Broadband Silicon Photonic Switch Integrated with CMOS Drive … · 2012-03-24 · Conference on...

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


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


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.


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


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]


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


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


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


§ Metrics for System Bandwidth– Spectral bandwidth

– Transition speed

§ Metrics for Practical Considerations– Temperature dependence

carrier lifetimes

Wavelength-insensitive Mach-Zehnder

50 µm50 µm


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


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


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


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


WIMZ Bandwidth & Crosstalk Maintained For Both Input Ports and Over Large Temperature Range

TT1111TT1212

T = 23°C T = 30°C

T = 50°C


[J. Van Campenhout et al., Optics Express 17 (26) 2009]

TT2121TT2222

TemperatureTemperature

Performance maintained over > 25°C temperature variation


Considerations for CMOS Driver

§ Forward-Biased PIN Diode Modeled by Capacitor

RSERIES I(Q)

C(Q)


§ 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


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



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)


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


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


– 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


Wire-Bonded Electronic/Photonic Circuits

photonicsphotonicschipchip

optical fiber probeoptical fiber probeelectrical probeelectrical probe


CMOSCMOSchipchip

1 mm1 mmoptical fiber probeoptical fiber probe


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]


TT1111

TT2121TT2222

TT1212


CMOS+WIMZ: Transient Performance

~ 0.8 dB ~ 0.8 dB ∆∆∆∆IL

TT1111

Switching Behavior: VIN = PRBS, λλλλ = 1530 nm


TT1111

TT2121TT2222

TT1212Extinction Ratio & Extinction Ratio & Crosstalk >> 15 dBCrosstalk >> 15 dB


CMOS+WIMZ: Transient Performance

OFF ONOFF ON ON OFFON OFF

Transition Times


tt10/9010/90 = 3.9 ns= 3.9 ns tt10/9010/90 = 1.4 ns= 1.4 ns


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


λλλλ RXattλλλλ

preamppreampEDFAEDFA

tunabletunablefilterfilter

tunabletunablefilterfilter

optical optical attenuatorattenuator

highhigh--speedspeedphotophoto--receiverreceiver


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


TT2222 (ON)(ON)

TT1212 (OFF)(OFF)

TT2121 (OFF)(OFF)

10 ps/div10 ps/div


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


1543 nm1543 nm 1550 nm1550 nm

TT2222 (ON)(ON)

TT1212 (OFF)(OFF)

TT2121 (OFF)(OFF)


BB

CMOS+WIMZ: Power and Energy Contributions

Switching Signal: Square-Wave(50% Duty Cycle)

Frequency, f (Hertz)

1/f1/f


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


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


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


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


§ 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.


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


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.


Extra Slides



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×


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]


Optical Spectrum Recorded Following the Booster EDFACMOS+WIMZ: Switching of 160-Gb/s Signal


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