1、BSI Standards PublicationCalibration of optical time-domain reflectometers (OTDR)Part 2 : OTDR for multimode fibresBS EN 61746-2:2011 Incorporating corrigendum September 2014BS EN 61746-2:2011ForewordThis British Standard is the UK implementation of EN 61746-2:2011, incorporating corrigendum Septemb
2、er 2014. It is identical to IEC 61746-2:2010.The UK participation in its preparation was entrusted to Technical Committee GEL/86, Fibre optics.A list of organizations represented on this committee can be obtained on request to its secretary.This publication does not purport to include all the necess
3、ary provisions of a contract. Users are responsible for its correct application. The British Standards Institution 2014. Published by BSI Standards Limited 2014ISBN 978 0 580 88109 1 ICS 33.180.01 Compliance with a British Standard cannot confer immunity from legal obligations.This British Standard
4、was published under the authority of the Standards Policy and Strategy Committee on 31 July 2011.Amendments/corrigenda issued since publicationDate Text affected30 November 2014BRITISH STANDARDImplementation of CENELEC corrigendum September 2014: Supersession information updated. Dual numbering remo
5、ved from front coverEUROPEAN STANDARD EN 61746-2 NORME EUROPENNE EUROPISCHE NORM CENELEC European Committee for Electrotechnical Standardization Comit Europen de Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Management Centre: Avenue Marnix 17, B - 1000 Brussels 201
6、1 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members. Ref. No. EN 61746-2:2011 E ICS 33.180.01 English version Calibration of optical time-domain reflectometers (OTDR) - Part 2: OTDR for multimode fibres (IEC 61746-2:2010) Etalonnage des rflectom
7、tres optiques dans le domaine de temps (OTDR) - Partie 2: OTDR pour les fibres multimodes(CEI 61746-2:2010) Kalibrierung optischer Rckstreumessgerte (OTDR) - Teil 2: OTDR fr Mehrmodenfasern (IEC 61746-2:2010) This European Standard was approved by CENELEC on 2011-01-02. CENELEC members are bound to
8、comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central
9、 Secretariat or to any CENELEC member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CENELEC member into its own language and notified to the Central Secretariat has the same statu
10、s as the official versions. CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, No
11、rway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. Incorporating corrigendum September 2014January 2011EN 61746-2:2011 - 2 - Foreword The text of document 86/336/CDV, future edition 1 of IEC 61746-2, prepared by IEC TC 86, Fibre optics, was submit
12、ted to the IEC-CENELEC parallel vote and was approved by CENELEC as EN 61746-2 on 2011-01-02. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN and CENELEC shall not be held responsible for identifying any or all such patent rig
13、hts. The following dates were fixed: latest date by which the EN has to be implemented at national level by publication of an identical national standard or by endorsement (dop) 2011-10-02 latest date by which the national standards conflicting with the EN have to be withdrawn (dow) 2014-01-02 Annex
14、 ZA has been added by CENELEC. _ Endorsement notice The text of the International Standard IEC 61746-2:2010 was approved by CENELEC as a European Standard without any modification. In the official version, for Bibliography, the following notes have to be added for the standards indicated: 2 IEC 6079
15、3-1-1 NOTE Harmonized as EN 60793-1-1. 3 IEC 60793-1-40 NOTE Harmonized as EN 60793-1-40. 4 IEC 60794-1-2 NOTE Harmonized as EN 60794-1-2. 5 IEC 60825-1 NOTE Harmonized as EN 60825-1. 6 IEC 60825-2 NOTE Harmonized as EN 60825-2. 7 IEC 61280-1-3 NOTE Harmonized as EN 61280-1-3. 8 IEC 61280-2-10 NOTE
16、Harmonized as EN 61280-2-10. 9 IEC 61300-3-6 NOTE Harmonized as EN 61300-3-6. _ BS EN 61746-2:2011- 3 - EN 61746-2:2011 Annex ZA (normative) Normative references to international publications with their corresponding European publications The following referenced documents are indispensable for the
17、application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. NOTE When an international publication has been modified by common modifications, indicated by (mod), the rele
18、vant EN/HD applies. Publication Year Title EN/HD Year IEC 60793-2-10 - Optical fibres - Part 2-10: Product specifications - Sectional specification for category A1 multimode fibresEN 60793-2-10 - IEC 60793-2-50 - Optical fibres - Part 2-50: Product specifications - Sectional specification for class
19、B single-mode fibres EN 60793-2-50 - IEC 61280-1-4 - Fibre optic communication subsystem test procedures - Part 1-4: General communication subsystems - Light source encircled flux measurement method EN 61280-1-4 - IEC 61280-4-1 - Fibre optic communication subsystem test procedures - Part 4-1: Instal
20、led cable plant - Multimode attenuation measurement EN 61280-4-1 - IEC 61745 - End-face image analysis procedure for the calibration of optical fibre geometry test sets - - ISO/IEC 17025 - General requirements for the competence of testing and calibration laboratories EN ISO/IEC 17025 - BS EN 61746-
21、2:2011 2 61746-2 IEC:2010(E) CONTENTS INTRODUCTION.6 1 Scope.7 2 Normative references7 3 Terms, definitions and symbols.7 4 Preparation for calibration.13 4.1 Organization13 4.2 Traceability13 4.3 Preparation13 4.4 Test conditions 13 4.5 Documentation 13 5 Distance calibration General 14 5.1 General
22、 .14 5.2 Location deviation model .14 5.3 Using the calibration results.16 5.4 Measuring fibre length .17 6 Distance calibration methods 17 6.1 General .17 6.2 External source method .17 6.2.1 Short description and advantage 17 6.2.2 Equipment .17 6.2.3 Calibration of the equipment 19 6.2.4 Measurem
23、ent procedure 20 6.2.5 Calculations and results.20 6.2.6 Uncertainties .21 6.3 Concatenated fibre method (using multimode fibres)23 6.3.1 Short description and advantages 23 6.3.2 Equipment .23 6.3.3 Measurement procedures.24 6.3.4 Calculations and results.24 6.3.5 Uncertainties .25 6.4 Recirculatin
24、g delay line method26 6.4.1 Short description and advantages 26 6.4.2 Equipment .27 6.4.3 Measurement procedure 28 6.4.4 Calculations and results.28 6.4.5 Uncertainties .29 7 Vertical scale calibration General .30 7.1 General .30 7.2 Loss difference calibration .31 7.2.1 Determination of the display
25、ed power level F31 7.2.2 Development of a test plan.31 7.3 Characterization of the OTDR source near field .33 7.3.1 Objectives and references .33 7.3.2 Procedure33 8 Loss difference calibration method34 BS EN 61746-2:201161746-2 IEC:2010(E) 3 8.1 General .34 8.2 Long fibre method34 8.2.1 Short descr
26、iption34 8.2.2 Equipment .34 8.2.3 Measurement procedure 36 8.2.4 Calculation and results.36 Annex A (normative) Multimode recirculating delay line for distance calibration.37 Annex B (normative) Mathematical basis 41 Bibliography44 Figure 1 Definition of attenuation dead zone .8 Figure 2 Representa
27、tion of the location deviation L(L).15 Figure 3 Equipment for calibration of the distance scale External source method .18 Figure 4 Set-up for calibrating the system insertion delay19 Figure 5 Concatenated fibres used for calibration of the distance scale.23 Figure 6 Distance calibration with a reci
28、rculating delay line .27 Figure 7 OTDR trace produced by recirculating delay line .28 Figure 8 Determining the reference level and the displayed power level 31 Figure 9 Region A, the recommended region for loss measurement samples 32 Figure 10 Possible placement of sample points within region A.33 F
29、igure 11 Linearity measurement with a long fibre 35 Figure 12 Placing the beginning of section D1outside the attenuation dead zone 35 Figure A.1 Recirculating delay line37 Figure A.2 Measurement set-up for loop transit time Tb.38 Figure A.3 Calibration set-up for lead-in transit time Ta.39 Table 1 A
30、dditional distance uncertainty.16 Table 2 Attenuation coefficients defining region A.32 BS EN 61746-2:2011 6 61746-2 IEC:2010(E) INTRODUCTION In order for an optical time-domain reflectometer (OTDR) to qualify as a candidate for complete calibration using this standard, it must be equipped with the
31、following minimum feature set: a) the ability to measure type A1a or A1b IEC 60793-2-10 fibres; b) a programmable index of refraction, or equivalent parameter; c) the ability to present a display of a trace representation, with a logarithmic power scale and a linear distance scale; d) two markers/cu
32、rsors, which display the loss and distance between any two points on a trace display; e) the ability to measure absolute distance (location) from the OTDRs zero-distance reference; f) the ability to measure the displayed power level relative to a reference level (for example, the clipping level). Ca
33、libration methods described in this standard may look similar to those provided in Part 1 of this series. However, there are differences: mix of different fibre types, use of mode conditioner or different arrangement of the fibres. This leads to different calibration processes as well as different u
34、ncertainties analysis. BS EN 61746-2:201161746-2 IEC:2010(E) 7 CALIBRATION OF OPTICAL TIME-DOMAIN REFLECTOMETERS (OTDR) Part 2: OTDR for multimode fibres 1 Scope This part of IEC 61746 provides procedures for calibrating multimode optical time domain reflectometers (OTDR). It covers OTDR measurement
35、 errors and uncertainties. The test of the laser(s) source modal condition is included as an optional measurement. This standard does not cover correction of the OTDR response. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated
36、 references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 60793-2-10, Optical fibres Part 2-10: Product specifications Sectional specification for category A1 multimode fibres IEC 60793-2-50, Optical fib
37、res Part 2-50: Product specifications Sectional specification for class B single-mode fibres IEC 61280-1-4, Fibre optic communication subsystem test procedures Part 1-4: General communication subsystems Light source encircled flux measurement method IEC 61280-4-1, Fibre optic communication subsystem
38、 test procedures Part 4-1: Installed cable plant Multimode attenuation measurement IEC 61745, End-face image analysis procedure for the calibration of optical fibre geometry test sets ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories 3 Terms, definitions
39、and symbols For the purposes of this document, the following terms, definitions and symbols apply. NOTE For more precise definitions, the references to IEC 60050-731 should be consulted. 3.1 attenuation A loss optical power decrease in decibels (dB) NOTE If Pin (watts) is the power entering one end
40、of a segment of fibre and Pout (watts) is the power leaving the other end, then the attenuation of the segment is BS EN 61746-2:2011 8 61746-2 IEC:2010(E) outin10log10 = PPA dB (1) IEV 731-01-48, modified 3.2 attenuation coefficient attenuation ( 3.1) of a fibre per unit length IEV 731-03-42, modifi
41、ed 3.3 attenuation dead zone for a reflective or attenuating event, the region after the event where the displayed trace deviates from the undisturbed backscatter trace by more than a given vertical distance F NOTE The attenuation dead zone (see Figure 1 below) will depend on the following event par
42、ameters: reflectance, loss, displayed power level and location. It may also depend on any fibre optic component in front of the event. Displayed power F(dB)Location (km) Attenuationdead zone Initial dead zone F IEC 1424/10 Figure 1 Definition of attenuation dead zone 3.4 calibration set of operation
43、s which establish, under specified conditions, the relationship between the values indicated by the measuring instrument and the corresponding known values of that quantity NOTE See ISO Guide International vocabulary of basic and general terms in metrology. 3.5 centroidal wavelength avgpower-weighte
44、d mean wavelength of a light source in vacuum IEC 61280-1-3, definition 2.1.4 BS EN 61746-2:201161746-2 IEC:2010(E) 9 3.6 displayed power level F level displayed on the OTDRs power scale NOTE 1 Unless otherwise specified, F is defined in relation to the clipping level (see Figure 8). NOTE 2 Usually,
45、 the OTDR power scale displays five times the logarithm of the received power, plus a constant offset. 3.7 distance D spacing between two features NOTE Usually expressed in metres. 3.8 distance sampling error Lsamplemaximum distance ( 3.7) error attributable to the distance between successive sample
46、 points NOTE 1 Usually expressed in metres. NOTE 2 The distance sampling error is repetitive in nature; therefore, one way of quantifying this error is by its amplitude. 3.9 distance scale deviation SLdifference between the average displayed distance ( 3.7) and the correspondent reference distance (
47、 3.27) Drefdivided by the reference distance ( 3.27) NOTE 1 Usually expressed in m/m. NOTE 2 SLis given by the following formula 1 = = refotdrrefrefotdrL is the displayed distance between two features on a fibre (actual or simulated) averaged over at least one sample spacing. 3.11 distance scale unc
48、ertainty uSLuncertainty of the distance scale deviation ( 3.9) NOTE 1 Usually expressed in m/m. BS EN 61746-2:2011 10 61746-2 IEC:2010(E) NOTE 2 uSLis given by the following formula =is the standard deviation expressing the uncertainty of the distance samples (on the basis of the location samples);
49、u/ represents the slope uncertainty due to inaccurate distance readout; it is equivalent to the standard deviation of the slope, SLin the location model of Equation (10) which includes the marker placement uncertainty and the distance sampling error; the least-squares algorithm used for the determination of SLcan be used to determine u; if applicable, Limay be averaged over the corres
