Ciena's shares tumbled 5.1% in premarket trading after the networking equipment maker reported strong first-quarter fiscal 2026 results but issued disappointing full-year guidance. The company posted adjusted EPS of $1.35, beating Wall Street estimates by $0.19, with revenue reaching $1.43 billion, up 33% year-over-year.

Despite the solid quarterly performance driven by AI-driven demand, investors focused on Ciena's fiscal 2026 revenue forecast of $5.9 billion to $6.3 billion. The midpoint of $6.1 billion falls well short of the $6.99 billion analyst consensus, triggering the selloff. For the second quarter, Ciena expects revenue of $1.5 billion, plus or minus $50 million.

The company's Optical Networking segment generated $1.02 billion in revenue, representing 71.7% of total sales. Three customers accounted for more than 10% of revenue each, totaling 47.4% of sales. Ciena repurchased approximately 0.4 million shares for $80.5 million during the quarter under its $1 billion share repurchase program.