By Josh Ong

Published: 11:55 PM EST (08:55 PM PST)

As fourth-quarter 2011 earnings reports for various companies within Apple's supply chain have begun to trickle in, analysts have taken suppliers' growing profitability as an early sign that the iPhone maker will report breakout profits for the holiday quarter.

UBS analyst Maynard Um cited the better-than-expected preliminary results of Apple supplier Multi-Fineline Electronix (MFLEX) as further evidence that Apple will report its "best holiday quarter in history" when it announces its results on Tuesday, Jan. 24. According to him, MFLEX provides Apple with printed circuit boards for some of its products, including the iPhone and iPad.

MFLEX announced on Wednesday that it expects net sales of approximately $239 million for its first quarter of fiscal 2012, which ended on Dec. 31, 2011. Street consensus had forecast $215 million in revenue during the period.

"We expect our net sales results to exceed the high end of our previous guidance range as the supply chain shortages from the flooding in Thailand improved throughout the quarter. We also saw an increase in shipments to our largest key customer," Chief Executive Officer Reza Meshgin said in a press release.

Um believes the company's "largest key customer," which it projects will represent 66 percent of net sales next quarter, is in fact Apple, especially given that MFLEX saw weakness in the third quarter of calendar 2011, the same quarter that Apple reported a sequential decrease in iPhone sales, much to Wall Street's disappointment.

MFLEX also noted on Wednesday that it expects "less of a seasonal decline" in the second fiscal quarter than usual due to continued strong demand for its flex assemblies for smartphones and tablets. Um took the guidance to be a likely indication of the "underlying demand strength" for iPhone and iPad devices.

In addition to MFLEX, Cirrus Logic, which provides analog chips for the iPad, iPod and iPhone, announced earlier this week healthy revenues as part of its preliminary unaudited financial results for the December quarter . The company posted estimated net revenue of $122 million for the period, beating its projection of between $102 million and $108 million. Cirrus also expects growth in the March quarter, noting that stronger-than-anticipated sales at the end of the most recent quarter indicate demand appears to have remained "robust."

Um went on to cite strong December results from Catcher, which produces metal casings for Apple's Mac computers, TPK, which supplies touch panels for the iPad 2, and Foxconn parent company Hon Hai, as pointing to Apple's strength. Hon Hai reported December sales of NT$316.9 billion (US$10.6 billion), up 3.2 percent month over month.

Meanwhile, Ticonderoga Securities analyst Brian White recently reported the best December on record for the firm's proprietary index of Apple suppliers, dubbed the "Apple Barometer." White revealed that preliminary results for the Barometer show 9 percent growth in December.

He also cautioned that the index may actually underestimate Apple's performance, as he believes the suppliers' non-Apple business, which is, of course, included in their revenue reports, is likely to have weakened during the period. White named Apple's stock the No. 1 pick for investors earlier this year, noting that it was the best performer among the 20 companies covered by Ticonderoga.

Strong sales performance from Apple's U.S. carrier partners has also been viewed as an indicator of an impending earnings blowout from Apple. Verizon reported last week that iPhone sales had doubled from 2 million in the third quarter of 2011 to 4.2 million in the fourth quarter. AT&T announced in early December that it was on track to easily best its sales record of 6.1 million smartphones in one quarter, as the carrier had already sold 6 million smartphones in October and November. Several analysts, including Um, have taken Verizon's and AT&T's sales figures to mean that Apple could break the 30 million unit milestone for iPhone sales in the most recent quarter.

Apple itself has expressed confidence in its ability to set an all-time high for iPhones in the December quarter. The company expects revenue of roughly $37 billion during the 14-week period.