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What: Shares of broadband equipment maker Calix (NYSE: CALX) fell as far as 12.1% in average-volume morning trading.

So what: Fears of economic trouble in Europe are hurting infrastructure stocks with trans-Atlantic exposure today, including a heavy toll on long-haul networking specialists: Alcatel-Lucent (NYSE: ALU) and Oclaro (Nasdaq: OCLR) saw double-digit declines, Ciena (Nasdaq: CIEN) dropped by 9%, and Finisar (Nasdaq: FNSR) fell as much as 6.4%.

Now what: Calix is mainly an American operator today, counting Verizon (NYSE: VZ) and Frontier Communications (NYSE: FTR) among its largest customers. But the company is fighting for market share in Europe, the Caribbean, and other new markets, so a lack of network infrastructure investments in Europe puts a huge crimp in Calix's growth prospects. The short-term implications of these market conditions may be severe, but a long-term investor should see nothing but a huge buy-in opportunity at this point. For more on long-distance networking stocks and the enormous opportunity in front of them, click here to read a totally free special report on the industry.

Fool contributor Anders Bylund holds no position in any of the companies discussed here. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool is investors writing for investors.