Corning

(GLW) - Get Report

was down 15.5% in early trading after hitting a 52-week low of $34.48.

In the wake of Nortel's warning, Corning reiterated its guidance of 28 to 31 cents a share earnings for the first quarter and $1.40 to $1.43 for 2001. The fiber-optic company said it will step up spending cuts to meet its targets.

JDS Uniphase

(JDSU)

was down 13.6% as the fallout from Nortel spread through the optical and networking groups.

Credit Suisse First Boston

sliced its price target to $65 from $100 and

Lehman Brothers

lowered its 2001 and 2002 forecasts.

Among other network equipment makers, giant

Cisco

(CSCO) - Get Report

was down 5.9% after dipping to a 52-week low of $27.72.

Ciena

(CIEN) - Get Report

, up Thursday on a strong forecast, was down 3.2%.