon and a merchant transceiver vendor — largely offset the NVIDIA decline. Needham's Ryan Koontz nonetheless read the datacom line as share loss at NVIDIA, "likely to Chinese competition", while keeping a $650 target. Guidance for the September quarter put revenue at $1.375–1.425bn but earnings at $4.10–4.25 a share, flat sequentially. Four customers each supplied a tenth or more of fiscal 2026 revenue: Cisco at 20%, NVIDIA 16%, Nokia 11% and Amazon 11%. The shares fell 17.5% the next session and 25.4% over five.

Three businesses, one price move

What separates these companies is what each keeps from a transmitted bit. Fabrinet's gross margin was 12.3% in the June quarter, and its annual figure has sat between 12.0% and 12.7% every year since 2022. Thirty-six percent revenue growth produced no expansion at the gross line at all; the leverage shows up lower down, where operating income rose 42.7% and operating margin reached 9.97%. That is the arithmetic of a contract assembler whose moat is process qualification measured in years, not pricing power.

Ciena sells the systems, not the assembly. Its coherent transport platforms carry traffic between data centers and across carrier networks, and in the quarter ended 2 May revenue grew 39.5% while gross margin expanded to 44.0% from 40.2%. Operating margin went from 3.1% to 15.1%. Cloud providers were 46% of sales and grew 70%, and backlog rose more than $600m sequentially to a record $7.7bn. Its claim is WaveLogic 6 Extreme, a 1.6-terabit-per-wavelength modem management says no rival matches in the wide-area network — a lead Nokia, which bought Infinera to add coherent silicon, is spending against.

Corning is the passive control: fiber, cable and connectors, alongside display glass. Group revenue grew 16.6% in the second quarter on a flat 36% gross margin, but Optical Communications, now 49% of sales, grew 32% to $2.07bn with segment net income up 77%. Enterprise sales rose 65% and data-center sales nearly doubled. The mechanism is physical: clusters above 130,000 graphics processors need three optical layers rather than two, adding half again as much content, and a fully optical scale-up would need 160 fibers per processor against about 16 today. Demand for the high-density products already exceeds Corning's capacity, which is why Meta, NVIDIA and Amazon have signed multiyear supply agreements.

The day none of it mattered

On 18 August nine optical names fell together and only one had reported. Fabrinet lost 17.5%, Coherent 12.8%, MaxLinear 16.0%, Ciena 8.9%, Corning 7.7%, Amphenol 5.0%. Two disclosures explain the rest: Anthropic told investors annualized revenue reached $65bn at the end of July, below the figures circulating privately, and a Wall Street Journal tally put roughly $3trn of off-balance-sheet commitments on nine tech balance sheets. Fabrinet's own downtrend had begun earlier: its 50-day average crossed below its 200-day on 6 August, twelve sessions before the print. Corning's did the same after its 28 July call, having already fallen 18.2% in late July and fully recovered by mid-August.

What the market now pays

Fabrinet trades at 28.1x trailing gross profit, down from about 50x in May and 42x in February, and 21.4x forward — on gross profit that grew 34.6% to $556.5m over the same stretch. It is cheaper than at any point this year and only marginally above the 24x it carried a year ago, with consensus 2027 earnings of $18.20 a share against $13.05 delivered.

Ciena and Corning are different. Ciena's 23.4x is a third off May's 39.6x but more than triple the 7.1x of a year ago, and its trailing price-to-earnings ratio is 128x. Corning's 20.9x has given back the entire 2026 re-rating yet remains nearly double the 11.4x of last August. Those declines are doing rational work against multiples that had tripled.

The anomaly is Amphenol, which makes electrical and fiber-optic connectors and interconnect systems. Its June-quarter revenue grew 55% with gross margin up more than four points to 40.5%; information-technology datacom was 43% of sales and rose 89%, orders hit a record $10.7bn for a book-to-bill of 1.23x, and management reported no material supply bottlenecks. It is the cheapest of the four on trailing gross profit at 17.3x — and the only one whose uptrend has held unbroken since mid-June.

The threat that would justify a permanent de-rating of Fabrinet is co-packaged optics, which moves the light source onto the switch package and cuts the pluggable module out. That is not yet happening at scale: co-packaged optics is about 0.5% of AI data-center optical modules, with NVIDIA's Rubin Ultra generation targeted for late 2027. Corning, meanwhile, mapped $10bn of photonics revenue by 2030 while calling scale-up adoption timing the biggest uncertainty in its plan and declining to guide 2027.

The setup

Where it stands — Three optical suppliers sold off together since May while revenue accelerated and margins held or expanded at each. Would confirm — Fabrinet's September-quarter datacom revenue returns to sequential growth as Amazon volumes ramp. Would invalidate — A second consecutive quarter of declining NVIDIA revenue, or gross margin below 12%. Watch next — Fabrinet reports fiscal first-quarter results in November; Ciena's fiscal third quarter lands in early September. Valuation — Fabrinet at 28.1x trailing and 21.4x forward gross profit, against 50.4x in May and 24.3x a year ago.