The march of earnings reports spilled over into the after-hours, where investors applied the knee-jerk theory and dragged some high-profile tech stocks deeper into the doldrums.

Fiber-optic Fallout

All the attention tonight was on

Cisco Systems

(CSCO) - Get Cisco Systems, Inc. Report

, which

warned after the bell of a sharp third-quarter earnings and revenue shortfall, citing "continued global economic challenges, the slowdown in the global telecom market, and the deceleration in corporate IT spending."

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Shares of the networking titan were lately tumbling 7% to $16 on

Instinet

on an avalanche of volume. On

Island

ECN, the shares were also down 7.2% to $15.96.

"The business environment that our segment of the IT industry is facing has never been more challenging," CEO John Chambers said in a prepared statement. "In fact, this may be the fastest any industry our size has ever decelerated, which has required us to make difficult business decisions at an unprecedented speed."

And

Finisar

(FNSR) - Get Finisar Corporation Report

was punished in a similar fashion after the company, which provides equipment for enabling high-speed data communications over local area networks and storage area networks, lowered its fourth-quarter guidance, amid order delays and the economic slowdown. Finisar's shares lately plummeted 15.9% to $9.50 on Instinet.

And the contagion effect grabbed fellow equipment makers

Juniper Networks

(JNPR) - Get Juniper Networks, Inc. (JNPR) Report

, which lately fell 3.4% to $46.74 on Instinet, and

Ciena

(CIEN) - Get Ciena Corporation Report

, which lost 3.4% to $49.75 on Island.

Nortel Networks

(NT)

also declined 4.9% to $14.50, while

Sycamore Networks

(SCMR)

drooped 9.5% to $8.51, also on Instinet.

Chip Dip

The telecom equipment makers weren't the only ones in the red tonight. Chips continued to slide, with

Vitesse Semiconductor

(VTSS)

releasing its first quarterly drop in revenue in more than eight years after experiencing a "dramatic" slowdown in sales of chips for communications and data storage.

Shares of the Camarillo, Calif., company, recently slid 8.5% to $22 on Instinet. Vitesse said tonight its second-quarter revenue was $121.8 million, off 26% from the same period last year and coming in at the low end of the company's own reduced forecast.

Vitesse posted pro forma income, excluding amortization and deferred compensation, of $18.8 million, or 10 cents a share, compared with $47.6 million, or 25 cents a share, in the prior quarter. Analysts polled by

Thomson Financial/First Call

lowered their earnings estimate to 10 cents a share after Vitesse slashed its sales forecast for the second quarter to between $120 million and $125 million and halved its per-share profit forecast to 10 cents to 11 cents from 21 cents to 22 cents.

The company also said tonight that near-term visibility at a majority of its customers "continues to be weak," and the company doesn't expect "a reversal in this trend in the current quarter."

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Other chip stocks, which led today's weakness in the

Nasdaq, were slammed. Chip giant

Intel

(INTC) - Get Intel Corporation (INTC) Report

was off 2.1% to $25.75 on Instinet, while communication chip supplier

Applied Micro Circuits

(AMCC)

slipped 6% to $18.80.

Xilinx

(XLNX) - Get Xilinx, Inc. (XLNX) Report

and

Applied Materials

(AMAT) - Get Applied Materials, Inc. Report

were also weaker.

Lehman Brothers

analyst Dan Niles became the beleaguered sector's

latest naysayer .

Seeing Red

Overall, investors sold off other tech stocks, including former high-fliers

Sun Microsystems

(SUNW) - Get Sunworks, Inc. Report

, off 3.9% to $15.71 on Instinet, and

Microsoft

(MSFT) - Get Microsoft Corporation (MSFT) Report

, falling 0.6% to $60.40. Mr. Softee plans to report earnings on Wednesday.

Software makers weren't spared, as after-hour players on both trading platforms fled

Veritas Software

(VRTS) - Get Virtus Investment Partners, Inc. Report

and

CheckPoint Software

(CHKP) - Get Check Point Software Technologies Ltd. Report

.

Singapore's electronics contract manufacturer

Flextronics

(FLEX) - Get Flex Ltd. Report

was also caught in the downward spiral, losing 9.4% to $17.50 on Instinet.

This information is provided by Instinet, a wholly owned subsidiary of Reuters (RTRSY) . For further information, please contact Instinet at www.instinet.com.

Island ECN offers trading, mainly in Nasdaq-listed stocks, from 7 a.m. to 8 p.m. EST.

Confused?

TheStreet.com

explains how the rules change when the sun goes down in Investing Basics: Night Owl, a section devoted to after-hours trading.