PETALUMA -- Telecommunications equipment and software developer Calix Inc. (NYSE: CALX) today released preliminary estimates for third-quarter revenue that were sharply lower than guidance from two months ago, and the company attributed the slowdown partly to slower-than-expected federal broadband infrastructure spending.

Revenue for the company's third quarter, ended Sept. 24, is estimated to be $83 million to $85 million, rather than $104 million, as the company projected on July 21. The third-quarter pro forma earnings per share estimate is 7 cents to 9 cents, rather than 20 cents as in the previous guidance.

By comparison, revenue in the third quarter of last year was $75.5 million. The new guidance is for 9 percent to 12 percent revenue growth from that period, revised from the nearly 38 percent year-over-year growth in the previous guidance. Second-quarter revenue was nearly $98 million, up nearly 38 percent from 12 months before.

"The revised estimates for the third quarter reflect a slowdown in business related to changes in macroeconomic conditions, fiber shortages in certain portions of the market and continued delays in broadband stimulus awards under the American Recovery and Reinvestment Act of 2009 becoming shippable orders," according to the company statement.

The news sent the company's stock price down from Monday by nearly 15 percent, or by $1.51 a share, to a new low of $8.75 a share. Calix shares started trading in April 2010 at nearly $14 a share and bested growth in the Dow Jones and S&P 500 indexes from December 2010 through mid-August.

The revised third-quarter guidance comes as Calix gears up for the Broadband World Forum conference and exhibition in Paris. The company noted that in the second quarter of this year it shipped more fiber-optic access ports than any other such vendor in North America, citing July reports from Dell'Oro Group and Infonetics Research.

Calix is a preferred vendor for more than 73 projects to which $1.3 billion federal economic-stimulus funds for broadband infrastructure programs have been allocated for telecom services and equipment.

Calix plans to report third-quarter results after the market closes on Oct. 20.