Your Imagination, Our Innovation

Trends In Data Rate And Link Length In Evolving OpticalStandards

David Cunningham
22nd September 2013

Your Imagination, Our Innovation

Outline• Building and Data Centre link lengths• Trends for standards-based electrical interfaces• Data rate, transmission media and optical technology trends• Multimode fibre link lengths• Form factor evolution• SummaryPage 2

Your Imagination, Our Innovation

Transmission Technologies For Data Centre Networking• Electrical Links:
Used for on-board, in chassis, and rack to rack.

• Optical Links:
Used where electrical can’t work!

• As signaling speeds increase and the size of data centres
expand, optics plays an increasing role.
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Your Imagination, Our Innovation

Standards Based Building Wiring Link Lengths
CampusDistributor• Campus to campus link length 10 km
1500 mBuilding
Distributor

Building
Distributor
500 m

Floor
Distributor

Floor
Distributor

Floor
Distributor

Floor
Distributor

300 m

90 m
Horizontal
OutletFixed installed cable lengths per ISO/IEC 11801
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Horizontal
OutletHorizontal
OutletYour Imagination, Our Innovation

Data Centres Now Use Structured Cabling Too• ISO/IEC 24764 Generic Cabling Systems for Data Centres• But data centres are getting huge and supported MMF link lengths are decreasing at higher
data rates
Multimode Fibre Link Lengths Versus Data Rate
1000

OM4900

OM3800From ThisRack

MMF LinkLengths Per
Fibre ChannelStandards

700

Link Length, m(>300 m)

600
500
400
300
200
1000051015Data rate, Gb/s

• SMF solutions for 500 m under active consideration for higher speeds
Page 5202530

Your Imagination, Our Innovation

Trends For Standards-Based Electrical Interfaces
As the electrical data rate seems to be expected
to increase with an exponential trend it willquickly get harder and harder to maintainelectrical signal integrity.

Electrical Lane Data Rate
120110100

Lane Rate, Gb/s

9080

SFI(128GFC)

Label Colour CodeBlack: 1 Lane
Blue: 4 Lanes
Purple: 8 Lanes
Brown: 10 Lanes
Red: 16 Lanes

CDAUI-4Error Correction Required
Multilevel Modulation Required•70
CEI-56-VSR
SFI(32GFC)

60
50

CEI-28-VSR

CDAUI-830
200
SBI-162000

XFI
XAUI-4100GBASE-KR4
100GBASE-KP4
SFI(16GFC)CAUI-4
CDAUI-16

Equalisation Required

XLAUI-4, CAUI-10, nPPI

2005

2010

2015

2020

Year Specification Technically Stable•Page 62025

Number of lanes:

16, 4, 1……10, 4, 1…..16, 8, 4 ,1…..

•

Clock Recovery•Equalization•Error Correction•Advanced Modulation Formats

XLAUI

40

10

Already, in order to maintain signal integrity, anevolution of various mitigation methods isobvious:

Unfortunately these mitigations increase therequired electrical power dissipation.
They also increase transmission latency.

Development of Electrical Interfaces For 50-56 Gb/s per lane via NRZ/PAM4 and FEC has already started.

Your Imagination, Our Innovation

Basic Optical Technologies For Data Centres
850nm VCSELs (Vertical- Cavity
Surface-Emitting Lasers)

Multimode Fibre (MMF)
coreCladding

Low-cost laser source
Low Current & Low Power
Compatible with MMF
Enable low-cost, low power transceivers

OM3 and OM4 50-micron core fibre is most common today.
Optimized for transmission using 850-nm VCSELs.
Easy to maintain, low-cost connectors, low cost transceivers

1310nm edge-emitting lasers Single mode Fibre (SMF)

Higher cost laser source
High Current & Power
Used predominantly with SMF
Various wavelengths for WDM applications
Typically more expensive to package
Used to power Si and InP Photonics
Page 7

SMF generally used for >300 links using 1310nm sourcesLong reach capable, low cost/meter
More expensive to connectorize than MMF

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Fibre Channel Data Rate & Encoding Roadmap
Data Rate

PAM4/Advanced Modulation(FEC Code)?

Fibre Channel Motto:“Keep it serial, keep it simple”

100 Gb/s

NRZ/PAM4(FEC Code)?

SFP+(1.5W)
256B/257B(FEC Code)

SMF & MMF
10 Gb/s

8B10B8B10B
8B10B

4G2G

64B66B

128G

64G

QSFP+ /QSFP28(3.5W)
4x32G (Parallel32G Multimode Fibres)

16G8G

•

Laser modulation rate not keeping pacewith desired data rate.

•Available optical link budget decreases asdata rate increases.

•More efficient encoding and FEC enabled
16GFC, 32GFC and 4x32GFC.

8B10B

Year

1 Gb/s
1995
Page 82000

2005

2010

2015

2020

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Ethernet Data Rate & Transmission Media Evolution
Data Rate

Parallel Singlemode Fibre (4)Parallel Multimode Fibre (OM4, 16 Lanes)
New MMF & CWDM

400Gigabit Ethernet

400G

100Gigabit Ethernet

100 G

10Gigabit Ethernet
10 G

Singlemode Fibre & WDM (4 Lanes)
Multimode Fibre (OM3)
Copper Twisted Pair (Cat 6, 4 Lanes)

Gigabit Ethernet
1G

Copper Twisted Pair (Cat 5)
Multimode Fibre (OM1,OM2)

Fast Ethernet
100 M

Singlemode Fibre & WDM (4 Lanes)
Parallel Multimode Fibre(OM4, 4 &10 Lanes)

40Gigabit Ethernet

Copper Twisted Pair (Cat 5)
Multimode Fibre (OM1, OM2)

10M
1990

1995

2000

2005

YearPage 92010

2015

2020

Your Imagination, Our Innovation

Ethernet Data Rate & Optical Device Technology Evolution
Data Rate
400Gigabit Ethernet
400G

100Gigabit Ethernet

100 G

SFP+Lasers & Laser Arrays(VCSEL, DFB’s, Modulators, Optical
Amplifiers, Si and InP Photonic Integration)

10Gigabit Ethernet
10 GLasers(VCSEL, FP and DFB)

Gigabit Ethernet
1G

Fast Ethernet

Lasers(VCSEL & FP)

100 M

Light emitting
diode (LED)

CFP-based 100GBASE-LR4

10M
1990

1995

2000

2005

YearPage 102010

2015

2020

Your Imagination, Our Innovation

Trend Of Multimode Fibre Link Lengths•The historical trend for multimode fibrelink lengths is shown in the graph.

•Methods are under discussion to ensure
at least 100 m operation for higher datarates.

Multimode Fibre Link Lengths Versus Data Rate
1000

OM4900

OM3800

MMF Link Lengths
Per Fibre ChannelStandards

Link Length, m

700
600

Methods under discussion include:

500•

VCSEL’s operating at longer wavelengths
than 850 nm: increases VCSEL bandwidthand decreases mode partition noise•

Multilevel modulation, which is enabled by
the emergence of PAM based electrical
specifications and FEC: even at 850 nm
PAM4 would enable 100 m links for 64GFC•VCSEL-based CWDM, wavelengths TBD

400300200
1000051015Data rate, Gb/s

202530The need to reduce the lane count for SMF optics and the lack of bandwidth ofthe SMF optical components means that multilevel modulation with FEC is also
being considered for next generation SMF links.
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100GBASE-SR4 Parallel MMF (4x 25.78125 Gb/s)
HOST ASIC
256b257b CAUI-4
FECInterfaceencoding

Page 12

CAUI-4

CAUI-4
RepeaterInterface

4 LaneVCSEL
Driver

VCSEL
Array

4 LaneTIA-Amp’s

4 PIN
Array

Coupling
opticsCouplingoptics•

Parallel MMF•

100 m OM4•

70 m OM3•

At 25.8 Gb/s MMF-based optics is bandwidth and noise challenged•

Therefore, 64b66b will be transcoded into 256b257b to provide FEC•

The Reed Solomon Code (RS (528,514)) provides about 3 dBo of coding gain•

The FEC reduces the optical power budget and ensures signal integrity•

Can expect that 100GBASE-SR4 will use QSFP+•Board mounted 4x25.8 Gb/s optics will also be available for high density applications

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Pluggable Form Factor Choices For 10G to 100G Applications
Which to choose?

SFP+(1.5W)

QSFP+ /QSFP28(3.5W)

CXP(3.5W)

CFP / CFP2 / CFP4(32W / 12W / 6W)~10G

8GFC,10GbE
Duplex MMF &SMF

4x10GbE / 1x40GbE
QDR-IB
Parallel MMF & SMF

12x10GbE /100G SR10QDR-IB
Parallel MMF only

CFP:100G MMF/SMF
CFP2: 100G SR10~14G

16GFC
Duplex MMF &SMF

16GFC
FDR-IB
MMF & SMF

FDR-IB
Proprietary inter.
Parallel MMF only

NA

~25G

32GFC
Duplex MMF &SMF

100GbE / EDR-IB
128GFCMMF & SMF

EDR-IB
Proprietary inter.
MMF only

CFP2: 100G SR4/LR4
CFP4 :100G SR4/LR4
MMF & SMF

It depends upon theapplication.

Lane Signaling Rate

Industry Pluggable Form factor (with Max power)

It is expected that a new form factor “CDCFP” will emerge for 400Gigabit
Ethernet.
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Pluggable Embedded Parallel Optics & CXP
Modules For High Density 100GbE & Infiniband

For MMF applications board mounted pluggable optics and front
panel pluggable CXP modules with electrical nPPI interfaces offer
higher density than front panel pluggable CFP# modules.
Page 14

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Summary• Standards-based electrical and optical lanes operating at 20 – 28 Gb/s arealmost specified and are getting ready for products.
• The next generation of standards-based electrical and optical lane rates will bearound 50-56 Gb/s.
• To support 50-56 Gb/s and higher lane rates various methods will be reused ordeveloped:• More lanes (via parallel conductors, fibres or wavelengths), Multilevel modulation,
FEC and integrated photonics.
• For multimode fibre applications new, higher bandwidth, longer wavelength,
VCSEL’s are likely to emerge along with a new MMF optimised for CWDM
operation at longer wavelengths. At a minimum these developments will maintainthe MMF worst case link distance of 100 m.
• Whilst 100GbE implementations continue to reduce their lane count, power,
size and cost, early implementations of 400GbE may start with 16 lanes of 25.8
Gb/s per lane in large packages and the cycle will continue again.
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Backup Slides

Page 16

Your Imagination, Our InnovationTrends For Standards-Based Electrical Interfaces
Interface Name
SBI
XAUI
XFI
SFI
SFI 16GFC
10GBASE‐KRXLAUI‐4CAUI‐10
CEI‐28‐VSR
SFI 32GFC
100GBASE‐KR4100GBASE‐KP4128GFC (4x32GFC)CAUI‐4
CDAUI‐16
CEI‐56‐VSR
SFI 64GFC
256GFC (4x64)
CDAUI‐8
XLAU
SFI 128GFC
CDAUI‐4Year
2000
2002
2005
2009
2009
2010
2011
2011
2014
2013
2013
2013
2014
2015
2017
2016
2016
2017
2018
2018
2020
2022

Per Lane Rate (Gb/s)
0.645
3.125
10.3125
10.3125
14.02510.31310.3125
10.3125
28.05028.05025.781326.5625
28.0500
25.781325.781356.156.1
56.1
51.562541.25
112.2
103.125

Number of Lanes
1641111
4
10
As required by application
1444416
As required by application
1481
14Modulation (Encoding)
NRZ (64B66B)
NRZ (8B10B)
NRZ (64B66B)
NRZ (64B66B)
NRZ (64B66B)
NRZ (64B66B)
NRZ (64B66B)
NRZ (64B66B)
NRZ (per application)
NRZ (256B/257B)
NRZ (256B/257B)
PAM4
NRZ (256B/257B)
NRZ (256B/257B)
NRZ (256B/257B)
PAM4
PAM4 ?
PAM4 ?
PAM4 ?
PAM4 ?
Complex Modulation ?
Complex Modulation ?

FEC
None
None
None
None
None
Optional
None
None
None
RS(528,514)
RS(528,514)
RS(544,514)
RS(528,514)
RS(528,514)
RS(528,514)?
Yes (TBD)
Yes (TBD)
Yes (TBD)
Yes (TBD)
Yes (TBD)
Yes (TBD)

Equalization Required
No
No
No
No
No
Yes
No
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes

The future trend, in blue, is based on the author’s interpretation of publicly available
roadmaps or predictions per IEEE 802.3, Fibre Channel and the OIF websites.
A graph might show the trend better than a table…… queue next slide.
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CFP2 100GBASE-SR10• 100 m on OM3• 150 m on OM4Page 18

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Optical Form Factor Options
Board mountedoptics

Pluggabletransceivers

Pluggable AOCs

Board mounted optics offer
density advantages.
Pluggable optics offer
flexibility.
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Slide taken from:http://www.ieee802.org/3/400GSG/public/13_07/maki_400_01_0713.pdf
Page 20