Optical Gigabit Ethernet Group F.O.R.E. Final Presentation Chris Abbott, Ronen Adato, David Larado 4/21/2005

Overview Purpose was to build physical layer of optical gigabit transceiver Selected active components based on availability, connectorization, quality Designed and laid out two transceiver printed circuit boards Built and tested boards Compiled prototype budget and production- scale bill of materials

IEEE 803.z Standard Extinction Ratio Eye-safe power level Criteria for testing Definition of Bit Error Rate Use of eye as guideline, but not for formal test

Test Board Built test board to learn soldering and testing techniques Test Setup (To oscilloscope) Soldered Test Board

Test Board Results No resistance/Full SetupHigh resistance/Full SetupIdeal resistance/Full Setup <-- High resistance / test board only Ideal resistance / test board only -->

VCSEL Selection Criteria for selecting VCSEL: Good performance (slope efficiency, threshold current) Availability Cost Connectorization (SC over LC)

VCSEL Performance Analysis

AOC vs Lasermate Performance Similar Lasermate costs more in small quantities (costs comparable in bulk) AOC is LC connectorized, Lasermate is SC Chose Lasermate due to SC connectorization (no patch cords)

ROSA vs. PD Past years have used PDs Requires external TIA ROSA contains TIA inside package Possible reduction in noise Easier layout Comparable prices, easier to find Leading PD vendor too expensive Chose ROSA

ROSA Selection Lasermate RSC-P85P Gb/s SC ROSA SC connectorized ROSA Costs: 2-3 = $36.00/unit >10,000 = $6.00/unit

Optical Link Budget

Schematic Design Schematics derived from: Maxim datasheets Maxim application notes Past group ’ s work Used three element power supply filters Conservatively coupled Vcc and ground with decoupling capacitors Designed for common anode VCSEL configuration

Transmitter Schematic

Receiver Schematic

PCB Layout Considerations Kept traces as short as possible to prevent transmission line behavior Avoided sharp corners on high-speed lines (used 45° angles when needed) Kept high-speed differential lines symmetrical Effectively separated ground plane of transmitter and receiver

Conservative Layout

Aggressive Layout

Conservative Board 1 Soldered all components and tested the Rx circuit for a clear eye SMA/QMA fiasco prevented BER testing for the Rx circuit, and any Tx circuit testing Rx Circuit Test Setup Eye Produced by Rx Circuit, Signal PRBS 7

Conservative Board 2 Rx Reused SMAs from test board, soldered a new board The Rx circuit failed to produce an eye It was determined that the LA (MAX3264) had been damaged Rx Circuit Waveform Measured Before LA Rx Circuit Waveform Measured After LA

Conservative Board 2 Tx Soldered board, but had to reuse VCSEL from conservative board 1 Voltage drop across VCSEL was 5V VCSEL could be damaged VCSEL could be connected incorrectly Removed VCSEL and checked behavior by pin-pin resistance

Aggressive Board 1 Decided to try Emcore VCSEL on aggressive design to get Tx working Aggressive Tx very similar to conservative Tx Made sure we knew how Emcore fit into board

Aggressive Board, TxRx We varied the attenuations with, the transceiver:  4dB 7dB  Using different combinations of the optical attenuators, we were able to try these also:  9dB 12dB 

Aggressive Board, BER BER of less than 10^-9 when each signal was tested PRBS7, at least 5 minutes test runtime

Financial Budget

Bill of Materials (BOM)

Gantt Chart

Future work Get Lasermate VCSEL working Write final report

Conclusions Project was a success Learned about entire design process