JDS Uniphase ( JDSU) plunged 7% late Wednesday after warning of a looming sales shortfall for the second time in a fortnight. The latest setback came as the company posted second-quarter results that met lowered guidance but drastically reduced third-quarter sales expectations. For its second quarter ended Dec. 31, the San Jose, Calif.-based maker of optical telecom components lost $43.5 million, or 3 cents a share, compared with the year-ago loss of $58.5 million, or 4 cents a share, a year earlier. Revenue rose 19% from a year ago to $180.5 million, though the latest-quarter top line represents an 8% drop from fiscal first-quarter levels. On a pro forma basis, excluding certain costs, the second-quarter loss was 2 cents a share, in line with the Wall Street estimate and with the guidance the company provided last week. JDS shares plunged last Tuesday after the company trimmed its second-quarter targets, blaming a sudden decline in orders from one of its optical and display component customers. The company said that pullback accounted for about $13 million worth of missed sales in the quarter. For the third quarter ending in March, JDS expects to lose about 2 cents a share on a pro forma basis, with sales sliding to $160 million or so. Wall Street was expecting a penny-a-share loss on sales of $192 million. Late Wednesday, JDS slipped 18 cents to $2.27.