Ciena ( CIEN) fell sharply in the premarket session after the network-equipment maker warned in its earnings release that second-quarter revenue would fall short of estimates. Ciena reported a loss of $56.7 million, or 17 cents a share, excluding one-time items, for the first quarter ended Jan. 31, compared with a year-earlier profit of $54.7 million, or 19 cents a share. Analysts had been predicting a loss of 17 cents a share after the company issued a profit warning earlier this month. First-quarter revenue was $162.2 million, down from about $352 million a year earlier. Ciena's bottom-line loss for the quarter was $70.6 million, or 22 cents a share. The company said it expects second-quarter revenue of about $100 million, some $48 million short of the consensus estimate compiled by Thomson Financial/First Call. Ciena's press release initially offered a slightly stronger $110 million estimate, but the company changed that after guiding analysts and investors to expect $100 million in its conference call. "There continues to be a high level of uncertainty surrounding service providers' near-term spending. In our ongoing conversations with our customers we continue to receive indications of further deployment delays," Ciena said. "We recently received information that leads us to believe that two of our historically most important customers may purchase significantly less from us than they had previously indicated." On Instinet, Ciena's shares were down 83 cents, or 9.5%, to $7.87.