silicon photonics and the data- centric datacenter · l. zhou et al. “towards athermal...
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© Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice. Confidentiality label goes here
Silicon photonics and the data-centric datacenter
Marco Fiorentino, HP LabsDate: 04/15/2011
© Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice. Confidentiality label goes here
Google (2009)
“In the last 7 years online data increased 56 times”
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Data-centric computing
• Data grows faster than computation
• Data-centric workloads
• From performance to efficiency
• Scalability
3
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4
Optical interconnects
$$$¢
100 101 103 104 105 10610-110-210-3
Distance (m)
Cost pressure
State of the art
Advantages
More bits per “wire” Less power per bit Better signal integrity
© Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice. Confidentiality label goes here
Outline
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• Architectures
• Devices• Waveguides• Modulators• Detectors• Lasers
R. G. Beausoleil “Large-Scale Integrated Photonics forHigh-Performance Interconnects,” to be published in ACM Transactions on Computational Logic
© Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice. Confidentiality label goes here
Architectures
6
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Network-on-Chip link topologies
Point-to-point
Sun/Oracle, MIT
Switched network
Cornell
Broadcast bus
Cornell, Northwestern
Multiple sender single receiver
HP
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MIT Local mesh to global switchArchitecture example 1
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− Point-to-point plus passive mesh− DRAM-centric architecture− 20W power envelope (network)− 10x improvement over electrical
Batten 2009
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HP CoronaArchitecture example 2
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Opticalhub
Arbitration
2 fixed drop filters
64 variable drop filters/detectors
L1-I
Core 0
Core 1
Core 2
Core 3
L1-D
L1-D
L1-I
L1-I
L1-D
L1-D
L1-I
L1 ↔
L2
Inte
rface
Hub
MC
NI
Through Silicon Via Array
Directory
L1 ↔
L2
Inte
rface
My
X-b
ar
Con
nect
ion
Pee
r X-b
ar
Con
nect
ionL2
Cache
Data&
Control
ModulatorsModulators
ModulatorsModulators
Modulators
Modulators
ModulatorsModulators
Modulators
Detectors
0123
N-1
NN+1
616263
4-waveguidebundles
Broadcast
Modulators Detectors
Splitters
Off-Chip
Modulators Detectors
Splitters
Fiber I/O’s to OCMs or Network
Package
Memory Controller/Directory/L2 Die
Processor/L1 Die
Analog Electronics Die
Optical DiepgcTSVs
Face to Face Bonds
Heat Sink
Laser
pgcTSVs
sTSVs
− Multiple-sender single-receiver links− 1 byte/flop on chip and to memory− 250W power envelope (compute + network)− 20x improvement over electrical
Vanatrease 2009
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HP HyperXArchitecture example 3
•Crossbar used in high-radix switches
•Switch enables high connectivity topology
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Optical Data Crossbar128 channels
inpu
t buf
fer
& ro
utin
g
inpu
t buf
fer
& ro
utin
g
inpu
t buf
fer
& ro
utin
g
inpu
t buf
fer
& ro
utin
g
outp
utbu
ffer
outp
utbu
ffer
outp
utbu
ffer
outp
utbu
ffer
….. 128 ….
….. 128 ….
Ahn 2009
© Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice. Confidentiality label goes here
Technology requirements
•DWDM: bandwidth density
•Silicon photonics: cost and scalability
•Ring resonators: technology of choice
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SiGe Doped
Modulator OFF Modulator ON Switch Detector
III-V
Laser
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Devices
12
© Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice. Confidentiality label goes here
Low-loss waveguides
Cladding
Core
Substrate
Cladding
Core
Substrate
Silicon wire
Loss 1 dB/cm
Rib waveguide
Loss 0.2 dB/cm
Cladding
Substrate
Slot
Slot waveguide
Loss 6.5 dB/cm
SWG waveguide
Loss 2.1 dB/cm (Bock 2010)
© Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice. Confidentiality label goes here
Modulation mechanisms
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Carrier injection
Cornell, HP
Carrier depletion
Sandia, Kotura
Carrier accumulation
Lightwire
Electro-optic polymer
Intel
metal metal
EO polymer
© Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice. Confidentiality label goes here
HP modulators results
10 μm silicon ring resonators
Results• 45 fJ/bit• 6 Gbps modulation (with pre-emphasis)
0
0.2
0.4
0.6
0.8
1
1.2
1318.3 1318.5 1318.7 1318.9
Nor
maliz
ed in
tens
ity
Wavelength (nm)
0V
1.1V
ON
OFF
Eye diagram NRZ 6 Gbps CW tuning
E-beam litho Photolitho
© Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice. Confidentiality label goes here
A detectors’ menagerie
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Intel Yin2007Vertical Ge PIN on rib WG BW 31 GHz
CEA-LETI & Paris Vivien2007Vertical Ge PIN coupled to wire BW 42 GHz
Lincoln Lab Geis2009Damaged silicon detector BW 35 GHz
Damaged silicon
n p
A*STAR Wang2008Horizontal Ge PIN BW 18 GHz
© Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice. Confidentiality label goes here
Laser: integrated vs. external
Integrated laser• The contenders
• Bonded lasers (UCSB, Intel, Ghent)• Germanium laser (MIT)• III-V grown on Si (Michigan)
• Pro• Less packaging• Cheaper
• Cons• Thermal issues• Fabrication issues
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External laser• The contenders
• Telecom grade commercial lasers• Quantum dot (Innolume)• Modulated (UC Davis)
• Pro• Power and thermal independent• Established technology
• Cons• Complexity• Cost
Van Campenhout 2008Zhou 2009
© Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice. Confidentiality label goes here
Integrated laser example: HP
• Idea: Hybrid Si/III-V laser with 12.5 Gb/s data rate• Wafer bonding + self-aligned process
• Results• 2.5 mW output, • < 4 mA min threshold• 5 GHz BW achieved, 10–12.5 GHz expected
• Future directions• Integration• Silicon on diamond
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CWDM optical engine
Cost ~ Area ~ 0.015 mm2
Power ~ 2 pJ/bit
Hybridmicrorings
Liang 2010
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External laser example: Innolume
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• Idea: quantum dot FP laser• MBE grown
• Results• 80 Ghz spacing• 8 lines• >-10dBm per line• Low RIN (-110 dB/Hz)
• Future directions• Add wavelengths
Wojcik 2009
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Open problems and future directions
Work to be done• Integration
• How do we put it all together?
• Co-design• Drivers and receivers
• Fabrication• What happens if we try to build 1000s of devices on a chip?
• Power consumption and thermal
…and most importantly• Business case• Solution roadmap• Supplier ecosystem
20
© Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice. Confidentiality label goes here
Thank you
© Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice. Confidentiality label goes here
BibliographyReview paperR. G. Beausoleil “Large-Scale Integrated Photonics for High-Performance Interconnects,” to be published in ACM Transactions on Computational LogicArchitectureC. Batten et al. “Building many-core processor-to-DRAM networks with monolithic CMOS silicon photonics,” IEEE Micro 29 8 (2009).D. Vantrease et al. “Corona: System implications of emerging nanophotonic technology,” In Proceedings of the 35th International Symposium on Computer Architecture (2009) 153A. V. Krishnamoorthy et al.“Computer Systems Based on Silicon Photonic Interconnects,” In Proceedings of the IEEE 97 p.1337 (2009)N. Kirman et al.“On-chip optical technology in future bus-based multicore designs,” IEEE Micro 27 56 (2007)Y. Pan et al. “Firefly: Illuminating Future Network-on-Chip with Nanophotonics,” In Proceedings of the 36th International Symposium on Computer Architecture (2010) 429K. Bergman et al. “Power effiecient photonic networks on-chip,” In Proc. Soc. Photo-Opt. Instrum. Eng. 6898 689813 (2008)J. H. Ahn et al.“HyperX: topology, routing, and packaging of efficient large-scale networks,” In Proceedings of the Conference on High Performance Computing Networking, Storage and Analysis (SC). ACM 1 (2009)WaveguidesR. Ding et al. “Low-loss strip-loaded slot waveguides in Silicon-on-Insulator,” Opt. Express 18 25062 (2010)P. J. Bock et al. “Subwavelength grating crossings for silicon wire waveguides,” Opt. Express 18 16146 (2010)M. Gnan “Fabrication of low-loss photonic wires in silicon-on-insulator using hydrogen silsesquioxane electron-beam resist,” Electron. Lett. 44 115 (2008)U. Fischer ”0.1 dB/cm waveguide losses in single-mode SOI rib waveguides,” IEEE Photon. Technol. Lett. 8 647 (1996)ModulatorsQ. Xu “Micrometre-scale silicon electro-optic modulator,” Nature 435 (2005) 325M. Watts “ Low-voltage, compact, depletion-mode, silicon Mach-Zehnder modulator, ” IEEE J. Select. Topics Quantum Electron. 16 159 (2010)D. D'Andrea “CMOS photonics today & tomorrow,” In Proceedings of the Optical Fiber Communication Conference (OFC) (2009)B.A. Block et al. “Electro-optic polymer cladding ring resonator modulators” Opt. Express 16 18326 (2008)
© Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice. Confidentiality label goes here
Bibliography (continued)DetectorsM. W. Geis et al. "Silicon waveguide infrared photodiodes with >35 GHz bandwidth and phototransistors with 50 AW-1 response," Opt. Express 17, 5193 (2009) J. Wang et al. “Low-voltage high-speed (18 GHz/V) evanescent-coupled thin-lm-Ge lateral PIN photodetectors integrated on Si waveguide,” 20, 1485 (2008)T. Yin et al. "31 GHz Ge n-i-p waveguide photodetectors on Silicon-on-Insulator substrate," Opt. Express 15, 13965-13971 (2007)L. Viviene et al. "High speed and high responsivity germanium photodetector integrated in a Silicon-On-Insulator microwaveguide," Opt. Express 15, 9843-9848 (2007)LaserL. Zhou et al. “Towards athermal optically-interconnected computing system using slotted silicon microring resonators and RF-photonic comb generation,” Appl. Phys. A 95, 1101 (2009)J. Van Campenhout et al. “Electrically pumped InP-based microdisk lasers integrated with a nanophotonic silicon-on-insulator waveguide circuit” Opt. Express 15, 6744 (2007)Jun Yang et al. "Integration of epitaxially-grown InGaAs/GaAs quantum dot lasers with hydrogenated amorphous silicon waveguides on silicon," Opt. Express 16, 5136 (2008)G. L. Wojcik et al. “A single comb laser source for short reach WDM interconnects,” In Proc. Soc. Photo-Opt. Instrum. Eng. 7230, 723021 (2009)J. Liu et al. "Ge-on-Si laser operating at room temperature," Opt. Lett. 35, 679(2010)D. Liang et al. “Electrically-pumped compact hybrid silicon microring lasers for optical interconnects,” Opt. Express 17, 20355 (2009)