100 Gbits/s Line Side Modulation Schemes and Impairments

DP-QPSK Transmitter Block DiagramThe Optical Internetworking Forum (OIF) has recommended using DP-QPSK (dual-polarization quadrature phase-shift keying) modulation format for 100 Gbit/s system design, since it is both spectrally efficient and highly resilient to CD and PMD (when coupled with suitable signal processing algorithms). The block diagram below shows the typical implementation recommend by the OIF.

RF1RF2RF5RF4

MZ4

MZ3

/2

/2MZ2B2

D1

B1MZ1

B3

B4 B6

B5

CW laser

D2

Typical implementation recommended by the Optical Internetworking Forum (OIF).

Eye DiagramThe eye diagram is a time-domain chart that shows transitions between logical 0 and 1. It overlaps several periods of the signal on a single chart. It is used to determine many characteristics of the signal: eye opening, the signal-to-noise ratio, rise time, fall time, etc.

T = 1/P

Jitter Rise time Eye width

Eye height

0

j

1

X-axis = time

Y-axis = power

Common QPSK Impairments

I/Q Quadrature Error

A rhombic constellation appears when the I and Q phases do not show a perfect 90 phase shift, which occurs when

bias B5 is not optimized.

I/Q Modulator Bias Error

This impairment, caused by an incorrect bias in the I-branch of the I/Q modulator (bias B1), results in an overshoot in the I direction and

an undershoot in the Q direction.

I/Q Gain Imbalance

This impairment, shown as a rectangular constellation, is due to a gain that is different in the I port with respect to

the Q port, i.e. the power of RF drive signals (RF3 and RF4) is not optimized.

Deterministic Data-Dependent Jitter

The I and Q RF drive signals (RF3 and RF4) may contain deterministic jitter originating from driver circuits or

SERDES that leads to a delay in the transitions.

Random Data Clock Jitter

An equal delay in the I and Q phases due to clock jitter (RF3 and RF4 drive signals) leads to an impairment that is

only visible in the eye diagram.

I/Q Data Skew

The opening in the center of the constellation is caused by a constant time delay between the I and Q RF drive signals

(RF3 and RF4).

Poor Signal-To-Noise Ratio Transmitter

Clouded constellation and eye diagrams are typically of poor SNR due to an instrument limitation.

Chirp

The S-shape transitions of the chirp impairment can stem from data modulation or from residual fiber dispersion.

Ideal QPSK Constellation

Constellation diagram Eye diagram

I phase

Q phase

Constellation DiagramA constellation diagram is a representation of a signal modulated by a digital modulation scheme (phase and/or amplitude). In other words, it shows the possible symbols that can be selected by a given modulation format as points in the complex plane.

Q

I

Example of a quadrature phase-shift keying (QPSK) constellation diagram

I = In-phase axis or real part of the signal Q = Quadrature axis or imaginary part of the signal

EXFOs PSO-200 Modulation Analyzer

> Supports data rates of 40 Gbit/s, 100 Gbit/s, 400 Gbit/s, 1 Tbit/s and beyond

> For NRZ, RZ, DPSK, DQPSK, QPSK, 16-QAM

> Single- or dual-polarization transmission

> Distortion-free signal recovery

Modulation Schemes

Quadrature Phase-Shift Keying (QPSK)

> Phase modulation

> Quadrature phase shifts are separated by 90 (e.g., 45, 135, 225, 315)

> Two bits encoding

Amplitude

01 11 01

t

Q

I

Dual Polarization Quadrature Phase-Shift Keying (DP-QPSK)

> Also called PM-QPSK

> Phase modulation on two orthogonal polarizations

> Quadrature phase shifts are separated by 90 (e.g., 45, 135, 225, 315)

> Four bits encoding

X-polarization

Amplitude

01 11 01t

Y-polarization

Amplitude

01 11 01t

Q

I

Examples of Constellation and Eye DiagramsIn the diagrams below, the X refers to the X polarization, while the Y refers to the Y polarization.

Examples of DP-QPSK eye diagrams Other examples of DP-16QAM eye diagrams

Constellation and time-resolved EVM diagrams of a 10 GBd 16-QAM signal

Time-resolved EVM of a 28 GBd QPSK signal with IQ-skew up to 8ps

Examples of DP-QPSK constellations

Other examples of DP-16QAM constellations

100GTECHNICAL POSTER

EXFO HEADQUARTERS 400 Godin AvenueQuebec City (Quebec)G1M 2K2 CANADA

T: +1 418 683-0211F: +1 418 683-2170

EXFO INDIA308, IRIS Tech Park, Sector-48 Sohna Road, Gurgaon-122018 Haryana, INDIA

Tel: + 91 124 4868370Fax: +91 124 4868378

sales.india@exfo.com

2013 EXFO Inc. All rights reserved. Printed in Canada 13/11 20110794v2 SAP1062575

Ethernet Frame Format and Rates IEEE 802.3ba Highlights

PCS Lane Skew > Skew is the difference in time it takes the signals traveling down one lane compared to the others

> Each element along the data path will contribute to the overall skew (i.e., CFP, fiber, etc.)

The maximum skew and skew variation at physically instantiated interfaces is specified at skew points SP1, SP2, and SP3 for the transmit direction and SP4, SP5 and SP6 for the receive direction.

In the transmit direction, the skew points are defined in the following locations:

> SP1 on the XLAUI/CAUI interface, at the input of the PMA closest to the PMD;

> SP2 on the PMD service interface, at the input of the PMD;

> SP3 at the output of the PMD, at the MDI.

In the receive direction, the skew points are defined in the following locations:

> SP4 at the MDI, at the input of the PMD;

> SP5 on the PMD service interface, at the output of the PMD;

> SP6 on the XLAUI/CAUI interface, at the output of the PMA closest to the PCS.

PCS Lane Markers PCS lane marker is the mechanism used to reorder and realign the PCS lanes

> The marker has the form of a specially defined 66b block (to maintain 1s density) and its format is as follows:

Bit Position

BIP7M6M5M4BIP3M2M1M010

0 1 2 9 10 17 18 25 26 33 34 41 42 49 50 57 58 65

M4-M6 are bit-wise inversion of M0-M2BIP7 is the bit-wise inversion of BIP3

> Provide physical-layer specifications which support:

100G Ethernet 40G Ethernet

40 km over SMF 100GBASE-ER4

10 km over SMF 100GBASE-LR4 40GBASE-LR4

100 m over OM3 MMF 100GBASE-SR10 40GBASE-SR4

10 m over copper cable 100GBASE-CR10 40GBASE-CR4

1 m over backplane 40GBASE-KR4

> Support a MAC data rate of 40 Gbit/s and 100 Gbit/s

> Provide a BER < 10-12 at the MAC layer

> Provide appropriate support for OTN

Legend

CAUI 100 Gbit/s Attachment Unit InterfaceCGMII 100 Gbit/s Media Independent InterfaceFEC Forward Error CorrectionMAC Media Access ControlMDI Medium Dependent InterfacePCS Physical Coding SublayerPMA Physical Medium AttachmentPMD Physical Medium DependentXLAUI 40 Gbit/s Attachment Unit InterfaceXLGMII 40 Gbit/s Media Independent Interfacen 4 or 10

Note 1: Optional or omitted depending on PHY type.

Preamble DestinationAddress

SourceAddress

Length 802.2Header

DATA FCS

8

Ethernet

IEEE 802.3

6 6 2 446-1500

Preamble DestinationAddress

SourceAddress

Length 802.2Header

DATA FCSSOF

7 6 6 2 446-15001

Ethernet Interface Line Rate

100G Ethernet 103.125 Gbit/s

40G Ethernet 41.25 Gbit/s

Skew Points

Maximum Skew (ns)

Maximum Skew for 40GBASE-R PCS Lane (UI)

Maximum Skew for 100GBASE-R PCS Lane (UI)

SP1 29 299 150

SP2 43 443 222

SP3 54 557 278

SP4 134 1382 691

SP5 145 1495 748

SP6 160 1649 824

At PCS receive

180 1856 928

100 GigE Packet TransmissionSimplified 802.3 stack

> Convert packets into 20 parallel streams of 64b/66b symbols

> Mux 20:10 (PCS lanes into CAUI lanes)

> Mux 10:4 (CAUI lanes into PMD lanes)

> Transmit 4 PMD lanes on SMF using LAN WDM

Media Access Control (MAC)

Reconciliation Sublayer

100G Media Independent Interface (CGMII)

100G Attachment Unit Interface (CAUI)

Physical Coding Sublayer (PCS)

Physical Medium Attachment (PMA)

Physical Medium Attachment (PMA)

Physical Medium Dependent (PMD)

PacketizationMAC

Symbols > LanesPCS

PMA20:10

PMA10:4

PMD

CFP

DestinationMAC Address

SourceMAC Address

EtherType Payload (46 - 1500 bytes) FCS

#41... ... ...#40 #39 #22 #21 #20 #19 #2 #1 #0 ...

#40 #20 #0 M0

#41 #21 #1 M1

#22 #2 M2

... ... ...

#39 #19 M19

PCS Lane #0

Round robindistribution

PCS Lane #1

PCS Lane #2

PCS Lane #19

IdleSymbol

80 03 01 7C 9F 3E 80 03 01 20 FB 1D 08 00 9B 3C 7A F1Pre-amble

45 58 AA 55 2D 9B

> Packetize Data

> Converted to 64b/66b symbols, and send to PCS lanes

> Add PCS lane markers periodically to ensure reordering and realignment

1. The PMA next to the PCS multiplexes 20 PCS lanes into 10 CAUI lanes

2. The PMA next to the PMD multiplexes 10 CAUI lanes into 4 PMD lanes

3. The PMD converts each PMD lane into optical NRZ and multiplexes them

4. The 4 optical lanes are transmitted over singlemode fiber

10:4 LAN

WDM(optical mux)

2:1

2:1

2:1

2:1

2:1

2:1

2:1

2:1

2:1

2:1

PCS/LogicalLanes

CAUI/PhysicalLanes

PMD Lanes

1 2 3 4

SMF Fiber

100G/40G Ethernet (IEEE 802.3ba)

OTU4/OTU3 (ITU-T G.709)

MAC andhigherlayers

Reconciliation

40GBASE-R PCS

100GBASE-R PCS

PMA (4:4)

PMA (20:10)

PMA (4:4)

PMA (20:10)

FEC1

FEC1

PMA (4:4)

PMA (20:10)

PMA (4:4)

PMA (10:n)

PMD

PMD

Medium

Medium

40GBASE-R

100GBASE-R

XLAUI

SP6

SP6

CAUI

XLGMII

CGMII

XLAUI

SP1

SP1

CAUI

SP2

SP5

SP2

SP5

PMDService

Interface

PMDService

Interface

SP3

SP4

SP3

SP4

MDI

MDI > The lane number is coded in the M1 byte field

> A BIP field is used for calculation of the BER per PCS lane

> Markers are not scrambled in order to allow the receiver to search and find the markers

> Bandwidth for the alignment markers is created by periodically deleting IPG

> Skew tolerance is 180 nsec maximum for both the 40G and 100G

Size Newly defined OTN container in G.709 of 1.25 Gig

Virtual container with no physical instance

Client Perfectly fits GigE, OC-3/STM-1 and OC-12/STM-4 services

Benefits Removes dependency on SONET/SDH for carrying GigE services

Provides OTN OAM capabilities

ODU1

ODU0

GbEODU0

GbE

OTNODU0

100/40 GigE Mapping into OTU4/OTU3

Client

Optical Channel Transport Layer (OTL)

OTLk.nOTLk.nOTLk.n

OCh Data Unit (ODU) Payload ODUOH

OCh Payload Unit (OPU) Payload OPUOH

OCh Transport Unit (OTU) Payload FECOTUOH

1 2 n

41.25G

40.117G

40.15052GOH

GMP

1x

40GE

ODU340.319G

Using 1024B/1027B

40 GigE with 64B/66BTranscoding

103.125G

104.355G

512 block payload512 block payload F2

OH

GMP

1xOTU3OTU4

100GE

ODU4104.794G

1st 513B block

1024B / 1027B blockP = Odd parity over the two block flag bits

2nd 513B block

F1

P 512 block payload512 block payloadF2

F1

OTL Type Bit Rate

OTL3.4 10.7 Gbit/s

OTL4.4 27.95 Gbit/s

OTL4.10 11.18 Gbit/s

1024B/1027B block construction

PCS Lane 0

Alignment marker

16383 blocks between alignment markers

PCS Lane 1

PCS Lane 2

PCS Lane n-1

Alignment markers are inserted every 16383 66b blocks on each PCS lanes or 210 sec

100G/40G Interfaces

Pluggable ModulesCFP optical transceiver

> 100 GE, 10 x 10G, WDM

> 100 GE, 4 x 25G, WDM

> 40 GE, 4 x 10G, WDM

> Dimensions: 82 x 154 x 14 mm

CXP

> 100 GE, 10 x 10G, parallel optics/electrical

> Dimensions: 20 x 54 x 11 mm

QSFP

> 40 GE, 4 x 10G, parallel optics/electrical

> Dimensions: 18.4 x 72 x 8.5 mm

100G/40G Interfaces and ReachInterface 40G Ethernet 100G Ethernet

Reach Interface Attributes Interface Attributes

Op

tica

l 40 km over SMF

CFP 100GBASE-ER4 4 x 25G WDM, 1305 nm, NRZ G.694.1, 800GHz spacing (~4.5nm) Data rate: 25.78125 Gbit/s per lane

10 km over SMF

CFP 40GBASE-LR4 4 x 10G, CWDM, G.694.2, NRZ1305 nm, 20 nm spacing Data rate: 10.3125 Gbit/s per lane

CFP 100GBASE-LR4 4 x 25G WDM, 1305 nm, NRZ G.694.1, 800GHz spacing, (~4.5nm) Data rate: 25.78125 Gbit/s per lane

100 m over OM3 MMF1

QSFP 40GBASE-SR4 4 x 10G, NRZ Parallel optics, 850 nm Data rate: 10.3125 Gbit/s per lane

CXP 100GBASE-SR10 10 x 10G, NRZ, Parallel optics, 850 nm Data rate: 10.3125 Gbit/s per lane

Ele

ctri

cal 10 m over

copper cable

QSFP 40GBASE-CR4 4 x 10G electrical, NRZData rate: 10.3125 Gbit/s per lane

CXP 100GBASE-CR10 10 x 10G electrical, NRZ Data rate: 10.3125 Gbit/s per lane

1 m over backplane

40GBASE-KR4 4 x 10G electrical, NRZData rate: 10.3125 Gbit/s per lane

CFP MSA Optical Wavelengths

100 GigE/OTU4Lane Center

FrequencyCenter Wavelength

Wavelength Range

L0 231.4 THz 1295.56 nm 1294.53 to 1296.59 nm

L1 230.6 THz 1300.05 nm 1299.02 to 1301.09 nm

L2 229.8 THz 1304.58 nm 1303.54 to 1305.63 nm

L3 229 THz 1309.14 nm 1308.09 to 1310.19 nm

40 GigE/OTU3Lane Center

WavelengthWavelength Range

L0 1271 nm 1264.5 to 1277.5 nm

L1 1291 nm 1284.5 to 1297.5 nm

L2 1311 nm 1304.5 to 1317.5 nm

L3 1331 nm 1324.5 to 1337.5 nm

10x10 MSA* Optical Wavelengths

Optical Specifications: WDM Channel Definition

Parameter Symbol Min Typ Max Unit Conditions

Wavelength L1 1520 1523 1526 nm Channel 1

L2 1528 1531 1534 nm Channel 2

L3 1536 1539 1542 nm Channel 3

L4 1544 1547 1550 nm Channel 4

L5 1552 1555 1558 nm Channel 5

L6 1560 1563 1566 nm Channel 6

L7 1568 1571 1574 nm Channel 7

L8 1576 1579 1582 nm Channel 8

L9 1584 1587 1590 nm Channel 9

L10 1592 1595 1598 nm Channel 10

* This approach is still not ratified by IEEE 802.3ba.

OTU4/OTU3 Over Parallel Optics

Frame Rates

SAPI

DAPI

Operator-Specific

0

1516

3132

63

SAPI

DAPI

Operator-Specific

0

1516

3132

63

01

255

TTI8 9 10

TTI BIP-81 2 3 4 5 6 7 8

BEI/BIAE RESBDI

IAE

1 2 3 4 5 6 7 8BEI STATBD

I

1 2 3 4 5 6 7 8BEI/BIAE STATBD

I

1 2 3 4 5 6 7 8 9 10 11 12 13 14

1 2 3 4 5 6 7 8 9 10 11 12 13 14

FAS

FAS OH OTU OH

GCCO

MFA

S

SM RES

123

234

4

ODU OH

OPU

OH OTU FEC(4 x 256 bytes)

OPU Payload(Client Signal)

1 2 3TTI BIP-8

Byte 10

1 14-15-16-17 3824-3825 4080

OTUFrame

RES TCM6 TCM5 TCM4TCM3 TCM2 TCM1 PM EXP

GCC1

15 161234 PSI

Map

ping

PT

Map

ping

GCC2 APS/PCC RES

TCMACT

OperatorIdentifierFIF

FTFL

PM and TCMi (i= 1 to 6)

PM

TCMiByte 3

Operator-Specific

OperatorIdentifierFIF

Operator-Specific

0 1 9-10 127

128 129 137-138 255

Forward

Backward

FIF = Fault Identification Field

FTFL

OTN Frame Structure

OTN Interface

Line Rate Corresponding Service

OTU3 43.018 Gbit/s OC-768/STM-256 40 GigE

OTU3e1 44.57 Gbit/s 4 x ODU2e (uses 2.5 Gig TS; total of 16)

OTU3e2 44.58 Gbit/s 4 x ODU2e (uses 1.25 Gig (ODU0) TS; total of 32)

OTU4 111.81 Gbit/s 100 GigE

Dispersion

Short LinksLong Traveling Distances

12

3

45

Green path example

Network section

Length (km)

CD Value at 1550 nm (ps/nm)

PMD (ps)

1 53 890 6.49

2 37 632 0.39

3 29 484 8.93

4 45 765 5.21

5 42 726 0.88

Total 206 3497 12.24Same transmitting station, two different route examples.

Dispersion Approaches

Domain B

TransportEquipment

Backbone NetworkDomain A

TransportEquipment

Inter-Domain

Backbone Network

CO

CO80 km

CO

CO80 km

1 km2 km

Good section (acceptable)Bad section (needs to be replaced)

Using a single-ended instrumenta CD and PMD test tool that can characterize a section between two sites without having instruments at both endsmeans that many sections can be characterized in a few minutes instead of a few hours from a single location. As a result, an entire network can be characterized in 66% less time than any other traditional test methods. This greatly reduces truck rolls and OPEX, while increasing speed to deliver new services and reducing time-to-cash.

Distributed PMD analysis reduces CAPEX by revealing the worst segments on a high-PMD route. Replacing a few kilometers of fiber, instead of an entire route, puts it back in service for higher bit-rate services and substantially reduces CAPEX.

With data rates reaching 40 Gbit/s and beyond, fiber characterization is critical. When adding 40Gbit/s wavelengths to a DWDM route or ring, at that time, it will be nearly impossible to temporarily remove dozens of active wavelengths from service to characterize the optical fiber carrying them. Its important to fully characterize optical fiber links while its possible: here ,in addition to being highly accurate, these future proof devices can be placed at several different positions, so a multitude of test points can be acquired, faster with high accuracy which together reduces test costs or the even greater cost of adding more fiber.

OPU4OTU4 0Ch

Client

OPU4

OPU4 (L)

OPU4 (H)

ODTUG4104.794G

111.809Gor

OPU3OTU3 0Ch

Client

OPU3

OPU3 (L)

OPU3 (H)

ODTUG340.319G

43.018Gor

OPU2OTU2 0Ch

Client

OPU2

OPU2 (L)

OPU2 (H)

ODTUG2

10.037G

10.709Gor

Mapping ODUk (L) = Low-Order ODU

Multiplexing ODUk (H) = High-Order ODU

OPU1OTU1 0Ch

Client

OPU1

OPU1 (L)

OPU1 (H)

ODTUG12.499G

2.666Gor

OPU0

Client

OPU0 (L)

1.244G

x80

x32

x8

x2

x40

x16

x4

x10

x4

x4

100/40 GigE Mapping into ODU Multiplexing

PacketizationMAC

Symbols > LanesPCS

PMA20:10

PMA10:4

PMD

CFP

DestinationMAC Address

SourceMAC Address

EtherType Payload (46 - 1500 bytes) FCS

#41... ... ...#40 #39 #22 #21 #20 #19 #2 #1 #0 ...

#40 #20 #0 M0

#41 #21 #1 M1

#22 #2 M2

... ... ...

#39 #19 M19

PCS Lane #0

Round robindistribution

PCS Lane #1

PCS Lane #2

PCS Lane #19

IdleSymbol

80 03 01 7C 9F 3E 80 03 01 20 FB 1D 08 00 9B 3C 7A F1Pre-amble

45 58 AA 55 2D 9B