Broadband Silicon Photonic SwitchBroadband Silicon Photonic SwitchIntegrated with CMOS Drive ElectronicsIntegrated with CMOS Drive Electronics
© 2010 IBM Corporation
B. G. LeeB. G. Lee, J. Van Campenhout, A. V. Rylyakov, C. L. Schow, W. M. J. Green,, J. Van Campenhout, A. V. Rylyakov, C. L. Schow, W. M. J. Green,S. Assefa, M. Yang, F. E. Doany, C. V. Jahnes, R. A. John, J. A. Kash, Y. A. VlasovS. Assefa, M. Yang, F. E. Doany, C. V. Jahnes, R. A. John, J. A. Kash, Y. A. VlasovIBM T. J. Watson Research Center
Conference on Lasers and Electro-Optics | May 2010 | San Jose, CA
Outline
§ Optical Interconnects for Computercom– Current Status & Future Technologies
– Optics at the Chip
§ Integration Platform– Targeting Monolithically Integrated CMOS + Photonics
– Initially Demonstrating Hybrid Integration
CThJ1: Broadband Silicon Photonic Switch Integrated with CMOS Drive Electronics2 © 2010 IBM Corporation
– Initially Demonstrating Hybrid Integration
§ Components– Broadband Photonic Switch
– Digital CMOS Driver
§ Integrated Switch & Driver
Conference on Lasers and Electro-Optics | May 2010 | San Jose, CA
Evolution of Optical Interconnects
WAN, MANmetro,long-haul
LANcampus, enterprise
Systemintra/inter-rack
Boardmodule-module
Modulechip-chip
Chipon-chip buses
1980’s 1990’s 2000’sTime of Commercial Deployment (Copper Displacement):
> 2011
CThJ1: Broadband Silicon Photonic Switch Integrated with CMOS Drive Electronics3 © 2010 IBM Corporation
Distance 10’s – 100’s km 100 m – 2 km< 10 m intra< 100 m inter
< 1 m < 10 cm < 2 cm
Density (Gb/s/mm2)
10-3 10 1000
Cost ($/Gb/s)
1000 1 10-5
Power (mW/Gb/s)
500 5 0.5
# of lines 10’s 1M’s100’s 1k’s 10k’s 100k’s
TelecomTelecom DatacomDatacom ComputercomComputercom
Includes WDMand chip-level
optical switching.
Integration requiredto meet cost, power,and density targets.
Conference on Lasers and Electro-Optics | May 2010 | San Jose, CA
Computercom Copper Displacement
IBM Roadrunner (2008)IBM Roadrunner (2008)
[M. Fields, Avago, OFC 2010, paper OTuP1]
IBM Blue Waters (2011)IBM Blue Waters (2011)Current System Implementations
microPODTM paralleloptical TX/RX
Fiber to the RackFiber to the Rack50,000 optical links
Fiber to the ModuleFiber to the Module1,000,000 optical links
CThJ1: Broadband Silicon Photonic Switch Integrated with CMOS Drive Electronics4 © 2010 IBM Corporation
Hub/switch module, with IC and 56 microPODs
Active optical cables plugged into back of switch rack
Node DrawerNode Drawer
[A. Benner, IBM, OFC 2010, paper OTuH1]
Conference on Lasers and Electro-Optics | May 2010 | San Jose, CA
Computercom Copper Displacement
[F. Doany et al., T. Adv. Packaging 2009]Terabus ProgramTerabus Program(Optics on the PCB)(Optics on the PCB)
0.5 Tb/s bisectional BW
Potential Technologies for Increased Integration
CThJ1: Broadband Silicon Photonic Switch Integrated with CMOS Drive Electronics5 © 2010 IBM Corporation
0.5 Tb/s bisectional BW
3D Chip Stack: (top) optical NoC, (center) memory layer, (bottom) processing cores
Advanced PhotonicAdvanced PhotonicSwitch ProgramSwitch Program
(Optics at the Chip)(Optics at the Chip)Targets MonolithicCMOS + Photonics
in 3D Integrated Stack
Conference on Lasers and Electro-Optics | May 2010 | San Jose, CA
Considerations for Photonic Switch Design
§ Metrics for System Scalability– Insertion loss
– Optical crosstalk
– Footprint
– Power/energy consumption
§ Metrics for System Bandwidth
Forward-biased PIN diode
TargetsTargets SolutionsSolutions
Surface-passivated waveguides for enhanced carrier lifetimes
CThJ1: Broadband Silicon Photonic Switch Integrated with CMOS Drive Electronics6 © 2010 IBM Corporation
§ Metrics for System Bandwidth– Spectral bandwidth
– Transition speed
§ Metrics for Practical Considerations– Temperature dependence
carrier lifetimes
Wavelength-insensitive Mach-Zehnder
50 µm50 µm
Conference on Lasers and Electro-Optics | May 2010 | San Jose, CA
WIMZ Provides Large Bandwidth & Low Crosstalk with CMOS-Compatible Drive Voltage
00
Reference MZ
§ Measured with TE-polarized broadband LED and OSA§ Normalized to total OFF-state power in both outputs
0 V 1 V
CThJ1: Broadband Silicon Photonic Switch Integrated with CMOS Drive Electronics7 © 2010 IBM Corporation
1.35 1.4 1.45 1.5 1.55 1.6 1.65-30
-25
-20
-15
-10
-5
0
wavelength (µm)
transm
ittance (d
B)
110 nm
1.35 1.4 1.45 1.5 1.55 1.6 1.65-30
-25
-20
-15
-10
-5
0
wavelength (µm)
transm
ittance (d
B)
30 nm
TT1111TT1212
0 V 1 V
[Van Campenhout et al., Opt. Exp. 17 (26) 2009]
VON = 1 VION = 3.5 mAT = 23 °C
-18 dB
Conference on Lasers and Electro-Optics | May 2010 | San Jose, CA
WIMZ Provides Large Bandwidth & Low Crosstalk with CMOS-Compatible Drive Voltage
0
§ Measured with TE-polarized broadband LED and OSA§ Normalized to total OFF-state power in both outputs
WIMZ
0 V 1 V
CThJ1: Broadband Silicon Photonic Switch Integrated with CMOS Drive Electronics8 © 2010 IBM Corporation
1.35 1.4 1.45 1.5 1.55 1.6 1.65-30
-25
-20
-15
-10
-5
0
wavelength (µm)
transm
ittance (d
B)
110 nm
BW BW (nm)(nm)
XTXTOFFOFF(dB)(dB)
XTXTONON(dB)(dB)
ILILONON(dB)(dB)
WIMZWIMZ 110110 --1818 --2323 0.80.8
MZMZ 3030 --1818 --2121 0.90.9
TT1111TT1212
0 V 1 V
[Van Campenhout et al., Opt. Exp. 17 (26) 2009]
VON = 1 VION = 3.5 mAT = 23 °C
-18 dB
Conference on Lasers and Electro-Optics | May 2010 | San Jose, CA
WIMZ Bandwidth & Crosstalk Maintained For Both Input Ports and Over Large Temperature Range
TT1111TT1212
T = 23°C T = 30°C
T = 50°C
CThJ1: Broadband Silicon Photonic Switch Integrated with CMOS Drive Electronics9 © 2010 IBM Corporation
[J. Van Campenhout et al., Optics Express 17 (26) 2009]
TT2121TT2222
TemperatureTemperature
Performance maintained over > 25°C temperature variation
Conference on Lasers and Electro-Optics | May 2010 | San Jose, CA
Considerations for CMOS Driver
§ Forward-Biased PIN Diode Modeled by Capacitor
RSERIES I(Q)
C(Q)
CThJ1: Broadband Silicon Photonic Switch Integrated with CMOS Drive Electronics10 © 2010 IBM Corporation
§ Forward-Biased PIN Diode Modeled by Capacitor§ Carrier Lifetime is Key
– Trade-off between switching speed and static power consumption
§ Low Series Resistance– Due to long device with large contact area
§ Optimum Driver: Ideal Voltage Source– Low source impedance
– Supplies whatever current is necessary to produce required output voltage
§ Can Be Well-Approximated by Properly Designed CMOS Inverter
Conference on Lasers and Electro-Optics | May 2010 | San Jose, CA
Custom Driver Circuit in Standard Digital 90-nm Bulk CMOS
50 Ω
1 2 5
pMOS (W/L):83 µm / 90 nm
nMOS (W/L):32 µm / 90 nm
166 µm / 90 nm
64 µm / 90 nm
1331 µm / 90 nm
512 µm / 90 nm
CThJ1: Broadband Silicon Photonic Switch Integrated with CMOS Drive Electronics11 © 2010 IBM Corporation
Conference on Lasers and Electro-Optics | May 2010 | San Jose, CA
Custom Driver Circuit in Standard Digital 90-nm Bulk CMOS
50 Ω
1 2 5
Preamp Supply (VPA) Output Stage Supply (VOS)
Input Voltage (VIN)
CThJ1: Broadband Silicon Photonic Switch Integrated with CMOS Drive Electronics12 © 2010 IBM Corporation
VPA = VOS = 0.8 V2 Gb/s
27-1 PRBSinto 50 Ω load
(200 ps/div)(200 mV/div)
CMOS Switching Performance
VPA = VOS = 1.2 V VPA = VOS = 1.6 V
Conference on Lasers and Electro-Optics | May 2010 | San Jose, CA
Interim Value of Hybrid Integration
§ Monolithic Integration– Achieves:
• Power and area reductions• Simplified assembly• Improved yield
– Complex process development required
Lower cost
PhotonicsPhotonicsDesign,Design,
Fabrication,Fabrication,and Testand Test
ElectronicsElectronics
CThJ1: Broadband Silicon Photonic Switch Integrated with CMOS Drive Electronics13 © 2010 IBM Corporation
– Complex process development required
§ Hybrid Integration Can Be Valuable Tool– Shortens iterative design loop
• Allows co-design of photonic and electronic circuits• Maintains independent fabrication processes
– Provides interoperability verification
ElectronicsElectronicsDesign,Design,
Fabrication,Fabrication,and Testand Test
Conference on Lasers and Electro-Optics | May 2010 | San Jose, CA
Wire-Bonded Electronic/Photonic Circuits
photonicsphotonicschipchip
optical fiber probeoptical fiber probeelectrical probeelectrical probe
CThJ1: Broadband Silicon Photonic Switch Integrated with CMOS Drive Electronics14 © 2010 IBM Corporation
CMOSCMOSchipchip
1 mm1 mmoptical fiber probeoptical fiber probe
Conference on Lasers and Electro-Optics | May 2010 | San Jose, CA
CMOS+WIMZ: Static PerformanceVIN = 1.0 V , λλλλ = 1530 nm At VAt VININ = 1 V= 1 VDCDC,,
PPONON = 4.2 mW= 4.2 mW
At VAt VININ = 0 V= 0 VDCDC,,PPOFFOFF = 32 µW= 32 µW
Digital Optical Switch:[J. Van Campenhout et al., CLEO 2010 CPDA12]
CThJ1: Broadband Silicon Photonic Switch Integrated with CMOS Drive Electronics15 © 2010 IBM Corporation
TT1111
TT2121TT2222
TT1212
Conference on Lasers and Electro-Optics | May 2010 | San Jose, CA
CMOS+WIMZ: Transient Performance
~ 0.8 dB ~ 0.8 dB ∆∆∆∆IL
TT1111
Switching Behavior: VIN = PRBS, λλλλ = 1530 nm
CThJ1: Broadband Silicon Photonic Switch Integrated with CMOS Drive Electronics16 © 2010 IBM Corporation
TT1111
TT2121TT2222
TT1212Extinction Ratio & Extinction Ratio & Crosstalk >> 15 dBCrosstalk >> 15 dB
Conference on Lasers and Electro-Optics | May 2010 | San Jose, CA
CMOS+WIMZ: Transient Performance
OFF ONOFF ON ON OFFON OFF
Transition Times
CThJ1: Broadband Silicon Photonic Switch Integrated with CMOS Drive Electronics17 © 2010 IBM Corporation
tt10/9010/90 = 3.9 ns= 3.9 ns tt10/9010/90 = 1.4 ns= 1.4 ns
Conference on Lasers and Electro-Optics | May 2010 | San Jose, CA
spectral spectral decorrelatordecorrelator(1(1--km SMF)km SMF)
boosterboosterEDFAEDFA1531 nm1531 nm
1537 nm1537 nm
1543 nm1543 nm
1549 nm1549 nm
passive passive combinercombiner
4040--Gb/sGb/smodulatormodulator
onon--chip Si 2chip Si 2××2 switch2 switch
Experimental Setup for 4-λλλλ × 40-Gb/s DemonstrationCMOS+WIMZ: Switching of 160-Gb/s Signal
CThJ1: Broadband Silicon Photonic Switch Integrated with CMOS Drive Electronics18 © 2010 IBM Corporation
λλλλ RXattλλλλ
preamppreampEDFAEDFA
tunabletunablefilterfilter
tunabletunablefilterfilter
optical optical attenuatorattenuator
highhigh--speedspeedphotophoto--receiverreceiver
Conference on Lasers and Electro-Optics | May 2010 | San Jose, CA
inputinput
TT1111 (ON)(ON)
1530 nm1530 nm 1537 nm1537 nm 1543 nm1543 nm 1550 nm1550 nmEye Diagrams Recorded with -3 dBm/Channel Average PowerCMOS+WIMZ: Switching of 160-Gb/s Signal
CThJ1: Broadband Silicon Photonic Switch Integrated with CMOS Drive Electronics19 © 2010 IBM Corporation
TT2222 (ON)(ON)
TT1212 (OFF)(OFF)
TT2121 (OFF)(OFF)
10 ps/div10 ps/div
Conference on Lasers and Electro-Optics | May 2010 | San Jose, CA
1530 nm1530 nm 1537 nm1537 nm
inputinput
TT1111 (ON)(ON)
BER Curves Recorded Using a 50-GHz Photo-ReceiverCMOS+WIMZ: Switching of 160-Gb/s Signal
CThJ1: Broadband Silicon Photonic Switch Integrated with CMOS Drive Electronics20 © 2010 IBM Corporation
1543 nm1543 nm 1550 nm1550 nm
TT2222 (ON)(ON)
TT1212 (OFF)(OFF)
TT2121 (OFF)(OFF)
Conference on Lasers and Electro-Optics | May 2010 | San Jose, CA
BB
CMOS+WIMZ: Power and Energy Contributions
Switching Signal: Square-Wave(50% Duty Cycle)
Frequency, f (Hertz)
1/f1/f
CThJ1: Broadband Silicon Photonic Switch Integrated with CMOS Drive Electronics21 © 2010 IBM Corporation
AA
Switching Power: P = Ef = Af + 0.5B
Full-Cycle Transition Energies, A (Joules)
ON-State Static Power, B (Watts)
Energy Per Cycle: E = A + (0.5B)/ f
Conference on Lasers and Electro-Optics | May 2010 | San Jose, CA
VIN = Square Wave with VH = 1 V & VL = 0 V; VOS = VPA = 1.0 V
Energy Energy Per Per
CycleCycle
Static ONStatic ON--State Power State Power
ConsumptionConsumption
PAPA 8.0 pJ 37 µW
OSOS 5.5 pJ 4.0 mW
TotalTotal 13.5 pJ 4.1 mW
CMOS+WIMZ: Ultralow Energy-Per-Bit
Preamp Supply (VPA) Output Stage Supply (VOS)
TotalOutput Stage Supply
CThJ1: Broadband Silicon Photonic Switch Integrated with CMOS Drive Electronics22 © 2010 IBM Corporation
TotalTotal 13.5 pJ 4.1 mW
Example System ParametersExample System Parameters
No. No. λλλλλλλλ 16
∆λ∆λ∆λ∆λ∆λ∆λ∆λ∆λ 6.4 nm
Data RateData Rate 20 Gb/s
Packet DurationPacket Duration 100 ns
Energy Per BitEnergy Per Bit ~ 6 fJ
Output Stage SupplyPreamp Supply
Conference on Lasers and Electro-Optics | May 2010 | San Jose, CA
Integrated Switch/Driver Performance Summary
§ Switch: Wavelength-Insensitive Mach Zehnder• > 100 nm bandwidth
• > 25°C temperature tolerance
• ~ 1 V driving voltage
• < -17 dB crosstalk
§ Driver: 5-Stage Buffer Chain
simultaneouslyachieved
(ELEC. + PHOT.)SingleDevice
16×16Array
CThJ1: Broadband Silicon Photonic Switch Integrated with CMOS Drive Electronics23 © 2010 IBM Corporation
§ Driver: 5-Stage Buffer Chain• delivers low-power operation
• < 50 ps transition times
§ Integrated Switch & Driver• ~ 2 mW average power consumption
• < 4 ns transition times
• 160-Gb/s bandwidth demonstrated withno observable penalty
(ELEC. + PHOT.)Device Array
Area(mm2)
0.02 5
Peak Bandwidth
(Tb/s)0.3 80
Power(mW)
2 500
Assuming example system parameters from previous slide.
Conference on Lasers and Electro-Optics | May 2010 | San Jose, CA
Conclusions
§ We have developed and demonstrated hybrid-integrated electronic and photonic circuits that can form a basis set for future monolithicallyintegrated switch fabrics.– Hybrid integration provides quick turnaround on design and test loop.
– Developed circuits can be included in future monolithic runs.
§ Growing complexity in computercom point-to-point links can be
CThJ1: Broadband Silicon Photonic Switch Integrated with CMOS Drive Electronics24 © 2010 IBM Corporation
The work at IBM has been partially supported by DARPA through the Advanced
Photonic Switch (APS) program.
§ Growing complexity in computercom point-to-point links can be addressed through these resulting monolithic chip-scale optical switch fabrics, which:– Provide dynamic link allocation
– Facilitate WDM encoding formats.
§ Dense optical integration will be requiredto achieve the cost, power, and densitytargets driven by future system demands.
Conference on Lasers and Electro-Optics | May 2010 | San Jose, CA
Extra Slides
CThJ1: Broadband Silicon Photonic Switch Integrated with CMOS Drive Electronics25 © 2010 IBM Corporation
Conference on Lasers and Electro-Optics | May 2010 | San Jose, CA
Carrier Lifetime Tuning Through Surface Passivation
1
102
103
carrier lifetim
e (ns)
vs = 500 cm/s
Si3N4 coated
lifetime can be tuned by over 100×
CThJ1: Broadband Silicon Photonic Switch Integrated with CMOS Drive Electronics26 © 2010 IBM Corporation
0 200 400 600 80010-1
100
101
waveguide width (nm)
carrier lifetim
e (ns)
vs = 40000 cm/s
reference
[Van Campenhout et al., Opt. Lett. 34 (10) 2009]
Conference on Lasers and Electro-Optics | May 2010 | San Jose, CA
Optical Spectrum Recorded Following the Booster EDFACMOS+WIMZ: Switching of 160-Gb/s Signal
CThJ1: Broadband Silicon Photonic Switch Integrated with CMOS Drive Electronics27 © 2010 IBM Corporation