Key Highlights

● Ciena was among the S&P 500's standout gainers, near $445 at one intraday reading.

● Arista, Astera Labs, MACOM, Corning and Dell also climbed.

● Marvell's targets and Nokia's comments lit the fuse.

● Nasdaq decliners outnumbered advancers 1,925 to 1,463.

Training and running large AI models requires more than powerful processors. Thousands of chips must talk to each other at enormous speed, inside servers, across racks and between data centers. That Job falls to switches, optical components, fiber and connectivity chips, and on Tuesday, Oct. 6, the companies that make them rallied together.

Ciena (NYSE:CIEN), which makes optical networking equipment, was among the standout gainers in the S&P 500. The stock jumped sharply, with one intraday reading near $445. Arista Networks (NYSE:ANET), a leading supplier of data-center switches, climbed with the group. Astera Labs (NASDAQ:ALAB), which makes connectivity chips for AI servers, jumped and traded near $392 at midday. Cisco Systems (NASDAQ:CSCO) also rose, closing at $117.94.

Marvell lit the fuse

The trigger was Marvell Technology (NASDAQ:MRVL)'s Investor Day in New York. Marvell raised its fiscal 2028 Revenue outlook to $20 billion from $18 billion and set a fiscal 2031 sales target of $70 billion to $90 billion. Chief executive Matt Murphy cited a $400 billion addressable market by 2030. Because a large part of Marvell's Business involves networking and optical chips for AI clusters, investors read its targets as a signal for the whole Supply chain. Marvell shares closed at $287.01, up $15.76.

A second boost came from Europe. Nokia (NYSE:NOK)'s chief executive dismissed concerns that the industry is overbuilding capacity, and Nokia's US-listed shares rose. Ciena's rally reflected both the Marvell targets and the Nokia commentary. Evercore ISI (NYSE:EVR) kept an Outperform rating on Ciena with a $550 price target.

Analysts and deals added fuel

Several companies had their own catalysts. MACOM (NASDAQ:MTSI) jumped after BMO Capital (NYSE:BMO) upgraded it to Outperform, citing interest in its 3.2-terabit optical chipset for AI data centers. Corning (NYSE:GLW) rose to about $166.77, linked to the AI infrastructure theme and to a $3 billion multi-year fiber agreement with AT&T announced a week earlier. Broadcom (NASDAQ:AVGO), a major player in custom AI chips and networking silicon, closed at $375.81.

Server maker Dell Technologies (NYSE:DELL) also climbed after Mizuho raised its price target, and Dell's chief operating officer, Jeff Clarke, struck a confident tone: "The AI opportunity shows no signs of slowing", he said.

A record day with a narrow base

The networking rally helped push the Nasdaq Composite to a record close just under 27,600, while the S&P 500 added 44.98 points to a record 7,818.93. Treasury yields eased, with the 10-year near 5.28, which tends to help companies valued on future growth.

Yet the gains were concentrated. On the Nasdaq, decliners outnumbered advancers 1,925 to 1,463, and the small-cap Russell 2000 slipped. Chip-equipment makers such as KLA (NASDAQ:KLAC) and Lam Research (NASDAQ:LRCX) fell, and hard-drive stocks were hit by worries about competition and capacity.

Cloud Spending Plans Will Decide the Networking Trade

The key question for the group is whether AI spending plans from the largest cloud companies keep rising. Investors will look to upcoming third-quarter earnings, which begin with the big banks on Oct. 13, and later reports from technology companies for clues. Applied Digital (NASDAQ:APLD), which builds AI data-center capacity, reports on Oct. 7. The Fed's September meeting minutes, due Oct. 7, and the September consumer price report on Oct. 14 will shape the interest-rate backdrop for growth stocks.