Internatonal Telecommuncaton Unon ITU-T O.72 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Amendment (6/8) SERIES O: SPECIFICATIONS OF MEASURING EQUIPMENT Equpment for the measurement of dgtal and analogue/dgtal parameters Jtter and wander measurng equpment for dgtal systems whch are based on the synchronous dgtal herarchy (SDH) Amendment Recommendaton ITU-T O.72 (5) Amendment
ITU-T O-SERIES RECOMMENDATIONS SPECIFICATIONS OF MEASURING EQUIPMENT General Mantenance access Automatc and sem-automatc measurng systems Equpment for the measurement of analogue parameters Equpment for the measurement of dgtal and analogue/dgtal parameters Equpment for the measurement of optcal channel parameters Equpment to perform measurements on IP networks Equpment to perform measurements on leased-crcut servces O. O.9 O. O.9 O. O.39 O. O.29 O.3 O.99 O. O.9 O. O.29 O.2 O.229 For further detals, please refer to the lst of ITU-T Recommendatons.
Recommendaton ITU-T O.72 Jtter and wander measurng equpment for dgtal systems whch are based on the synchronous dgtal herarchy (SDH) Amendment Summary Amendment to Recommendaton ITU-T O.72 ncludes changes to the measurement bandwdth, measurement accuracy, jtter transfer measurement accuracy, Appendces VII and VIII. Source Amendment to Recommendaton ITU-T O.72 (5) was approved on 29 June 8 by ITU-T Study Group 4 (5-8) under Recommendaton ITU-T A.8 procedure. Rec. ITU-T O.72 (5)/Amd. (6/8)
FOREWORD The Internatonal Telecommuncaton Unon (ITU) s the Unted Natons specalzed agency n the feld of telecommuncatons, nformaton and communcaton technologes (ICTs). The ITU Telecommuncaton Standardzaton Sector (ITU-T) s a permanent organ of ITU. ITU-T s responsble for studyng techncal, operatng and tarff questons and ssung Recommendatons on them wth a vew to standardzng telecommuncatons on a worldwde bass. The World Telecommuncaton Standardzaton Assembly (WTSA), whch meets every four years, establshes the topcs for study by the ITU-T study groups whch, n turn, produce Recommendatons on these topcs. The approval of ITU-T Recommendatons s covered by the procedure lad down n WTSA Resoluton. In some areas of nformaton technology whch fall wthn ITU-T's purvew, the necessary standards are prepared on a collaboratve bass wth ISO and IEC. NOTE In ths Recommendaton, the expresson "Admnstraton" s used for concseness to ndcate both a telecommuncaton admnstraton and a recognzed operatng agency. Complance wth ths Recommendaton s voluntary. However, the Recommendaton may contan certan mandatory provsons (to ensure e.g. nteroperablty or applcablty) and complance wth the Recommendaton s acheved when all of these mandatory provsons are met. The words "shall" or some other oblgatory language such as "must" and the negatve equvalents are used to express requrements. The use of such words does not suggest that complance wth the Recommendaton s requred of any party. INTELLECTUAL PROPERTY RIGHTS ITU draws attenton to the possblty that the practce or mplementaton of ths Recommendaton may nvolve the use of a clamed Intellectual Property Rght. ITU takes no poston concernng the evdence, valdty or applcablty of clamed Intellectual Property Rghts, whether asserted by ITU members or others outsde of the Recommendaton development process. As of the date of approval of ths Recommendaton, ITU had not receved notce of ntellectual property, protected by patents, whch may be requred to mplement ths Recommendaton. However, mplementers are cautoned that ths may not represent the latest nformaton and are therefore strongly urged to consult the TSB patent database at http://www.tu.nt/itu-t/pr/. ITU 9 All rghts reserved. No part of ths publcaton may be reproduced, by any means whatsoever, wthout the pror wrtten permsson of ITU. Rec. ITU-T O.72 (5)/Amd. (6/8)
Recommendaton ITU-T O.72 Jtter and wander measurng equpment for dgtal systems whch are based on the synchronous dgtal herarchy (SDH) Amendment ) Introducton Ths amendment contans extensons to the 5 verson of Recommendaton ITU-T O.72. 2) Addtons 2.) Clause 9.3, Measurement bandwdths Replace Table 7 wth the followng table, whch adds the measurement bandwdth for f 2 hgh-pass flter for STM-64 rate. Table 7/O.72 Jtter measurement functon bandwdth for SDH lne sgnals Sgnal f (Hz) hgh-pass Jtter measurement bandwdth ( 3 db cut-off frequences) f 2 (Hz) hgh-pass f 3 (Hz) hgh-pass f 4 (Hz) low-pass STM-e, STM- k k STM-e 5 65 k.3 M STM- 5 2 k 65 k.3 M STM-4 k 2 k 25 k 5 M STM-6 5 k 2 k M M STM-64 k 5 k 4 M M STM-256 k 6 M 3 M NOTE Values for STM- are based on the requrements of ANSI T.5.3 [2]. NOTE 2 Values for STM-256 are to be consdered provsonal, snce network requrements are not yet defned n ITU-T Rec. G.825 [3]. NOTE 3 The f 2 hgh-pass flter s optonal. 2.2) Clause 9.4, Measurement accuracy Replace Table 8 wth the followng table, whch adds the fxed error for structured sgnal n the f 2 - f 4 band for STM-64 rate. Rec. ITU-T O.72 (5)/Amd. (6/8)
Table 8/O.72 Fxed error (W) of SDH lne jtter measurements Sgnal Structured sgnal Maxmum peak-to-peak jtter error (UIpp) for gven dgtal sgnals Clock sgnal f -f 4 f 2 -f 4 f 3 -f 4 f -f 4 f 2 -f 4 f 3 -f 4 STM-e FFS FFS FFS FFS STM-.7.35.5.3 STM-e.7.25.5.2 STM-.7.35.35.5.3.3 STM-4..35.35.5.3.3 STM-6..35.35.5.3.3 STM-64..35.35.5.3 STM-256.5.5.5.3 Replace paragraph b) n clause 9.4. wth the followng: b) An optcal sgnal n conformance wth ITU-T Rec. G.957 [4] or G.69 [] and wth a nomnal power n the range dbm to 2 dbm. Operaton at hgher nput power levels may be permtted n accordance wth the mnmum mean launch powers specfed n ITU-T Rec. G.957 [4] or G.69 [] or G.693 [2]. 2.3) Clause 9.5, Jtter transfer measurement accuracy Add the followng underlned part to the text of clause 9.5: The total measurement error n the jtter frequency range f L =. f C and f H = f C or f 4, f f 4 s lower than f C, when usng nput jtter ampltude equal to the applcable jtter tolerance masks, shall be less than: ±.5 db ±.2 g where g s the measured jtter transfer gan at the jtter frequency f m n db, and f L, f C, and f H are accordng to Table 5-2 of ITU-T Rec. G.783. Ths measurement error apples for g greater than or equal to 45 db. No accuracy s specfed for g less than 45 db. 2.4) Appendx VII, Method for verfcaton of measurement result accuracy and ntrnsc fxed error 2.4.) Clause VII.2, System mplementaton a) Replace the followng text n clause VII.2: It s recommended the relatve oscllator ampltudes be adjusted up to mui phase modulaton, ths can be calbrated usng the spectrum analyser usng normal FM theory technques. The operaton of the pulse generator s used to gate the Oscllator 2 clock, thus drectly controllng the modulaton burst tme. The synchronzaton of the modulaton burst relatve to the frame structure s for further study. To mnmze potental phase dscontnutes, the modulaton burst shall be ether synchronzed to the zero crossngs of the snusodal modulaton sgnal or alternatvely shall have a maxmum on/off transton tme gven approxmately by the followng relaton. 2 Rec. ITU-T O.72 (5)/Amd. (6/8)
b) Add the followng text to the end of clause VII.2: The synchronzaton of the modulaton burst relatve to the "SDH" frame structure s for further study. 2.4.2) Clause VII.3, Results and nterpretaton Replace Table VII. wth the followng table, whch adds new Note 5. Table VII./O.72 Combnatons of modulaton frequency, burst wdth and repetton rate Sgnal STM- STM-4 STM-6 STM-64 a) Modulaton frequency f m Mnmum burst wdth t mn Burst wdths > t mn khz a) 2 ms 65 khz a) 3 μs μs ms 3 khz 6.7 μs μs ms.3 MHz.5 μs μs μs ms khz a) μs ms 25 khz a) 8 μs μs ms MHz 2 μs μs μs ms 5 MHz ns μs μs ms 5 khz a) μs μs ms MHz a) 2 μs μs μs ms 5 MHz ns μs μs ms MHz ns μs μs μs ms khz a) μs μs ms 3 MHz a) 667 ns μs μs ms MHz ns μs μs μs ms MHz 25 ns ns μs μs μs ms The burst repetton rate shall be n the range from Hz to khz. NOTE Applcable only when hgh-pass f s used for the jtter measurement. NOTE 2 The measurement perod should be seconds. NOTE 3 Mnmum burst repetton rate of Hz s chosen for measurement repeatablty and s based on test pattern PRBS repetton. NOTE 4 Burst wdths of μs and ms can only be used wth burst repettons less than khz and khz respectvely. NOTE 5 STM-256 s for further study, because achevng reference transmtter for STM-256 by usng current technology may be dffcult. 2.5) Appendx VIII, Method for characterzaton of transmt ntrnsc jtter 2.5.) Clause VIII.2, Method Replace tem 4) of clause VIII.2. wth the followng: 4) If there s no correspondng SDH sgnal edge for a partcular, assgn to x =. Measure x to cover one perod of the SDH frame,.e., the sze of the dataset, [x.. x N ] s N = 25 6 f, where f s the correspondng bt rate. Then generate mathematcally a new sequence by usng the followng Formula VIII-. Rec. ITU-T O.72 (5)/Amd. (6/8) 3
24 n= 24 n= x n x = (VIII-) p n where p represents the pattern densty nformaton. Assgn p = when an SDH edge exsts, assgn p = when no transton data s present. See Fgure VIII.2. Substtute x ' values nto seres x where no measured SDH edge value exsts. For the long test pattern lke PRBS-23 descrbed n clause VIII.3, generate mathematcally a new sequence by usng followng Formula VIII-2, nstead of usng Formula VIII-. 64 n n= 64 h n x = (VIII-2) h p n n= x n where h n seres (n =, 2,..., 64) s the coeffcent of an LPF wth a cut-off frequency of.32f o. For example, half of the coeffcents, h -32, are gven as follows; the other remanng coeffcents, h 33-64, are symmetrcal wth h -32. h -32 = 4.6e-5, 9.982e-4, 3.25e-3, 4.628e-3,.399e-4,.447e-3, 3.87e-3, 4.237e-3, 3.595e-4,.982e-3, 4.35e-3, 3.342e-3, 6.39e-4, 2.584e-3, 4.69e-3,.852e-3, 3.87e-4,.64e-2, 4.3e-2, 6.7e-2, 3.89e-3, 2.7e-2, 4.65e-2, 6.5e-2, 6.9e-3, 2.77e-2, 5.233e-2, 6.3e-2,.4e-2, 3.397e-2, 5.759e-2, 6.927e-2. NOTE 2 The errors assocated wth these phase nserton algorthms are less than 4%. Ths s an estmaton from ten samples whch s evaluated n clause VIII.5. 2.5.2) Clause VIII.3, Dagnostc test pattern Replace the whole clause VIII.3 ncludng Fgures VIII.4 and VIII.5 wth the followng: ) Fgures VIII.4 and VIII.5 below defne dagnostc SDH test patterns. These are sutable for use at STM-64 and STM-6. The remander of the SDH frame s an all H scrambled 2 7 pattern or a PRBS-23 scrambled 2 7 pattern for each test pattern. When usng an all H scrambled 2 7 pattern, the test pattern smulates short perodc patterns. Here, the scrambler shall be reset to "" at the last byte of the frst row of SOH for every SDH frame. On the other hand, when usng a PRBS-23 scrambled 2 7 pattern, the test pattern smulates long perodc patterns. Here, the scrambler and the shft regsters to generate the PRBS-23 bt stream shall be reset smultaneously to "" and " ", respectvely, at the last byte of the frst row of SOH for every SDH frames. 4 Rec. ITU-T O.72 (5)/Amd. (6/8)
Fgure VIII.4/O.72 Test pattern 2) STM-256 pattern s for further study. 2.5.3) New clause VIII.5 Fgure VIII.5/O.72 Test pattern 2 VIII.5 Evaluaton of the error assocated wth the phase nserton algorthm The phase nserton methods of tem 4) n clause VIII.2. were desgned consderng the characterstcs of wdeband clock recovery (WCR) used n tradtonal jtter measurement equpment that satsfes ths Recommendaton. Although these nserton methods are easy and effectve, they have algorthm error for the phase nserton values obtaned by real WCR output. Ths clause verfes the algorthm error. Frst, how to obtan the phase nserton values by usng an deal WCR s explaned as follows: Ths WCR phase nserton algorthm conssts of the followng three steps. Refer to Fgure VIII.7 for the sgnal form n each step. ) Measure the pattern-dependent phase values, x, wth a resoluton of mui at the SDH sgnal edges, accordng to tems ) through 3) n clause VIII.2.. Rec. ITU-T O.72 (5)/Amd. (6/8) 5
2) Make a smplfed SDH sgnal sequence, s k, by usng x. Here, the ampltude value of s k s or, and the samplng nterval of s k s / tmes the correspondng SDH bt rate. Assgn x to the phase error value at the correspondng data edges of s k. 3) Input the sequence s k to the deal WCR acheved by the dgtal sgnal processng shown n Fgure VIII.8. The clock sgnal sequence, c k, s output from the WCR. Detect the phase error sequence, x ', at every rsng edge of c k. Use sequence x ' for sequence x n tem 5) n clause VIII.2.. () SDH Sgnal x x 2 x 3 x 5 x 7 x x 2 3 4 5 6 7 8 9 2 t [UI] (2) Smplfed SDH sgnal sequence, s k (The samplng perod of s k s / tmes the bt rate,.e., the phase resoluton of s k s mui.) x x 3 x 2 x 5 x 7 x x 2 3 4 5 6 7 8 9 2 Sample, k [ ] (3) Clock sgnal sequence, c k x' x' 2 x' 3 x' 4 x' 5 x' 6 x' 7 x' 8 x' 9 x' x' 2 3 4 5 6 7 8 9 2 Sample, k [ ] Fgure VIII.7/O.72 Phase nserton algorthm usng wdeband clock recovery Fgure VIII.8 shows an example of the block dagram of the deal WCR acheved by dgtal sgnal processng. The delay outputs the delayed sequence, s k-5, whch s delayed by the half cycle of the SDH bt rate. The XOR outputs exclusve-or between s k and s k-5. The BPF s a dgtal flter n whch the centre frequency s the SDH bt rate; ts pass-band wdth should be at least four tmes the cut-off frequency f 4 of the jtter measurement low-pass flter. For example, the pass-band s GHz ±3 MHz for STM-64 (f 4 = MHz). The Lmter outputs c k = when the nput s a postve value, and c k = when the nput s a negatve value. 6 Rec. ITU-T O.72 (5)/Amd. (6/8)
Fgure VIII.8/O.72 Example of block dagram of wdeband clock recovery The crteral jtter result y s obtaned by usng x ' generated by the WCR algorthm mentoned above. Table VIII. shows the verfed dfferences between jtter results y obtaned from the phase nserton methods n tem 4 n clause VIII.2. and jtter results y obtaned from the abovementoned WCR model. Here, the pattern-dependent phase values of the actual STM-64 sgnals (Example -) observed by an osclloscope were used as the nput sequence x. The algorthm errors of the phase nserton methods are less than 4% or less than 2% when usng Formula VIII- or Formula VIII-2, respectvely. The seres of the jtter results y of Example - are shown n Fgure VIII.9. All graphs are extracted at the SOH sectons wth a large peak-peak. Table VIII./O.72 Algorthm error of phase nserton method Transmsson sgnal (STM-64) Jtter result of WCR model [muipp] Dfference of Jtter results [%] Formula VIII- 24 x n x = n= 24 p n n= Formula VIII-2 64 hn x n x = n= 64 hn p n n= Example 8 Example 2 Example 3 9 Example 4 23 4 2 Example 5 35 Example 6 2 Example 7 99 Example 8 98 Example 9 Example 49 2 Rec. ITU-T O.72 (5)/Amd. (6/8) 7
jtter result, y - - - 'Eq_' jtter result, y - - - 'Eq_' - 5 5 25 3 35 45 5 a) Example - 5 5 25 3 35 45 5 b) Example 2 jtter result, y - - 'Eq_' jtter result, y - - 'Eq_' - - - 5 5 25 3 35 45 5 c) Example 3-5 5 25 3 35 45 5 d) Example 4 jtter result, y - - - 'Eq_' jtter result, y - - - 'Eq_' - 5 5 25 3 35 45 5 e) Example 5-5 5 25 3 35 45 5 f) Example 6 jtter result, y - - - 'Eq_' jtter result, y - - - 'Eq_' - 5 5 25 3 35 45 5 g) Example 7-5 5 25 3 35 45 5 h) Example 8 jtter result, y - - - 'Eq_' - 5 5 25 3 35 45 5 ) Example 9 jtter result, y - - - 'Eq_' - 5 5 25 3 35 45 5 j) Example Fgure VIII.9/O.72 Example of jtter results, y, wth each phase nserton algorthm 8 Rec. ITU-T O.72 (5)/Amd. (6/8)
SERIES OF ITU-T RECOMMENDATIONS Seres A Seres B Seres C Seres D Seres E Seres F Seres G Seres H Seres I Seres J Seres K Seres L Seres M Seres N Seres O Seres P Seres Q Seres R Seres S Seres T Seres U Seres V Seres W Seres X Seres Y Seres Z Organzaton of the work of ITU-T Avalable Avalable General tarff prncples Overall network operaton, telephone servce, servce operaton and human factors Non-telephone telecommuncaton servces Transmsson systems and meda, dgtal systems and networks Audovsual and multmeda systems Integrated servces dgtal network Cable networks and transmsson of televson, sound programme and other multmeda sgnals Protecton aganst nterference Constructon, nstallaton and protecton of cables and other elements of outsde plant Telecommuncaton management, ncludng TMN and network mantenance Mantenance: nternatonal sound programme and televson transmsson crcuts Specfcatons of measurng equpment Telephone transmsson qualty, telephone nstallatons, local lne networks Swtchng and sgnallng Telegraph transmsson Telegraph servces termnal equpment Termnals for telematc servces Telegraph swtchng Data communcaton over the telephone network Avalable Data networks, open system communcatons and securty Global nformaton nfrastructure, Internet protocol aspects and next-generaton networks Languages and general software aspects for telecommuncaton systems Prnted n Swtzerland Geneva, 9