Ciena and Arista climb 4% as AI network spending splits sector from Cisco

The rally in Ciena and Arista comes after a sharp pullback in their shares over the prior week, and both are now running well ahead of the wider technology group. Ciena's fiscal Q3 2026 results offer a concrete backdrop: adjusted EPS of $2.11 against a $1.73 consensus, revenue up 37% year over year to $1.67 billion, and cloud providers accounting for 53% of revenue on 82% year over year growth. Management raised its fiscal 2026 revenue guidance to $6.42 billion and issued a preliminary fiscal 2027 outlook calling for at least 30% revenue growth, while the company ended Q3 with $8.5 billion in backlog and projects to exit fiscal 2026 with over $10 billion.

Ciena and Arista occupy different parts of the same AI data center spending wave. Ciena sells optical networking equipment that links data centers, with pluggables revenue more than doubling year over year in Q3 as the WaveLogic 6 Nano ramped. Arista sells the Ethernet switches inside data centers, and its EtherLink adoption has spread to a broader roster of cloud, AI and neocloud customers. Cisco, which also sells switches and routers, did not participate in the move, with its stock practically unchanged at $107.06. Ciena's next growth leg is scale-across networks connecting AI training clusters across multiple data centers, with its RLS HyperRail line system on track for initial customer adoption by year-end and material revenue through 2027.

Supply, not demand, remains the constraint Ciena cites, with management stating on the earnings call that "The demand is absolutely there" and not projecting the market to return to balance before 2028. The company's growth carries concentration risk, since two customers made up 41.7% of its Q3 revenue, and its outlook assumes continued AI infrastructure spending by cloud providers, stable optical component supply and no material change to tariff policy. Next quarter's results could show whether Ciena can hit its fiscal Q4 2026 revenue guidance of $1.75 billion under tight component supply.