implementing a 10 gb/s vcsel driven transmitter for short range applications irfan n. ali michael c....
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Implementing a 10 Gb/s VCSEL Driven Transmitter for Short Range Applications
Irfan N. AliMichael C. Clowers
David S. FinkSean K. Garrison
Jeff A. Magee
Georgia Institute of TechnologySchool of Electrical & Computer Engineering
March 3, 2008
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Project Objectives & Parameters
Objective: Design and implement 10 Gb/s VCSEL transmitter for fiber optic Ethernet systems
Client: Telecom service providers, server management groups, etc.
Projected Unit Cost: Approx. $700
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• Design and implement a 10 Gb/s optical link• Digital/electrical input• Signal processing via laser driver• Electrical-Optical Signal conversion via VCSEL• Analog/optical output • Fiber optic data transmission• Bit-error-ratio tester (BERT)
Technical Objectives
Laser Driver
VCSELFiber Optic Cable
Pattern Generat
orBERT
Driver Board Interface Board
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Technical Specifications
Bit Rate 10 Gb/s Nominal Wavelength 850 nm Power Supply 3.3 V Output Fiber 50-um Multimode Output Connector LC Board Dimensions Variable Max Transmission Range 100 m
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Design Approach
• Three parallel approaches:• Modify MAXIM Inc. evaluation board• Populate existing Analog Devices (AD)
driver board• Design driver board for TI chip
Laser Driver
VCSELDigitalInput
IMOD
IBIAS
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Analog Devices Board
• Pre-designed board• Needs to be populated and tested• Has analog control of output currents
Laser Driver
Digital Inputs
Output to VCSEL
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Maxim Inc. Evaluation Board
• Evaluation board designed for laser diode
• Interface board designed to deliver limited modulation and bias currents to VCSEL
Digital Inputs
Laser Driver
Tuning Potentiometers
Output to Interface Board
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TI Driver Board Schematic
• Driver board designed using PCB Artist• Provides digital control of output currents• Works with an interface board to connect to VCSEL
MCU InputDigital InputsPower Supply
Digital Outputs
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VCSEL Interface Board Schematic
• Interfaces the TI and MAXIM Inc. boards with the VCSEL
• Includes resistance networks to limit current to VCSEL
Digital Input
Digital Inputs
Analog VCSEL Output
Analog VCSEL Output
MAXIM Interfa
ce
TI Interfa
ce
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System Configuration
Note: SMA connections use coax cables Optical cables use LC connectors
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Demonstration Plan
• Test by using the transmitter with a pattern generator to a send 10 Gb/s signal to error detector connected to optical receiver
• Measure bit-error-ratio (BER) versus optical power at receiver and compare to acceptable value of BER at 10-10
• Capture optical eye diagram using a high-speed oscilloscope
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Problems/Issues
• Transmission lines for interface board need to be designed for high speeds
• SMA pad size on AD board does not match the SMA connector specification
• VCSEL connection to AD board may be incompatible with available VCSELs
• TI driver chip has 0.5 mm spacing between pins which will be difficult to solder by hand
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Budget & Cost Analysis
Unit Cost Analysis
Fringe Benefits (% of labor) 25%
Overhead (% total labor, parts, fringe) 50%
Marketing (% sales price) 25% Warranty (% sales price) 5%
Costs (per unit) Materials $220
Labor $20
Testing $20
Fringe Benefits (25% labor cost) $5 Overhead $133
Sales/Marketing $250
Warranty $50
Amortized Development Costs $2.28
Cost Subtotal $700
Devices Acquired MAXIM Inc. Eval Board $300 Circuit Components Free Driver Chips Free Predesigned PCB Free Total Costs $300 Non-Budget Spending TI MCUs $80 Future Spending Circuit Components TBA SMA Connectors TBA
Power Supplies TBA
PCB Boards $80
•TI MCUs were bought as general use for the Senior Design Lab and therefore will not come out of the budget•Pre-designed PCB board
provided free of charge from Dr. Ralph’s lab
•Costs are based on total unit sale of 15000 over 5 years
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Projected Schedule
Major Events Before Spring Break:•Completing PCB design and fabrication•Populating pre-designed board•Testing at TSRB
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Current Status
• MAXIM Inc. evaluation board acquired• AD board partially populated• TI and interface boards designed • PCB mounting design initialized
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Questions/Comments
Thank You