Transcript See How Your Community Can Benefit

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:
P 
r=0 if the optical signal is
completely extinguished
during a logical “0”
r=1 if the optical power
during a “0” equals that
during a “1”
in this case the power
required approaches 
1/2

1  r 
h Q i 2
1  r  q 
For APD detectors with gain
the effect of the multiplied
noise during the “0” is more
severe, this case is shown in
the graph to the left. k is the
ratio of the hole and electron
ionization coefficients and is a
property of the material in the
avalanche multiplication region
Traditional Laser Transmitter Approaches
Use a transmission line and impedance match
Bonding Inductance
Matching Resistor
Bonding Inductance
Transmission Line
Junction
Capacitance
Pad
Capacitance
Keep it close and don’t worry about the match
Contact
Resistance
Laser
Junction
Bonding
Inductance
Drive
Transistor
Contact
Resistance
Laser
Junction
Pad
Capacitance
-Vee
Junction
Capacitance
-Vee
Packaged Laser Driver
Thin Film
Resistor
Laser Diode
Laser Driver
Transmission Line
Packaged Laser Driver
Packaged Laser
Laser
Bondwire
Laser Driver
Laser Diode
Laser Driver Stabilization
Moni t or Phot odi ode
Laser
Moni t or Phot odi ode
Laser
-
Vr ef
-
Vr ef
Lav
+
+
Dat a
Vr ef 1
Vr ef 2
Vr ef 1
Dat a
Dat a
Dat a
Dat a
-
Vr ef 2
Dat a
-
+
-5V
+
Lpp
Dut y Cycl e
Measur ement
-5V
Peak Det ect or
Average Power and Mark Density Compensation
Bi as Adj ust
Laser
Average Power, Mark Density and Modulation
Monit or Phot odi ode
-
Bi as
+
-
-5V
Average
Power
+
Int egrat or
Modul at ed Power Adj ust
Dat a
Dat a
-5V
Modul ati on
-5V
+
Int egrat or
+
+
Peak Det ect or
Average and Peak Power Stabilization
Peak- pea
Power
A variety of feedback
approaches are available to
compensate for laser
imperfections and the
consequences of temperature
variation and aging
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
4

n
r
2 
 
2
 1 
 2   rE
n 