The near-quadrupling of Marvell Technology Group ( MRVL) in its stunning stock market debut on Tuesday, coupled with the tripling of Accelerated Networks ( ACCL) on its first day of trading last Friday, have certainly caught the attention of investors. But it is probably premature to proclaim that the red-hot market for initial public offerings has returned, some analysts say. "The environment has improved somewhat," said Steven Tuen, head of research at IPO Value Monitor. "But a lot of investors are still cautious and taking limited bets." Marvell's near-300% leap notwithstanding. The designer of integrated circuits that store and transmit data at high speeds closed up 41 5/8, or 269%, at 56 5/8, even more than expected by George Nichols, a research analyst at Morningstar.com, who predicted that Marvell would have the biggest opening-day pop this week. Marvell, based in Sunnyvale, Calif., boasts impressive numbers: net income of $13 million on revenue of $81 million. It also helped that the company, which sold 6 million shares to the public at $15 each for a total offering of $90 million, only offered 7% of its total shares. "That's an unusually thin slice," Nichols commented. "There are a lot of investors chasing after a few shares, which magnifies the pop." Marvell's rise may be tied as much to the limited supply of high-quality names as to company-specific factors. The last quarter saw as many as 20 IPOs a week. For the first time in a long time, there are that many slated to list this week, but some will inevitably be postponed. A better example of how the new issue market has yet to fully come back is Stratos Lightwave ( STLW), yet another IPO poised to take advantage of investor hunger for optical networking plays. The supplier of optical networking gear such as transceivers and fiber-optic connectors sold 8.75 million shares at $21 each for a total offering of $183.75 million, above the pricing range of $16 to $18. Stratos closed its first day at 34 1/4, up 13 1/4 or 63%, after rising as much as 167% earlier in the day. Though a respectable performance, Stratos' first-day gains hardly matched those of its optical networking peers, which jumped despite lackluster market conditions. New Focus ( NUFO) rose 155% on May 18, Sonus Networks ( SONS) rose 120% on May 25 and ONI Systems ( ONIS) rose 230% on June 1. The Chicago-based Stratos has a stellar list of clients -- including Canada's Nortel Networks ( NT), Cisco Systems ( CSCO) and Alcatel ( ALA) of France -- and can boast of profitability, having earned $3.8 million for the year ended in April and booked profits every quarter over the past two years. However, "its 55% sales growth year on year is not as fast as its competitors and it's not the clear market leader," Nichols explained. Stratos is a division of Methode Electronics ( METHA), and its chief competitors include Agilent Technologies ( A), Finisar ( FNSR), Molex ( MOLX) and Germany's Infineon Technologies ( IFX). Despite his cautious stance, Nichols still called this the "best Tuesday we've had in a quarter." Even so, before he calls a recovery, he wants to see a greater quantity of IPOs in the market.