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 Finisar (NASDAQ:FNSR) have gained nearly 15% today after the company announced that its fiscal first quarter (ending in July) will be above earlier expectations -- both its own and Wall Street's. The company so impressed the market that trading had to be halted following the early surge.

So what: Finisar's preliminary first-quarter guidance now pegs its revenue at $266 million, above both the analyst consensus of $253.4 million and the former high end of its guidance range, which had been $245 million to $260 million in revenue. Finisar also expects its earnings per share to be either $0.30 or $0.31, well ahead of Wall Street's $0.24 consensus and its own previous range of $0.22 to $0.26.

Finisar also notes that its (preliminary) record-setting revenue rose primarily on strong sales of Ethernet transceivers, which helped push gross margins up from the previously estimated 33% range to a range of 34.5% to 35%.

Now what: Finisar's had a strong summer, as its stock is now up 60% in the past three months. However, there's nothing here that indicates a screaming buy -- Finisar is still losing money on an officially reported trailing 12-month basis, and its most recent free cash flow figures give it a price-to-free-cash-flow ratio of about 35.7 after the pop. There could be more growth ahead, but there might also not be -- Finisar's earnings history shows a lot of ups and downs in earnings and free cash flow.

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