SIST EN 60793-1-20:2004
(Main)Optical fibres -- Part 1-20: Measurement methods and test procedures - Fibre geometry
Optical fibres -- Part 1-20: Measurement methods and test procedures - Fibre geometry
Gives four methods for measuring the geometry of uncoated optical fibres. Parameters include: cladding diameter, cladding non-circularity, core diameter, core non-circularity, core-cladding concentricity error, and theoretical numerical numerical aperture.
Lichtwellenleiter -- Teil 1-20: Messmethoden und Prüfverfahren - Fasergeometrie
Fibres optiques -- Partie 1-20: Méthodes de mesure et procédures d'essai - Géométrie de la fibre
Présente quatre méthodes destinées à mesurer la géometrie des fibres optiques nues. Les paramètres suivants sont décrits: diamètre de la gaine, non-circularité de la gaine, diamètre du coeur, non-circularité du coeur, erreur de concentricité entre le coeur et la gaine, et ouverture numérique théorique.
Optična vlakna – 1-20. del: Metode merjenja in preskusni postopki - Geometrija vlakna (IEC 60793-1-20:2001)*
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SIST EN 60793-1-20:2004SLOVENSKIseptember 2004
STANDARDOptična vlakna – 1-20. del: Metode merjenja in preskusni postopki - Geometrija vlakna (IEC 60793-1-20:2001)*Optical fibres - Part 1-20: Measurement methods and test procedures - Fibre geometry (IEC 60793-1-20:2001)©
Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljenoReferenčna številkaSIST EN 60793-1-20:2004(en)ICS33.180.10
EUROPEAN STANDARDEN 60793-1-20NORME EUROPÉENNEEUROPÄISCHE NORMMarch 2002CENELECEuropean Committee for Electrotechnical StandardizationComité Européen de Normalisation ElectrotechniqueEuropäisches Komitee für Elektrotechnische NormungCentral Secretariat: rue de Stassart 35, B - 1050 Brussels© 2002 CENELEC -All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.Ref. No. EN 60793-1-20:2002 EICS 33.180.10Partly supersedes EN 188000:1992English versionOptical fibresPart 1-20: Measurement methods and test procedures –Fibre geometry(IEC 60793-1-20:2001)Fibres optiquesPartie 1-20: Méthodes de mesureet procédures d'essai –Géométrie de la fibre(CEI 60793-1-20:2001)LichtwellenleiterTeil 1-20: Messmethodenund Prüfverfahren –Fasergeometrie(IEC 60793-1-20:2001)This European Standard was approved by CENELEC on 2002-03-05. CENELEC members are bound tocomply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration.Up-to-date lists and bibliographical references concerning such national standards may be obtained onapplication to the Central Secretariat or to any CENELEC member.This European Standard exists in three official versions (English, French, German). A version in any otherlanguage made by translation under the responsibility of a CENELEC member into its own language andnotified to the Central Secretariat has the same status as the official versions.CENELEC members are the national electrotechnical committees of Austria, Belgium, Czech Republic,Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands,Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.
EN 60793-1-20:2002- 2 -ForewordThe text of document 86A/685/FDIS, future edition 1 of IEC 60793-1-20, prepared by SC 86A, Fibresand cables, of IEC TC 86, Fibre optics, was submitted to the IEC-CENELEC parallel vote and wasapproved by CENELEC as EN 60793-1-20 on 2002-03-05.This European Standard supersedes subclause 2.6 (test method 101), subclause 2.7 (test method102) and subclause 2.9 (test method 104) of EN 188000:1992.The following dates were fixed:–latest date by which the EN has to be implementedat national level by publication of an identicalnational standard or by endorsement(dop)2002-12-01–latest date by which the national standards conflictingwith the EN have to be withdrawn(dow) 2005-03-01Annexes designated "normative" are part of the body of the standard.In this standard, annexes A, B, C, D and ZA are normative.Annex ZA has been added by CENELEC.Compared to IEC 60793-1:1989 and IEC 60793-2:1992, IEC/SC 86A has adopted a revised structureof the new IEC 60793 series: The individual measurement methods and test procedures for opticalfibres are published as "Part 1-XX"; the product standards are published as "Part 2-XX".The general relationship between the new series of EN 60793 and the superseded EuropeanStandards of the EN 188000 series is as follows:ENTitlesupersedesEN 60793-1-XXOptical fibres -- Part 1-XX: Measurement methodsand test proceduresIndividual subclauses ofEN 188000:1992EN 60793-2-XXOptical fibres -- Part 2-XX: Product specificationsEN 188100:1995EN 188101:1995EN 188102:1995EN 188200:1995EN 188201:1995EN 188202:1995EN 60793-1-2X consists of the following parts, under the general title: Optical fibres:- Part 1-20: Measurement methods and test procedures – Fibre geometry- Part 1-21: Measurement methods and test procedures – Coating geometry- Part 1-22: Measurement methods and test procedures – Length measurement__________Endorsement noticeThe text of the International Standard IEC 60793-1-20:2001 was approved by CENELEC as a EuropeanStandard without any modification.__________
- 3 -EN 60793-1-20:2002Annex ZA(normative)Normative references to international publicationswith their corresponding European publicationsThis European Standard incorporates by dated or undated reference, provisions from otherpublications. These normative references are cited at the appropriate places in the text and thepublications are listed hereafter. For dated references, subsequent amendments to or revisions of anyof these publications apply to this European Standard only when incorporated in it by amendment orrevision. For undated references the latest edition of the publication referred to applies (includingamendments).NOTEWhen an international publication has been modified by common modifications, indicated by (mod), the relevantEN/HD applies.PublicationYearTitleEN/HDYearIEC 61745- 1)End-face image analysis procedure forthe calibration of optical fibre geometrytest sets--
1) Undated reference.
NORMEINTERNATIONALECEIIECINTERNATIONALSTANDARD60793-1-20Première éditionFirst edition2001-09Fibres optiques –Partie 1-20:Méthodes de mesure et procédures d'essai –Géométrie de la fibreOptical fibres –Part 1-20:Measurement methods and test procedures –Fibre geometry Commission Electrotechnique Internationale International Electrotechnical CommissionPour prix, voir catalogue en vigueurFor price, see current catalogue IEC 2001
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60793-1-20 © IEC:2001– 3 –CONTENTSFOREWORD.5INTRODUCTION.91Scope.112Normative references.113Overview of method.114Definitions.135Reference test method.156Apparatus.157Sampling and specimens.158Procedure.159Calculations.1710Results.1711Specification information.17Annex A (normative)
Requirements specific to method A – Refracted near-field.19Annex B (normative)
Requirements specific to method B – Transverse interference.27Annex C (normative)
Requirements specific to method C – Near-field light distribution.35Annex D (normative)
Requirements specific to method D – Mechanical diameter.47Bibliography.53Figure A.1 – Refracted near-field method — Schematic diagram.21Figure A.2 – Typical arrangement of the refracted near-field test set.21Figure B.1 – Test apparatus.27Figure B.2 – Refractive index profile – Ring pattern.33Figure C.1 – Cross-sectional core diameter – Near-field intensity scan, option 1.43Figure C.2 – Cross-sectional core diameter – Near-field intensity scan, option 2.45Figure C.3 – Near-field intensity distribution in the region of the core-cladding boundary.45Figure D.1 – Top view of a typical electronic micrometer system.47Table 1 – Measurement methods.13
60793-1-20 © IEC:2001– 5 –INTERNATIONAL ELECTROTECHNICAL COMMISSION_____________OPTICAL FIBRES –Part 1-20: Measurement methods and test procedures –Fibre geometryFOREWORD1)The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprisingall national electrotechnical committees (IEC National Committees). The object of the IEC is to promoteinternational co-operation on all questions concerning standardization in the electrical and electronic fields. Tothis end and in addition to other activities, the IEC publishes International Standards. Their preparation isentrusted to technical committees; any IEC National Committee interested in the subject dealt with mayparticipate in this preparatory work. International, governmental and non-governmental organizations liaisingwith the IEC also participate in this preparation. The IEC collaborates closely with the International Organizationfor Standardization (ISO) in accordance with conditions determined by agreement between the twoorganizations.2)The formal decisions or agreements of the IEC on technical matters express, as nearly as possible, aninternational consensus of opinion on the relevant subjects since each technical committee has representationfrom all interested National Committees.3)The documents produced have the form of recommendations for international use and are published in the formof standards, technical specifications, technical reports or guides and they are accepted by the NationalCommittees in that sense.4)In order to promote international unification, IEC National Committees undertake to apply IEC InternationalStandards transparently to the maximum extent possible in their national and regional standards. Anydivergence between the IEC Standard and the corresponding national or regional standard shall be clearlyindicated in the latter.5)The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for anyequipment declared to be in conformity with one of its standards.6)Attention is drawn to the possibility that some of the elements of this International Standard may be the subjectof patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.International Standard IEC 60793-1-20 has been prepared by subcommittee 86A: Fibres andcables, of IEC technical committee 86: Fibre optics.This standard, together with the other standards in the IEC 60793-1-2X series, cancels andreplaces the first edition of IEC 60793-1-2, of which it constitutes a technical revision.The text of this standard is based on the following documents:FDISReport on voting86A/685/FDIS86A/724/RVDFull information on the voting for the approval of this standard can be found in the report onvoting indicated in the above table.This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.Annexes A, B, C and D form an integral part of this standard.
60793-1-20 © IEC:2001– 7 –IEC 60793-1-2X consists of the following parts, under the general title: Optical fibres:• Part 1-20: Measurement methods and test procedures – Fibre geometry• Part 1-21: Measurement methods and test procedures – Coating geometry• Part 1-22: Measurement methods and test procedures – Length measurementThe committee has decided that the contents of this publication will remain unchangeduntil 2003. At this date, the publication will be•reconfirmed;•withdrawn;•replaced by a revised edition, or•amended.
60793-1-20 © IEC:2001– 9 –INTRODUCTIONPublications in the IEC 60793-1 series concern measurement methods and test procedures asthey apply to optical fibres.Within the same series several different areas are grouped, as follows:• parts 1-10 to 1-19:General• parts 1-20 to 1-29:Measurement methods and test procedures for dimensions• parts 1-30 to 1-39:Measurement methods and test procedures for mechanical charac-teristics• parts 1-40 to 1-49:Measurement methods and test procedures for transmission and opticalcharacteristics• parts 1-50 to 1-59:Measurement methods and test procedures for environmental charac-teristics.
60793-1-20 © IEC:2001– 11 –OPTICAL FIBRES –Part 1-20: Measurement methods and test procedures –Fibre geometry1 ScopeThis part of IEC 60793 establishes uniform requirements for measuring the geometricalcharacteristics of uncoated optical fibres.The geometrical characteristics of uncoated optical fibres are fundamental values and arenecessary for carrying out subsequent procedures such as handling, splicing, connectorization,cabling and measurements.2 Normative referencesThe following referenced documents are indispensable for the application of this document. Fordated references, only the edition cited applies. For undated references, the latest edition ofthe referenced document (including any amendments) applies.IEC 61745, End-face image analysis procedure for the calibration of optical fibre geometry testsets3 Overview of methodThis standard gives four methods for measuring fibre geometry characteristics which are givenin terms of the following parameters:–cladding diameter;–cladding non-circularity;–core diameter (category A fibre only);–core non-circularity (category A fibre only);–core-cladding concentricity error;–theoretical numerical aperture (optional – category A fibre only).
60793-1-20 © IEC:2001– 13 –Table 1 – Measurement methodsMethodCharacteristics coveredFibre category(ies) coveredFormerdesignationA Refracted near-fieldAllAll A and B a, bIEC 60793-1-A1AB TransverseinterferenceCore diameter, core non-circularity and theoreticalnumerical apertureAll A bIEC 60793-1-A1BC Near-field lightAll but theoretical numericalapertureA1, A2, A3, all B cIEC 60793-1-A2D Mechanical diameterCladding diameter and claddingnon-circularity onlyAll dIEC 60793-1-A4a
The core diameter of single-mode fibres is not specified.b
Measurement of core diameter and the maximum theoretical numerical aperture of category A1 fibres may also bemade by this method.c
The single near-field scan method can be used to determine a cross-sectional diameter of the core of category A1fibres. This cross-sectional diameter may deviate from the core diameter determined by method C due to effectsof core non-circularity. A core non-circularity value can be determined by scanning in multiple axes.d
In practice, for smooth and substantially circular fibres, method D gives a similar result to that obtained bymethods A, B and C, in which case non-circularity of fibre can also be determined.Information common to all four methods appears in clauses 2 to 10, and information pertainingto each individual method appears in annexes A, B, C and D, respectively.4 DefinitionsFor the purpose of this part of IEC 60793, the following definitions apply.4.1reference surfacesurface defined in the detail specification, which may be either core or cladding4.2core concentricity errordistance between the centre of the cladding and–the centre of the near field profile for category B fibres;–the centre of the core, for category A fibres.4.3core diameter of category A multimode fibredefined from the refractive index profile as that diameter passing through the core centre andintersecting the index profile at the points n3 such that:n3 = n2
+ k(n1 − n2)wheren2 is the refractive index of the homogeneous cladding;n1 is the maximum refractive index;k
is a constant commonly called the "k factor".The refractive index profile can be measured by profiling techniques such as the refractednear-field (RNF) or transverse interferometry (TI) measurements, and by measurement of thenear field of a fully illuminated core such as the transmitted near-field measurement (TNF).
60793-1-20 © IEC:2001– 15 –It is recommended that curve fitting be used with both the index profiling and the TNFtechniques to improve the measurement precision of the core diameter.NOTE 1
Typically, k = 0,025 for either the fitted profiling methods or the unfitted TNF method, and is equivalent tok = 0 for the fitted TNF method.NOTE 2
For fibres with refractive index profiles that have gradual transition region at their core/cladding boundary,a value of k = 0,05 for the unfitted TNF method is equivalent to k = 0 for the fitted TNF method.NOTE 3
For category B fibres, the centre of the core is defined as the centre of the near field profile and not of therefractive index profile. The core boundary is not defined. Instead, the mode field diameter is defined and specified.5 Reference test methodThe reference test method (RTM), which shall be the one used to settle disputes, depends onfibre category such as:–category A fibres: method CNOTE
The characteristics of the core of category A fibres are defined in terms of refractive index profile, whichis measured with method A. Use method C to settle disputes with regard to cladding diameter, cladding non-circularity and core-cladding concentricity error of category A fibres.–category B fibres: method C.6 ApparatusAnnexes A, B, C and D include layout drawings and other equipment requirements for each ofthe methods A, B, C and D, respectively.7 Sampling and specimens7.1 Specimen lengthSee annexes A, B, C and D, respectively, for the applicable requirements.7.2 Specimen end faceFor methods A and C only, prepare a clean, flat end face, perpendicular to the fibre axis, at theinput and output ends of each specimen. The accuracy of measurements performed bymethods A and C is affected by a non-perpendicular end face. End angles less than 1° arerecommended.See C.2 for the tighter requirements on end faces when using method C.Because method D is side-view only, it does not have tight end face requirements.8 ProcedureUse the procedures given in IEC 61745 for calibration. Annexes A, B, C and D document theprocedures for methods A, B, C and D, respectively.
60793-1-20 © IEC:2001– 17 –9 CalculationsSee annexes A, B, C and D for methods A, B, C and D, respectively.10 ResultsThe following information shall be provided with each measurement:–date and title of measurement;–identification and description of specimen;–measurement results for each parameter specified (see applicable annex).The following information shall be available upon request:–measurement method used: A, B, C, or D;–specimen length;–arrangement of measurement set-up;–details of measurement apparatus (see applicable annex);–relative humidity and ambient temperature at the time of the measurement;–most recent calibration information.11 Specification informationThe detail specification shall specify the following information:–type of fibre to be measured;–failure or acceptance criteria;–information to be reported;–any deviations to the procedure that apply.
60793-1-20 © IEC:2001– 19 –Annex A (normative)Requirements specific to method A –Refracted near-fieldThe refracted near-field measurement directly measures the refractive index variation acrossthe fibre (core and cladding). The method can be calibrated to give absolute values ofrefractive indexes. It can be used to obtain profiles of both single-mode and multimode fibres.A.1 ApparatusSee figures A.1 and A.2 for schematic diagrams of the test apparatus.A.1.1 SourceProvide a stable laser giving a few milliwatts of power in the TEM00.A HeNe laser, which has a wavelength of 633 nm, may be used, but apply a correction factor tothe results for extrapolation at different wavelengths.Introduce a quarter-wave plate to change the beam from linear to circular polarization becausethe reflectivity of light at an air-glass interface is strongly angle and polarization-dependent.If necessary, place a spatial filter, such as a pin-hole, at the focus of lens 1.A.1.2 Launch opticsArrange the launch optics to overfill the numerical aperture (NA) of the fibre. This brings abeam of light to a focus on the flat end of the fibre. The optical axis of the beam of light shouldbe within 1° of the axis of the fibre. Determine the resolution of the equipment by the size of thefocused spot, which should be as small as possible in order to maximize the resolution, e.g.less than 1,5 µm. The equipment enables the focused spot to be scanned across the fibrediameter.A.1.3 Liquid cellThe liquid in the liquid cell shall have a refractive index slightly higher than that of the fibrecladding.
60793-1-20 © IEC:2001– 21 –Figure A.1 – Refracted near-field method — Schematic diagramFigure A.2 – Typical arrangement of the refracted near-field test setIEC
573/01IEC
574/01
60793-1-20 © IEC:2001– 23 –A.1.4 SensingProvide a suitable way to collect the refracted light and bring it to the detector, making surethat all the refracted light is captured. By calculation, determine the required size of the discand its position along the central axis.NOTE
Typically the blocking disc is chosen so that it subtends a numerical aperture (NA) approximately equal tothe NA of the launch optics divided by 2.A.2 Sampling and specimensUse a length of fibre less than 2 m.Remove all fibre coatings from the section of fibre to be immersed in the liquid cell.A.3 ProcedureFigure A.2 is a schematic diagram of the test apparatus.A.3.1 Fibre index profile plotImmerse the launch end of the fibre to be measured in a liquid cell whose refractive index isslightly higher than that of the fibre cladding. The location of the fibre can be determined by amethod such as back illumination with a tungsten light. Lenses 2 and 3 produce a focusedimage of the fibre.Adjust the position of lens 3 to centre and focus the fibre image, and simultaneously centre andfocus the laser beam on the fibre.Centre the disc on the output cone. For category A multimode fibre, position the disc on theoptical axis to just block the leaky modes. For category B single-mode fibre, position the disc togive optimum resolution.Collect the refracted modes passing the disc and focus them onto a photodiode. Traverse thefocused laser spot across the fibre end, and directly obtain a plot of the fibre refractive indexvariation.A.3.2 Equipment calibrationDuring the measurement, the angle of the cone of light varies according to the refractive indexseen at the entry point to the fibre (hence the change of power passing the disc). With the fibreremoved and the liquid index and cell thickness known, this change in angle can be simulatedby translating the disc along the optic axis. By moving the disc to a number of predeterminedpositions, the profile can be scaled in terms of relative index. Absolute indices, i.e. n1 and n2,can only be found if the cladding index or the liquid index, at the measurement wavelength andtemperature, is known accurately.A multi-level calibration artifact, such as available from national standards institutes, may alsobe used to complete calibration, according to the instructions provided.
60793-1-20 © IEC:2001– 25 –A.4 CalculationsFrom the raster scan of the cross-section of the profile, calculate any or all of the followingquantities:–core diameter;–cladding diameter;–core/cladding concentricity error;–core non-circularity;–cladding non-circularity;–maximum theoretical numerical aperture;–index difference;–relative index difference;–indications of accuracy and reproducibility.Different techniques for determining the cladding boundary can be used; one example is thedecision-level technique. It is essential to use the same decision level for the claddingboundary as the one used in the calibration procedure.A.5 ResultsIn addition to the results listed in clause 10, and depending on the specification requirements,the following information shall be provided on request:A.5.1
Profiles through core and cladding centres calibrated for a given wavelength.A.5.2
Profiles along the core major and minor axes calibrated for a given wavelength.A.5.3
Profiles along the cladding major and minor axes calibrated for a given wavelength.A.5.4
Equipment arrangement and wavelength correction procedure.
60793-1-20 © IEC:2001– 27 –Annex B (normative)Requirements specific to method B –Transverse interferenceThis test method establishes procedures to be followed for determining the refractive indexprofile, n(r), of an optical fibre specimen by transverse interferometry. The glass geometrycharacteristic parameters are then obtained by calculations involving the measured refractiveindex profile.The method is based on the use of an interference microscope focused on the side view of afibre specimen that is illuminated perpendicular to its axis so as to generate a fringe pattern.The refractive index profile is obtained from video detection and digitization of the interferencefringes under computer control.This method is particularly suited for the measurement of a core diameter and a maximumtheoretical numerical aperture of a category A fibre, but is less well suited for parametersrelated to the cladding.B.1 ApparatusFigure B.1 shows the equipment necessary to make this measurement.Figure B.1 – Test apparatusIEC
575/01
60793-1-20 © IEC:2001– 29 –B.1.1 Transmitted light-interference microscopeThis special-purpose microscope is a combination of two microscopes and an interferometerallowing the magnified image of the test objects to appear together with the interferencefringes. A parallel condenser and objective lens system create a sample test path and a refer-ence path for the quasi-coherent illuminating light obtained using a narrow-band filter and awhite light source.B.1.2 Television camera and monitorThe camera produces an electronic picture that permits the quantification of fringe shading sothat analytical methods can be utilized to locate precisely the centre coordinates of a fringe. Italso permits measurements to be made at wavelengths outside the visible spectrum. Themonitor allows the operator to view the test specimen easily and aids in the set-up proceduresnecessary to provide proper adjustment of the specimen and the fringes.B.1.3 Video digitizerThis unit operates with the camera and computer controller so that the output field of themicroscope as seen by the camera can be digitized. The computer addresses a location on thecamera vidicon, and the digitizer returns to the calculator, for example, an 8-bit binary numberindicating shade of grey at the addressed location. The location of the point being encoded isindicated by a dot cursor on the monitor as an operator aid.B.1.4 Computer and plotterThe computer accumulates intensity versus position data so that the displacement of a fringefrom its cladding level can be determined as a function of core radial position. The computercalculates ∆n and then plots the index profile along with the radial coordinates. The computerthen determines a best-fit power-law curve to the index profile, and the curve is drawn by theplotter.B.2 Sampling and specimensUse a 20 mm length of clean, uncoated fibre for the specimen.B.3 ProcedureB.3.1 PreparationPlace the specimen on its side under the test objective of the microscope on an optically flatspecimen plate (supplied with the microscope). Then place equal amounts of oil having arefractive index equal to that of the cladding on the specimen plate and on the reference plate.Using ×100 immersion objectives, raise the stage of the microscope until the objectives are incontact with the oil. Then locate the fibre in the field of view of the objective and focus it withthe reference beam blocked. Then unlock the reference beam and adjust the microscopecontrols to produce a high-contrast fringe pattern, as illustrated on the display monitor infigure B.1, where the curves in the fringes are caused by the core.B.3.2 Axis orientationOrient the fibre axis perpendicular to the fringe lines and adjust the separation between fringelines using microscope controls so that approximately four fringes are visible on the monitor.For convenience of analysis, make the fringe lines parallel to the horizontal scan lines of thecamera, again using microscope controls.
60793-1-20 © IEC:2001– 31 –B.3.3 ScanningOnce the fringes are properly oriented, the programmable calculator and digitizer automaticallyscan a selected fringe to obtain the amount of shift (Y axis) in the core, using the position ofthe fringe in the cladding as the zero shift (Y = 0) position. Make a separate scan verticallyacross two adjacent fringes in the cladding to obtain the fringe separation,
L. Once the fringeshave been scanned, determine a set of fringe-shift points, Qp, and fringe separation, L, for usein calculating np. Here p is the number of radial positions at
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