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Final Report 1394b:Optoelectronic Data Communications Group G9: Tiffany Lovett, gte291r Tornya Moore, gte668r Mareisha Winters, gte824t ECE 4006C April 23, 2002 Key features of 1394? • It is a hardware and software standard for transporting data at 100, 200, or 400 Mbps • It is a digital interface - no need to convert digital data into analog • It is physically small and can replace larger, more expensive interfaces • It is easy to use Key features of 1394? • It is hot pluggable - users can add or remove 1394 devices while the bus is active • It is inexpensive • It is a scaleable architecture - can mix 100, 200, and 400 Mbps devices on a bus • It has a flexible topology • It is non-proprietary - there is no licensing problem to use for products. 1394 Cable • Is a small, thin serial cable • Contains six wires: two of the wires carry power; the remaining four wires are grouped into two twisted signal pairs How 1394 Works • Supports both asynchronous and isochronous data transfers • 1394 device requests control of the physical layer • Asynchronous: The address if the sender & receiver is transmitted by the packet data. Once the receiver accepts the packet, an acknowledgement is returned to the original sender • Isochronous: The sender requests an isochronous channel with a specific bandwidth. Isochronous channel IDs are transmitted followed by the packet data. The receiver monitors the incoming data’s channel ID Why 1394b? • 1394b is a revision of the initial 1394 standard • 1394b is twice the speed, and allows for longer distances • It provides new connection options such as Plastic Optical Fiber, Glass Optical Fiber and UTP-S. Previously 1394 could only be connected via copper cabling • 1394b is a prime choice for connecting personal computers with digital devices (i.e. cameras, DVD players, and camcorders) Photodetectors • Optoelectronic device that senses and measures the output of a typical light source • There are three steps in the photodetection process: (1) absorption of optical energy and generation of carriers (2) transportation of the photogenerated carriers across the absorption region (3) carrier collection and generation of a photocurrent • The three main types are photoconductors, PIN photodiode, and Avalanche photodiodes • For high-speed applications the PIN photodiode is the best choice because it has no internal gain and can attain very large bandwidths. Design Considerations for the Photodetector • Two candidates: – Lasermate RSC-M85A306 – Hamamatsu S5973 • Responsivity-measures how much light input is required to produce a given current • Capacitance of the photodiode must not exceed the maximum input capacitance of the MAXIM board. • Rise/Fall Time Comparison of Two Photodiode Candidates Lasermate RSC-M85A306 Hamamatsu S5973 Design of the Photodetector Board • Both unconnectorized and connectorized photodectector were used in the circuit. • The resistance for the unconnectorized is 53.1 and for the connectorized it is 66.4 • According the data on Murata’s website, the ideal value for both of the capacitors is .01F. Design of the Photodetector Board (cont’d) • Once all of the components were gathered they were mounted on the board and soldered onto the board. Connectorized Unconnectorized Testing • Tested the connectorized photodetector board by connecting it to the GTS 1250 and then to the Agilent board. • The board did not produce an eye diagram. • To analyze why no eye diagram was produced, simple average value singles were looked at along with Fourier analysis and incoming data stream. • Received a signal from the connectorized photodetector but did not get a signal from the unconnectorized photodetector. Testing (cont’d) • Simple square wave test with connectorized photodetector Testing (cont’d) • Spectrum analysis with photodetector not connected Emitters • Three types are LEDs, Edge emitting lasers, and VSCELs • LEDs produce light by a process known as spontaneous emission, resulting in incoherent light • Lasers produce light by stimulated emission, which results in coherent light • For high-speed applications VCSELs are superior to LEDs and Edge emitting lasers because they achieve high data rates easier and they are less expensive Design Considerations for the VCSEL • Two candidates: – Honeywell HFE4380-521 – Honeywell HFE4384-522 • Threshold current-minimum amount of current needed for the VCSEL to emit light • Slope Efficiency-tells how many amps it takes to produce a given power output • Rise/Fall Times Comparison of Two VCSEL Candidates HFE4380-521 HFE4384-522 Link Budget Analysis • Will the system work for the proposed link? • For this project the purpose of the link budget is to determine whether the transmitter and receiver system provide sufficient current to drive the post amp. • Link Budget = Power Incident on Photodetector x Responsivity of the Photodetector • Power Incident on Photodetector = [Modulation Current of Transmitter x Slope Efficiency of VCSEL] – Losses Due to Connectors and Fiber Link Budget Analysis (Cont’d) HFE4380-521HFE4384-522 Ith(m A) 6 6 DCbiasoflaser(m A) 7.2 7.2 SlopeEfficiency(m W /m A) 0.04 0.15 ModulationCurrentofTX(m A) 30 30 RangeofPowerOutput(m W ) 0.288-1.2 1.08-4.5 RangeofPowerOutput(w/ Loss)(m W ) 0.144-0.6 0.54-2.25 ResponsivityofLaserm atePD(A/W ) 0.4 0.4 ResponsivityofHam am atsuPD(A/W ) 0.47 0.47 RangeofCurrentfromLaserm atePD(uA) 57.6-240 216-900 RangeofCurrentfromHam am atsuPD(uA) 67.7-282 253.8-1057.5 Design of the VCSEL Board • In order to minimize reflections the VCSEL circuit had to have a total resistance of 50 • A surface mount resistor of 25 was placed in series with the VCSEL. Which has a typical resistance of 25 • A DC bias T (2k resistor in series with the 5V power supply) was connected to the circuit to allow connect to the AC coupled GTS 1250 pattern generator Design of the VCSEL Board (cont’d) • Once all of the components were gathered they were mounted on the board and soldered onto the board. Testing • The two pieces of equipment that will be used to verify the functionality of the components are the Tektronix GTS 1250 pattern generator and Tektronix 7000 Series Oscilloscope. Testing (cont’d) • Initially tested the Agilent opto-electronic board from the previous semester to generate an eye diagram • GTS 1250 was connected to the transmitter portion of the board,the oscilloscope was connected to the receiver portion, and a fiber cable was used to loop the receiver and transmitter together • Tested the VCSEL board by connecting it to the GTS 1250 and then to the Agilent board • Tested the VCSEL board with the MAXIM transmitter board Testing (cont’d) • Block diagram of test setup for VCSEL Testing (cont’d) • Eye diagram of Agilent board Testing (cont’d) • Eye diagram of VSCEL board Testing (cont’d) • Eye diagram of VSCEL board with 1394b TX MAXIM board Design of Etched Board • Using the design software SuperPCB an etched board was designed and created. SuperPCB layout of etched board top layer of etched board Testing • The VCSEL components were mounted on the board, but no eye diagram appeared when tested • It was determined that the traces on the board exceed the maximum amount allowed therefore a new etched board must be created with the appropriate trace lengths Bottom layer of etched board Top layer of etched board Conclusion • The VCSEL board worked according to the design and specifications and an eye diagram was produced with both the Intel/Agilent board and the 1394b MAXIM transmitter board • The photodetector board was unable to produce an eye diagram mainly because no signal could be identified from the photodetector. • Another possible problem with the photodetector board is that the circuit itself could be wrong • These problems should be looked into in further detail before further testing can begin