Source: Finisar.

Shares of fiber-optic networking specialist Finisar (NASDAQ:FNSR) fell as much as 20% in after-market trading today, following the release of disappointing fourth-quarter results.

Finisar's sales increased 26% year-over-year to $306 million, exceeding Wall Street's $303 million consensus estimate. On the bottom line, non-GAAP earnings landed at $0.36 per diluted share, up from $0.20 per share in the year-ago period. Here, analysts were looking for $0.38 per share.

Both earnings and sales fell within management's guidance ranges for the quarter, albeit below the midpoint of the earnings span.

In commentary on the quarter, management preferred to focus on discussing strong sales while avoiding the reasons behind the disappointing earnings. Adjusted earnings did not include an $8.3 million gain on the sale of Finisar Korea during the quarter. If included, this line item would have added $0.08 per share to the bottom line.

Looking ahead, Finisar expects first-quarter sales of approximately $327 million and adjusted earnings near $0.32 per share. That's a mixed bag, as analysts currently see earnings of $0.41 per share on roughly $317 million in sales for this period/

Finisar CEO Eitan Gartel sees further growth on the horizon, driven by higher-speed optical transceivers. "Demand for transceivers operating at 10Gb/s and faster continued to be strong during the quarter," Gartel said in a prepared statement. "Demand was also strong for our transceivers for LTE wireless applications."

Finisar shares had nearly doubled year-over-year before the market reaction to the fourth-quarter report took the edge off those gains. If current after-hours prices hold until the morning, Finisar would open Friday's session with a 50% annual gain under its belt.