Demonstrating Effective All-Optical Processing for ...web.mit.edu/jpwang/Public/defense.pdf · MIT...
Transcript of Demonstrating Effective All-Optical Processing for ...web.mit.edu/jpwang/Public/defense.pdf · MIT...
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PhD Defense-1JPW 6/11/2008
MIT Lincoln Laboratory
All-Optical Processing for Ultrafast Data Networks Using
Semiconductor Optical AmplifiersJade P. Wang
Ph.D. Thesis Defense
Thesis Committee: Professor Erich P. Ippen, Dr. Scott A. Hamilton, Professor Rajeev J. Ram
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MIT Lincoln LaboratoryPhD Defense-2JPW 6/11/2008
Today’s Data Networks
• Transmission over optical fiber– Wavelength division multiplexing (WDM) : multiple wavelength channels per fiber– Erbium-doped fiber amplifiers (EDFAs): multi-wavelength amplification – Electronic regenerators with O/E/O conversion & demultiplexing
• Electronic routers with O/E/O conversion & demultiplexing
• WDM: 80+ channels, 10-40 Gb/s per channel
• EDFA: 60-80 km spacing• Regenerator: Every 2-3 spans
(120-240 km)• Routers: 100+ ports with 1+
Tb/s throughput
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MIT Lincoln LaboratoryPhD Defense-3JPW 6/11/2008
Increasing Demand for Capacity
0100200300400500600700
PB/m
onth
1990 1993 1996 1999 2002 2005Year
U.S. Internet Traffic*
*Odlyzko et al., “Internet Growth Trends and Moore’s Law”http://www.dtc.umn.edu/mints/igrowth.html
Global Projected Traffic Growth**
**Cisco, “The Exabyte Era”, 2008
• Steady growth estimated at 50%-100% / year• Increasing video traffic (YouTube, IPTV, Video on Demand)• High-end users: storage networks, data centers, grid computing, scientific processing• Growing number of internet users around the world
Increasing channel bit rates and number of channels
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MIT Lincoln LaboratoryPhD Defense-4JPW 6/11/2008
Outline
• Motivation/Background
• Ultrafast all-optical logic gates
• Routing: 40-Gb/s all-optical header processing
• Performance optimization of optical logic gates
• Regeneration
• Future SOA-MZI gates
• Conclusion
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MIT Lincoln LaboratoryPhD Defense-5JPW 6/11/2008
Outline
• Motivation/Background: Why all-optical processing?
• Ultrafast all-optical logic gates
• Routing: 40-Gb/s all-optical header processing
• Performance optimization of optical logic gates
• Regeneration
• Future SOA-MZI gates
• Conclusion
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MIT Lincoln LaboratoryPhD Defense-6JPW 6/11/2008
Optical Signal Processing
• Ultrafast performance
– Capable of 100-Gb/s bitwise switching, 640-Gb/s wavelength conversion
• Channel-rate processing
– No demultiplexing to lower bit-rates
• Fewer O/E/O conversions
• Network flexibility
– Payload transparency to bit rate & modulation format
Decrease size, power, weight COST
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MIT Lincoln LaboratoryPhD Defense-7JPW 6/11/2008
Outline
• Motivation/Background: Routing and Regeneration
• Ultrafast all-optical logic gates
• Routing: 40-Gb/s all-optical header processing
• Performance optimization of optical logic gates
• Regeneration
• Future SOA-MZI gates
• Conclusion
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MIT Lincoln LaboratoryPhD Defense-8JPW 6/11/2008
Routers: All Electronic
Router functions:– Routing– Forwarding– Contention
resolution– Buffering– Switching
• Challenges with increasing bit rates:– Limited electronic switch speeds (10-40 Gb/s) – Requires multiple lower-speed channels– Duplication of low-speed O/E/O, buffers, switches– Requires conversion and storage of every bit
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MIT Lincoln LaboratoryPhD Defense-9JPW 6/11/2008
Routers: All-Optical Header Processing
Router functions:– Routing– Forwarding– Contention
resolution– Buffering– Switching
• All-optical payload path:– High-speed optical switching capable of channel-rate processing– Reduce O/E/O conversions (reduce size, weight, and power consumption)– Offers payload transparency for flexible networking
• All-optical packet processing:– Reduce packet processing latencies– Minimize buffering requirements
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MIT Lincoln LaboratoryPhD Defense-10JPW 6/11/2008
The Need for Regeneration
• Linear and nonlinear effects in optical fiber
• Dispersion compensation cancels 2nd order dispersion
• Amplifiers compensate for loss
• Amplitude variation• Pulse shape distortion• Timing jitter (not
simulated)– Due to amplifier and
transmitter noise
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MIT Lincoln LaboratoryPhD Defense-11JPW 6/11/2008
Electronic and Optical Regeneration
• All-optical regenerator– High-speed optical switching capable of channel-rate
processing– Reduce O/E/O conversions – Size, weight, power improvements
Re-AmplifyRe-TimeRe-ShapeRe-Polarize
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MIT Lincoln LaboratoryPhD Defense-12JPW 6/11/2008
Challenges for All-Optical Signal Processing
• Challenges– Electronic technology more mature and offers more
functionality than optical switches
– Optical switches still costly compared with electronic techniques
• This thesis– Demonstrate increased functionality for all-optical
processing
– Improve practicality of all-optical logic gates
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MIT Lincoln LaboratoryPhD Defense-13JPW 6/11/2008
Outline
• Motivation/Background
• Ultrafast all-optical logic gates
• Routing: 40-Gb/s all-optical header processing
• Performance optimization of optical logic gates
• Regeneration
• Future SOA-MZI gates
• Conclusion
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MIT Lincoln LaboratoryPhD Defense-14JPW 6/11/2008
Ultrafast Interferometric All-Optical Switching
• Semiconductor optical amplifier– Strong nonlinearity (~10-12 cm2/W)– Slow recovery time (~ 100 ps)– Potential for integration
(semiconductor processes)• Quantum dot SOA
– Fast recovery time (~10 ps)– Strong nonlinearity?
• Fiber– Weak nonlinearity (10-16 cm2/W)– Fast response (~fs)– No integration – long lengths
required• Photonic crystal fiber, highly
nonlinear fiber– Fast, strong nonlinearity– Integration potential?
• Interferometric switch: change index of refraction (phase)
• Ultrafast performance• Spatial switching
NonlinearMedium
control
signal LinearMedium
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MIT Lincoln LaboratoryPhD Defense-15JPW 6/11/2008
SOA Operation
InP
p-InP
n-InPInGaAsP
Injected current
• Interaction of optical waves with SOA carriers – Stimulated recombination of electrons and holes creates gain– Optical waves change carrier distribution– Changes gain and index of refraction optical switching
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MIT Lincoln LaboratoryPhD Defense-16JPW 6/11/2008
SOA Operation
• Interaction of optical waves with SOA carriers – Stimulated recombination of electrons and holes creates gain– Optical waves change carrier distribution– Changes gain and index of refraction optical switching
• How does the incident light affect the carrier density?– Phenomenological model– Focus on time scales ~ 10 ps (100 Gb/s)
InP
p-InP
n-InPInGaAsP
Injected current
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MIT Lincoln LaboratoryPhD Defense-17JPW 6/11/2008
A Phenomenological Model
,)( 22 ENNaNqVIND
tN o
c ωτ h
−−−+∇=
∂∂
Rate equation describing carrier evolution
Key assumptions: ( )gainindex
gain⋅=−=
αoNNa
Carrier diffusion
Current injection
Spontaneousrecombination
Stimulatedrecombination
zIV = volumeN = carrier density
E
G. P. Agrawal and N. A. Olsson, IEEE J. Quantum Electronics, 25 (11), 1989.
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MIT Lincoln LaboratoryPhD Defense-18JPW 6/11/2008
A Phenomenological Model
,)( 22 ENNaNqVIND
tN o
c ωτ h
−−−+∇=
∂∂
,02
2
22 =
∂∂
−∇tE
cE ε
( ) ( )oo
o
NNaicnN
Nn
−⋅+−=
+=
αω
χ
χε
)(
)(
Rate equation describing carrier evolution
Wave equation describing optical propagation
Key assumptions: ( )gainindex
gain⋅=−=
αoNNa
Backgroundindex
Gain/Loss
Index of refraction
zIV = volumeN = carrier density
E
G. P. Agrawal and N. A. Olsson, IEEE J. Quantum Electronics, 25 (11), 1989.
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MIT Lincoln LaboratoryPhD Defense-19JPW 6/11/2008
A Phenomenological Model
,)( 22 ENNaNqVIND
tN o
c ωτ h
−−−+∇=
∂∂
,02
2
22 =
∂∂
−∇tE
cE ε
( ) ( )oo
o
NNaicnN
Nn
−⋅+−=
+=
αω
χ
χε
)(
)(
( )
)(21)()(
)()(
1)()()(
),()(
)(
)(
0
ταττ
ττ
ττ
τττ
ττ
τ
τ
h
ePP
eE
PhLgh
dzzgh
inout
hinout
h
sat
in
c
o
L
−Φ=Φ
=
−−−
=∂
∂
= ∫
Rate equation describing carrier evolution
Wave equation describing optical propagation
Coupled equations describing gain evolution,optical pulse amplitude and phase propagation
Key assumptions: ( )gainindex
gain⋅=−=
αoNNa zI
V = volumeN = carrier densityh(τ) = integrated gain
E
G. P. Agrawal and N. A. Olsson, IEEE J. Quantum Electronics, 25 (11), 1989.
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MIT Lincoln LaboratoryPhD Defense-20JPW 6/11/2008
A Phenomenological Model
,)( 22 ENNaNqVIND
tN o
c ωτ h
−−−+∇=
∂∂
,02
2
22 =
∂∂
−∇tE
cE ε
( ) ( )oo
o
NNaicnN
Nn
−⋅+−=
+=
αω
χ
χε
)(
)(
( )
)(21)()(
)()(
1)()()(
),()(
)(
)(
0
ταττ
ττ
ττ
τττ
ττ
τ
τ
h
ePP
eE
PhLgh
dzzgh
inout
hinout
h
sat
in
c
o
L
−Φ=Φ
=
−−−
=∂
∂
= ∫
Rate equation describing carrier evolution
Wave equation describing optical propagation
Coupled equations describing gain evolution,optical pulse amplitude and phase propagation
Key assumptions: ( )gainindex
gain⋅=−=
αoNNa
• Gain saturates and recovers• Phase ∝ gain
zIV = volumeN = carrier densityh(τ) = integrated gain
E
G. P. Agrawal and N. A. Olsson, IEEE J. Quantum Electronics, 25 (11), 1989.
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MIT Lincoln LaboratoryPhD Defense-21JPW 6/11/2008
Carrier Recovery Time Limitation
• Long carrier recovery time creates pulse patterning• Limits switching speed to ~10 Gb/s• Solution: balanced interferometer approach
• 2-ps pulses, 40 Gb/s• 5 fJ input pulse energy
• τc = 80 ps• Initial gain: 30 dB• L = 1 mm• Esat = 1 pJ• α = 5
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MIT Lincoln LaboratoryPhD Defense-22JPW 6/11/2008
Balanced Interferometer Design
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MIT Lincoln LaboratoryPhD Defense-23JPW 6/11/2008
Balanced Interferometer Design
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MIT Lincoln LaboratoryPhD Defense-24JPW 6/11/2008
Balanced Interferometer Design
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MIT Lincoln LaboratoryPhD Defense-25JPW 6/11/2008
Balanced Interferometer Design
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MIT Lincoln LaboratoryPhD Defense-26JPW 6/11/2008
Balanced Interferometer Design
slow carrier recoverycancels
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MIT Lincoln LaboratoryPhD Defense-27JPW 6/11/2008
Balanced Interferometer Design
slow carrier recoverycancels
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MIT Lincoln LaboratoryPhD Defense-28JPW 6/11/2008
Balanced Interferometer Design
slow carrier recoverycancels
Non-inverting
S
C
S
C
Inverting
S • C S • C
2-ps signal and control pulses 2-ps signal and control pulses
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MIT Lincoln LaboratoryPhD Defense-29JPW 6/11/2008
Outline
• Motivation/Background
• Ultrafast all-optical logic gates
• Routing: 40-Gb/s all-optical header processing
• Performance optimization of optical logic gates
• Regeneration
• Future SOA-MZI gates
• Conclusion
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MIT Lincoln LaboratoryPhD Defense-30JPW 6/11/2008
40-Gb/s All-Optical Header Processing
• Goal: Demonstrate ultrafast packet processing functionality for routing
• Previous work*:– Ultrafast all-optical header processing of single packets– Applicable to add/drop nodes, ring networks
• This work:– Multi-packet all-optical header processing demonstration– Scalable topology: can be easily extended to larger switches– Applicable to wide variety of networks, including multi-
degree mesh nodes– Increased packet processing functionality
*Cardakli et al. (2000), Glesk et al. (1994), Cotter et al. (1995), Hamilton et al. (2002), Ramos et al. (2005).
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MIT Lincoln LaboratoryPhD Defense-31JPW 6/11/2008
Header Processing Logic
Ek = Empty/Full bitAk = Address bit
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MIT Lincoln LaboratoryPhD Defense-32JPW 6/11/2008
Header Processing Logic
00 10 11 01
00
10
11
01
A1A2
E1E2
X X X X
0 1 1 0
X 1 X 0
1 1 0 0
Ek = Empty/Full bitAk = Address bit
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MIT Lincoln LaboratoryPhD Defense-33JPW 6/11/2008
Header Processing Logic
00 10 11 01
00
10
11
01
A1A2
E1E2
X X X X
0 1 1 0
X 1 X 0
1 1 0 0
Ek = Empty/Full bitAk = Address bit
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MIT Lincoln LaboratoryPhD Defense-34JPW 6/11/2008
Header Processing Logic
00 10 11 01
00
10
11
01
A1A2
E1E2
X X X X
0 1 1 0
X 1 X 0
1 1 0 0
Ek = Empty/Full bitAk = Address bit
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MIT Lincoln LaboratoryPhD Defense-35JPW 6/11/2008
Header Processing Logic
00 10 11 01
00
10
11
01
A1A2
E1E2
X X X X
0 1 1 0
X 1 X 0
1 1 0 0
• Multi-packet processing (2 incoming packets to 2 outgoing ports)• Scalable: 2 optical logic gates for each 2x2 switch• Potential for integration (SOA-based logic)
Ek = Empty/Full bitAk = Address bit
R
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MIT Lincoln LaboratoryPhD Defense-36JPW 6/11/2008
Optical Logic Gate Implementation: Ultrafast Nonlinear Interferometer (UNI)
12”
N. S. Patel, K. L. Hall, and K. A. Rauschenbach, Optics Letters, 21 (18), 1996.
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MIT Lincoln LaboratoryPhD Defense-37JPW 6/11/2008
Optical Logic Gate Implementation: Ultrafast Nonlinear Interferometer (UNI)
12”
N. S. Patel, K. L. Hall, and K. A. Rauschenbach, Optics Letters, 21 (18), 1996.
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MIT Lincoln LaboratoryPhD Defense-38JPW 6/11/2008
Full System Experimental Schematic
• Packet Architecture– 27-1 PRBS
2-ps
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MIT Lincoln LaboratoryPhD Defense-39JPW 6/11/2008
Full System Experimental Schematic
• Packet Architecture– 27-1 PRBS– 4000 bits/packet– 100 ns packet
address bit
packet data
2-ps
2-ps
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MIT Lincoln LaboratoryPhD Defense-40JPW 6/11/2008
Full System Experimental Schematic
address bit
packet data
• Packet Architecture– 27-1 PRBS– 4000 bits/packet– 100 ns packet
2-ps
2-ps
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MIT Lincoln LaboratoryPhD Defense-41JPW 6/11/2008
Ultrafast All-Optical Header Processor
• Ultrafast operation: Header error rate of 1x10-6 with 40-Gbit/s line rate• Comparable with current electronic router error rates• Low switching-energy: 60.5 fJ/packet
PER 1.7x10-9
PER 3x10-9Am
plitu
de
J. Wang et al., “Demonstration of 40-Gb/s Packet Routing Using All-Optical Header Processing”, IEEE Photonics Technology Letters, 18 (21), 2006.
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MIT Lincoln LaboratoryPhD Defense-42JPW 6/11/2008
The Need For Integration
• Successful demonstration of 2-port forwarding using discrete all-optical logic gates.
• What is required to expand this functionality? – Integration: Discrete logic gates are
infeasible for practical implementation• Size, weight, cost
• Ease of installation & operation
– Simple method for optimizing each logic gate for optimal performance
• Currently requires time-intensive search overa large parameter space
12”
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MIT Lincoln LaboratoryPhD Defense-43JPW 6/11/2008
Outline
• Motivation/Background
• Ultrafast all-optical logic gates
• Routing: 40-Gb/s all-optical header processing
• Performance optimization of optical logic gates
• Regeneration
• Future SOA-MZI gates
• Conclusion
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MIT Lincoln LaboratoryPhD Defense-44JPW 6/11/2008
SOA Mach-Zehnder Interferometer: An Integrated Optical Logic Gate
• Integrated optical logic gate: SOA-MZI
• Conceptually similar to the UNI: balanced interferometer
• Waveguide and coupling losses require amplifying SOAs
• Complex parameter space makes optimization difficult
Developed by Alphion Corporation.
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MIT Lincoln LaboratoryPhD Defense-45JPW 6/11/2008
SOA Mach-Zehnder Interferometer: An Integrated Optical Logic Gate
• Focus on single-ended operation to observe SOA dynamics• Key operating parameters
– I4, I5– Signal and control average power
– Signal and control pulse power– Signal-control delay (Δt)
Developed by Alphion Corporation.
Static interferometer bias
Switching dynamics
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MIT Lincoln LaboratoryPhD Defense-46JPW 6/11/2008
• Bias map measurement:− Sweep I4 current at 1 Hz
• Measure current on SOA using hall-effect probe− Measure output power on oscilloscope− Full 2D scan taken on the order of minutes
Static Interferometer Bias Map
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MIT Lincoln LaboratoryPhD Defense-47JPW 6/11/2008
• Bias map measurement:− Sweep I4 current at 1 Hz
• Measure current on SOA using hall-effect probe− Measure output power on oscilloscope− Full 2D scan taken on the order of minutes
Static Interferometer Bias Map
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MIT Lincoln LaboratoryPhD Defense-48JPW 6/11/2008
• Bias map measurement:− Sweep I4 current at 1 Hz
• Measure current on SOA using hall-effect probe− Measure output power on oscilloscope− Full 2D scan taken on the order of minutes
Static Interferometer Bias Map
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MIT Lincoln LaboratoryPhD Defense-49JPW 6/11/2008
• Bias map measurement:− Sweep I4 current at 1 Hz
• Measure current on SOA using hall-effect probe− Measure output power on oscilloscope− Full 2D scan taken on the order of minutes
Static Interferometer Bias Map
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MIT Lincoln LaboratoryPhD Defense-50JPW 6/11/2008
Switching Window Measurement
• Fix current bias (I4, I5)• Measure average output power at every control-signal delay
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MIT Lincoln LaboratoryPhD Defense-51JPW 6/11/2008
Switching Window Measurement
• Fix current bias (I4, I5)• Measure average output power at every control-signal delay
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MIT Lincoln LaboratoryPhD Defense-52JPW 6/11/2008
Switching Window Measurement
• Fix current bias (I4, I5)• Measure average output power at every control-signal delay
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MIT Lincoln LaboratoryPhD Defense-53JPW 6/11/2008
Switching Window Measurement
• Fix current bias (I4, I5)• Measure average output power at every control-signal delay
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MIT Lincoln LaboratoryPhD Defense-54JPW 6/11/2008
Switching Window Measurement
• Fix current bias (I4, I5)• Measure average output power at every control-signal delay• Continuous measurement can be obtained using a difference-
frequency technique
B. Robinson, MIT PhD Thesis, 2003
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MIT Lincoln LaboratoryPhD Defense-55JPW 6/11/2008
Switching Window Measurement
• Fix current bias (I4, I5)• Measure average output power at every control-signal delay• Continuous measurement can be obtained using a difference-
frequency technique• Switching dynamics
• Extinction, Recovery timeB. Robinson, MIT PhD Thesis, 2003
Extinction
Recovery time
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MIT Lincoln LaboratoryPhD Defense-56JPW 6/11/2008
Combined Measurement: Dynamic Bias Scan
• Simultaneous pump-probe measurement at all bias points− At each signal delay, measure a bias map
MLFL = mode-locked fiber laser
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MIT Lincoln LaboratoryPhD Defense-57JPW 6/11/2008
Dynamic Pump-Probe Bias Scan
• Simultaneous pump-probe measurement at all bias points− At each signal delay, measure a bias map
• Measures the effect of optical control pulse on interferometer bias at all operating points: 4-dimensional plot
J. Wang et al., “A Performance Optimization Method for SOA-MZI Devices”, OFC 2007.
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MIT Lincoln LaboratoryPhD Defense-58JPW 6/11/2008
Dynamic Bias Scan
J. Wang et al., “A Performance Optimization Method for SOA-MZI Devices”, OFC 2007.
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MIT Lincoln LaboratoryPhD Defense-59JPW 6/11/2008
• Extinction map: Extract extinction measurement from dynamic bias scan• Inverting mode gives higher extinction, but logic functions often require
non-inverting operation
Extinction Map
Non-inverting operation
Invertingoperation
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MIT Lincoln LaboratoryPhD Defense-60JPW 6/11/2008
• Demonstration of effectiveness of dynamic bias map: wavelength conversion
Wavelength Conversion at Selected Operating Point
I4 = 905.5 mA
I5 = 476.6 mA
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MIT Lincoln LaboratoryPhD Defense-61JPW 6/11/2008
Wavelength Conversion at Selected Operating Point
I4 = 905.5 mA
I5 = 476.6 mA
• Demonstration of effectiveness of dynamic bias map: wavelength conversion
• Compare with nearby operating point found by typical manual optimization
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MIT Lincoln LaboratoryPhD Defense-62JPW 6/11/2008
Wavelength Conversion at Selected Operating Point
I4 = 905.5 mA
I5 = 476.6 mA
Achievements:• Highly accurate characterization technique for optimization of ultrafast
switch performance• Improves practical, multi-gate functionality of integrated optical logic
J. Wang et al., “Efficient performance optimization for SOA-MZI devices”, Optics Express 16 (5), 2008.
• Demonstration of effectiveness of dynamic bias map: wavelength conversion
• Compare with nearby operating point found by typical manual optimization
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MIT Lincoln LaboratoryPhD Defense-63JPW 6/11/2008
Outline
• Motivation/Background
• Ultrafast all-optical logic gates
• Routing: 40-Gb/s all-optical header processing
• Performance optimization of optical logic gates
• Regeneration
• Future SOA-MZI gates
• Conclusion
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MIT Lincoln LaboratoryPhD Defense-64JPW 6/11/2008
10,000-km, 100-pass All-Optical Regeneration
• Goal: Demonstrate all-optical error-free regeneration with the SOA-MZI logic gate
• Previous work*:– Error-free regeneration with paired SOA-MZI logic gates
(inverting operation)
• This work:– Wavelength-maintaining regenerator– Non-inverting operation (requires only a single logic gate)– Polarization insensitive
* Z. Zhu et al., IEEE Photonics Technology Letters 18 (5), 2006.
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MIT Lincoln LaboratoryPhD Defense-65JPW 6/11/2008
100-km Recirculating Loop Experiment
• Simulates regenerator performance in real-world system• Tests SOA-MZI in cascading operation• Dispersion compensation cancels 2nd order dispersion• 10 Gb/s, 231-1 pseudo-random bit sequence
S. J. Savage, “200-pass Picosecond Pulse Transmission through a Regenerative Recirculating Fiber Loop”, CLEO 2006.
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MIT Lincoln LaboratoryPhD Defense-66JPW 6/11/2008
100-km Recirculating Loop Experiment
• Wavelength converter + SOA-MZI = wavelength-maintaining regenerator • Single SOA-MZI regenerator, non-inverting operation• Optimal operating point found via dynamic bias map• Very stable regenerator operation
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MIT Lincoln LaboratoryPhD Defense-67JPW 6/11/2008
Regenerator Results: Cross-Correlation and BER
• Cross-correlation & BER measured after regenerator• 0.5-dB penalty after 100 passes (10,000 km)
J.P. Wang, et al., “Regeneration using an SOA-MZI in a 100-pass 10,000-km Recirculating Fiber Loop,” CLEO 2007.
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MIT Lincoln LaboratoryPhD Defense-68JPW 6/11/2008
Thus Far...
• Electronic techniques rapidly outgrowing size, weight, power limitations
• Optical signal processing techniques can help:– Ultrafast, multi-packet header processing
• Scalable• Low switching energy• Network flexibility from payload transparency• Reduced O/E/O conversions
– Practical, easily optimized integrated logic gates• Accurate, fast optimization• Insight into switching dynamics
– Cascadable, single-gate wavelength-maintaining regeneration• Polarization insensitive• Potential for integration• 10,000-km, 100 pass demonstration
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MIT Lincoln LaboratoryPhD Defense-69JPW 6/11/2008
Outline
• Motivation/Background
• Ultrafast all-optical logic gates
• Routing: 40-Gb/s all-optical header processing
• Performance optimization of optical logic gates
• Regeneration
• Future SOA-MZI gates: What’s next?
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MIT Lincoln LaboratoryPhD Defense-70JPW 6/11/2008
Integration Platforms
• Hybrid Integration– Incompatible materials
integrated on a wafer– Passive material: silicon,
silica– Active material: InGaAsP (III-V
semiconductors)– Challenge: Alignment and
fabrication cost
• Monolithic integration– Compatible materials grown
together for both active and passive devices
– Challenge:• Silicon: active devices• InGaAsP: low loss
– Challenge: high yields
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MIT Lincoln LaboratoryPhD Defense-71JPW 6/11/2008
• Asymmetric twin waveguide approach
Integration Platforms
• Hybrid Integration– Incompatible materials
integrated on a wafer– Passive material: silicon,
silica– Active material: InGaAsP (III-V
semiconductors)– Challenge: Alignment and
fabrication cost
• Monolithic integration– Compatible materials grown
together for both active and passive devices
– Challenge:• Silicon: active devices• InGaAsP: low loss
– Challenge: high yields
• Potential for close to 100% coupling
• Potential for high yield• Tolerance for fabrication errors
• Collaboration with MIT Integrated Photonics Devices and Materials group
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MIT Lincoln LaboratoryPhD Defense-72JPW 6/11/2008
Multi-gate Integrated Optical Logic
• Previous work:– Simulation and design of SOA-MZI gates (A. Markina)– Fabrication of 1st and 2nd generation logic chips (R. Williams)
• This work:– Characterization of 2nd generation logic chip– Recommendations for next generation integrated chips
• Future work:– Fabrication and design of 3rd generation chips (T. Shih)
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MIT Lincoln LaboratoryPhD Defense-73JPW 6/11/2008
Integration Progress: Size, Power
12”1”
1 logic gate 1 logic gate Multiple logic gates
Characterization results:• Demonstrated SOA gain, active/passive coupling• Loss is currently an issue• Fabrication improvements will solve these issues
Enable complex logic on a single chip
0.4”
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MIT Lincoln LaboratoryPhD Defense-74JPW 6/11/2008
Conclusion
• Demonstrated functionality of all-optical signal processing in routing and regeneration
– 40 Gb/s multi-packet header-processing
– 10,000-km, 100-pass error free regeneration
• Addressed practical implementation of all-optical signal processing
– Developed a simple optimization technique for all-optical logic gate performance
– Demonstrated potential of asymmetric waveguide design for integrated multi-gate logic on a single chip
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MIT Lincoln LaboratoryPhD Defense-75JPW 6/11/2008
Acknowledgements
• Professor Erich Ippen• Scott Hamilton• Professor Rajeev Ram
Lincoln Laboratory• Bryan Robinson• Shelby Savage• Claudia Fennelly• Paul Juodawlkis• Jason Plant• Reuel Swint• Todd Ulmer• Neal Spellmeyer• Matthew Grein• Jeffrey Roth• David Caplan• Mark Stevens• Don Boroson• William Keicher
MIT• Professor Leslie Kolodziejski• Gale Petrich• Ta-Ming Shih• Ryan Williams (graduated)• Aleksandra Markina (graduated)• Tauhid Zaman• Ali Motamedi• Reja Amatya
Alphion Corporation• Boris Stefanov• Leo Spiekman• Hongsheng Wang• Ruomei Mu
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MIT Lincoln LaboratoryPhD Defense-76JPW 6/11/2008
Rough Power Comparison
Electronic 3R Regenerator*• Total power: 10W • 2 channels• 2.5 Gb/s per channel• 40 Gb/s
– 8 modules– 80 W
• 100 Gb/s– 20 modules– 200 W
Optical 3R Regenerator• 1 optical logic gate• 1 channel• Bias power: 600 mW
– 2 SOAs– 200 mA x 1.5 V = 300 mW per
SOA• Switching energy: 40 fJ/bit
– 40 Gb/s: 1.6 mW– 100 Gb/s: 4 mW
• 40 Gb/s– 1 switch– 600 mW
• 100 Gb/s– 1 switch– 600 mW* Cisco WDM Transponder
negligible
But electronic regenerator offers more functionality than just 3R regeneration!
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MIT Lincoln LaboratoryPhD Defense-77JPW 6/11/2008
Power Consumption Shortfall
G. Epps, Cisco Routing Research Symposium (2006).
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MIT Lincoln LaboratoryPhD Defense-78JPW 6/11/2008
Commercial Electronic Routers
Juniper T1600
3 ft
18 "2.5 ft
Throughput: 1.6 Tb/sPower: 9.1 kWWeight: 680 lb.
Cisco CSR-1
7 ft
Throughput: 1.2 Tb/sPower: 10.9 kWWeight: 1595 lb.
2 ft
3 ft
Power Consumption Allocation by Subsystems* (%)
SP1%
CPU9%
Routing Engine61%
Fabric11%
Misc.3%
Power Conv15%
* Data from G. Epps, Cisco Routing Research Symposium (2006).