My portfolio is smarting today.

Voice and video networking expert Sonus Networks (Nasdaq: SONS) was supposed to break even in the first quarter, but it shocked the Street -- and us shareholders -- with a non-GAAP loss of $0.04 per share.

Revenue rose a modest 7.9% year-over-year to $67.3 million, beating analyst targets with impunity, but the bottom-line miss resonated more strongly with investors today. To the doomsday strains of Bach's Toccata and Fugue organ masterpiece, they streamed for the exits. Shares fell as much as 17.7% overnight and after a brief rebound this morning continued their descent.

The earnings miss and revenue jump both came from a telecom deal that was signed three years ago. Bahamas Telecom finally got around to installing a large amount of networking equipment after signing a contract with Sonus back in 2008, moving a big chunk of deferred revenue into the sales column. Unfortunately, the deal included an unusually large amount of Calix (NYSE: CALX) hardware, which lowered gross margins from last quarter's 64.4% to a terrifying 40.3%.

Management assures us that this was a one-time event that won't happen again. The Calix component was announced in 2008 along with the whole Bahamas Telecom deal, but I don't think the margin impact of it was made obvious.

Going forward, management sees gross margins not only recovering to pre-Bahamas levels but also climbing beyond that: Full-year gross margins are projected at 65.5%, give or take 2.5%. That's a more than respectable margin target in Sonus' circle of voice and data infrastructure peers, where Calix goes to about 43%, Westell Technologies (Nasdaq: WSTL) stops at 34%, and ADTRAN (Nasdaq: ADTN) has to settle for 59%.

There's still room for improvement and margin leverage, as shown by the 80% gross takes at F5 Networks (Nasdaq: FFIV) and Acme Packet (Nasdaq: APKT). Economies of scale make a difference when you're wrangling hardware, and I see plenty of runway ahead of Sonus as its voice-over-IP technologies work their way into more and larger telecom deployments. The company is hiring more engineers and sales staff, which I take as a sign of good health.

All things considered, I'm sticking by my Sonus investment because nothing in this report contradicted my original investment thesis: I still see a low-risk entryway into the VoIP market and expect tremendous returns over the next five years or so. Feel free to treat today's free-fall as a buy-in opportunity. At the very least, you should add Sonus to your Foolish watchlist and follow this exciting growth story as it plays out.

Fool contributor Anders Bylund owns shares of Sonus Networks but holds no other position in any of the companies discussed here. Don't cry for Anders today -- his Sonus investment is still 16% in the black. Acme Packet is a Motley Fool Rule Breakers selection. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. You can check out Anders' holdings and a concise bio if you like, and The Motley Fool is investors writing for investors.