silicon photonics and the datacenter -...

© Copyright 2012 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.

Silicon Photonics and the Datacenter

Marco Fiorentino

HP Labs05/19/2015

© Copyright 2012 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.

“In the last 7 years online data increased 56 times”

Google (2009)

© Copyright 2012 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.3

Data-centric computing

Data grows faster than computation

Data-centric workloads

From performance to efficiency

Scalability


HP’s “The Machine”

Electrons

Photons

Ions

Compute

Communicate

Store

http://www.hpl.hp.com/research/systems-research/themachine/


almostSilicon Photonics is here


Optical interconnects

$$$¢

100 103 104 105 10610-110-210-3

Distance (m)

Cost pressure

State of the art

Advantages

More bits per “wire” Less power per bit Better signal integrity

102

New architectures


HP CoronaArchitecture example 1

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


Modulators

Modulators


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

Vantrease, Dana, et al. "Corona: System implications of emerging nanophotonic technology." ACM SIGARCH Computer Architecture News. Vol. 36. No. 3. IEEE Computer Society, 2008.


HP HyperXArchitecture example 2

•Crossbar used in high-radix switches•Switch enables high connectivity topology

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, Jung Ho, et al. "HyperX: topology, routing, and packaging of efficient large-scale networks." Proceedings of the Conference on High Performance Computing Networking, Storage and Analysis. ACM, 2009.


Technology requirements

•DWDM: bandwidth density•Silicon photonics: cost and scalability•Ring resonators: technology of choice

•Packaging evolution

SiGe Doped

Modulator OFF Modulator ON Switch Detector

III-V

Laser

Logic Connector Transceiver Logic TransceiverLogic

Transceiver

Active optical cables On-board In package


1318.6 1318.7 1318.8 1318.9 1319-20

-15

-10

-5

0

Wavelength (nm)

Opt

ical

inte

nsity

(dB)

0V0.86V

Carrier-injection-based microring modulator

• Slow carrier dynamics pre-emphasis equalization

• Sensitive wavelength shifts closed-loop stabilization

ON

OFF

Q > 10,000

18dB

• P-I-N junction low optical loss beneficial for link power budget

• Large change in refractive index high modulation depth beneficial for link power budget

• Adjustable bias current alternative tuning mechanism

(blue-shift)

p+ Si n+ Si

Si substrate

BOX

Metal 1

Metal 2

W-plug

Optical mode

Waveguide


Si Photonics DWDM link

Comb laser• InAs/GaAs quantum-dot Fabry-Perot laser module @ 1.3μm• Multi-channels with 80GHz spacing at operating point• Improved performance at higher temperature• high wall plug efficiency (20%)

Hybrid integration• 1st generation: wirebonding• 2nd generation: flip-chip bonding

Transmitter• Carrier-injection-based microring modulator• Driver with pre-emphasis + thermal & bias tuning

Receiver• Drop filter + Ge waveguide Photodiode (PD)• Self-adaptive data receiver + forward clock

recovery

Multi-λlight source Optical

fiber

CMOSDriver

Tuningcircuitry

Waveguide

Microring

Tx module

Optical coupler

CMOSReceiver

PD

Rx module


Prototype 5-channel transceiver

Tx: 5 microring modulators + integrated monitor PD + heaterRx: 5 microring drop filters + integrated Rx PD + heater

Photonic chip manufactured by LETI

Footprint limited by flip-chip bonding pads and CMOS circuit (TSMC 65 nm)

1mm

2mm

2.8mm

1.7mm

Electrical I/O & power

OpticalPower supply


Photonic IC

Metal 1

Metal 2Waveguide

Heater

Isolation trench

Tx

Rx

Flip-chip bonding pads to CMOS

Wirebonding pads to PCB

Power grid for CMOS

For high-speed modulation

For heater tuning

On-chip link


Transmitter results

Dual-edge pre-emphasis with pulse width controlled by tunable delay cells (30ps~60ps)Cascode output stage used to meet high modulation swing requirement


Open problems and future directions

HP sees Photonics as the future of datacom•Integration• How do we put it all together?

•Co-design• Drivers and receivers

•Fabrication• 1000s of devices on a chip?

•Power consumption and thermal

…and most importantly

Business case

Solution roadmap

Supplier ecosystem


Acknowledgements

HP Labs• Ray Beausoleil (Group leader)• Janet Chen (SiP design and testing)

• Cheng Li (CMOS design, area estimates)• Al Davis & the architecture Group

CEA-Leti• Sylvie Menezo & the SiP team

Our collaborators• Sam Palermo at Texas A&M

• Patrick Chiang at Oregon State

silicon photonics and the datacenter -...

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