Tellabs ( TLAB) dropped nearly 6% after cutting its estimates for the fourth quarter because of lower-than-expected revenue from some large North American customers and an unfavorable shift in product mix.

For the quarter ended Dec. 29, Tellabs expects revenue of $455 million to $470 million and adjusted earnings of 10 cents to 12 cents a share. Adjusted profits exclude charges for equity-based compensation of about 2 cents, as well as amortization of intangibles and restructuring costs.

Analysts surveyed by Thomson Financial were looking for earnings of 14 cents a share and a top line of $534.2 million.

"Uncertainty surrounding telecom industry consolidation led to lower-than-expected revenue in North America during the fourth quarter," said Krish A. Prabhu, Tellabs president and chief executive. "We expect the revenue impact to be temporary since, as 2007 begins, our customers continue to see growing user demand for bandwidth. Tellabs remains well-positioned to benefit from this."

Shares of Tellabs were off 62 cents at $10.10.