Gigabit Ethernet PMDOpto-Link, Inc. – Progress Summary

Vinh Nguyen, Clifton Kerr, Andrew Meyerson, Bryan Justice

April 21, 2005

Project objective

Design, assemble, and test the Physical Medium Dependent (PMD) layer of a Gbps Ethernet optoelectronic link

Defining Success

IEEE compliance is necessary at a minimum Staying within our allowed budget Assuming the specs are met, the most

successful board will feature the least costly BOM.

Project Planning

Project Planning To ensure that the project was completed on

time, a Gantt chart was developed The Gantt chart shows the scheduled tasks

and the progress made on each task The Gantt chart also shows whether work is

proceeding on-schedule

Initial Gantt Chart

Gantt Chart Revisions An initial Gantt chart developed based on

project objectives and deadlines Actual progress rapidly deviated from initial

Gantt chart The initial Gantt chart revised based on rate

of progress The Gantt chart finalized after ~4 weeks

Final Gantt Chart

Final Gantt Chart Cont.

Hindsight Time crunch towards end of semester Should have allocated more time to

testing Should have worked harder/allocated

less time to early project phases

Ideal Gantt Chart

Ideal Gantt Chart Cont.

Project Specifications

Project Specifications PMD should conform to the IEEE 802.3

specifications for type 1000BASE-SX (Short Wavelength Laser)

Key specs: Bit-Error rate < 1 x E9 Proper operation with 7dB attached attenuation Open and defined eye diagram (low noise) Extinction ratio > 9dB Eyesafe laser output (< 1mW)

Transmit characteristics (from 802.3z standard)

Receive characteristics (from 802.3 Standard)

Part Selection

Part Selection Process Factors in part selection were: Product specs (chosen parts must result in an

IEEE compliant optical link budget) Ability to contact and get responses from

companies and vendors Stocking and a sufficiently fast lead time for

us to obtain the parts in time to build our prototype

VCSEL Selection AOC HFE419x-541 Suited to our specifications Available within two weeks Best pricing

Suitable Emcore sample VCSELs were also secured

AOC HFE419x-541 4-Corner AnalysisExtinction Ratio (dB): 9.00000

Maximum Output Power Pmax (mW): 1.00000

Minimum Output Power Pmin (mW): 0.12589

VCSEL Model: Advanced Optical Components HFE419x-541Cost (1 Unit):Cost (10000 Units):Availability:Delivery Time:

VCSEL ParametersParameter: Symbol: MIN TYP MAX

Threshold Current (mA): Ith 0.5 1.80000 2.50000

Slope Efficiency (mW/mA): η 0.04000 0.12500 0.16000

VCSEL Current RequirementsIth η Imax Imin Ibias Imod

(mA) (mW/mA) (mA) (mA) (mA) (mA)0.50000 0.04000 25.50000 3.64731 14.57366 21.852690.50000 0.16000 6.75000 1.28683 4.01841 5.463172.50000 0.04000 27.50000 5.64731 16.57366 21.852692.50000 0.16000 8.75000 3.28683 6.01841 5.46317

Sales Information:Location: General Sales and Support Chuck HanrahanPhone: Anaheim, CA? Eastern USA Sales Rep (Anaheim, CA?)E-Mail: 1-866-MY-VCSEL (585) 218-4281

support@adopco.com chuck.hanrahan@adopco.com

LC connectorized 2.5 gbps TOSA

PD Selection AOC HFE3180-108 ROSA Suited to specifications Delivery within two weeks Relatively inexpensive in all quantities We would eventually find that incorporating

the PD and TIA into one can completely eliminated crosstalk issues.

HFE3180-108 ROSA 4-Corner AnalysisVCSEL Extinction Ratio: 9.00000Max VCSEL Power Output (mW): 1.00000Min VCSEL Power Output (mW): 0.12589Optical Fiber Loss (dB): 7.50000Optical Connector Loss (dB): 0.00000Total Loss (dB): 7.50000Max Received Power Input (mW): 0.17783Min Received Power Output (mW): 0.02239

ROSA Model: Advanced Optical Components HFD3180-108High-Speed Response 2.5 GbpsCost (1 Unit): 10.00$ Cost (10000 Units): 5.00$ Availability:Delivery Time:

Parameter: Symbol: MIN TYP MAXResponsivity (V/W) R 1500.00000 2500.00000 3500.00000

Rise/Fall Time (ps) τr/τf 120.00000 150.00000

Supply Voltage (V) Vcc 3.00000 3.30000 3.60000

Supply Current (mA) Icc 25.00000 35.00000

Differential Output Voltage (mV,p-p) Vout 100.00000 150.00000 220.00000

Upper 3 dB Bandwidth (GHz) BWupper 1.40000 2.00000

Photodetector Voltage Requirements

P R VO

(mW) (V/W) (mV)0.02239 1500.00000 33.580820.02239 3500.00000 78.355240.17783 1500.00000 266.741910.17783 3500.00000 622.39779

Sales Information:Contact: General Sales and Support Chuck HanrahanLocation: Anaheim, CA? Eastern USA Sales Rep (Anaheim, CA?)Phone: 1-866-MY-VCSEL (585) 218-4281E-Mail: support@adopco.com chuck.hanrahan@adopco.com

Product Notes:LC connectorized

Optical Link Budget

Optical Link Budget Description An optical link budget was computed to

ensure that all active components would function together

Data from the 4-Corners analysis of the VCSEL and the ROSA was used

Optical Link BudgetVCSEL Extinction Ratio: 9.00000

MAX3286 Laser Driver Characteristics:Min Modulation Current (mA): 2.00000Max Modulation Current (mA): 30.00000

MAX3264 Limiting Amp Characteristics:Min Input Voltage (mV): 5.00000Max Input Voltage (mV): 1200.00000

VCSEL: Advanced Optical Components HFE419x-541ROSA: Advanced Optical Components HFD3180-108

Parameter:Low Power (Zero) High Power (One) Low Power (Zero) High Power (One)

VCSEL Parameters:Threshold Current (mA)Slope Efficiency (mW/mA)DC Bias Current (mA)Modulation Current (mA)VCSEL Output Power (mW) 0.12589 1.00000 0.12589 1.00000

Fiber Loss:Optical Fiber Loss (dB):

Receiver Parameters:Received Input Power (mW): 0.02239 0.17783 0.02239 0.17783ROSA Responsivity (mV/mW):Output Voltage (mV) 33.58082 266.74191 78.35524 622.39779

Worst Case Best Case

16.57366 4.0184121.85269 5.46317

2.500000.04000

0.500000.16000

7.50000 7.50000

1500.00000 3500.00000

Design and Assembly

The Design Process Schematics based largely off of past designs, with

some modification. Filtering and decoupling a major focus, to make sure

everything worked as planned. PDs no longer widely available; ROSA replacing both the

PD and the trans-impedance amp and simplifying circuit Schematic design translated to PCB layout

In translation, emphasis on correctness first and spacing second

Transmission line considerations important

Transmitter Design Schematic

Receiver Design Schematic

Board Layout

Board Construction First design assembled

with no problems. 0603 components very

small and hard to solder, in part due to smaller pads

Don’t underestimate how long it takes to put together a board

Board Construction (continued) Second design

construction was rushed after first failed to work Communication mishap

(and the depths of Hudson) left one person to assemble board

Soldering alone is no fun. Bring a solder buddy, as one person only has two hands.

Board Construction (continued) Aggressive design construction – last ditch attempt to

get a working board Primarily done because debugging the then-broken

common-cathode design was not efficient. Something had failed, but we couldn’t isolate it.

While soldering, the cause of our previous failures became clear. Corrected on this assembly.

Returned later to add a receiver to this design Needed to do our most aggressive loop-back test. The solder job was rushed once, and the receiver wasn’t

perfect the first time around. Limiting amp had to be replaced.

Testing and Troubleshooting

Receiver Board Testing

First receiver circuit constructed worked from the start No appreciable signal loss with 7dB optical attenuation No errors detected with the BER tester in 5+ minutes of operation

Receiver eye with no attenuation Receiver eye with 7dB optical attenuation

Receiver Board Testing (continued)

Second receiver circuit wasn’t so easy Eye not clean on regular test (but loopback was no

worse) Error rate of about 10%, so signal was good enough for

the equipment to get a lock but not much better.

Bad receiver eye with 7dB optical attenuation

Receiver Board Testing (continued)

But was easily fixed Limiting amp poorly attached and multiple pins

bridged/ BER of at worst 1e-10 once repaired

Fixed receiver eye with 7dB optical attenuation

Transmitter Testing First two transmitters

didn’t work so well. First, no optical output

as the laser was in “upside down”

Fixed orientation, and got a very messy noise band with the traces of an eye inside. Insufficient signal?

Transmitter PRBS7 Signal with no attenuation

Transmitter Testing (continued) Troubleshooting

accidentally led to part failures. We blew two VCSELs

and a handful of ferrite bead inductors.

Replaced parts, and then got the “magic probe” effect Probing the output pins

of the laser driver cleaned up the eye

Signal output when using the probe across the output pins

Transmitter Testing (continued) Third time was the charm

Aggressive design transmitter just worked. Same eye as with the “magic probe” on the other design At minimum currents, 1e-10 BER with 7dB optical

attenuation Tracked down the source of the “Magic Probe” while

testing the good transmitter… Only happened when probe touched laser driver output

pins Pushing down on the chip with excessive force produced

the same result Bad solder joint!

The Loop-Back Test Once we got a working transmitter and receiver on

one board, it just worked. Lots of jitter on the eye, but lots on the clock too

Connection seems to be getting less reliable with time at the splitter

Did not effect bit error rate measurements After 15 minutes of continuous testing, still no errors

and a BER of 0 Eye totally disappears when optical cable is removed,

so entirely a product of transmitted light and not electrical cross-talk.

The Loop-Back Test

A good, clean eye with a tiny bit of clock-induced trigger jitter

Budget and Ordering

Preliminary Budgeting (estimation) AOC VCSEL: $14.50 (2) AOC ROSA: $10.00 (2) Two board fabs: $70.00 Maxim driver and limiting amp, Digikey

passives, and Murata inductors, plus allowances for shipping costs: $80.00

Total projected budget: Approximately $210.00

Estimated Budget Realized that our preliminary budget was very

off (i.e. didn’t even add up right) More itemized for actual parts we intended to

use as well as quantities of parts Based on previous shipping costs estimated

total costs for entire project Still under budget, although not by much

($327.85 for the project)

Final Budget Determined that a second board fabrication

was unnecessary since first design was adequate

Includes total amounts paid for parts, shipping Total of $268.85 for the project, which is

almost $100 below budget

Final BudgetPart Description: Manufacturer: Vendor: Vendor Part Number: Unit Cost: Quantity: Total Part Cost:

CAP 10000PF 50V CERAMIC X7R 0603 (back ordered) BC Components Digi-Key BC1252CT-ND $ 0.0290 100 $ 2.90

RES 30.0 OHM 1/10W 1% 0603 SMD Rohm Digi-Key RHM30.0HCT-ND $ 0.0760 10 $ 0.76 RES 100 OHM 1/10W 1% 0603 SMD Rohm Digi-Key RHM100HCT-ND $ 0.0760 10 $ 0.76 RES 115 OHM 1/10W 1% 0603 SMD Rohm Digi-Key RHM115HCT-ND $ 0.0760 10 $ 0.76 RES 3.00K OHM 1/10W 1% 0603 SMD Rohm Digi-Key RHM3.00KHCT-ND $ 0.0760 10 $ 0.76 POT 1.0K OHM 3/8" SQ CERM SL MT Bourns Inc Digi-Key 3296W-102-ND $ 2.5000 5 $ 12.50 POT 10K OHM 3/8" SQ CERM SL MT Bourns Inc Digi-Key 3296W-103-ND $ 2.5000 5 $ 12.50

FERRITE CHIP 1000 OHM 100MA 0603Murata Electronics North America

Digi-Key 490-1034-1-ND $ 0.1200 50 $ 6.00

PCB Fabrication Run Express PCB Express PCB $ 59.0000 1 $ 59.00

AOC 2.5 Gbps VCSEL Advanced Optical Components Advanced Optical Components HFE419x-541 $ 14.5000 4 $ 58.00

AOC 1.25/2.5 Gbps ROSA Advanced Optical Components Advanced Optical Components HFD3180-103 $ 10.0000 4 $ 40.00

CONN PWR JACK 2.1MM SMD CUI Inc. Digi-Key CP-002APJ-ND $ 0.7300 6 $ 4.38 Right-Angle SMA Jack Amphenol Jameco 188525 $ 4.2000 10 $ 42.00

CAP 10000PF 50V CERAMIC X7R 0603 BC Components Digi-Key BC1252CT-ND $ 0.0169 100 $ 1.69 RES 100 OHM 1/10W 1% 0603 SMD Rohm Digi-Key RHM100HCT-ND $ 0.0760 20 $ 1.52 RES 200 OHM 1/10W 1% 0603 SMD Rohm Digi-Key RHM200HCT-ND $ 0.0760 10 $ 0.76 RES 2.00K OHM 1/10W 1% 0603 SMD Rohm Digi-Key RHM2.00KHCT-ND $ 0.0760 10 $ 0.76 RES 24.9 OHM 1/10W 1% 0603 SMD Rohm Digi-Key RHM24.9HCT-ND $ 0.0760 10 $ 0.76 RES 34.8 OHM 1/10W 1% 0603 SMD Rohm Digi-Key RHM34.8HCT-ND $ 0.0760 10 $ 0.76 Shipping and Handling $ 22.28

Total: $ 268.85

Bill of Materials Total cost of mass producing the board was

found to be $23.93

Bill of Materials

Ordering Vendors included

Digi-Key Jameco PCB Express

All parts were received in timely fashion and progress was never delayed due to waiting for parts

Ordering It was learned that Digi-Key has a $5

handling charge for any orders under $25 Therefore it is a good idea to know and get all

of your parts at once in order to save some money

Back-ordered parts are not good Sometimes you pay for next day shipping

when ground is what you wanted

In Retrospect When determining the number of parts to order, it

should be assumed that you will need both multiple board fabrications as well as extra parts. This means you should initially order more than 10 ferrite beads.

Although individual parts may be more expensive from a certain vendor, it is still best to order as many parts as possible from the same vendor

It is possible to hide embezzlement under the line “Shipping and Handling” in the budget