Arista's Margins Top Ciena's $8.5 billion Backlog Bet

Both Ciena and Arista Networks tell the same story: AI is driving fast growth in network traffic, and both sell the equipment that carries it. Both raised revenue outlooks in their latest reports, and both said they could ship more if supply loosened. That is where the similarity ends.

Ciena's outlook leans on orders it already holds, while Arista's improved supply position supports its raise. Ciena expects its backlog to top $10 billion by the end of fiscal 2026 and says it covers most of a fiscal 2027 revenue growth outlook of at least 30%. Neither management expects supply to catch up before 2028, so Ciena's backlog makes its outlook safer only if it can ship those orders. Ciena has signed long-term agreements for certain key components through 2029 and expects operating cash flow to dip in its fiscal fourth quarter of 2026 as it pays for them. Price is another lever: Ciena expects increases from high single-digits to the low twenties, and some will reach orders already in backlog.

Arista sells the switches that knit AI clusters together, with more than 100 cumulative customers for its Etherlink switches for AI networks. Its CFO says the company has about two quarters of visibility with customers, far less than Ciena's order book. The obvious question is whether Ciena can convert its backlog into revenue before supply constraints bite. If it can, the gap in valuation and margins may narrow; if it cannot, Arista's profit already on the books is likely to remain the safer bet.