Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of Oclaro (Nasdaq: OCLR) fell more than 15% in intraday trading on a sectorwide sell-off of companies whose optical (i.e., light-based) components help power telecommunications networks.

So what: The move appears to have been precipitated by less-than-optimistic fourth-quarter projections offered by Infinera's (Nasdaq: INFN) management. That stock is down more than 30% as I write this. Finisar (Nasdaq: FNSR), an Oclaro competitor, is down more than 10%.

Now what: If you're a long-term investor, you could argue that all three of these drops are buying opportunities. In Oclaro's case, the stock is priced at a discount to the 20% annual growth analysts expect the company to achieve over the next five years.

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