Shares of Ciena Corp. swung higher in premarket trade Thursday, as upbeat revenue growth guidance on the post-earnings conference call offset an earnings miss. The stock sank as much as 9.6% ahead of the open soon after fiscal second-quarter results were reported at 7:00 a.m. ET, then started climbing sharply after the conference call with analysts started at 8:30 a.m., and was last up 1.5%. Chief Financial Officer James Moylan said on the call fiscal 2018 revenue growth was expected to be 7% to 9% over a year ago, according to a transcript provided by FactSet. "You will note that this is up significantly from our previous guidance, and it clearly shows that number and the size of opportunities to take market share that we are seeing," Moylan said. The FactSet consensus for 2018 revenue of $2.95 billion implies 5.2% growth. Moylan said the pressure seen on gross margin is because the company is taking advantage of opportunities to grab market share. Over the past three months, Ciena's stock has gained 3.8% through Wednesday, while the Nasdaq Composite has tacked on 2.6% and the S&P 500 has edged up 0.4%.