In this slidecast, Brian Welch from Luxtera presents: Silicon Photonics for HPC Interconnects. Luxtera is the first company to overcome the complex technical obstacles involved with integrating high performance optics directly with silicon electronics on a mainstream CMOS chip, bringing direct “fiber to the chip” connectivity to market.

1. Silicon Photonics for HPC Interconnects
Brian Welch
Luxtera
www.luxtera.com

2. Silicon Photonics
• Silicon Photonics Technology:
− Silicon material system and silicon processing techniques to manufacture integrated optical devices
− Passive photonic functions + optical modulation + optical detection (+ electronic circuits)
− Development started in earnest in early 2000s when sub 0.5 micron lithography became available
• Goal of Silicon Photonics:
− Leverage as much as possible from the integrating electronic industry:
o Design infrastructure and methodologies
o Wafer manufacturing and methodologies
o Packaging & Test infrastructure and methodologies
− Enable very high levels of integration:
o Increased functionality and density
o Simplification of optical and electrical packaging & test
• Silicon Photonics Applications:
− Most silicon photonics applications are in the area of high-speed communications
− Also significant efforts emerge in the area of biochemical sensing and sensor applications in general
• Luxtera:
− Produces Silicon Photonics based optical transceivers and chipsets since 2009, those are used in high
performance computing applications and advanced datacenters.
− Developing chipsets and IP for high performance optical transceiver functions (Nx26 G and beyond)
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3. Silicon Photonics Example: 4x28 Gbps Chipset
RX1
RX2
Digital
Core
RX3
RX optical
Inputs
RX4
TX1
TX2
Laser
input
TX optical
Outputs
TX3
TX4
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4. HPC Interconnect Needs
HPC Performance Projection
HPC Interconnect Projection
100,000.00
Bi-Directional Interconnect Throughput (Pbps)
1,000,000.00
100,000
System Performance (Pflops)
1,000,000
10,000
1,000
100
10
1
10,000.00
1,000.00
100.00
10.00
1.00
2010
2015
2020
2025
2030
2010
2015
2020
2025
2030
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5. HPC Interconnect Needs
• HPC performance projected to increase by 10x every 34 years
− Increasing from about 30 Pflops today to over 1 Exaflop by the
end of the decade.
• HPC interconnect performance needs to meet this
trend
− Increasing from about 190 Pbps today to over 5 Ebps by the
end of the decade
• This exponential increases in performance cannot have
commensurate increases in power or cost.
− Contemporary systems already approaching the practical limits
of power
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6. High Speed Optical Interconnect Evolution II
CONTEMPORARY – Today
• Traditional MSA compliant pluggable
modules and AOCs on card edge
• Considerable SI issues (electrical
connectors, long traces on host PCBA)
require re-timers.
• Front panel interconnect density limited
by module size (physical implementation
+ module power dissipation)
Switch ASIC
Re-timer
Optical Module
PCBA
Power dissipation per bidirectional XCVR
(Host + Module): 15 – 20 mW/Gbps
EMERGING – 2014/15
• Embedded optical transceivers located
closer around ASIC
• Shorter traces on PCB alleviate SI issues
• Optical fibers bring IOs to optical
connectors on front panel
• Front panel interconnect density limited
by size optical connectors
• Very high reliability required
Switch ASIC
Embedded
optical module
Fiber
PCBA
Power dissipation per bidirectional XCVR
(Host + Module): 5 – 15 mW/Gbps
STRATEGIC DIRECTION – 2015+
• Optical transceivers co-packaged w/ ASIC
• Minimized electrical interconnect
eliminates SI issues
• Optical fibers bring IOs to optical
connectors on front panel
• Lowest system power dissipation
• Highest front panel density and smallest
potential system form factor
• Very high reliability required
Switch ASIC w/ photonics
Fiber
PCBA
Power dissipation bidirectional XCVR: 0.5 –
2.5 mW/Gbps
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7. HPC ‘like’ Datacenters… (QTS, Suwanee GA)
Systems getting more homogenous, utilizing HPC type silicon photonics interconnects
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8. Silicon Photonics Opportunity
• Speed: Silicon photonics BW practical limitations set by CMOS
node.
− Optical component BW very high compared to electrical components
− Allows HPC interconnects to increase with speed as CMOS improves
• Integration: Integration of silicon photonics ‘Optical I/O’s in
place of electrical I/O’s.
− Allows for significant power and cost reductions through simplification of
system.
− Allows for much higher density than can be realized using discrete optical
interconnects
• Advanced functions: Higher order encoding and improved link
monitoring
− Real time optical diagnostics and data gathering
− Interconnect speeds beyond electronics baud rate
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9. Future Scaling – 100 Gbps Optical Interconnect
100 Gbps Optical Link using Silicon Photonics PAM4 Enconding
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10. Silicon Photonics Community is Growing
• Other Silicon Photonics providers looking to enter
commercial markets:
− Intel: OCP Initiatives
− IBM: Currently in research, product initiative TBD
− Cisco: 100G-LR4 Module for 10km interconnects
− Mellanox: Infiniband interconnects expected
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