MACOM sells the optical front end OCP says suppliers still lack, and CoreWeave credit fear cut the stock 20%

The shortage MACOM says it already fills

On September 17, MACOM, a Lowell, Massachusetts semiconductor supplier, announced a front-end chipset for 3.2T optical links: eight channels at 448 Gbps PAM-4, the modulation behind next-generation AI data center interconnects ¹. The set pairs new quad transimpedance amplifiers, the receive chips that turn a photodiode's current into voltage, with a photodiode rated above 100 GHz of bandwidth and transmit drivers introduced earlier, and the release called every product "readily available"↗ ¹.

Research published this morning from the Open Compute Project summit↗, the hyperscaler hardware conference held in San Jose from October 12 to 15, met MACOM▲+3.91% — MACOM, up 3.91 percent today among more than twenty optical-interconnect companies and still recorded the front end as the bottleneck: DSPs, TIAs and drivers for 400G per lane "are not yet available from suppliers" ².

A 41 percent step, guided before the rout

The September quarter was MACOM's strongest: revenue of $342.2 million, up 35.8 percent year over year and 18.4 percent sequentially, adjusted EPS of $1.40 against a $1.35 consensus ³⁴. The fiscal fourth quarter guide, issued August 6↗, calls for revenue of $415 to 425 million, up to 16 percent above the Street's $365.86 million, and adjusted EPS of $1.97 to 2.03, a 41 to 45 percent step above the September quarter in one print ³⁴.

Someone else's credit took a fifth of the value

In the week to October 16, none of that was company news ⁵. The stock opened Monday at $324.20, touched $257.12 Thursday and closed Friday at $262.24, down 20.55 percent while the S&P 500 slipped 1.95 percent ⁵.

The sector did the selling: the Philadelphia Semiconductor Index fell more than 12 percent in eight sessions↗ toward its longest losing streak since 2006, shorts booked roughly $32 billion of paper profits in seven days, and credit-default swaps on CoreWeave▼−0.01% — CoreWeave, down 0.01 percent today, an AI cloud computing firm, implied better-than-even odds of default inside five years ⁶. The same tape cut Ciena▲+6.11% — Ciena, up 6.11 percent today, Coherent▲+2.53% — Coherent, up 2.53 percent today and Applied Optoelectronics by about a quarter, with four Ciena officers selling $2.6 million of stock↗ ⁷.

The insiders sold at $326 and $300

MACOM's insiders sold from higher ground. Chief financial officer John Kober sold 7,389 shares for $2.41 million at an average $326.08 on August 17, 18 percent of his direct holding, under a preset 10b5-1 trading plan; senior vice president Ambra Roth sold 653 shares at $300.00 on October 1; ninety-day insider sales total 8,294 shares for $2.67 million ⁸.

A Form 144 notice of a proposed insider sale, dated October 18↗, surfaced on October 19 with no amount attached, and EDGAR's MACOM page still listed the newest such filing as October 1 when checked on October 21 ⁹¹⁰.

The November print settles it

The sell side has not followed the tape down: sixteen analysts, none rating the stock below hold, a consensus target of $395.33 and a floor of $300, itself 14 percent above the rout-week close, for a stock at roughly 83 times trailing earnings ⁴⁵. If the front end is the binding constraint, that multiple sits on a guide stepping EPS up 41 percent; if the buyers' funding is the constraint, component makers get cut before any module backlog can show it ⁴⁵.

The fiscal Q4 report, estimated for November 5, carries the two numbers that decide: whether $415 to 425 million of revenue lands, and what the first fiscal 2027 guide says about hyperscaler orders ⁴. The market has stopped asking whether the parts exist and started asking who pays for them.