Infinera Corp. (Nasdaq: INFN) shares are up 30 percent after the optical gear vendor posted surprisingly good fourth-quarter results yesterday.

Shares climbed $3.63 (35.6%) to $13.82 by mid-afternoon today.

The cause for the jubilation was obvious: Infinera's sales came in about 10 percent higher than consensus analyst estimates, and non-GAAP earnings beat the Street by 15 cents per share, according to Thomson Financial . (See Infinera Obliterates Q4 Estimates.)

The strong earnings prompted Jefferies & Company Inc. analyst George Notter to slap a Buy rating on Infinera in a research note this morning.

Notter cited the company's increased customer diversification, declining reliance on Level 3 Communications Inc. (NYSE: LVLT), and strong forecast as reasons for the upgrade.

Notter also sees the possibility of a future big-name carrier win. "It's logical that Tier 1 operators should also view Infinera's value proposition as positively as customers like Level 3, XO, Cox, and Global Crossing do," he writes.

— Ryan Lawler, Reporter, Light Reading