Ciena Tumbles 10% as In-Line Guidance Overshadows Earnings Beat, Arista Edges Higher

Ciena (CIEN) fell 10% to $320.38 despite posting a fiscal Q3 beat — adjusted EPS of $2.11 vs. $1.72 consensus and revenue of $1.67B vs. $1.63B estimate (up 37% YoY) — as an in-line Q4 revenue outlook triggered a de-rating in a stock that had rallied 51% YTD. The sell-off is company-specific: peer Arista (ANET) rose 3% to $191.65 on AI networking momentum, Cisco (CSCO) was roughly flat, and both SPY and IYW traded higher, confirming the broader networking demand story remains intact.

Why it matters: Ciena's elevated valuation and customer concentration (two customers drove 42% of quarterly revenue) mean the December Q4 report is the next real inflection point, with the stock already down 18% over the past month.