1、 International Telecommunication Union ITU-T O.175TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (10/2012) SERIES O: SPECIFICATIONS OF MEASURING EQUIPMENT Equipment for the measurement of digital and analogue/digital parameters Jitter measuring equipment for digital systems based on XG-PON Recommen
2、dation ITU-T O.175 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 for the measurement of digital and analo
3、gue/digital parameters O.130O.199Equipment for the measurement of optical channel parameters O.200O.209 Equipment to perform measurements on IP networks O.210O.219 Equipment to perform measurements on leased-circuit services O.220O.229 For further details, please refer to the list of ITU-T Recommend
4、ations. Rec. ITU-T O.175 (10/2012) i Recommendation ITU-T O.175 Jitter measuring equipment for digital systems based on XG-PON Summary Recommendation ITU-T O.175 specifies test instrumentation that is used to generate and measure timing jitter in digital systems based on the XG-PON. History Edition
5、Recommendation Approval Study Group 1.0 ITU-T O.175 2012-10-29 15 ii Rec. ITU-T O.175 (10/2012) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommuni
6、cation 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 Assembl
7、y (WTSA), 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 WTSA Resolution 1. In some areas of information technology which
8、fall within ITU-Ts 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. Compliance with this
9、 Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words “shall“ or some other obligatory langua
10、ge such as “must“ and the negative equivalents are used to express requirements. The use of such words does not suggest 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 Re
11、commendation 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
12、approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may 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
13、TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2013 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T O.175 (10/2012) iii Table of Contents Page 1 Scope 1 2 References. 1 3 Definitions 2 4 Ab
14、breviations and acronyms 2 5 Conventions 3 6 Functional block diagram . 3 7 Interfaces. 3 7.1 XG-PON interfaces 3 7.2 External reference clock input 4 8 Jitter generation function 4 8.1 Modulation source 4 8.2 Clock generator 4 8.3 Digital test pattern generator 4 8.4 Sinusoidal jitter generation fu
15、nction 4 9 Jitter measurement function 6 9.1 Reference timing signal 6 9.2 Measurement capabilities . 6 9.3 Measurement bandwidths . 7 9.4 Measurement accuracy . 8 9.5 Additional facilities 9 10 Operating environment . 9 Appendix I Jitter evaluation methods for an optical network unit burst mode tra
16、nsmitter 10 I.1 Introduction 10 I.2 Evaluation using wideband real-time oscilloscope 10 I.3 Evaluation using sampling oscilloscope . 12 I.4 Evaluation using BERT 13 Bibliography. 15 Rec. ITU-T O.175 (10/2012) 1 Recommendation ITU-T O.175 Jitter measuring equipment for digital systems based on XG-PON
17、 1 Scope The test instrumentation consists principally of a jitter measurement function and a jitter generation function. Measurements can be performed at the physical layer of XG-PON systems. A bit-error rate test (BERT) set may also be required for certain types of measurements; this may be part o
18、f the same instrumentation or it may be physically separate. Test instrumentation for the generation and measurement of jitter in digital systems based on synchronous digital hierarchy (SDH) is specified in ITU-T O.172. It is recommended that ITU-T G.987.2 should be read in conjunction with this Rec
19、ommendation. 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 subje
20、ct to revision; 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. The reference to a document w
21、ithin this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. ITU-T G.703 Recommendation ITU-T G.703 (2001), Physical/electrical characteristics of hierarchical digital interfaces. ITU-T G.783 Recommendation ITU-T G.783 (2006), Characteristics of synchronous
22、digital hierarchy (SDH) equipment functional blocks. ITU-T G.810 Recommendation ITU-T G.810 (1996), Definitions and terminology for synchronization networks. ITU-T G.987 Recommendation ITU-T G.987 (2012), 10-Gigabit-capable passive optical network (XG-PON) systems: Definitions, abbreviations, and ac
23、ronyms. ITU-T G.987.1 Recommendation ITU-T G.987.1 (2010), 10-Gigabit-capable passive optical networks (XG-PON): General requirements. ITU-T G.987.2 Recommendation ITU-T G.987.2 (2010), 10-Gigabit-capable passive optical networks (XG-PON): Physical media dependent (PMD) layer specification. ITU-T G.
24、987.3 Recommendation ITU-T G.987.3 (2010), 10-Gigabit-capable passive optical networks (XG-PON): Transmission convergence (TC) specifications. ITU-T G-Sup.48 ITU-T G-series Recommendations Supplement 48 (2010), 10-Gigabit-capable passive optical networks: Interface between media access control with
25、serializer/deserializer and physical medium dependent sublayers. ITU-T O.3 Recommendation ITU-T O.3 (1992), Climatic conditions and relevant tests for measuring equipment. ITU-T O.172 Recommendation ITU-T O.172 (2005), Jitter and wander measuring equipment for digital systems which are based on the
26、synchronous digital hierarchy (SDH). 2 Rec. ITU-T O.175 (10/2012) IEEE 802.3 IEEE Standard 802.3-2008, Information technology Telecommunications and information exchange between systems Local and metropolitan area networks Specific requirements Part 3: Carrier Sense Multiple Access with Collision De
27、tection (CSMA/CD) Access Method and Physical Layer Specifications. 3 Definitions This Recommendation uses the following terms defined elsewhere: 3.1 (timing) jitter: ITU-T G.810. 3.2 10-gigabit-capable passive optical network (XG-PON): ITU-T G.987. 3.3 XG-PON1: ITU-T G.987. 3.4 XG-PON2: ITU-T G.987.
28、 Note that ITU-T G.987 provides additional definitions and abbreviations used in timing and synchronization Recommendations. They also provide background information on the need to limit phase variation and impairments on digital systems. 4 Abbreviations and acronyms This Recommendation uses the fol
29、lowing abbreviations and acronyms: BER Bit Error Ratio BERT Bit Error Rate Tester B-PON Broadband Passive Optical Network FEC Forward Error Correction FTTx Fibre to the x (B building, business; H home; C cabinet, curb, P premises) G-PON Gigabit-capable Passive Optical Network HEC Hybrid Error Correc
30、tion LOB Loss Of Burst LODS Loss Of Downstream Synchronization LOS Loss Of Signal NRZ Non Return to Zero OLT Optical Line Terminal ONT Optical Network Terminal ONU Optical Network Unit PLL Phase-Locked Loop PON Passive Optical Network ppm parts per million PRBS Pseudo Random Binary Sequence RMS Root
31、 Mean Square TIE Time Interval Error TJ Total Jitter Rec. ITU-T O.175 (10/2012) 3 UI Unit Interval UIpp Unit Interval, peak-to-peak UNI User Network Interface XG-PON 10-Gigabit-capable Passive Optical Network, ITU-T G.987-series Recommendations. 5 Conventions For the purposes of this Recommendation,
32、 the following convention is adopted: a) The particular interface signals used are denoted either by their standardized signal formats, e.g., XG-PON1, or by their bit rate, e.g., 2.48832 Gbit/s for upstream, and 9.95328 Gbit/s for downstream. The default physical format of XG-PON interfaces is consi
33、dered to be optical. 6 Functional block diagram Figure 1 shows the general block diagram of the equipment and identify the main functions covered in this Recommendation. The figure does not describe a specific implementation. Figure 1 Functional block diagram for jitter test set 7 Interfaces 7.1 XG-
34、PON interfaces The equipment shall be capable of operating at one or more of the following XG-PON interfaces. Table 9-1 of ITU-T G.987.2 lists the interfaces supporting XG-PON. Test signal input*1Jitter result Jitter measurement function *1Jitter measurement functionin this figure is applicable toXG
35、-PON interfaces. Interfaces Reference timing signal Phase detector Measurementfilter Jitter generation function Interfaces External reference clock input Jitter modulation source Clock generator Test signaloutput 4 Rec. ITU-T O.175 (10/2012) 7.2 External reference clock input The measuring equipment
36、 shall support reference data signals at bit rates of 1 544 kbit/s or 2 048 kbit/s. If 2 048 kbit/s can be accepted, the equipment shall also accept a clock signal at 2 048 kHz as a reference. The characteristics of clock signals shall be in accordance with ITU-T G.703. 8 Jitter generation function
37、Tests of digital equipment may be made with either a jittered or a non-jittered digital signal. This will require the digital test pattern generator, clock generator and modulation source shown in Figure 1. 8.1 Modulation source The modulation source, required to perform tests conforming to relevant
38、 Recommendations may be provided within the clock generator and/or digital test pattern generator, or may be provided separately. This Recommendation defines a sinusoidal modulation source for jitter generation. The sinusoidal jitter generation functions are defined in clause 8.4. 8.2 Clock generato
39、r It shall be possible to phase-modulate the clock generator from the modulation source and to indicate the peak-to-peak phase deviation of the modulated signal. The generated peak-to-peak jitter and the modulating frequencies shall meet the minimum requirements of Figure 2. The generated peak-to-pe
40、ak jitter and the modulating frequencies for XG-PON1 and XG-PON2 shall meet ITU-T G.987.2. The burst signal measurement methodology is defined in Appendix I. 8.2.1 Accuracy of clock generator The frequency deviation of the internal clock signal from its nominal value shall be less than 32 ppm (strat
41、um-4 clock) excluding locked operation. As an option, the clock generator may provide adjustable frequency offset of sufficient magnitude to facilitate tests across the clock tolerance range of the equipment under test, e.g., 10 ppm to 50 ppm as defined for the various bit rates listed in Table 9-1
42、of ITU-T G.987.1. It shall be possible to phase-lock the generation function to an external reference clock source of arbitrary accuracy; refer to clause 7.2. 8.3 Digital test pattern generator The jitter measurement function will normally be used in conjunction with any suitable digital test patter
43、n generator supporting the following facility. a) XG-PON signal in accordance with ITU-T G.987.3. 8.4 Sinusoidal jitter generation function The ability to generate sinusoidal jitter for jitter tolerance measurements as described in ITU-T G.987.2 may be provided. The following requirements shall be m
44、et to ensure sufficiently accurate, robust and consistent measurements. 8.4.1 Minimum sinusoidal jitter generation capability The jitter amplitude/frequency characteristics of the generation function shall meet the minimum requirements of Figure 2 for XG-PON signals. Rec. ITU-T O.175 (10/2012) 5 Sig
45、nal (Gbit/s) Minimum peak-to-peak jitter amplitude (UIpp) Jitter frequency breakpoints (Hz) A1 A2 f1f2 f3 f4 2.48832 2 0.2 10 100k 1M 20M 9.95328 2 0.2 10 400k 4M 80M NOTE Values based on requirements of Table 9-8 of ITU-T G.987.2 Figure 2 Minimum amplitude of adjustable generated sinusoidal jitter
46、amplitude versus jitter frequency for XG-PON signals 8.4.2 Generation accuracy The sinusoidal test signal source shall be compatible with the jitter measurement function so that the overall measuring accuracy is not substantially deteriorated. The generation accuracy may be increased by measuring th
47、e jitter applied to the unit under test using a corresponding jitter measuring device. The generating accuracy of the sinusoidal jitter generation function depends on several factors, such as fixed intrinsic error, setting resolution, distortion and frequency response error. In addition, some error
48、is a function of the actual setting. 8.4.2.1 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 Table1 for XG-PON signals. The frequencies f1 and f4used in Table 1 are defined in Figure 2. NOT
49、E This Recommendation excludes any wideband intrinsic jitter components. Table 1 Variable error (Q) of XG-PON signal jitter generation Signal Error, Q Frequency range XG-PON 10% f1to f4NOTE Value of jitter range is for further study. Peak-to-peak Wander amplitude (log scale) Frequency (log scale)A1A2f1f2 f3f46 Rec. ITU-T O.175 (10/2012) 8.4.2.2 Intrinsic jitter of generation function The intrinsic jitter of the jitter generation function measured in the bandwidth f1-f4, as defin
