T rec-g.825-200003-i!!pdf-e

INTERNATIONAL TELECOMMUNICATION UNION
ITU-T G.825
TELECOMMUNICATION
STANDARDIZATION SECTOR
OF ITU
(03/2000)
SERIES G: TRANSMISSION SYSTEMS AND MEDIA,
DIGITAL SYSTEMS AND NETWORKS
Digital networks – Quality and availability targets
The control of jitter and wander within digital
networks which are based on the synchronous
digital hierarchy (SDH)
ITU-T Recommendation G.825
(Formerly CCITT Recommendation)

ITU-T G-SERIES RECOMMENDATIONS
TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS
INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS G.100–G.199
INTERNATIONAL ANALOGUE CARRIER SYSTEM
GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-
TRANSMISSION SYSTEMS
G.200–G.299
INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE
SYSTEMS ON METALLIC LINES
G.300–G.399
GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE
SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH
METALLIC LINES
G.400–G.449
COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY G.450–G.499
TERMINAL EQUIPMENTS G.700–G.799
DIGITAL NETWORKS G.800–G.899
General aspects G.800–G.809
Design objectives for digital networks G.810–G.819
Quality and availability targets G.820–G.829
Network capabilities and functions G.830–G.839
SDH network characteristics G.840–G.849
Management of transport network G.850–G.859
SDH radio and satellite systems integration G.860–G.869
Optical transport networks G.870–G.879
DIGITAL SECTIONS AND DIGITAL LINE SYSTEM G.900–G.999
For further details, please refer to the list of ITU-T Recommendations.

ITU-T G.825 (03/2000) i
The control of jitter and wander within digital networks which are based
on the synchronous digital hierarchy (SDH)
Summary
This ITU-T Recommendation specifies the maximum network limits of jitter and wander that shall
not be exceeded and the minimum equipment tolerance to jitter and wander that shall be provided at
any relevant transport or synchronization interfaces which are based on the Synchronous Digital
Hierarchy (SDH).
The requirements for the jitter and wander characteristics that are specified in this ITU-T
Recommendation must be adhered to in order to ensure interoperability of equipment produced by
different manufacturers and a satisfactory network performance.
Source
ITU-T Recommendation G.825 was revised by ITU-T Study Group 13 (1997-2000) and approved
under the WTSC Resolution 1 procedure on 10 March 2000.
Keywords
Clocks, Input Jitter Tolerance, Input Wander Tolerance, Network Limits, Output Jitter, Output
Wander, Synchronization, Timing.

ii ITU-T G.825 (03/2000)
FOREWORD
The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of
telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of
ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations
on them with a view to standardizing telecommunications on a worldwide basis.
The World Telecommunication Standardization Conference (WTSC), which meets every four years,
establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these
topics.
The approval of ITU-T Recommendations is covered by the procedure laid down in WTSC Resolution 1.
In some areas of information technology which fall within ITU-T’s purview, the necessary standards are
prepared on a collaborative basis with ISO and IEC.
NOTE
In this Recommendation, the expression "Administration" is used for conciseness to indicate both a
telecommunication administration and a recognized operating agency.
INTELLECTUAL PROPERTY RIGHTS
ITU draws attention to the possibility that the practice or implementation of this Recommendation may
involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence,
validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others
outside of the Recommendation development process.
As of the date of approval of this Recommendation, ITU had not received notice of intellectual property,
protected by patents, which may be required to implement this Recommendation. However, implementors are
cautioned that this may not represent the latest information and are therefore strongly urged to consult the
TSB patent database.
ã ITU 2001
All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU.

ITU-T G.825 (03/2000) iii
CONTENTS
Page
1 Scope........................................................................................................................... 1
2 References................................................................................................................... 1
3 Definitions .................................................................................................................. 2
4 Abbreviations.............................................................................................................. 2
5 Network limits for the maximum output jitter and wander at any hierarchical
interface ...................................................................................................................... 3
5.1 Network limits for jitter.............................................................................................. 3
5.2 Network limits for wander.......................................................................................... 4
6 The specification of individual digital equipment...................................................... 4
6.1 Jitter and wander tolerance for STM-N input ports.................................................... 4
6.1.1 STM-N input wander tolerance..................................................................... 6
6.1.2 STM-N input jitter tolerance ......................................................................... 6
6.2 Jitter and wander generation....................................................................................... 10
6.3 Jitter and wander transfer............................................................................................ 10
Appendix I − Relationship between network interface jitter requirements and input jitter
tolerance...................................................................................................................... 11
I.1 Network interface jitter requirements......................................................................... 11
I.2 Input jitter tolerance of network equipment ............................................................... 12
Appendix II − Measurement methodology for output wander of synchronous interfaces ...... 14
Appendix III − SDH Line systems and Interworking implications ......................................... 14

iv ITU-T G.825 (03/2000)
Introduction and background
In a digital network, jitter and wander accumulate on transmission paths according to the jitter and
wander generation and transfer characteristics of each equipment interconnected. This equipment
may be different types of multiplexers/demultiplexers, cross-connects, clocks and line systems, for
example.
An excessive amount of jitter and wander can adversely affect both digital (e.g. by generation of bit
errors, slips and other abnormalities) and analogue signals (e.g. by unwanted phase modulation of
the transmitted signal). The consequences of such impairment will, in general, depend on the
particular service that is being carried and the terminating or adaptation equipment involved.
It is therefore necessary to set limits on the maximum magnitude of jitter and wander, and the
corresponding minimum jitter and wander tolerance at network interfaces, in order to guarantee a
proper quality of the transmitted signals and a proper design of the equipment.
These network limits are independent from the particular service that is being carried.

ITU-T G.825 (03/2000) 1
The control of jitter and wander within digital networks which are based
on the synchronous digital hierarchy (SDH)
1 Scope
The scope of this ITU-T Recommendation is to define the parameters and the relevant values that are
able to control satisfactorily the amount of jitter and wander present at the SDH network-network
interfaces (NNI).
SDH network interfaces, to which this ITU-T Recommendation is applicable, are defined in terms of
bit rates and frame structures in ITU-T Recommendation G.707; their electrical characteristics are
described in ITU-T Recommendation G.703 and the optical characteristics in ITU-T
Recommendations G.957 and G.691.
Additional information regarding the architecture of SDH networks is found in ITU-T
Recommendation G.803.
Jitter and wander requirements for PDH and synchronization networks are specified in ITU-T
Recommendation G.823, for networks based on the first level bit rate of 2048 kbit/s, and in ITU-T
Recommendation G.824 for networks based on the first-level bit rate of 1544 kbit/s.
The jitter and wander control philosophy is based on the need:
– to recommend a maximum network limit that should not be exceeded at any relevant
interface;
– to recommend a consistent framework for the specification of individual digital equipment
(i.e. jitter and wander transfer, tolerance and generation requirements);
– to provide sufficient information and guidelines for organizations to measure and study jitter
and wander accumulation in any network configuration.
2 References
The following ITU-T Recommendations and other references contain provisions which, through
reference in this text, constitute provisions of this Recommendation. At the time of publication, the
editions indicated were valid. All Recommendations and other references are subject to revision; all
users of this Recommendation are therefore encouraged to investigate the possibility of applying the
most recent edition of the Recommendations and other references listed below. A list of the currently
valid ITU-T Recommendations is regularly published.
– ITU-T Recommendation G.691 (draft), Optical interfaces for single-channel STM-64,
STM-256 and other SDH systems with optical amplifiers.
– ITU-T Recommendation G.703 (1998), Physical/electrical characteristics of hierarchical
digital interfaces.
– ITU-T Recommendation G.707 (1996), Network Node interface for the Synchronous Digital
Hierarchy (SDH).
– ITU-T Recommendation G.783 (1997), Characteristics of synchronous digital hierarchy
(SDH) equipment functional blocks.
– ITU-T Recommendation G.803 (2000), Architecture of transport networks based on the
synchronous digital hierarchy (SDH).

2 ITU-T G.825 (03/2000)
– ITU-T Recommendation G.810 (1996), Definitions and terminology for synchronization
networks.
– ITU-T Recommendation G.811 (1997), Timing characteristics of primary reference clocks.
– ITU-T Recommendation G.812 (1998), Timing requirements of slave clocks suitable for use
as node clocks in synchronization networks.
– ITU-T Recommendation G.813 (1996), Timing characteristics of SDH equipment slave
clocks (SEC).
– ITU-T Recommendation G.823 (2000), The control of jitter and wander within digital
networks which are based on the 2048 kbit/s hierarchy.
– ITU-T Recommendation G.824 (2000), The control of jitter and wander within digital
networks which are based on the 1544 kbit/s hierarchy.
– ITU-T Recommendation G.832 (1998), Transport of SDH elements on PDH networks −
Frame and multiplexing structures.
– ITU-T Recommendation G.957 (1999), Optical interfaces for equipments and systems
relating to the synchronous digital hierarchy.
– ITU-T Recommendation O.171 (1997), Timing jitter and wander measuring equipment for
digital systems which are based on the Plesiochronous Digital Hierarchy (PDH).
– ITU-T Recommendation O.172 (1999), Jitter and wander measuring equipment for digital
systems which are based on the Synchronous Digital Hierarchy (SDH).
3 Definitions
This ITU-T Recommendation defines the following terms. Additional definitions relating to
synchronization networks are provided in ITU-T Recommendation G.810.
3.1 synchronous interface: These interfaces provide an output signal with frequency that is
normally traceable to a PRC.
3.2 asynchronous interface: These interfaces provide an output signal with frequency that is
not traceable to a PRC and that meets the frequency offset requirements given in ITU-T
3.3 synchronization interface: These interfaces are synchronous and network wander limits are
specified using Maximum Time Interval Error (MTIE) and Time Deviation (TDEV) parameters with
values given in this ITU-T Recommendation.
4 Abbreviations
This ITU-T Recommendation uses the following abbreviations. Additional abbreviations will be
added.
CMI Code Mark Inversion
ITU-T International Telecommunication Union – Telecommunication Standardization Sector
MRTIE Maximum Relative Time Interval Error
MS-AIS Multiplex Section Alarm Indication Signal
MTIE Maximum Time Interval Error
NE Network Element
NNI Network Node Interface

ITU-T G.825 (03/2000) 3
pk-pk Peak-to-Peak
RTIE Relative Time Interval Error
SDH Synchronous Digital Hierarchy
TDEV Time Deviation
TIE Time Interval Error
UI Unit Interval
UNI User Network Interface
5 Network limits for the maximum output jitter and wander at any hierarchical interface
5.1 Network limits for jitter
The limits given in Table 1 represent the maximum permissible levels of jitter at interfaces within a
digital network. Jitter as measured over a 60 second interval shall not exceed the limits given in
Table 1, when using the specified measurement filters. The limits shall be met for all operating
conditions and regardless of the amount of equipment preceding the interface. In general, these
network limits are compatible with the minimum tolerance to jitter that all equipment input ports are
required to provide. Guidelines for the derivation of the parameters values of Table 1 are given in
Appendix I.
There is a close relationship between network limits and input tolerance such that the jitter
measurement filter cut-off frequencies used in Table 1 have the same values as the jitter tolerance
mask corner frequencies used in 6.1. Appendix I provides further information about this relationship.
The high-pass measurement filters of Table 1 have a first-order characteristic and a roll-off of
20 dB/decade. The low-pass measurement filters have a maximally-flat, Butterworth characteristic
and a roll-off of −60 dB/decade.
ITU-T Recommendation O.172 contains a functional description of equipment appropriate for
measurement of jitter in SDH systems. Further specifications for the frequency response of the jitter
measurement function such as measurement filter accuracy and additional allowed filter poles are
also given in ITU-T Recommendation O.172.
Table 1/G.825 −−−− Maximum permissible jitter at network interfaces
Interface
Measurement bandwidth,
−−−−3 dB frequencies (Hz)
Peak-to-peak amplitude
(UIpp)
500 to 1.3 M 1.5STM-1e
(Notes 1, 2) 65 k to 1.3 M 0.075
500 to 1.3 M 1.5STM-1
(Note 4) 65 k to 1.3 M 0.15
1 k to 5 M 1.5STM-4
(Note 4) 250 k to 5 M 0.15
5 k to 20 M 1.5STM-16
(Note 4) 1 M to 20 M 0.15

4 ITU-T G.825 (03/2000)
Table 1/G.825 −−−− Maximum permissible jitter at network interfaces (concluded)
Interface
Measurement bandwidth,
−−−−3 dB frequencies (Hz)
(UIpp)
20 k to 80 M 1.5STM-64
(Note 4) 4 M to 80 M 0.15 (Note 3)
NOTE 1 − Electrical format CMI-encoded, according to G.703.
NOTE 2 − For networks deployed with G.813 Option II clocks or G.812 Type II,
III or IV clocks, STM-1 requirements apply to STM-1e.
NOTE 3 − The effect of dispersion and non-linearities on the eye opening and on
the choice of this value is for further study.
NOTE 4 − STM-1 1 UI = 6.43 ns
STM-4 1 UI = 1.61 ns
STM-16 1 UI = 0.402 ns
STM-64 1 UI = 0.100 ns
5.2 Network limits for wander
STM-N interfaces are defined as synchronization interfaces. Network limits for wander at
synchronization interfaces are specified in ITU-T Recommendation G.823 for networks based on the
2048 kbit/s hierarchy, and in ITU-T Recommendation G.824 for networks based on the 1544 kbit/s
hierarchy.
6 The specification of individual digital equipment
To help ensure that the interconnection of digital equipment does not result in accumulated jitter that
exceeds network limits, the jitter transfer and jitter generation characteristics of individual equipment
are defined. Also to help ensure equipment can operate properly, given the specified network limits,
jitter tolerance characteristics are defined.
6.1 Jitter and wander tolerance for STM-N input ports
This subclause specifies the jitter and wander tolerance for SDH input ports. Jitter and Wander
tolerance for PDH input ports to SDH equipment are specified in ITU-T Recommendations G.823
and G.824.
In order to ensure that, in general, any equipment can be connected to any appropriate interface
within a network, it is necessary to arrange that the input ports of all equipment are capable of
accommodating levels of jitter and wander up to at least the minimum limits defined in 6.1.1
and 6.1.2.
The jitter and wander tolerance of an SDH interface indicates the minimum level of phase noise that
the input port shall accommodate whilst:
• not causing any alarms;
• not causing any slips; and
• not causing any bit errors; except for optical STM-N interfaces at jitter frequencies above fp
(fp is 6.5 kHz for STM-1, 25 kHz for STM-4, 100 kHz for STM-16 and 400 kHz for
STM-64), where an equivalent 1 dB optical power penalty shall not be exceeded.

ITU-T G.825 (03/2000) 5
All digital input ports of equipment shall be able to tolerate a digital signal that has:
a) electrical characteristics in accordance with the requirements of ITU-T Recommendation
G.703, or the optical characteristics of ITU-T Recommendations G.957 and G.691;
b) a frequency offset (relative to the nominal value) within the range defined in Table 2;
c) a sinusoidal phase deviation having an amplitude-frequency relationship, defined in the
following subclauses, which indicates the appropriate limits for the different interfaces.
In principle, these requirements shall be met regardless of the information content of the digital
signal. However, for test purposes, the content of the signal with jitter and wander modulation
should be a structured test sequence as defined in Annex A/O.172.
When specifying or assessing interface tolerance, two equipment operating conditions can be
distinguished:
• asynchronous operation, where the receiving equipment is not being timed from a source
that is synchronous with the interface under consideration. In this case, it is the equipment
capability to accommodate phase variation on the incoming signal (in terms of clock
recovery circuitry and synchronizer/desynchronizer buffers) that is of interest.
• synchronous operation, where the receiving equipment is being timed from a source that is
synchronous with the interface under consideration. In this case, slip buffer dimension and
operation is also of interest.
Unless otherwise stated, the tolerance specifications in 6.1.1 and 6.1.2 apply to both asynchronous
and synchronous operating conditions.
The jitter and wander limit above 10 Hz reflects the maximum permissible jitter magnitude in a
digital network. However, the limit below 10 Hz does not aim to represent the maximum permissible
wander that might occur in practice. Below 10 Hz the limits are derived such that where necessary,
the provision of this level of buffer storage at the input of equipment facilitates the accommodation
of wander generated in a large proportion of real connections.
For convenience of testing, the required tolerance is defined in terms of the peak-to-peak amplitude
and frequency of sinusoidal jitter which modulates a digital test pattern. It is important to recognize
that this test condition is not, in itself, intended to be representative of the type of jitter found in
practice in a network.
Guidance on the measurement set-up for input jitter and wander tolerance is provided in
Appendix III/G.823. Instrumentation in accordance with ITU-T Recommendation O.172 is
appropriate for generation of jitter and wander in SDH systems.
Table 2/G.825 −−−− Maximum frequency offset at STM-N interfaces
Maximum frequency
offset (±ppm)
Example application
4.6 SDH NEs deployed with G.813 Option I clocks
20
MS-AIS in SDH regenerator sections and NEs
deployed with G.813 Option II clocks
Requirements for regenerators are provided in ITU-T Recommendation G.783. Appendix III
provides additional information.

6 ITU-T G.825 (03/2000)
6.1.1 STM-N input wander tolerance
STM-N interfaces used as synchronization interfaces shall meet wander tolerance specifications in
ITU-T Recommendations G.812 and G.813. ITU-T Recommendations G.812 and G.813 contain
requirements for two network types. For equipment deployed in networks based on the 1544 kbit/s
hierarchy, wander tolerance requirements are specified in Option II of ITU-T Recommendation
G.813 and for clock types II, III and IV contained in ITU-T Recommendation G.812. For SDH
equipment deployed in networks based on the 2048 kbit/s hierarchy, wander tolerance requirements
are specified in Option I of ITU-T Recommendation G.813 and for clock types I, V and VI in ITU-T
NOTE − Traffic interfaces are also required to tolerate frequency offsets of at least 20 ppm for the purposes of
detection of MS-AIS.
6.1.2 STM-N input jitter tolerance
Specific requirements for jitter tolerance for individual STM-N rates are given in the following
subclauses. These requirements specify the minimum levels of jitter that must be accommodated at
an STM-N interface. Guidance on test sequences suitable for SDH systems is provided in ITU-T
Recommendation O.172.
As noted in 6.1.1, SDH equipment can be deployed in different networks. Although the basic jitter
tolerance requirements are the same for both networks, the low frequency region of the jitter
tolerance requirement will differ to be compatible with the specific network wander requirements
that are specified in ITU-T Recommendations G.824 and G.825. These differences are noted in the
requirements below.
6.1.2.1 STM 1/1e jitter tolerance
The level of jitter that must be accommodated by STM-1 and STM-1e SDH interfaces is specified in
Tables 3 and 4 respectively, and are illustrated in Figures 1 and 2. Specifications are given for both
optical (STM-1) and electrical (STM-1e) interfaces. Equipment deployed in existing networks may
have jitter generation for STM-1e based on STM-1 requirements contained in ITU-T
Recommendation G.813. Inter-working between older equipment and equipment meeting the
STM-1e requirements in Table 4 is for further study. For networks based on the 1544 kbit/s
hierarchy, STM-1e interfaces shall be required to meet the more stringent STM-1 jitter tolerance
requirement.
Table 3/G.825 −−−− STM-1 input jitter tolerance limit
Frequency
f (Hz)
Requirement
(Peak-Peak)
2048 kbit/s networks 1544 kbit/s networks
− 10 < f ≤ 68.7 10.9 UI
10 < f ≤ 19.3 − 38.9 UI (0.25 µs)
19.3 < f ≤ 68.7 − 750 f
−1
UI
68.7 < f ≤ 500 750 f
−1
UI
500 < f ≤ 6.5 k 1.5 UI
6.5 k < f ≤ 65 k 9.8 × 10
3
f
−1
UI
65 k < f ≤ 1.3 M 0.15 UI

ITU-T G.825 (03/2000) 7
Table 4/G.825 −−−− STM-1e input jitter tolerance limit
Frequency
f (Hz)
Requirement
(Peak-Peak)
10 < f ≤ 19.3 38.9 UI (0.25 µs)
19.3 < f ≤ 500 750f
−1
UI
500 < f ≤ 3.3 k (Note 2) 1.5 UI
3.3 k < f ≤ 65 k 4.9 × 10
3
f
−1
UI
65 k < f ≤ 1.3 M 0.075 UI
NOTE 1 − STM-1e interface is CMI-encoded, according to ITU-T
NOTE 2 − When STM-1e interfaces are deployed in networks based on the
1544 kbit/s hierarchy they must meet the requirements for STM-1 in Table 3.
T1316810-99
Frequency (Hz)
Pk-PkPhaseAmplitude(UI)
(Note)
NOTE – The dashed curve is the requirement for 1544 kbit/s networks for frequencies less than 68.7 Hz.
1.0E+00
1.0E+01
1.0E+02
1.0E+01 1.0E+03 1.0E+05
1.0E–01
1.0E+00 1.0E+02 1.0E+04 1.0E+06 1.0E+07
Figure 1/G.825 −−−− STM-1 jitter tolerance
T1316820-99
100
10
1
1.0E+01 1.0E+03 1.0E+051.0E+02 1.0E+04
Frequency (Hz)
1.0E+06 1.0E+07
0.1
0.01
UnitIntervals(UIpp)
Figure 2/G.825 −−−− STM-1e jitter tolerance requirement
(applies to 2048 kbit/s networks only)

8 ITU-T G.825 (03/2000)
6.1.2.2 STM-4 jitter tolerance
The level of jitter that must be accommodated by STM-4 SDH interfaces is specified in Table 5 and
illustrated in Figure 3.
Frequency
f (Hz)
Requirement
(Peak-Peak)
− 10 < f ≤ 18.5 277.5 f
−1
UI
− 18.5 < f ≤ 100 15 UI
9.65 < f ≤ 100 − 1500 f
−1
UI
100 < f ≤ 1000 1500 f
−1
UI
1 k < f ≤ 25 k 1.5 UI
25 k < f ≤ 250 k 3.8 × 10
4
f
−1
UI
250 k < f ≤ 5 M 0.15 UI
T1316830-99
1.0E+00
1.0E+01
1.0E+02
1.0E+01 1.0E+03 1.0E+05
1.0E–01
1.0E+00 1.0E+02 1.0E+04
Frequency (Hz)
1.0E+06 1.0E+07
1.0E+03
(Note)
NOTE – The dashed curve is the requirement for 1544 kbit/s networks for frequencies less than 100 Hz.

ITU-T G.825 (03/2000) 9
Frequency
f (Hz)
Requirement
(Peak-Peak)
− 10 < f ≤ 70.9 1063.5 f
−1
UI
− 70.9 < f ≤ 500 15 UI
10 < f ≤ 12.1 − 622 UI
12.1 < f ≤ 500 − 7500 f
−1
UI
500 < f ≤ 5 k 7500 f
−1
UI
5 k < f ≤ 100 k 1.5 UI
100 k < f ≤ 1 M 1.5 × 10
5
f
−1
UI
1 M < f ≤ 20 M 0.15 UI
T1316840-99
1.0E+00
1.0E+01
1.0E+02
1.0E+01 1.0E+03 1.0E+05
1.0E–01
1.0E+00 1.0E+02 1.0E+04
Frequency (Hz)
1.0E+06 1.0E+07
1.0E+03
1.0E+08
(Note)
NOTE – The dashed curve is the requirement for 1544 kbit/s networks for frequencies less than 500 Hz.
For the purposes of practical conformance testing, the characteristics of the transmit eye mask need
to be carefully considered. This is for further study.

10 ITU-T G.825 (03/2000)
Table 7/G.825 −−−− STM-64 input jitter and wander tolerance limit
Frequency
f (Hz)
Requirement
(Peak-Peak)
− 10 < f ≤ 296 4446
−1
UI
− 296 < f ≤ 2000 15 UI
10 < f ≤ 12.1 − 2490 UI (0.25 µs)
12.1 < f ≤ 2000 − 3.0 × 10
4
f
−1
2000 < f ≤ 20 k 3.0 × 10
4
f
−1
20 k < f ≤ 400 k 1.5 UI
400 k < f ≤ 4 M 6.0 × 10
5
f
−1
UI
4 M < f ≤ 80 M 0.15 UI
T1316850-99
1.0E+00
1.0E+01
1.0E+02
1.0E+01 1.0E+03 1.0E+05
1.0E–01
1.0E+00 1.0E+02 1.0E+04
Frequency (Hz)
1.0E+06 1.0E+07
1.0E+03
1.0E+08
(Note)
1.0E+04
NOTE – The dashed curve is the requirement for 1544 kbit/s networks for frequencies less than 2 kHz.
6.2 Jitter and wander generation
For SDH equipment, jitter and wander generation requirements are given in ITU-T
Recommendations G.783, G.812 and G.813. Guidelines for the measurement of wander are included
in Appendix II.
6.3 Jitter and wander transfer
Jitter and wander transfer for SDH equipment is dependent on the synchronization method used in
each type of equipment. Jitter and wander transfer requirements for SDH equipment are specified in
ITU-T Recommendations G.783, G.812 and G.813.

ITU-T G.825 (03/2000) 11
APPENDIX I
Relationship between network interface jitter requirements and input jitter tolerance
I.1 Network interface jitter requirements
For all SDH bit rates, two network limits are specified in Table 1: one for a wide-band measurement
filter and one for a high-band measurement filter. The general form of this specification is shown in
Table I.1 and is applicable to all SDH rates.
At any SDH network interface, the following output jitter specifications must be met:
Timing jitter as measured over a 60-second interval with a band pass filter with a lower cut-off
frequency f1 and a minimum upper cut-off frequency f4 shall not exceed A2 Unit Intervals (UI) peak-
to-peak. Also, timing jitter as measured over a 60-second interval with a band pass filter with a lower
cut-off frequency f3 and a minimum upper cut-off frequency f4 shall not exceed A1 Unit Intervals
(UI) peak-to-peak. The roll off at lower cut-off frequency, f1 and f3, shall be 20 dB/decade. The roll
off at the upper cut-off frequency, f4, shall be −60 dB/decade in accordance with ITU-T
Recommendation O.172.
Table I.1/G.825 −−−− General form for SDH interface jitter requirements
Measurement filter
Measurement
bandwidth
(UIpp)
Wide-band f1 to f4 A2
High-band f3 to f4 A1
The value of f1 reflects the narrowest timing circuit cutoff frequency expected in a line system. The
timing circuit may time a regenerator's output signal and could be implemented as a Phase-Locked
Loop (PLL). Jitter at frequencies higher than the bandwidth of this PLL will be partially absorbed by
the PLL's buffer. The portion not absorbed could cause transmission errors due to buffer spill. Jitter
at frequencies lower than this bandwidth will simply pass through without affecting transmission
performance. The value of f1 therefore represents the narrowest bandwidth that might be used in this
output timing circuit. The value of f3 is related to the bandwidth of input timing acquisition circuitry.
Jitter at frequencies higher than this bandwidth will constitute alignment jitter and will cause an
optical power penalty due to its effect on the eye pattern. This high frequency jitter must therefore be
limited to the same degree that equipment specifications limit optical power penalty through jitter
tolerance.
The value of f4 reflects reasonable measurement limitations and is listed to establish minimum
measurement bandwidth requirements. f4 is chosen to include all expected, significant alignment
jitter. A value one decade beyond the widest expected cutoff frequency was chosen (see ITU-T
Recommendation G.783).
The values of A1 and A2 are directly related to input sinusoidal jitter tolerance. These parameters
have built-in margin and are reasonably conservative because:
1) sinusoidal jitter represents worst case jitter with respect to input jitter tolerance; and
2) accumulated SDH line jitter will not be sinusoidal (instead, it will be noisy).

12 ITU-T G.825 (03/2000)
I.2 Input jitter tolerance of network equipment
The general form of the weighting filters used for measuring output jitter at a network interface
given in Table I.1 are reproduced below in Figure I.1. The filter responses are given in equations
I.2-1 and I.2-2.
T1316860-99
f (Hz)
)2(1 ftjH π
)2(2 ftjH π
f1 f3 f4
1
Figure I.1/G.825 −−−− Weighting filters for measuring network interface output jitter
3
4
2
4
2
4
3
3
4
1
1
22
)(
ω+ω+ω+
ω
⋅
ω+
=
ssss
s
sH (I.2-1)
3
4
2
4
2
4
3
3
4
3
2
22
)(
ω+ω+ω+
ω
⋅
ω+
=
ssss
s
sH (I.2-2)
443311 222 fff π=ωπ=ωπ=ω
The first term of the function H1(s) represents the phase error transfer function He(s) of some PLL,
and its amplitude of A2 = 1.5 UIpp represents its phase error tolerance.
Then the corresponding input phase tolerance of the PLL is given by:
)2(
)(
1
2
1
fjH
A
fAtol
π
= (I.2-3)
Similarly, the input phase tolerance corresponding to H2(s) and its amplitude of A1 = 0.UIpp is given
by:
)2(
)(
2
1
2
fjH
A
fAtol
π
= (I.2-4)
These sinusoidal jitter tolerance masks are illustrated in Figure I.2. If unweighted sinusoidal jitter at
a network interface satisfies both of these masks, it also satisfies (i.e. lies below) a single mask that
is the lower of the two masks for each frequency. Such a combined mask is shown as a dashed curve
in Figure I.3.

ITU-T G.825 (03/2000) 13
T1316870-99
f1 f3 f4 f (Hz)
UIpp
)(2 fAtol
)(1 fAtol
A2
A1
Amplitude
1.5
0.15
Figure I.2/G.825 −−−− Upper bounds on sinusoidal jitter amplitude
Figure I.3 compares this combined mask with the STM-1(optical) input jitter/wander sinusoidal
tolerance mask. They are the same in the range 19.3 < f < 1.3 MHz. In the wander region of phase
(f < 19.3 Hz), there are no interface specifications that use weighting filters to check the peak-to-
peak phase. (The 10 Hz low-pass wander measurement filter might be considered a weighting filter,
but for wander it is MTIE or TDEV that is measured rather than peak-to-peak phase).
T1316880-99
f1
f3 f4
f (Hz)
f2
A2
A1
UIpp
0.125 19.3 6.5k 65k 1.3M500
Figure 1/G.825
1.5
0.15
38.9
Amplitude
Lower of Atol1(f) or Atol2(f)
Figure I.3/G.825 −−−− Upper bound on sinusoidal output jitter at an STM-1(Optical) interface
[lower of Atol1(f) or Atol2(f)] compared with input jitter/wander tolerance mask

14 ITU-T G.825 (03/2000)
APPENDIX II
Measurement methodology for output wander of synchronous interfaces
Instrumentation in accordance with ITU-T Recommendation O.172 is appropriate for measurement
of wander parameters.
When the signal is synchronous (i.e. normally PRC-traceable), and is used to carry synchronization,
its wander is measured by comparing its phase with that of another PRC. The test procedure for
measuring MTIE of a synchronous signal is shown in Figure II.1 (the standard estimator formula for
calculating MTIE is given in Annex B/G.810).
The PRC used for the wander measurement need not be the same as that used to originate the
synchronous signal, for most measurement applications. However, it should be noted that the
worst-case frequency difference between two PRCs could give rise to a phase difference of the order
of 2 µs per day.
T1316890-99
Phase Wander MTIE
PRC
Measurement
Reference
Source Reference
PRC
Phase
Detector
10-Hz
LPF
Calculate
MTIE
Transport
Network
Terminating
Element
Figure II.1/G.825 −−−− MTIE measurement of synchronous signals
APPENDIX III
SDH Line systems and Interworking implications
ITU-T Recommendation G.783 identifies two different types of regenerators, Type A and Type B,
which can be used in SDH line systems. The different regenerator types exhibit different jitter
characteristics. Type B regenerators exhibit reduced jitter tolerance. Performance penalties due to
excessive alignment jitter place restrictions on the use of both Type A and Type B equipment in the
same SDH line system. Moreover, the amplitude/frequency characteristics of the accumulated jitter
can adversely affect transmission-performance. These limitations must be taken into account by
carrier entities who are administering the particular SDH line system.
At network interfaces (e.g. those at international boundaries), STM-N signals must meet interface
limits regardless of the individual carrier's equipment choice. It is therefore desirable that the
interface requirement is compatible with the type of jitter expected to appear on both Type A and
Type B line systems.

ITU-T G.825 (03/2000) 15
Interworking implications
Taking into account the characteristics of the Type A and Type B regenerators and the above
interface specifications, the following equipment interworking implications can be derived:
1) the magnitude of jitter expected to accumulate on all SDH line systems employing only
Type A equipment falls-within the bounds specified in Table 1;
2) the magnitude of jitter expected to accumulate on all SDH line systems employing only
Type B equipment falls within the bounds specified in Table 1;
3) equipment exhibiting Type A jitter tolerance characteristics will tolerate that jitter which
meets the limits given in Table 1;
4) equipment exhibiting Type B jitter tolerance characteristics will tolerate the jitter expected
to accumulate on Type B SDH line systems. Such equipment, however, may require some
jitter reduction for input signals that just approach the limits given for the appropriate line
rates in Tables 3, 5, 6 or Table 7. This is expected to be the case when Type B equipment
follows a chain of Type A regenerators. This represents the only interworking consideration
required by the SDH Interface specifications proposed in this ITU-T Recommendation.

Geneva, 2001
SERIES OF ITU-T RECOMMENDATIONS
Series A Organization of the work of ITU-T
Series B Means of expression: definitions, symbols, classification
Series C General telecommunication statistics
Series D General tariff principles
Series E Overall network operation, telephone service, service operation and human factors
Series F Non-telephone telecommunication services
Series G Transmission systems and media, digital systems and networks
Series H Audiovisual and multimedia systems
Series I Integrated services digital network
Series J Transmission of television, sound programme and other multimedia signals
Series K Protection against interference
Series L Construction, installation and protection of cables and other elements of outside plant
Series M TMN and network maintenance: international transmission systems, telephone circuits,
telegraphy, facsimile and leased circuits
Series N Maintenance: international sound programme and television transmission circuits
Series O Specifications of measuring equipment
Series P Telephone transmission quality, telephone installations, local line networks
Series Q Switching and signalling
Series R Telegraph transmission
Series S Telegraph services terminal equipment
Series T Terminals for telematic services
Series U Telegraph switching
Series V Data communication over the telephone network
Series X Data networks and open system communications
Series Y Global information infrastructure and Internet protocol aspects
Series Z Languages and general software aspects for telecommunication systems

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