Ciena vs. ADTRAN: Which Optical Networking Stock is the Better Buy?

Ciena (CIEN) holds a backlog exceeding $10 billion extending into fiscal 2028, positioning the optical networking vendor ahead of rival ADTRAN Holdings, Inc. (ADTN) as both companies ride demand from AI and data-center buildouts. Zacks Investment Research assigned CIEN a Rank #1 (Strong Buy) while downgrading ADTN to Rank #4 (Sell), citing diverging operational momentum.

CIEN is seeing accelerating product adoption and upward earnings revisions, supporting a premium valuation of 16.98 times price-to-book. ADTN trades at 4.54 times price-to-book but faces supply constraints, product-mix pressure, and customer deployment timing issues that have triggered significant downward earnings revisions.

The backlog visibility through 2028 gives CIEN a multi-year revenue cushion as hyperscalers expand optical networking infrastructure. ADTN's operational headwinds suggest execution risk that may weigh on near-term results despite the same end-market tailwinds benefiting its larger competitor.