Allen DuncanCurtis GrensKenny Haulk

Chris LambrechtNassisa-Geda Techane

April 24, 2003

2

Group Management - Overview

Group LeaderChris Lambrecht

Writing/Editing Reports

Nassisa-Geda Techane

Schematic/PCB Layout Design

Kenny Haulk

Budget/Vendor Relations

Allen Duncan

Assembly/TestingCurtis Grens

3

Overall Progress

• Devised Effective Group Management Plan

• Researched & Selected Necessary Components

• Prepared Comprehensive Optical Link Budget

• Designed Schematics and PCB Layout for Gigabit Ethernet TX/RX

• Assembled and Tested

• Analyzed & Debugged Variety of Problems with Transceiver

• Satisfied IEEE 802.3z Standards

• Evaluated Performance Characteristics, e.g., Alignment Tolerance

• Stayed Within Research/Development Budget of $350

4

Testing•Baseline Testing

•Attenuation Testing

•5 dB

•10 dB

•Alignment Tolerance

5

Baseline Transceiver Tests• Initial Results:

Baseline Tx Results Baseline Rx Results

• Observations– No Problems with Baseline Testing

6

Receiver Sensitivity – Attenuation• Initial Results:

5 dB Rx Results with Tx “On”5 dB Rx Results with Tx “off”

7

Receiver Sensitivity – Attenuation

• Observations– Rx gives better eye when Tx is “on”

– Rx with Tx on is better but still poor

• Hypotheses – Possible reasons why results differ when Tx is on

• Crosstalk

– Possible causes to Rx degradation• Crosstalk

• Poor PD characteristics

• Poor connections

8

Receiver Sensitivity – Attenuation

• Discovering the Problem– Test Simultaneous Operation

w/ RX Input Disconnected• Result: Bit-Pattern Present

• Conclusion: Crosstalk Evident

9

Receiver Sensitivity – Attenuation• Determining the Problem

– Checked all connections• Result: Found Atten. Were not firmly connected

• Analysis: Eyes were cleared up considerably

Firm Connect, Tx Off Firm Connect, Tx On

10

Receiver Sensitivity – Attenuation• Additional Problems

– With Tx on, eye-diagram is still cloudy• Crosstalk still a problem

– Possible Solution: Shielding

11

X-Talk experiments: Shielding• Shielding between entire TX and RX

Aluminum Shield Setup between TX and RX

12

Receiver Sensitivity – Attenuation• Shielding

– Significant improvement in shielding Tx and Rx

Tx on, no shielding Tx on, shielded

13

Receiver Sensitivity – Attenuation• Conclusion

– EMI caused significant degradation of signal with 5 dB or more attenuation

• Improved with shielding

– Connectors must have secure connections• Firm connection resulted in a receiver eye

– Crosstalk can be very misleading!

14

Performance Characteristics – Alignment Tolerance

• Region where we get acceptable results is basically circular

• Although, we may have estimated the center wrong

• Able to get a good eye, at center, up to 820um away

15

Rx Sensitivity – Alignment Tolerance

Alignment Tolerance (z=0)

-30

-25

-20

-15

-10

-5

0

5

10

15

20

25

-30 -25 -20 -15 -10 -5 0 5 10 15 20

y-alignment

x-a

lig

nm

en

t

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Important Details:

IEC Eye-Safe Optical Power Output Limit: 1 mW

Typical Optical Power Output of GDS1250: 0.364 mW

5 dB Attenuation from GDS1250 TX:

17

Wrap-Up

• Basic Functionality Confirmed

• Probably Complies with IEEE 802.3x Standards

• Room To Improve Performance w/ Better Shielding and/or Improved Layout

• Overall, A Working Gigabit Optoelectronic Link