energy optimization of interconnection networks using ...§improving energy efficiency while...

Energy Optimization of Interconnection NetworksUsing Silicon Photonics

Romesh Nandwana

Cisco Systems, Allentown, PA

© 2018 Cisco and/or its affiliates. All rights reserved. 2

§ Market Trends

§ Design challenges for next gen Data-Center Interconnects

§ Silicon Photonics based transceivers

§ Conclusion

Outline


By 2021, Global Internet Growth and Trends

Source: Cisco VNI Global IP Traffic Forecast, 2016–2021

Key Digital Transformers

2016

2021

3.3 Billion

4.6 Billion

17.1 Billion

27.1 Billion

27.5 Mbps

53.0 Mbps

73% of Traffic

82% of Traffic

More Devices & Connections

Faster Broadband Speeds

More Video Viewing

More Internet Users


Global Mobile Data Traffic Growth / Top-LineAverage Traffic per User

Average Traffic per Connection2016

902 MB per month

2021

4,226 MB per month

2016 2021

1,456 MB per month 8,423 MB per month

Source: Cisco VNI Global Mobile Data Traffic Forecast, 2016–2021

0

10

20

30

40

50

60

2016 2017 2018 2019 2020 2021

35

7

Exab

ytes

per M

onth

24

1711

49

47% CAGR 2016–2021

7x increase from 2016 to 2021

Global Mobile Data Traffic Growth


§ Cisco Global Cloud Index àProjecting global IP traffic to increase 3X à2016 to 2021

§ $ per Gb/s in Dell O’ro chart is the aggregated cost of port bandwidth in the data switch market

Traffic Growth & Cost Trends

0

5

10

15

20

25

2016 2017 2018 2019 2020 2021

6 .8

17 .1

Zetta

byte

s pe

r Yea

r

14.111.6

9.1

20.625% CAGR 2016–2021

Global Data Center IP-Traffic Growth

0

4

8

12

16

20

0

20

40

60

80

100

2016 2017 2018 2019 2020 2021 2022

$pe

rGb/s

Ports

(mill

ions

)

400GE 100GE50GE 40GE25GE 10GE$perGb/s

DellO'ro EthernetSwitchDataCenterForecastJan'18

Data Center Ethernet Switch Market


Global Data Center Traffic by Destination, 2021A

B

C

Data Center to User14.9% Within Data Center

71.5%Data Center to

Data Center13.6%

Storage, production and development data, authentication

Within Data Center (71.5%)

Data Center to Data Center (13.6%)

Data Center to User (14.9%)

Replication, CDN, intercloud links

Web, email, internal VoD, WebEx…Source: Cisco VNI Global Cloud Index, 2016–2021

Most Data Center Events/Content Stays Within the Data Center


Current Trends in Wireline Link Design

Increase in data-rate at the expense of power-efficiency degradation

Daly, IEEE Solid-State Circuits Magazine 10.1 (2018): 30-46.


Backplane Channels in Data-Center EnvironmentInsertion Loss

Crosstalk

~60dB Loss @ 28GHz

NRZ


What’s Next ?

Increase data-rates à complex modulation schemes are needed


§ PAM-4 bandwidth ~ NRZ bandwidth/2 à 2X timing margin

§ SNR loss = 20 log (1/3) ~ 9.5 dB§ Forward Error Correction (FEC) to compensate for additional loss

§ Transimpedance Amplifier (TIA) has to be linear

Backplane Channels in Data-Center EnvironmentInsertion Loss

Crosstalk

~31dB Loss @ 14GHz

~60dB Loss @ 28GHz

NRZ

PAM-4


§ Accelerating traffic growth demands higher port speed + high switch & router BW

§ Higher SERDES IO & port speeds are being adopted at faster rates to enable efficiencies

§ Pluggable optics transition to higher speeds & higher densities

Market Transitions Increasing PaceEvolution of Module Faceplate BW Density


§ IP traffic growth → Driving need for more & higher capacity data centers

§ IP traffic growth → Driving Optics transitions to higher & higher speeds§ 10G → 40G → 100G → 400G → 1Tb

§ To support the tsunami in traffic growth, highest volume optics deployment will be in the Data Center → Also the most cost sensitive !

§ Power management in Data Center is critical → Silicon Photonics

§ Single Mode fiber deployment in Data Centers is the defacto standard → Silicon Photonics

§ Higher speed ports are driving lower bandwidth costs per Gb/s

§ Volume of ports will drive scale & cost

Data Center Trends


L Lower level of integration

L Poor signal integrity

L Low yield

L Small wafer/high cost

L Thermal sensitivity

L Hermetic sealing

III-V Vs Silicon Photonics LinksRX

CDR

TXCDR

ROSA

TOSA

Pwr

μCtrl

ElectricalICSi-PhotonicIC

Pwr

μCtrl

J High density integration

J Excellent signal integrity

J CMOS yield/ wafer level testing

J Large wafer/low cost

J Wide thermal operating range

J Non-hermetic package

III-V Module Silicon-Photonics Module


4x25 Gbps NRZ

HOST

HOST SERDES

SerializerMZI Driver

PAM Decoder

ADC-CDR

53 GBd Linear TIA

CMOS Electrical ICOptical IC

53 GBd

Mach Zehnder

Modulator53 GBd

LINE

4x25 Gbps NRZ

Photodiode

PAM Encoder

§ Electrical IC flip-chipped on Optical IC

§ Segmented MZI driver for multilevel data transmission

§ Linear TIA integrated with transceiver SoC

Electro-Optical System in Package


§ Efficient: Charge at peak of optical intensity

§ VπLπ ~ 2 V.mm

§ Low voltage operation 1.0 V (CMOS)

§ Short MZI modulators ~ 400µm

§ Lumped element operation

The SISCAP ModulatorSISCAP – Silicon Insulator Silicon CAPacitor

Optical Intensity

+ + + + + + + + - - - - - - - - - -

P+

N+

Poly-Si

SOIGate Oxide


§ Temperature performance of modulator important for silicon photonic applications

§ Typical results shown for 1550nm SISCAP ( from 10 sites across wafer)

SISCAP Temperature Behavior

Measured phase behavior Measured attenuation behavior

o T=30C+ T=90C

o T=30C+ T=90C

Optical Intensity

+ + + + + + + + - - - - - - - - - -

P+

N+

Poly-Si

SOIGate Oxide


§ CMOS (limiting driver) directly drives MZI segments

§ Eliminates the need for an Electrical DAC + Linear Driver

§ Good Potential for PAM and QAM applications

SISCAP Segmented MZI ModulatorLSB MSB

B0 B1

Digital CMOS Drivers Optical Phase

Optical Power bias point

Phase Modulation by segments

MZI Response


§ Performance to 28 GBd/s and beyond

§ Operates over 1310nm and 1550nm wavelengths

Silicon Photonics Transmitter Performance

*M.Mazzinietal,CiscosystemsInc,OFC2015

**B.Milivojevicetal,CiscoSystemsInc,OFC2016

Direct-Detection Coherent


Receiver Test Fixtures

Electrical Optical

PCB

Electrical Interposer

Electrical IC

PCB

Electrical IC

Optical IC

Fiber


TDECQ = 1.22 dB

RLM = 0.982

TDECQ = 1.78 dB

RLM = 0.956

TIA Electrical IC

Optical IC

PAM-4 Pattern Generator[106.25 Gb/s PRBS13]

Sampling Scope With

5-Tap EqualizerOpticalElectricalLaser

SourceLiNbO3

ModulatorOptical

PAM-4 Measurement setup

TDECQ = N/A

RLM = 0.956

*K.Lakshmikumaretal,CiscosystemsInc,CICC2018


FEC Limit = 4.8E-4

Symbol rate = 53.125GBd

RX Sensitivity: Symbol Error Rate vs. Input OMA*K.Lakshmikumaretal,CiscosystemsInc,CICC2018


§ IP traffic growth → Driving transitions to higher & higher speeds

§ Improving energy efficiency while increasing data rate is difficult with traditional means

§ Silicon photonics based links provide an excellent alternative to III-V as well as backplane copper to improve performance even further§ Low cost§ Wide temperature range§ Improved signal integrity

§ Low voltage CMOS MZI drivers, and linear TIA provides an energy efficient solution for data center interconnects

Conclusion

Thank you.


Questions?


Direct Detection Vs Coherent

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