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									EE 230: Optical Fiber Communication Lecture 10




          Special Broadband to the User Presentation
                         Transmitters




                                                       From the movie
                                                       Warriors of the Net
First Mile: Bringing the Broadband Infrastructure
Home




                     Fred Cohn, City of Monterey
                     Dick DeWees, City of Lompoc
                     Susan Estrada, CENIC
                     Seth Fearey, Connected Communities
                     Bryan Wassom, Alcatel
           League of California Cities Planners Institute
                 March 31, 2004 Monterey, CA
The One Gigabit or Bust™ Initiative


>   The Mission
     • Establish an action plan
       that will bring one
       gigabit to every home,
       business, and school in
       California by 2010.
     • Our job = catalyzing
       innovation


                           California has the most to gain from action
                                      and the most to lose by inaction.
                                                     — The Gartner Report
Three Hottest Trends in Digital
Home Communications Terminals




              1. DVR




                  2. HDTV




               3. xOD
The Services of Tomorrow
      Enable Advanced Services


       Replacement Services   Visionary Services and Capabilities


              Internet           Movies-on-Demand        Distance Learning

           Broadcast TV            Time-Shifted TV         Telemedicine

         Internet Telephony      Notification Services   Multiplayer Gaming

                                 Videoconferencing       Community Intranet

                                   Security Video         Power Metering

                                  Home Automation         Voice Response
Next Generation Broadband

>   “It’s not about capacity. It’s about the capabilities
    made available by the capacity.” Nitin Shaw,
    Arraycom
>   Historical evolution of bandwidth requirements
    support one gigabit per second by 2010
>   We need the big red circle.
Bandwidth Comparisons
Broadband and Economic Development

>   Broadband equals J-O-B-S
     • Gartner study said 2 million new jobs in California

>   “No business will settle in a town that doesn’t have
    broadband access.” NYT, 3/24/04


>   Question:
    • What had made your communities think about installing
      next generation broadband? Are you losing jobs? Do
      you think broadband helps with business development?
Laser Diode Transmitter Block Diagram
Source-Fiber Coupling – Lambertian
Sources
                                     Lambertian Source
                                     radiance distribution




                                             Generalized
                                             Coupled Power
Step and Graded Index Fiber Coupling
Graded Index Fiber Coupling Continued
Source Fiber Coupling - II




                                                 Schematic of a typical assembly
                                                      of coupling optics




Transmitters employing a) butt-coupling and b)
            lens-coupling designs
Turn-on delay



                   J  Jb 
      td   N ln 
                  J J    
                        th 
Extinction Ratio Penalty

If the transmitter does not turn all the way “off” during the transmission of a “zero” then
 the extinction ratio r ( the ratio to a power transmitted during a “0” to that during a “1”)
will cause a bit error rate penalty and a reduction in sensitivity.

For a PIN receiver the peak power required for a given signal to noise ratio will become:

                                        1  r h  2 1/2
                                                   Q i
                                 P 
r=0 if the optical signal is            1  r  q 
completely extinguished                                                 For APD detectors with gain
during a logical “0”                                                    the effect of the multiplied
                                                                        noise during the “0” is more
r=1 if the optical power                                                severe, this case is shown in
during a “0” equals that                                                the graph to the left. k is the
during a “1”                                                            ratio of the hole and electron
                                                                        ionization coefficients and is a
in this case the power                                                  property of the material in the
required approaches                                                    avalanche multiplication region
Traditional Laser Transmitter Approaches

Use a transmission line and impedance match                        Keep it close and don’t worry about the match

                                                                                 Bonding Inductance
   Bonding Inductance                Matching Resistor

                                                                 Drive
                                                                 Transistor                               Contact
                 Transmission Line              Contact                                                   Resistance
                                                Resistance
          Pad                 Junction
          Capacitance         Capacitance        Laser                                                    Laser
                                                               Pad
                                                 Junction      Capacitance                                Junction
                              Bonding
                              Inductance                                  -Vee           Junction
                                                                                         Capacitance
 -Vee
                                                                   Packaged Laser Driver          Laser


                                                 Laser Diode                       Bondwire
                              Thin Film
                              Resistor                           Laser Driver                     Laser Diode
        Laser Driver


                       Transmission Line
Packaged Laser Driver                Packaged Laser
Laser Driver Stabilization


                                            i            i
                                         Mon t or Phot od ode
                            Laser
                                                                                                                                                             Moni t or Phot odi ode
                                                                                                                                    Laser
                                                                -

                                                                                                                                                                          -
                             Vr ef                                                                      Vr ef
                                                                                                                                                                                            Vr ef 1    Vr ef 2
                                                                +                                                                                                                  Lav
                                                                                                                                                                          +
                                                                                                                                                                                  Vr ef 1
             Dat a                                                                     Dat a
                                                                                                                                               -                                               Dat a   Dat a
                                                                                                                          Dat a   Dat a
                                                                                                                                                   Vr ef 2                    -

                                                                                                                                               +
       -5V
                                                                                                                                                                              +                        Dut y Cycl e
                                                                                                                                                                                  Lpp                  Measur ement
                                                                                                                    -5V
                                                                                                                                                                   Peak Det ect or



        Average Power and Mark Density Compensation                                                                   Average Power, Mark Density and Modulation


                                                                                  i     d
                                                                                  B as A j ust    oi      ht i
                                                                                                 Mn t or P o od ode
                       Laser
                                                                                                                                            A variety of feedback
                                                                          -
                                                                                                           -
                                                                                                                                            approaches are available to
                               B as
                                i                                                     -5V
                                                                          +
                                                                                                           +
                                                                                                                       r
                                                                                                                    Ave age
                                                                                                                     o r
                                                                                                                    P we
                                                                                                                                            compensate for laser
                                                                       t rt r
                                                                    I n eg a o
                                                       Mdu a ed P we Ad ust
                                                        o l t    o r j
                                                                                                                                            imperfections and the
       Dt a
        a            Dt a
                      a                     -
                                                   -5V
                                                                                                               -                            consequences of temperature
                                                                              -
  Mdu a i on
   o l t                                    +
                                                                                                               +
                                                                                                                   P ak- pea
                                                                                                                    e
                                                                                                                                            variation and aging
 -5V                                    t rt r
                                     I n eg a o                               +
                                                                                                                    o r
                                                                                                                   P we
                                                                                                  e e
                                                                                                 P ak D t ect or




                        Average and Peak Power Stabilization
Packaging




Drawing of Packaging Approach                                              Optical Module (a), Electrical module (b)
                                             •10 Channels
                                             •12.5 Gb/s aggregate bandwidth
                                             •1300 nm commercial laser array
                                             •50/125 Multimode fiber ribbon
                                             •130 mW/channel
                                             •CMOS Driver Array
                                             •BER<10-14
                                             •1.2 km transmission with no
                                             BER degradation
   Close-up of assembled module
                                                                                      Completed module integrated on test board

                  Bostica et. al., IEEE Transactions on Advanced Packaging, Vol. 22, No 3, August 1999
Example Commercial Transmitter Module




             Palomar Technologies
DFB-HEMT OEIC Laser Transmitter



                  Transistor Technology
                  •InGaAs-InAlAs HEMT
                  •1.5 mm gate length

                  Laser
                  •Distributed Feedback Laser
                  •Self-Aligned Constricted Mesa (SACM)
                  •7 MHz linewidth at 3 mW output power
                  •19 GHz –3db frequency
                  •8 mA average threshold

                  Fabrication
                  • l/4 shifted cavity fabricated by e-beam
                  •2-step MOCVD

                  OEIC Performance:
                  •Clean output eyes for all pattern lengths
                  up to 5 Gb/s
                  •Operation at shorter patterns up to 10 Gb/s
                  •Demonstrated link operation over 29 km
                  at 5 Gb/s




                             Lo et. al. IEEE Photonics Technology Letters, Vol. 2, No. 9, September 1990
Polarization

>   In molecules, P=μ+αE+βE2+γE3+…
>   In materials, P=X(o)+X(1)E+X(2)E2+X(3)E3+…


If multiple electric fields are applied, every possible cross term is
    generated.
At sufficiently high values of E, quadratic or higher terms become
   important and nonlinear effects are induced in the fiber.
Electro-Optic Coefficient r



                     n4r
            2  
                      2


              1 
             2   rE
             n 

								
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