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1、BRITISH STANDARD BS EN 62429:2008 Reliability growth Stress testing for early failures in unique complex systems ICS 03.120.01; 21.020; 29.020 ? BS EN 62429:2008 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 July 2008 BSI 2008 ISBN 978 0
2、 580 56825 1 National foreword This British Standard is the UK implementation of EN 62429:2008. It is identical to IEC 62429:2007. The UK participation in its preparation was entrusted by Technical Committee DS/1, Dependability and terotechnology, to Subcommittee DS/1/1, Dependability. A list of org
3、anizations represented on this committee can be obtained on request to its secretary. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard cannot confer immunity from legal oblig
4、ations. Amendments/corrigenda issued since publication DateComments EUROPEAN STANDARD EN 62429 NORME EUROPENNE EUROPISCHE NORM April 2008 CENELEC European Committee for Electrotechnical Standardization Comit Europen de Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung C
5、entral Secretariat: rue de Stassart 35, B - 1050 Brussels 2008 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members. Ref. No. EN 62429:2008 E ICS 03.120.01; 03.120.99 English version Reliability growth - Stress testing for early failures in unique
6、complex systems (IEC 62429:2007) Croissance de fiabilit - Essais de contraintes pour rvler les dfaillances prcoces dun systme complexe et unique (CEI 62429:2007) Zuverlssigkeitswachstum - Beanspruchungsprfung auf Frhausflle in einzelnen komplexen Systemen (IEC 62429:2007) This European Standard was
7、approved by CENELEC on 2008-03-01. CENELEC members are bound to 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
8、national standards may be obtained on application to the Central 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 lan
9、guage and notified to the Central Secretariat has the same status as the official versions. CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Cyprus, the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, La
10、tvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. Foreword The text of document 56/1232/FDIS, future edition 1 of IEC 62429, prepared by IEC TC 56, Dependability, was submitted to the IEC-CEN
11、ELEC parallel vote and was approved by CENELEC as EN 62429 on 2008-03-01. 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) 2008-12-01 latest date by which the national standard
12、s conflicting with the EN have to be withdrawn (dow) 2011-03-01 Annex ZA has been added by CENELEC. _ Endorsement notice The text of the International Standard IEC 62429:2007 was approved by CENELEC as a European Standard without any modification. _ BS EN 62429:2008 2 w w w . b z f x w . c o m CONTE
13、NTS 1 Scope.4 2 Justification of measurement 4 3 Apparatus.5 3.1 General.5 3.2 Light source 5 3.3 Polarizer and analyzer.5 3.4 Sample fibre preparation .5 3.5 Variable phase compensator .5 3.6 Optical intensity detection .6 3.7 Data acquisition 6 4 Data analysis and formula 6 4.1 General.6 4.2 1-D s
14、tress profile for a fibre with a cylindrically symmetric structure 7 4.3 2-D stress profile for a fibre with a cylindrically non-symmetric structure .8 5 Measurement procedure.11 5.1 Alignment of polarizer and analyzer.11 5.2 Fibre mounting 11 5.3 Taking transmitted intensity data ),(yI.11 5.4 Calcu
15、lation of 1-D stress profile for a fibre with a cylindrically symmetric structure11 5.5 Calculation of 2-D stress profile for a fibre with a cylindrically non-symmetric structure11 6 Documentation .11 6.1 Information to be reported for each measurement .11 6.2 Information that should be available up
16、on request.12 Bibliography13 Figure 1 Polariscopic phase retardation measurement setup for an optical fibre 5 Figure 2 Measured transmission intensity as a function of fibre radius and external phase .6 Figure 3 Propagation of laser light across the fibre cross-section.7 Figure 4 Stress profile for
17、a fibre with depressed inner cladding and jacketed tube8 Figure 5 Examples of projected phase retardation measurement )(y for a PM fibre as a function of fibre radius y when the projected angle is 0, 45, 90, and 1359 Figure 6 Measured projected phases ),(y of a PM fibre for various projected angles
18、as a function of fibre radius .10 Figure 7 Calculated 2-D stress profile of a PM fibre .10 Annex ZA (normative) Normative references to international publications with their corresponding European publications.15 BS EN 62429:2008 3 w w w . b z f x w . c o m GUIDANCE FOR RESIDUAL STRESS MEASUREMENT O
19、F OPTICAL FIBRE 1 Scope The measurement of residual stress distribution in an uncoated glass optical fibre is considered to be important as it affects critical fibre parameters such as refractive index, intrinsic polarization mode dispersion, mode field diameter and dispersion. The optical polarimet
20、ric method is a well-established technique to measure the residual stress of an optical material. This technical report describes a transverse polarimetric method to measure the residual stress profile of any type of optical fibre. The principle and detailed procedure for measuring the optical trans
21、verse stress profile of a fibre, which is cylindrically symmetric, is described in detail. It is based on a polariscope, which is constructed with a fixed polarizer, a quarter-wave plate and an analyzer. An optical tomographic technique is also described for measuring the stress profile of a fibre w
22、ith a cylindrically non-symmetric structure. 2 Justification of measurement Residual stress in an optical fibre is induced by the combination of the fibre construction and the drawing process. The stress information is important because it affects many important parameters of an optical fibre due to
23、 the following reasons. Temperature dependent changes of fibre parameters are larger for a fibre with larger residual stress, and these are responsible for the statistical behaviour of polarization mode dispersion (PMD) changes in deployed fibre links. (See references 10-12.)1) The variation of impo
24、rtant fibre parameters such as chromatic dispersion, mode field diameter, PMD depends on the intrinsic residual stress of an optical fibre. (See references 13-17.) The asymmetric residual stress profile of a fibre causes fibre curl, which affects cleaving quality for an optical fibre ribbon. The asy
25、mmetric residual stress of a fibre is a major cause of the intrinsic PMD of an optical fibre. (See references 18-20.) Excessive residual stress can lead to core cracking that might be seen in, for example, the preparation of the ends for connectors. The design of polarization retaining fibres normal
26、ly involves inducing a non-symmetric stress field. This measurement can be used to confirm these designs. Much progress has been made in measuring the residual stress profile of an optical fibre (see references 1-9) such that spatial resolution can be as small as 0,6 and accuracy in measuring stress
27、 can be as low as 0,4 MPa. Depending on the application, either one- or two-dimensional stress data may be needed. This document describes methods by measuring the polarization rotation of a transversely exposed laser light across a fibre cross-section using a polarimetric method. 1) Figures in squa
28、re brackets refer to the Bibliography. BS EN 62429:2008 4 w w w . b z f x w . c o m 3 Apparatus 3.1 General An optical transverse phase retardation measurement method is used to determine the residual stresses in a fibre. Figure 1 shows a simple polariscopic phase retardation measurement setup consi
29、sting of a polarizer, fibre sample, Babinet variable phase compensator, and an analyzer. Stressed material shows stress-induced birefringence for light propagating through the medium. By measuring the polarization dependent phase retardation of light transmitted through a sample, the stress can be m
30、easured. 3.2 Light source The light source shall be a laser with a specified optical wavelength and narrow optical spectrum bandwidth (maximum 2 nm at FWHM full width at half maximum). A collimated laser light source is recommended. When a laser is used, a rotating diffuser is recommended in order t
31、o remove coherent interference effects. 3.3 Polarizer and analyzer The polarizer and the analyzer shall have a minimum polarization dependent transmission contrast of 1:200. The transmission angles of the polarizer and the analyzer are set perpendicular with each other within 0,1-degree accuracy. 3.
32、4 Sample fibre preparation The fibre sample shall be a few centimetres long. The jacket or plastic coating on the sample shall be removed. The prepared sample is placed between the polarizer and the analyzer. Immerse the sample in an index matching gel or fluid. The refractive index difference betwe
33、en the cladding material of the fibre and the index matching material shall be less than 0,005. The angle between the fibre axis and the polarizer or the analyzer shall be 45 within 0,1- degree accuracy. Figure 1 Polariscopic phase retardation measurement setup for an optical fibre For measuring a t
34、wo-dimensional stress profile, a fixture that holds the fibre on a constant axis at the holding position and allows the fibre to be rotated through 180 is required. The fixture is required in order to be rotated with a motorized stage with an accuracy of 0,1. 3.5 Variable phase compensator A Babinet
35、 variable phase compensator is placed just after a fibre sample to add an external phase term, which is used for an accurate phase retardation measurement. If the fibre sample has non-zero axial stress components, it acts as a phase retarder due to stress-induced X Analyzer 45 Babinet compensator Op
36、tical fibre Polarizer +45 Z Y Laser input IEC 1690/07 BS EN 62429:2008 5 w w w . b z f x w . c o m birefringence. Without a fibre sample and the Babinet phase compensator, no light can pass through the analyzer. 3.6 Optical intensity detection An optical intensity detection system is needed to detec
37、t the transmitted light intensity after the optical analyzer shown in Figure 1. Such a device may consist of a single optical detector with a small aperture size in the order of a few microns combined with a motorized linear scanning system. A detector array may be used to provide a more precise loc
38、ation of the deflections than might be obtained by a single detector. Such a system might include a detector array or a CCD with a frame grabber. 3.7 Data acquisition A computer is recommended to provide motion control, acquire data and perform computations. 4 Data analysis and formula 4.1 General T
39、he transmitted optical intensity )(yI as a function of the transverse distance of a fibre y, can be written as: ()2)(sin),( 2 +=yIyI o , (1) where o Iis background intensity, is the external phase retardation term from the Babinet compensator and )(y is the phase shift induced by linear birefringenc
40、e due to the stress profile of the fibre sample located between the polarizer and the analyzer. Figure 2 shows typical sine square intensity profiles as a function of for each ray displaced y value from the centre of the fibre sample. Figure 2 Measured transmission intensity as a function of fibre r
41、adius and external phase 0,0 0,1 0,2 0,3 50 100 150 60 30 0 30 60 Phase,retardation radian Intensity I(y,) a.u. Distance y m IEC 1691/07 BS EN 62429:2008 6 w w w . b z f x w . c o m As illustrated in Figure 3, laser light passes through the fibres cross-section along the x axis and c is the outer ra
42、dius of a fibre. For each transversely propagating ray through the cross- section its phase )(y can be expressed as: = = 22 22 22 22 2 )( 2 )( yc yc z yc yc yz dxC dxnny (2) where z n is the refractive index along the fibre axis z, y n is the refractive index along the transverse axis y, c is the ou
43、ter radius of a fibre, is the wavelength of a light source and z is the axial stress of a fibre. Here, C is the stress optic coefficient of silica given as 113 10 5 ,35 =PaC 1. Figure 3 Propagation of laser light across the fibre cross-section. 4.2 1-D stress profile for a fibre with a cylindrically
44、 symmetric structure By using the Abel transformation 1-5, the stress profile )(r z of an axially symmetric fibre can be obtained as: = c r z dy ry dyyd C r 22 2 / )( 2 )( (3) Fibre cross-section Ray c y x c2 y2 IEC 1692/07 BS EN 62429:2008 7 w w w . b z f x w . c o m Figure 4 shows a typical calcul
45、ated stress profile for a jacketed depressed inner cladding fibre. It shows large stress peaks for the boundary between the substrate and the jacketing tube as well as the boundary between the core and inner cladding. Inner cladding Core Jacketed tube Substrate Fiber radius m 60 30 0 30 60 40 200 20
46、 40 60 Stress Mpa IEC 1693/07 Figure 4 Stress profile for a fibre with depressed inner cladding and jacketed tube 4.3 2-D stress profile for a fibre with a cylindrically non-symmetric structure For a fibre with a non-axially symmetric stress distribution such as a polarization maintaining (PM) fibre
47、, a two-dimensional (2-D) cross-sectional stress profile can be determined from one or more projected phase profiles with different projection angles between 0 and 180 6,7. Figure 5 illustrates an example of the measurement procedure of projected phase retardation measurements for a PM fibre. The PM
48、 fibre is rotated along the fibre axis by 45 for each measurement. The phase retardation ),(y is measured as a function of the fibre radius y for each projection angle . For a certain projection angle , the projected phase retardation profile can be written as a line integral: dxnn2)y,( yz = (4) Figure 6 shows projected phases for fifty different projection angles between 0 and 180 for a PM fibre. Such phase retardation profiles with many different projection angles form a 2-D projected phase retardation profile and are used to calculate the 2-D axial str