1、 International Telecommunication Union ITU-T O.173TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (03/2007) SERIES O: SPECIFICATIONS OF MEASURING EQUIPMENT Equipment for the measurement of digital and analogue/digital parameters Jitter measuring equipment for digital systems which are based on the O
2、ptical Transport Network (OTN) ITU-T Recommendation O.173 ITU-T O-SERIES RECOMMENDATIONS SPECIFICATIONS OF MEASURING EQUIPMENT General O.1O.9 Maintenance access O.10O.19 Automatic and semi-automatic measuring systems O.20O.39 Equipment for the measurement of analogue parameters O.40O.129 Equipment f
3、or the measurement of digital and analogue/digital parameters O.130O.199 Equipment for the measurement of optical channel parameters O.200O.209 Equipment to perform measurements on IP networks O.210O.219 For further details, please refer to the list of ITU-T Recommendations. ITU-T Rec. O.173 (03/200
4、7) i ITU-T Recommendation O.173 Jitter measuring equipment for digital systems which are based on the Optical Transport Network (OTN) Summary This Recommendation specifies instrumentation that is used to generate and measure jitter in digital systems based on the OTN. Measurement requirements for cl
5、ient interfaces, e.g., SDH line interfaces are not addressed in this Recommendation. The requirements for the characteristics of the jitter measuring equipment that are specified in this Recommendation must be adhered to in order to ensure consistency of results between equipment produced by differe
6、nt manufacturers. Source ITU-T Recommendation O.173 was approved on 16 March 2007 by ITU-T Study Group 4 (2005-2008) under the ITU-T Recommendation A.8 procedure. Keywords Input jitter tolerance, input wander tolerance, jitter generation, jitter measurement, jitter transfer function, output jitter.
7、ii ITU-T Rec. O.173 (03/2007) 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, opera
8、ting and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, pr
9、oduce Recommendations on these topics. The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In t
10、his Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure e.g. in
11、teroperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words “shall“ or some other obligatory language such as “must“ and the negative equivalents are used to express requirements. The use of such words does not suggest
12、 that compliance with the Recommendation is required of any party. 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 evidenc
13、e, 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
14、be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2007 All rights reserved. No part of this publication may be r
15、eproduced, by any means whatsoever, without the prior written permission of ITU. ITU-T Rec. O.173 (03/2007) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions 2 4 Abbreviations and acronyms 2 5 Functional block diagram . 2 6 Interfaces. 3 6.1 Optical interfaces 3 6.2 Electrical interfaces 3 6
16、.3 External reference clock input 3 6.4 Input interface sensitivity . 3 7 Jitter generation function 3 7.1 Modulation source 4 7.2 Clock generator 4 7.3 Digital test pattern generator 4 7.4 Minimum jitter generation capability. 4 7.5 Generation accuracy . 5 8 Jitter measurement function 6 8.1 Refere
17、nce timing signal 6 8.2 Measurement capabilities . 6 8.3 Measurement bandwidths. 7 8.4 Measurement accuracy . 8 8.5 Analogue output . 10 8.6 Jitter transfer measurement accuracy . 10 9 Operating environment . 10 Annex A OTUk test signals for jitter measurement 11 A.1 Introduction 11 A.2 Test signal
18、structure for OTN signals. 11 iv ITU-T Rec. O.173 (03/2007) Introduction The timing performance of OTN networks and OTN equipment elements is specified in ITU-T G.8251, using jitter and wander parameters. This Recommendation specifies the various characteristics of jitter measuring equipment, which
19、are needed in order to support the requirements of ITU-T G.8251 and to perform other test and measuring tasks. While functional and characteristic requirements are given for the measuring equipment, the realization of the equipment configuration is not covered and should be given careful considerati
20、on by the designer and user. In particular, it is not required that all features described in this Recommendation shall be provided in one piece of equipment. Users may select those functions, which correspond best to their applications. ITU-T Rec. O.173 (03/2007) 1 ITU-T Recommendation O.173 Jitter
21、 measuring equipment for digital systems which are based on the Optical Transport Network (OTN) 1 Scope This Recommendation specifies test instrumentation that is used to generate and measure timing jitter in digital systems based on the Optical Transport Network (OTN). The test instrumentation cons
22、ists principally of a jitter measurement function and a jitter generation function. Measurements can be performed at the physical layer of OTN network node interfaces (NNIs). A bit error rate test set may also be required for certain types of measurements; this may be part of the same instrumentatio
23、n or it may be physically separate. It is recommended that ITU-T G.8251 and ITU-T G.709 be read in conjunction with this Recommendation. 2 References The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recom
24、mendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other refere
25、nces listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. ITU-T G.693 ITU-T Recommendation G.693 (2006), Optical interfaces for int
26、ra-office systems. ITU-T G.703 ITU-T Recommendation G.703 (2001), Physical/electrical characteristics of hierarchical digital interfaces. ITU-T G.709 ITU-T Recommendation G.709/Y.1331 (2003), Interfaces for the Optical Transport Network (OTN). ITU-T G.810 ITU-T Recommendation G.810 (1996), Definitio
27、ns and terminology for synchronization networks. ITU-T G.959.1 ITU-T Recommendation G.959.1 (20012006), Optical transport network physical layer interfaces. ITU-T G.8251 ITU-T Recommendation G.8251 (2001), The control of jitter and wander within the optical transport network (OTN). ITU-T O.3 ITU-T R
28、ecommendation O.3 (1992), Climatic conditions and relevant tests for measuring equipment. ITU-T O.172 ITU-T Recommendation O.172 (20012005), Jitter and wander measuring equipment for digital systems which are based on the Synchronous Digital Hierarchy synchronous digital hierarchy (SDH). 2 ITU-T Rec
29、. O.173 (03/2007) 3 Definitions For the purposes purpose of this Recommendation, the following definitions apply (refer to ITU-T G.810): 3.1 (timing) jitter: The short-term variations of the significant instances of a digital signal from their ideal positions in time (where “short-term“ implies that
30、 these variations are of frequency greater than or equal to 10 Hz). 3.2 wander: The long-term variations of the significant instances of a digital signal from their ideal position in time (where “long-term“ implies that these variations are of frequency less than 10 Hz). It may be useful to note tha
31、t ITU-T G.810 provides additional definitions and abbreviations used in timing and synchronization Recommendations. It also provides background information on the need to limit phase variation and the impairments on digital systems. 4 Abbreviations and acronyms This Recommendation uses the following
32、 abbreviations and acronyms: OPUk Optical channel Payload Unit-k OTN Optical Transport Network OTUk completely standardized Optical channel Transport Unit-k ppm parts per million PRBS Pseudo Random Binary Sequence SDH Synchronous Digital Hierarchy UI Unit Interval UIpp Unit Interval peak-to-peak 5 F
33、unctional block diagram Figure 1 shows the block diagram of the instrumentation in general form, identifying the main functions that are addressed in this Recommendation. The figure does not describe a specific implementation. ITU-T Rec. O.173 (03/2007) 3 O.173(07)_F01Externalreferenceclock inputMod
34、ulationsourceClockgeneratorPatterngeneratorInterfacesJittergenerationfunctionTe stsignaloutputReferencetimingsignalPhasedetectorMeasurementfilterJittermeasurement functionJitterresultTe s tsignalinputInterfacesFigure 1 Functional block diagram for jitter test set 6 Interfaces 6.1 Optical interfaces
35、The instrumentation shall be capable of operating at one or more of the following OTUk bit rates and corresponding optical interface characteristics as defined in the appropriate clauses of ITU-T G.959.1. OTU1 255/238 * 2 488 320 kbit/s 2 666 057.143 kbit/s OTU2 255/237 * 9 953 280 kbit/s 10 709 225
36、.316 kbit/s OTU3 255/236 * 39 813 120 kbit/s 43 018 413.559 kbit/s 6.2 Electrical interfaces As an option, the jitter measurement function shall be capable of measuring jitter at an electrical clock output port when such an access is provided on digital equipment. 6.3 External reference clock input
37、The measuring equipment shall accept data signals at bit rates of 1544 kbit/s or 2048 kbit/s as a reference. If 2048 kbit/s can be accepted, the equipment shall also accept a clock signal at 2048 kHz as a reference. The characteristics of the clock signals shall be in accordance with ITU-T G.703. 6.
38、4 Input interface sensitivity The jitter measurement function is required to operate satisfactorily under the input conditions as specified in ITU-T G.959.1 and ITU-T G.693. 7 Jitter generation function Tests of OTN equipment may be made with either a jittered or a non-jittered digital signal. This
39、will require the digital test pattern generator, clock generator and modulation source shown in Figure 1. 4 ITU-T Rec. O.173 (03/2007) 7.1 Modulation source The modulation source, required to perform tests in conformance with relevant Recommendations, may be provided within the clock generator and/o
40、r digital test pattern generator or it may be provided separately. In this Recommendation, the modulation source is defined to be sinusoidal. 7.2 Clock generator It shall be possible to phase-modulate the clock generator from the modulation source and to indicate the peak-to-peak phase deviation of
41、the modulated signal. The generated peak-to-peak jitter and the modulating frequencies shall meet the minimum requirements of Table 1 and Figure 1. If the output interfaces for the modulated clock signal and/or the external timing reference signal are provided, the minimum amplitude shall be 1 Volt
42、peak-to-peak into 75 or 0.25 Volt peak-to-peak into 50 . 7.2.1 Accuracy of the clock generator The frequency deviation of the internal clock signal from its nominal value shall be less than: 4.6 ppm As an option, the clock generator may provide adjustable frequency offset of sufficient magnitude to
43、facilitate testing across the clock tolerance range of the equipment-under-test, e.g., 10 ppm to 100 ppm. It shall be possible to phase-lock the generation function to an external reference clock source of arbitrary accuracy; refer also to clause 7.3. 7.3 Digital test pattern generator The digital t
44、est pattern generator (see Annex A) shall be capable of providing OTUk signals with a frame structure and payload mapping of a NULL client or PRBS test signal into OPUk in accordance with clauses 17.4.1 and 17.4.2 of ITU-T G.709. 7.4 Minimum jitter generation capability The jitter amplitude/frequenc
45、y characteristic of the generation function shall meet the minimum requirements of Table 1 and Figure 2 and Table 1. 2. Table 1 Minimum amplitude of adjustable generated jitter amplitude versus jitter frequency for OTUk signals Minimum peak-to-peak jitter amplitude (UIpp) Jitter frequency breakpoint
46、s (Hz) Signal A1 A2 A3 f0 f1 f2 f3 f4 OTU1 20 2 0.2 500 5 k 100 k 1 M 20 M OTU2 20 2 0.2 2 k 20 k 400 k 4 M 80 M OTU3 20 8 0.2 8 k 20 k 400 k 16 M 320 M ITU-T Rec. O.173 (03/2007) 5 O.173(07)_F02Peak-to-peakjitter amplitude(log scale)Frequency (log scale)A1A2A3f0f1f2f3f4Figure 2 Generated jitter amp
47、litude versus jitter frequency 7.5 Generation accuracy The test signal source shall be compatible with the jitter measurement function in such a way that the overall measuring accuracy is not substantially deteriorated. The generation accuracy may be increased by measuring the jitter applied to the
48、unit under test using a corresponding jitter measuring device. The generating accuracy of the jitter generation function is dependent upon several factors such as fixed intrinsic error, setting resolution, distortion and frequency response error. In addition, there is an error that is a function of
49、the actual setting. 7.5.1 Phase amplitude error The amplitude error of sinusoidal jitter generation shall be less than: Q% of setting 0.02 UIpp where Q is a variable error specified in Table 2. NOTE This Recommendation excludes any wideband intrinsic jitter/wander components. Table 2 Variable error (Q) of OTUk jitter generation Signal Error, Q Frequency range 10% 500 Hz to 5 kHz 8% 5 kHz to 500 kHz 12% 500 kHz to 2 MHz OTU1 15% 2 MHz to 20 MHz 10% 2 kHz to 20 kHz 8% 20 kHz to 1 MHz 12% 1 MHz to 4 MHz OTU2
