1、 International Telecommunication Union ITU-T O.172TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Amendment 2(07/2010) 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 2: Alternative clock and jitter generation and a new verification method for STM-256 reference transmitter intrinsic jitter Recommendation ITU-T O.172 (2005) Amendment 2 ITU-T O-SERIES RECOMMENDATIONS SPECIFICATIONS OF MEASURING EQUI
3、PMENT 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 analogue/digital parameters O.130O.199Equipment for the measurement of optical channel
4、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 Recommendations. Rec. ITU-T O.172 (2005)/Amd.2 (07/2010) i Recommendation ITU-T O.172 Jitte
5、r and wander measuring equipment for digital systems which are based on the synchronous digital hierarchy (SDH) Amendment 2 Alternative clock and jitter generation and a new verification method for STM-256 reference transmitter intrinsic jitter Summary Amendment 2 to Recommendation ITU-T O.172 conta
6、ins an alternative implementation of clock and jitter generation for Appendix VII and a new verification method for the reference transmitter intrinsic jitter for STM-256, as Appendix IX. History Edition Recommendation Approval Study Group 1.0 ITU-T O.172 1999-03-26 4 2.0 ITU-T O.172 2001-03-15 4 2.
7、1 ITU-T O.172 (2001) Amend. 1 2003-03-29 4 3.0 ITU-T O.172 2005-04-13 4 3.1 ITU-T O.172 (2005) Amend. 1 2008-06-29 4 3.2 ITU-T O.172 (2005) Amend. 2 2010-07-29 15 ii Rec. ITU-T O.172 (2005)/Amd.2 (07/2010) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized age
8、ncy in the field of telecommunications, information and communication technologies (ICTs). 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
9、 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, produce Recommendations on these topics. The approval of ITU-T Recommendati
10、ons 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 this Recommendation, the expression “Administration“ is used for concisene
11、ss 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., interoperability or applicability) and compliance with the Recommendation
12、 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 that compliance with the Recommendation is required of any party. INTE
13、LLECTUAL 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, w
14、hether 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, implementers are
15、 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 2010 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permissio
16、n of ITU. Rec. ITU-T O.172 (2005)/Amd.2 (07/2010) iii CONTENTS Page 1) Clause 8.5, minimum jitter/wander generation capability 1 2) Clause VII.1 1 3) Clause VII.2 2 4) New Appendix IX . 2 Rec. ITU-T O.172 (2005)/Amd.2 (07/2010) 1 Recommendation ITU-T O.172 Jitter and wander measuring equipment for d
17、igital systems which are based on the synchronous digital hierarchy (SDH) Amendment 2 Alternative clock and jitter generation and a new verification method for STM-256 reference transmitter intrinsic jitter 1) Clause 8.5, minimum jitter/wander generation capability Replace Table 3 of clause 8.5 with
18、 the following table: Table 3 Minimum amplitude for adjustable generated jitter/wander amplitude versus jitter/wander frequency for SDH line signals Signal Minimum peak-to-peak jitter/wander amplitude UIpp Jitter/wander frequency breakpoints Hz A0A1A2A3A4f0f12f11f10f9f8f1f2f3f4STM-0e, STM-0 * * 20 2
19、 0.2 * * * * 10 30 300 2 k 20 k 400 kSTM-1e, STM-1 3600 400 50 2 0.2 12 178 1.6 m 15.6 m 125 m 19.3 500 6.5 k 65 k 1.3 MSTM-4 14400 1600 200 2 0.2 12 178 1.6 m 15.6 m 125 m 9.65 1 k 25 k 250 k 5 M STM-16 57600 6400 800 2 0.2 12 178 1.6 m 15.6 m 125 m 12.1 5 k 100 k 1 M 20 M STM-64 230400 25600 3200
20、2 0.2 12 178 1.6 m 15.6 m 125 m 12.1 20 k 400 k 4 M 80 M STM-256 FFS FFS 12800 8 0.2 FFS FFS FFS FFS 10 50 80 k 400 k 16 M 320 MNOTE 1 Values denoted by “*“ are undefined. NOTE 2 Values are based on the requirements of Rec. ITU-T G.825 13. NOTE 3 Values for STM-0 are based on the requirements of ANS
21、I T1.105.03 21. NOTE 4 FFS denotes that the value is for further study. 2) Clause VII.1 a) Replace the second paragraph of clause VII.1 with the following text: The scheme uses a high-quality optical transmitter and pattern generator with minimal pattern dependent jitter at the line rate under test.
22、 A target would be less than 10 mUI peak-peak measured in bandwidth f1-f4. A generic jitter modulator is also described with the capability to generate pulse sinusoidal jitter. Both techniques can be verified with general purpose test equipment. The method described in Appendix VIII or that of Appen
23、dix IX may be used to verify the intrinsic jitter of the optical pattern generator for STM-16/64. In the case of STM-256, the method described in Appendix IX may be used to verify the intrinsic jitter of the reference transmitter. b) Replace Note 1 of the paragraph below Table VII.1 with the followi
24、ng text: NOTE 1 The error associated with the intrinsic jitter of the reference transmitter for STM-16/64 is verified as described in Appendix VIII or Appendix IX. The error associated with the intrinsic jitter of the reference transmitter for STM-256 is verified as described in Appendix IX. 2 Rec.
25、ITU-T O.172 (2005)/Amd.2 (07/2010) 3) Clause VII.2 a) Replace the second and third paragraphs of clause VII.2 with the following text: Figures VII.2, VII.2a, VII.3 and VII.4 are example implementations of the generic test system in Figure VII.1. These illustrate potential means to produce independen
26、tly verifiable bursts of clock jitter and a means of eliminating data jitter from an optical pattern, these do not restrict other implementation methods. One example block diagram of the clock section is shown in Figure VII.2. This is implemented using two high quality synthesizers, Oscillator 1 and
27、 Oscillator 2, to generate the line rate clock and sinusoidal jitter phase modulation. The relative amplitude levels of these oscillators will determine the jitter amplitude generated, while the relative frequencies determine the jitter modulation. For example, if Oscillator 1 is set to the line rat
28、e clock, and Oscillator 2 to the line rate plus (or minus) an offset, the sinusoidal phase modulation will be generated at the offset frequency, on the line clock. b) Add the following new paragraph and figure in clause VII.2, below Figure VII.2: Figure VII.2a below shows an alternative implementati
29、on of the clock and jitter generation. The pulse generator and oscillator 2 in Figure VII.2 could be replaced by an arbitrary waveform generator (AWG) supporting sinusoidal pulses corresponding to Table VII.1. Figure VII.2a Alternative clock and jitter generation block diagram 4) New Appendix IX Add
30、 the following new appendix: Appendix IX Method for characterization of STM-256 reference transmitter intrinsic jitter (This appendix does not form an integral part of this Recommendation) This appendix describes the intrinsic jitter verification method for the reference transmitter described in App
31、endix VII, and is especially suitable for STM-256 but can be used for STM-16/64. Appendix VIII is suitable for the intrinsic jitter verification method for the reference transmitter for only STM-16/64. Oscillator Fc AWG Bursted Modulation Phase Modulator Line clock Optical data generator Trigger Jit
32、ter clock Precision dataPrecision clock and modulation generator Fc = 9.95328GHz Rec. ITU-T O.172 (2005)/Amd.2 (07/2010) 3 IX.1 Method This verification method estimates the intrinsic jitter of the reference transmitter assuming that the pattern dependent jitter (PDJ) and random jitter (RJ) of the r
33、eference transmitter and the intrinsic jitter of the jitter measurement device are not correlated with each other. The verification method consists of two steps. In step 1, the RJ and PDJ suppression ratio of the reference transmitter are evaluated by a spectrum analyser or a phase noise measurement
34、 device. In step 2, the intrinsic jitter including the PDJ and the RJ of the reference transmitter are estimated from the measurement result of the jitter measurement device. IX.1.1 Step 1: Measurement of RJ and PDJ suppression ratio 1) The set-up is shown in Figure IX.1. Here, the block diagram of
35、the reference transmitter to be verified is based on the block diagram shown in Figure VII.3. The oscillator in Figure IX.1 outputs the 40-GHz line clock. This oscillator corresponds to Oscillator 1 in Figure VII.2. The clock modulator in Figure IX.1 corresponds to the other modulation functions of
36、Figure VII.2. Note that the following two internal connections of the reference transmitter in Figure IX.1 are changed from those in Figure VII.3 in order to evaluate the reference transmitter intrinsic jitter. The input of Phase adjust is just connected with the oscillator output. The output of the
37、 data modulator is an external output shown in Optical data (B). Figure IX.1 Example reference transmitter verification block diagram (Step 1) 2) Turn off the modulation of the clock modulator, and set the electrical pattern data generator to produce a 1010.data sequence (20-GHz clock). Since the 10
38、10.data sequence without clock modulation does not generate PDJ, the dominant jitter component of the intrinsic jitter of optical data (A) is RJ due to the oscillator. Apply Optical data (A) to the spectrum analyser through the wide-bandwidth O/E converter. A phase noise measurement device can be us
39、ed instead of the spectrum analyser. Use the SSB noise at the centre frequency of 20 GHz to determine the RMS jitter, RJ, of Optical data (A) for the jitter measurement bandwidth f1-f4. Here, refer to steps 2) to 4) of clause VIII.2.2 to determine the RMS jitter from the SSB noise. Modulation: (1) O
40、FF (2) Sinusoidal (20 MHz, 100 mUIp-p) or wideband noise (320 MHz-BW) Optical data (A) Laser 1010. Data (20 GHz)NRZ jitter dataElectrical pattern data generator Data modulator line rate carving pulses Phase adjust NRZ low jitter data RZ low jitter data Pulse carving modulator NRZ jitter data 1010.da
41、ta (20 GHz) 1010.data (20 GHz) Spectrum analyser or Phase noise measurement device Optical data (B)DUT: Reference transmitter Oscillator (Fc = 40 GHz) Clock modulator jitter clock Wide-bandwidth O/E converter Line clock Optical pulse stretcher 4 Rec. ITU-T O.172 (2005)/Amd.2 (07/2010) Table IX.1 sho
42、ws an example of the SSB phase noise performance, which is suitable for the STM-256 reference transmitter, at the centre frequency of 20 GHz. This phase noise achieves the RJ of 2 mUIpp for a measurement interval of T = 60 s in the bandwidth 80 kHz to 320 MHz. NOTE The error associated with the wide
43、-bandwidth O/E converter, spectrum analyser and phase noise measurement device is for further study. Table IX.1 Example of phase noise performance at centre frequency of 20 GHz suitable for STM-256 reference transmitter (RJ = 2 mUIpp for bandwidth 80 kHz to 320 MHz) Offset frequencyPhase noise (dBc/
44、Hz)10 kHz 151 100 kHz 154 1 MHz 154 10 MHz 154 100 MHz 154 320 MHz 154 3) Set the clock modulator to turn on sinusoidal modulation to generate pseudo-PDJ on the 1010.data sequence. For example, set a sinusoidal modulation with modulation frequency fm= 20 MHz and an amplitude of 100 mUIpp. Apply Opti
45、cal data (A) to the spectrum analyser or the phase noise measurement device and measure the modulation spectral intensity, PA(in dB), at the frequency of 20 GHz + fm. In the same way, apply Optical data (B) to the spectrum analyser or the phase noise measurement device and measure the spectral inten
46、sity, PB (in dB), at the frequency of 20 GHz + fm. Determine the PDJ suppression ratio, z = 10(PAPB)/20, using the measured PAand PB. The PDJ suppression ratio z represents the input-to-output RMS jitter transfer ratio of the pulse carving modulator. For example, for PA= 38 dB and PB = 15 dB, z = 10
47、(38+15)/20 0.07. Wideband noise modulation with a bandwidth exceeding 320 MHz can be used instead of sinusoidal modulation to verify the PDJ suppression ratio, not in a specific modulation frequency, but in the entire jitter measurement bandwidth. In this case, measure the integrated SSB noise power
48、 of Optical data (A) and Optical data (B) for bandwidth f1-f4and determine the PDJ suppression ratio by calculating the difference of the measured integrated SSB noise for Optical data (A) and Optical data (B). If the PDJ suppression performance of the pulse carving modulator is independent of the j
49、itter modulation frequency fm, the calculated value of z will be the same regardless of sinusoidal or wideband noise modulation. IX.1.2 Step 2: Estimating intrinsic jitter 1) Prepare the set-up shown in Figure IX.2. The difference from Figure IX.1 is that the spectrum analyser (or phase noise measurement device) is replaced by the jitter measurement device. Turn off modulation of the clock modulator, and set the electrical pattern data generator to produce a test pattern sequence (e.g., unframed PRBS-
