1、 International Telecommunication Union ITU-T O.172TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Amendment 1(06/2008) SERIES O: SPECIFICATIONS OF MEASURING EQUIPMENT Equipment for the measurement of digital and analogue/digital parameters Jitter and wander measuring equipment for digital systems wh
2、ich are based on the synchronous digital hierarchy (SDH) Amendment 1 Recommendation ITU-T O.172 (2005) Amendment 1 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
3、 measurement of analogue parameters O.40O.129 Equipment for 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 Equipment to perform measurements on le
4、ased-circuit services O.220O.229For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T O.172 (2005)/Amd.1 (06/2008) i Recommendation ITU-T O.172 Jitter and wander measuring equipment for digital systems which are based on the synchronous digital hierarchy (SDH) Amendment
5、1 Summary Amendment 1 to Recommendation ITU-T O.172 includes changes to the measurement bandwidth, measurement accuracy, jitter transfer measurement accuracy, Appendices VII and VIII. Source Amendment 1 to Recommendation ITU-T O.172 (2005) was approved on 29 June 2008 by ITU-T Study Group 4 (2005-20
6、08) under Recommendation ITU-T A.8 procedure. ii Rec. ITU-T O.172 (2005)/Amd.1 (06/2008) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication
7、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 Assembly (WTSA
8、), 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 fall wi
9、thin 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 Recomm
10、endation 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 language such a
11、s “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 Recommendat
12、ion 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
13、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 TSB paten
14、t database at http:/www.itu.int/ITU-T/ipr/. ITU 2009 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.172 (2005)/Amd.1 (06/2008) 1 Recommendation ITU-T O.172 Jitter and wander measuring equipment fo
15、r digital systems which are based on the synchronous digital hierarchy (SDH) Amendment 1 1) Introduction This amendment contains extensions to the 2005 version of Recommendation ITU-T O.172. 2) Additions 2.1) Clause 9.3, Measurement bandwidths Replace Table 7 with the following table, which adds the
16、 measurement bandwidth for f12high-pass filter for STM-64 rate. Table 7/O.172 Jitter measurement function bandwidth for SDH line signals Jitter measurement bandwidth (3 dB cut-off frequencies) Signal f1(Hz) high-pass f12(Hz) high-pass f3(Hz) high-pass f4(Hz) low-pass STM-0e, STM-0 100 20 k 400 k STM
17、-1e 500 65 k 1.3 M STM-1 500 12 k 65 k 1.3 M STM-4 1 k 12 k 250 k 5 M STM-16 5 k 12 k 1 M 20 M STM-64 20 k 50 k 4 M 80 M STM-256 80 k 16 M 320 M NOTE 1 Values for STM-0 are based on the requirements of ANSI T1.105.03 21. NOTE 2 Values for STM-256 are to be considered provisional, since network requi
18、rements are not yet defined in ITU-T Rec. G.825 13. NOTE 3 The f12high-pass filter is optional. 2.2) Clause 9.4, Measurement accuracy Replace Table 8 with the following table, which adds the fixed error for structured signal in the f12-f4band for STM-64 rate. 2 Rec. ITU-T O.172 (2005)/Amd.1 (06/2008
19、) Table 8/O.172 Fixed error (W) of SDH line jitter measurements Maximum peak-to-peak jitter error (UIpp) for given digital signals Structured signal Clock signal Signal f1-f4f12-f4f3-f4f1-f4f12-f4f3-f4STM-0e FFS FFS FFS FFS STM-0 0.07 0.035 0.05 0.03 STM-1e 0.07 0.025 0.05 0.02 STM-1 0.07 0.035 0.03
20、5 0.05 0.03 0.03 STM-4 0.1 0.035 0.035 0.05 0.03 0.03 STM-16 0.1 0.035 0.035 0.05 0.03 0.03 STM-64 0.1 0.035 0.035 0.05 0.03 STM-256 0.15 0.05 0.05 0.03 Replace paragraph b) in clause 9.4.1 with the following: b) An optical signal in conformance with ITU-T Rec. G.957 14 or G.691 1 and with a nominal
21、 power in the range 10 dBm to 12 dBm. Operation at higher input power levels may be permitted in accordance with the minimum mean launch powers specified in ITU-T Rec. G.957 14 or G.691 1 or G.693 2. 2.3) Clause 9.5, Jitter transfer measurement accuracy Add the following underlined part to the text
22、of clause 9.5: The total measurement error in the jitter frequency range fL= 0.01 fCand fH= 100 fCor f4, if f4is lower than 100 fC, when using input jitter amplitude equal to the applicable jitter tolerance masks, shall be less than: 0.05 dB 0.12g where g is the measured jitter transfer gain at the
23、jitter frequency fmin dB, and fL, fC, and fH areaccording to Table 15-2 of ITU-T Rec. G.783. This measurement error applies for g greater than or equal to 45 dB. No accuracy is specified for g less than 45 dB. 2.4) Appendix VII, Method for verification of measurement result accuracy and intrinsic fi
24、xed error 2.4.1) Clause VII.2, System implementation a) Replace the following text in clause VII.2: It is recommended the relative oscillator amplitudes be adjusted up to 100 mUI phase modulation, this can be calibrated using the spectrum analyser using normal FM theory techniques. The operation of
25、the pulse generator is used to gate the Oscillator 2 clock, thus directly controlling the modulation burst time. The synchronization of the modulation burst relative to the frame structure is for further study. To minimize potential phase discontinuities, the modulation burst shall be either synchro
26、nized to the zero crossings of the sinusoidal modulation signal or alternatively shall have a maximum on/off transition time given approximately by the following relation. Rec. ITU-T O.172 (2005)/Amd.1 (06/2008) 3 b) Add the following text to the end of clause VII.2: The synchronization of the modul
27、ation burst relative to the “SDH“ frame structure is for further study. 2.4.2) Clause VII.3, Results and interpretation Replace Table VII.1 with the following table, which adds new Note 5. Table VII.1/O.172 Combinations of modulation frequency, burst width and repetition rate Signal Modulation frequ
28、ency fmMinimum burst width tminBurst widths tmin1 kHza)2 ms 65 kHza)31 s 100 s 1 ms 300 kHz 6.7 s 100 s 1 ms STM-1 1.3 MHz 1.5 s 10 s 100 s 1 ms 10 kHza)200 s 1 ms250 kHza)8 s 100 s 1 ms 1 MHz 2 s 10 s 100 s 1 ms STM-4 5 MHz 400 ns 10 s 100 s 1 ms 50 kHza)40 s 100 s 1 ms 1 MHz a) 2 s 10 s 100 s 1 ms
29、 5 MHz 400 ns 10 s 100 s 1 ms STM-16 20 MHz 100 ns 1 s 10 s 100 s 1 ms 200 kHza)10 s 100 s 1 ms 3 MHza)667 ns 10 s 100 s 1 ms 20 MHz 100 ns 1 s 10 s 100 s 1 ms STM-64 80 MHz 25 ns 100 ns 1 s 10 s 100 s 1 ms a)The burst repetition rate shall be in the range from 10 Hz to 10 kHz. NOTE 1 Applicable onl
30、y when high-pass f1is used for the jitter measurement. NOTE 2 The measurement period should be 60 seconds. NOTE 3 Minimum burst repetition rate of 10 Hz is chosen for measurement repeatability and is based on test pattern PRBS repetition. NOTE 4 Burst widths of 100 s and 1 ms can only be used with b
31、urst repetitions less than 10 kHz and 1 kHz respectively. NOTE 5 STM-256 is for further study, because achieving reference transmitter for STM-256 by using current technology may be difficult. 2.5) Appendix VIII, Method for characterization of transmit intrinsic jitter 2.5.1) Clause VIII.2, Method R
32、eplace item 4) of clause VIII.2.1 with the following: 4) If there is no corresponding SDH signal edge for a particular i, assign to xi= 0. Measure xito cover one period of the SDH frame, i.e., the size of the dataset, x1xN is N = 125 106 f0, where f0is the corresponding bit rate. Then generate mathe
33、matically a new sequence by using the following Formula VIII-1. 4 Rec. ITU-T O.172 (2005)/Amd.1 (06/2008) =241241nninniipxx (VIII-1) where pirepresents the pattern density information. Assign pi= 1 when an SDH edge exists, assign pi= 0 when no transition data is present. See Figure VIII.2. Substitut
34、e xi values into series xiwhere no measured SDH edge value exists. For the long test pattern like PRBS-23 described in clause VIII.3, generate mathematically a new sequence by using following Formula VIII-2, instead of using Formula VIII-1. =641641nninnniniphxhx (VIII-2) where hnseries (n = 1, 2, .
35、, 64) is the coefficient of an LPF with a cut-off frequency of 0.032fo. For example, half of the coefficients, h1-32, are given as follows; the other remaining coefficients, h33-64, are symmetrical with h1-32. h1-32= 4.406e-05, 9.982e-04, 3.215e-03, 4.628e-03, 1.399e-04, 1.447e-03, 3.817e-03, 4.237e
36、-03, 3.595e-04, 1.982e-03, 4.315e-03, 3.342e-03, 6.391e-04, 2.584e-03, 4.619e-03, 1.852e-03, 3.087e-04, 1.614e-02, 4.031e-02, 6.207e-02, 3.189e-03, 2.171e-02, 4.650e-02, 6.560e-02, 6.809e-03, 2.771e-02, 5.233e-02, 6.803e-02, 1.114e-02, 3.397e-02, 5.759e-02, 6.927e-02. NOTE 2 The errors associated wi
37、th these phase insertion algorithms are less than 4%. This is an estimation from ten samples which is evaluated in clause VIII.5. 2.5.2) Clause VIII.3, Diagnostic test pattern Replace the whole clause VIII.3 including Figures VIII.4 and VIII.5 with the following: 1) Figures VIII.4 and VIII.5 below d
38、efine diagnostic SDH test patterns. These are suitable for use at STM-64 and STM-16. The remainder of the SDH frame is an all 00Hscrambled 271 pattern or a PRBS-23 scrambled 271 pattern for each test pattern. When using an all 00Hscrambled 271 pattern, the test pattern simulates short periodic patte
39、rns. Here, the scrambler shall be reset to “1111111“ at the last byte of the first row of SOH for every SDH frame. On the other hand, when using a PRBS-23 scrambled 271 pattern, the test pattern simulates long periodic patterns. Here, the scrambler and the shift registers to generate the PRBS-23 bit
40、 stream shall be reset simultaneously to “1111111“ and “1111111111 1111111111 111“, respectively, at the last byte of the first row of SOH for every SDH frames. Rec. ITU-T O.172 (2005)/Amd.1 (06/2008) 5 Figure VIII.4/O.172 Test pattern 1 Figure VIII.5/O.172 Test pattern 2 2) STM-256 pattern is for f
41、urther study. 2.5.3) New clause VIII.5 VIII.5 Evaluation of the error associated with the phase insertion algorithm The phase insertion methods of item 4) in clause VIII.2.1 were designed considering the characteristics of wideband clock recovery (WCR) used in traditional jitter measurement equipmen
42、t that satisfies this Recommendation. Although these insertion methods are easy and effective, they have algorithm error for the phase insertion values obtained by real WCR output. This clause verifies the algorithm error. First, how to obtain the phase insertion values by using an ideal WCR is expl
43、ained as follows: This WCR phase insertion algorithm consists of the following three steps. Refer to Figure VIII.7 for the signal form in each step. 1) Measure the pattern-dependent phase values, xi, with a resolution of 1 mUI at the SDH signal edges, according to items 1) through 3) in clause VIII.
44、2.1. 6 Rec. ITU-T O.172 (2005)/Amd.1 (06/2008) 2) Make a simplified SDH signal sequence, sk, by using xi. Here, the amplitude value of skis 0 or 1, and the sampling interval of skis 1/1000 times the corresponding SDH bit rate. Assign xito the phase error value at the corresponding data edges of sk.
45、3) Input the sequence skto the ideal WCR achieved by the digital signal processing shown in Figure VIII.8. The clock signal sequence, ck, is output from the WCR. Detect the phase error sequence, xi, at every rising edge of ck. Use sequence xi for sequence xiin item 5) in clause VIII.2.1. Figure VIII
46、.8 shows an example of the block diagram of the ideal WCR achieved by digital signal processing. The delay outputs the delayed sequence, sk-500, which is delayed by the half cycle of the SDH bit rate. The XOR outputs exclusive-OR between skand sk-500. The BPF is a digital filter in which the centre
47、frequency is the SDH bit rate; its pass-band width should be at least four times the cut-off frequency f4of the jitter measurement low-pass filter. For example, the pass-band is 10 GHz 320 MHz for STM-64 (f4 = 80 MHz). The Limiter outputs ck= 1 when the input is a positive value, and ck= 0 when the
48、input is a negative value. (The sampling period of skis 1/1000 times the bit rate, i.e., the phase resolution of skis 1 mUI.) x11x7x5x1x3x2x4x6x8 x9 x10 x11x7x5x3x1x2x100 1 2 3 4 5 6 7 8 9 10 11 12 t UI (1) SDH Signal (2) Simplified SDH signal sequence, skx11x7x5x1x3x2x100 1 2 3 4 5 6 7 8 9 10 11 12 Sample, k 1000 1 0 1 2 3 4 5 6 7 8 9 10 11 12 Sample, k 1000 (3) Clock signal sequence, ck1 Figure VIII.7/O.172 Phase insertio
