Marvell Buys Lumentum for $115 Billion. Why Did Both Stocks Fall?

On Monday, chipmaker Marvell Technology agreed to buy Lumentum, a maker of lasers and optical components, in an all-stock deal valued at about $115 billion including debt. It’s one of the largest technology acquisitions on record. By the close, Marvell’s shares were down almost 13% and Lumentum’s down about 18%.

Takeover targets usually rise on the news. Here’s why this one didn’t, and what the deal says about where AI infrastructure is heading.

The bet: light instead of copper

Training and running large AI models means moving enormous amounts of data between thousands of chips. Inside a server rack, much of that still travels over copper wiring. Copper struggles as speeds rise and distances grow: signals degrade, and it consumes more power. Optical links, which carry data as pulses of light, handle higher speeds over longer distances with less loss.

Marvell designs the electrical side: custom chips, switching, and the components that connect processors. Lumentum makes the optical side: lasers, transceivers and optical switches. In the companies’ announcement, Marvell’s chief executive, Matt Murphy, said AI infrastructure “is undergoing a fundamental architectural shift toward optical connectivity.” The two companies claim a combined addressable market of $550 billion and more than $1 billion a year in cost savings.

Why the buyer fell

In an all-stock deal, the buyer pays with its own shares rather than cash. Each Lumentum share will be exchanged for 4.5 Marvell shares. When the deal closes, Lumentum’s holders will own about a third of the combined company.

The acquirer’s stock often falls on announcement for three reasons:

1. Dilution. Marvell is issuing a large number of new shares. Existing holders own a smaller slice of the company, and they’re betting the extra earnings justify it.
2. The premium. The terms value Lumentum at about $1,132 a share, roughly 24% above its price before deal speculation started. Investors often worry a buyer is overpaying, especially at the top of an investment cycle.
3. Execution risk. Combining two large companies is hard, and the deal isn’t expected to close until the first half of 2028. That’s a long time for things to go wrong in a fast-moving industry.

Why the target fell too

This is the less familiar part. With a fixed exchange ratio, Lumentum’s share price is now largely tied to Marvell’s. Lumentum is worth whatever 4.5 Marvell shares are worth, minus a discount for the risk that the deal falls apart. When Marvell dropped, Lumentum had to follow.

Lumentum fell even further because its price had already risen on deal speculation since October 28. Some of the expected premium was already in the stock. The remaining gap between Lumentum’s price and the value of 4.5 Marvell shares is called the merger arbitrage spread. It reflects the market’s estimate of the risk that the deal won’t close: regulators, shareholder votes, and a long timeline.

The bigger picture: AI money keeps moving

This deal fits a pattern from the past week. Investors are questioning how the giant cloud companies will pay for AI. Oracle also fell 8% on Monday after announcing plans to raise $20 billion in new shares and bonds for its data centre build-out.

Yet the companies that supply the build-out are still betting big on its continuation. Marvell is staking a third of its company on demand for optical connections staying strong for years. If the hyperscalers slow spending, suppliers like these feel it first. If spending keeps growing, the deal could look prescient.

For investors, a $115 billion merger in a sector this volatile is a reminder of the difference between a technology trend and an investment return. Optical connectivity may well win. Whether the price paid for it turns out to be sensible is a separate question, and it won’t be settled until well after 2028.