JDSU sync

Jitter and Wander Testing inHigh-Speed Telecom NetworksAndreas Alpert

ITSF 2006

AgendaNetwork evolutionJitter and wander aspectsApplication scenariosCase studyConclusion

© 2006 JDSU. All rights reserved. 3

Evolution of optical transport data rates

Source: Infonetics Research, February 2006

Increase of data rate by 4 and by 10

CY82 CY86 CY92 CY97

155M

622M

2.5G

10G

40G

?

2.7G

10.7G

43G

Hardware Ports

SDH/SONET

OTN G.709

10BASE

100BASE

1GE

10GE

100GE Ethernet

40GE ?

40G


Combining TDM and packet switched networks

SDH/SONET

CWDM DWDM DWDMOTN 43G

NG SDH/SONET

FC

Ethernet

GigE

OTN 10.7G

10GE

10GE

High-speed service 10GE:WAN (9.9G), WAN OTN (10.7G), LAN (10.3G), LAN OTN (11.1G)


Transport of IP over optical medium

3 play

IP

Ethernet

GFP

NG SDH/SONET

Optical medium (WDM, dark fiber)

VC/LCAS

PPP

Services

CC

Routing

Transport

Physical

OTN


SDH network synchronization – well implemented

GPS controlled PRCSSU (TNC or LNC)SEC (G.811)

OTN is not required to transport synchronization

OTN allows the transport of synchronization via SDH client connections


Timing distribution via Ethernet – an example

Timing is distributed from PRC to IWF across the packet switched network

Ethernet switches are part of the synchronization network

TDM TDMPacket SwitchedNetwork

Synchronizationnetwork

G.8261/Annex A:

PRC

IWF IWF

Interworkingfunction



Difference between jitter and wander

Frequency

10 Hz

Measurement time

Time

+ peak

- peak

MTIE

Observation timeTime

TIEat tend

TIE max

TIE min

Jitterin UI

peakpeak

Wanderin ns

Wander range Jitter range


ITU-T Recommendations for OTN/SDH/PDH

Primary Reference Clocks (PRC)

G.812

G.813

G.823

G.824

G.811

Synchronisation Supply Unit (SSU)

SDH Equipment Slave Clocks (SEC)

PDH Network Interfaces (2 Mb/s)

PDH Network Interfaces (1.5 Mb/s)

G.825 SDH Network Interfaces

Jitter/wander generation, tolerance and transfer

G.8251 OTN Network Interfaces

Definitions and terminologyG.810

G.783 SDH Equipment Functional Blocks


Rec. for synchronization over packet networks

Network time protocol (NTP) – accuracy in ms

IETF RFC2030

IETF RFC1305

Simple network time protocol (SNTP) – accuracy in s

Timing and synchronization in packet networksITU-T G.8261

Precision Clock Synchronization ProtocolIEEE 1588

Precision Time Protocol (PTP) is able to synchronize distributed clockswith an accuracy of less than one microsecond

poor precision

TDM over packets needs to be compliant to existing TDM timing standards

physical layer (layer 1)vs.

in-band (layer 2)

How to transport the timing information

ITU

IEEE


ITU-T Recommendations for test equipment

Jitter and wander measuring equipment for SDH

O.173

O.172

Jitter measuring equipment for OTN

Jitter and wander measuring equipment for PDHO.171

MOD

CLK

PTN IF

ext.sync.

Generator

IF CR

REF PD

ext.ref.

Analyzer (jitter, wander)

FIL

HP+LPLP

PPRMSTIEMTIETDEV



Jitter and wander applications

Jitter/wander SDH/SONET/PDHOTN (wander not required)

Ethernet

Generation BERT scan (Bathtub curve)

Tolerance Stressed eye

Transfer not applicable

DUT

Network Network


Requirements for wander test equipment

Generation of wander amplitudes/frequenciesAnalysis of TIE, MTIE, TDEV, frequency offset and drift rateBuilt-in masks that comply with ITU-T, Telcordia, ETSI and ANSISample rates 1/ s, 30/ s, 60/ s, 1000/ sReference input for clock 1.5/ 2/ 5/ 10MHz and data 1.5/ 2Mbs

Referenceclock

Output port:e.g. STM-N

Networkor NE


Commissioning test configurations

Tests on network element (NE) level prior to installationTests on synchronisation interfaces after installation

NE

Timing reference

STM-N

Wander generation

NE

Timing reference

STM-N

Wander tolerance

NE

Timing reference

Wander transfer

Synch. IF


Acceptance test configurations

Tests on interfaces handing over timing between telecom networksTests on reference clock sources

REF

Timing reference

REF

Network

Timing reference

Characterizationof timing transport

Characterizationof timing quality

Network

Synchronized configuration

STM-N STM-N

Non-synchronized configuration


Test configuration for asynchronous signals

AsyncClock

Timing reference

Characterizationof network wanderwith elimination ofclock offset ±x ppm

±x ppm

TIE with frequency offsetOffset corrected TIE

Network

Maximum relative time interval error (MRTIE)

SignalSource

e.g. 2Mb/s


Wander on OTN network elements

OTN NE

Mapper (byte stuffing)

Optical TransportNetwork

OTN (G.709)

OTN 10.7G

SDH 10G

De- mapper

FIFO

OTN NE

10G IF

10G Clock

SDH 10G

Filling level

OTN 10.7G

Mapping processWander on OTU clockleads to byte stuffingwhich introduces wanderinto recovered 10G

Long term OTUk bit rate shiftleads to adjustments of 10Gdepending on the filling level ofthe FIFO used for bit rate adaption

The OTN physical layer is not required to transport network synchronization There is no need for specification of network wander limits (ITU-T G.8251)Our recommendation: Wander measurement at OTU interfaces to ensure proper operation at SDH interfaces



Examples for wander analysis

Whitenoise

Frequencyoffset

TIE MTIE/TDEVMODSRC


Examples for wander analysis

Sine0.1 Hz

Sine+ noise+ offset

TIE MTIE/TDEVMODSRC



Conclusion

Carriers try to converge new and legacyservices on to a single platform, a packet switched network such as metro Ethernet. Thiswill allow them to reduce both capital and operating costs.Synchronization is essential to enable real-time and high-speed transmission for telecom networks.As telecom networks migrate to packet networks, the debate is about how the„synchronization” is passed from one networknode to another.Several standard bodies are working on that topic.Carriers need to evaluate and decide whether“in-band” or “physical layer” is the preferredtechnique to transport the timing information.


Thank youThank youfor your attentionfor your attention

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