SIST EN 60793-1-48:2004
(Main)Optical fibres -- Part 1-48: Measurement methods and test procedures - Polarization mode dispersion
Optical fibres -- Part 1-48: Measurement methods and test procedures - Polarization mode dispersion
Applies to three methods of measuring PMD. Uniform requirements for measuring the PMD of optical fibre, thereby assisting in the inspection of fibres and cables for commercial purposes are established.
Lichtwellenleiter -- Teil 1-48: Messmethoden und Prüfverfahren - Polarisationsmodendispersion
Fibres optiques -- Partie 1-48: Méthodes de mesure et procédures d'essai - Dispersion de mode de polarisation
S'applique à trois méthodes de mesure de la dispersion de mode de polarisation (PMD). Elle établit les prescriptions uniformes pour mesurer la PMD de la fibre optique contribuant ainsi au contrôle des fibres et des câbles dans les relations commerciales.
Optična vlakna – 1-48. del: Metode merjenja in preskusni postopki - disperzija z načinom polarizacije (IEC 607993-1-48:2003)*
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SIST EN 60793-1-48:2004SLOVENSKIseptember 2004
STANDARDOptična vlakna – 1-48. del: Metode merjenja in preskusni postopki - disperzija z načinom polarizacije (IEC 607993-1-48:2003)*Optical fibres - Part 1-48: Measurement methods and test procedures - Polarization mode dispersion (IEC 607993-1-48:2003)©
Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljenoReferenčna številkaSIST EN 60793-1-48:2004(en)ICS33.180.10
EUROPEAN STANDARD
EN 60793-1-48 NORME EUROPÉENNE EUROPÄISCHE NORM
November 2003 CENELEC European Committee for Electrotechnical Standardization Comité Européen de Normalisation Electrotechnique Europäisches Komitee für Elektrotechnische Normung
Central Secretariat: rue de Stassart 35, B - 1050 Brussels
© 2003 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 60793-1-48:2003 E
ICS 33.180.10
English version
Optical fibres Part 1-48: Measurement methods and test procedures –
Polarization mode dispersion (IEC 60793-1-48:2003)
Fibres optiques Partie 1-48: Méthodes de mesure
et procédures d'essai –
Dispersion de mode de polarisation (CEI 60793-1-48:2003)
Lichtwellenleiter Teil 1-48: Messmethoden
und Prüfverfahren – Polarisationsmodendispersion (IEC 60793-1-48:2003)
This European Standard was approved by CENELEC on 2003-11-01. 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 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 language and notified 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, Hungary, Iceland, Ireland, Italy, Lithuania, Luxembourg, Malta, Netherlands, Norway, Portugal, Slovakia, Spain, Sweden, Switzerland and United Kingdom.
EN 60793-1-48:2003 - 2 -
Foreword The text of document 86A/849/FDIS, future edition 1 of IEC 60793-1-48, prepared by SC 86A, Fibres and cables, of IEC TC 86, Fibre optics, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as EN 60793-1-48 on 2003-11-01. This European Standard is to be read in conjunction with EN 60793-1-1:2003. 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) 2004-08-01 – latest date by which the national standards conflicting
with the EN have to be withdrawn
(dow) 2006-11-01
Annexes designated "normative" are part of the body of the standard.
Annexes designated "informative" are given for information only.
In this standard, annexes A, B, C and ZA are normative and annexes D to K are informative. Annex ZA has been added by CENELEC. EN 60793-1-4X consists of the following parts, under the general title: Optical fibres: - Part 1-40: Measurement methods and test procedures – Attenuation - Part 1-41: Measurement methods and test procedures – Bandwidth - Part 1-42: Measurement methods and test procedures – Chromatic dispersion - Part 1-43: Measurement methods and test procedures – Numerical aperture - Part 1-44: Measurement methods and test procedures – Cut-off wavelength - Part 1-45: Measurement methods and test procedures – Mode field diameter - Part 1-46: Measurement methods and test procedures – Monitoring of changes in optical transmittance - Part 1-47: Measurement methods and test procedures – Macrobending loss - Part 1-48: Measurement methods and test procedures – Polarization mode dispersion - Part 1-49: Measurement methods and test procedures – Differential mode delay __________ Endorsement notice The text of the International Standard IEC 60793-1-48:2003 was approved by CENELEC as a European Standard without any modification. __________
- 3 - EN 60793-1-48:2003
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications This European Standard incorporates by dated or undated reference, provisions from other publications. These normative references are cited at the appropriate places in the text and the publications are listed hereafter. For dated references, subsequent amendments to or revisions of any of these publications apply to this European Standard only when incorporated in it by amendment or revision. For undated references the latest edition of the publication referred to applies (including amendments). NOTE When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD applies. Publication Year Title EN/HD Year IEC 60793-1-1 - 1) Optical fibres Part 1-1: Measurement methods and test procedures - General and guidance
EN 60793-1-1 2003 2) IEC 60793-1-44 2001 Part 1-44: Measurement methods and test procedures - Cut-off wavelength
EN 60793-1-44 2002 IEC 60793-1-50 2001 Part 1-50: Measurement methods and test procedures - Damp heat (steady state)
EN 60793-1-50 2002 IEC 60793-2-50 2002 Part 2-50: Product specifications - Sectional specification for class B single-mode fibres
EN 60793-2-50 2002 IEC 60794-3 2001 Optical fibres cables Part 3: Sectional specification - Outdoor cables
EN 60794-3 2002 IEC 61280 Series Fibre optic communication subsystem test procedures
EN 61280 Series IEC/TR 61282-3 2002 Fibre optic communication system design guides Part 3: Calculation of polarization mode dispersion - -
1) Undated reference. 2) Valid edition at date of issue.
NORMEINTERNATIONALECEIIECINTERNATIONALSTANDARD60793-1-48Première éditionFirst edition2003-05Fibres optiques –Partie 1-48:Méthodes de mesure et procédures d'essai –Dispersion de mode de polarisationOptical fibres –Part 1-48:Measurement methods and test procedures –Polarization mode dispersionPour prix, voir catalogue en vigueurFor price, see current catalogue© IEC 2003
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Copyright - all rights reservedAucune partie de cette publication ne peut être reproduite niutilisée sous quelque forme que ce soit et par aucun procédé,électronique ou mécanique, y compris la photocopie et lesmicrofilms, sans l'accord écrit de l'éditeur.No part of this publication may be reproduced or utilized in anyform or by any means, electronic or mechanical, includingphotocopying and microfilm, without permission in writing fromthe publisher.International Electrotechnical Commission,
3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, SwitzerlandTelephone: +41 22 919 02 11
Telefax: +41 22 919 03 00
E-mail: inmail@iec.ch
Web: www.iec.chCODE PRIXPRICE CODEXACommission Electrotechnique InternationaleInternational Electrotechnical Commission
60793-1-48 © IEC:2003– 3 –CONTENTSFOREWORD.7INTRODUCTION.111Scope.132Normative references.133General.133.1Reference test method.173.2Applicability.194Apparatus.194.1Light source and polarizers.194.2Input optics.214.3Input positioner.214.4Cladding mode stripper.214.5High-order mode filter.214.6Output positioner.234.7Output optics.234.8Detector.234.9Computer.235Sampling and specimens.235.1Specimen length.255.2Deployment.256Procedure.276.1Deploy the fibre or cable and prepare the ends.276.2Attach the ends to the input and output optics.276.3Engage the computer to complete the scans and measurements foundin Annexes A, B, and C for the three measurement methods.276.4Complete documentation.277Calculation or interpretation of results.278Documentation.278.1Information required for each measurement.278.2Information to be available.299Specification information.29Annex A (normative)
Fixed analyser measurement method.31Annex B (normative)
Stokes evaluation method.47Annex C (normative)
Interferometry method.61Annex D (informative)
PMD intercomparison results and observations.69Annex E (informative)
Strategies for improving precision.77Annex F (informative)
Peak identification algorithm for extrema counting used inMethod A.81Annex G (informative)
Fourier analysis theoretical background for Method A.85Annex H (informative)
Determination of mode-coupling regime from DGD values.91
60793-1-48 © IEC:2003– 5 –Annex I (informative)
Formalistic equivalence of PSA and JME and result comparison.97Annex J (informative)
PMD determination by Method C for an interferogram with anauto-correlation peak.111Annex K (informative)
Glossary.117Bibliography.119Figure A.1 – Block diagrams for fixed analyser.31Figure A.2 – Examples of the R-function for the fixed analyser method.37Figure A.3 – PMD by Fourier analysis.45Figure B.1 – Block diagram for Method B.47Figure B.2 – DGD versus wavelength.51Figure B.3 – Histogram of DGD values.51Figure C.1 – Schematic diagram for Method C.61Figure C.2 – Typical data obtained by Method C.65Figure D.1 – PMD wavelength scan data round robin.71Figure H.1 – Example assessments of PMD measurement statistics – measured andideal DGD values with superimposed Maxwell curves.95Figure I.1 – DGD versus optical frequency.101Figure I.2 – PSP trajectories on the Poincaré sphere.103Figure I.3 – Differences between PSP trajectories and the three Stokes parametersfrom Figure I.2.103Figure I.4 – Rectangular system of coordinates defined by the response Stokes vectorsand direction angles of
the polarization dispersion vector in this system of coordinates.105Figure I.5 – Arc of a circle described by the output SOP in the interval [ω,ω + ∆ω].107Table D.1 – Comparison of PMD methods and calculations from the COST 241 PMDRound Robin.73Table D.2 – Matrix of PMD measurement methods.75
60793-1-48 © IEC:2003– 7 –INTERNATIONAL ELECTROTECHNICAL COMMISSION____________OPTICAL FIBRES –Part 1-48: Measurement methods and test procedures –Polarization mode dispersionFOREWORD1)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 InternationalOrganization for Standardization (ISO) in accordance with conditions determined by agreement between thetwo organizations.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 60793-1-48 has been prepared by subcommittee 86A: Fibres andcables, of IEC technical committee 86: Fibre optics.The text of this standard is based on the following documents:FDISReport on voting86A/849/FDIS86A/858/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.This standard is to be read in conjunction with IEC 60793-1-1.
60793-1-48 © IEC:2003– 9 –IEC 60793-1-4X consists of the following parts, under the general title Optical fibres:Part 1-40:Measurement methods and test procedures – AttenuationPart 1-41:Measurement methods and test procedures – BandwidthPart 1-42:Measurement methods and test procedures – Chromatic dispersionPart 1-43:Measurement methods and test procedures – Numerical aperturePart 1-44:Measurement methods and test procedures – Cut-off wavelengthPart 1-45:Measurement methods and test procedures – Mode field diameterPart 1-46:Measurement methods and test procedures – Monitoring of changesin optical transmittancePart 1-47:Measurement methods and test procedures – Macrobending lossPart 1-48:Measurement methods and test procedures – Polarization mode dispersion1Part 1-49:Measurement methods and test procedures – Differential mode delay2The committee has decided that the contents of this publication will remain unchangeduntil 2005. At this date, the publication will be•reconfirmed;•withdrawn;•replaced by a revised edition, or•amended.___________1 To be published.2 To be published.
60793-1-48 © IEC:2003– 11 –INTRODUCTIONPolarization mode dispersion (PMD) causes an optical pulse to spread in the time domain.This dispersion could impair the performance of a telecommunications system. The effect canbe related to differential phase and group velocities and corresponding arrival times δτ ofdifferent polarization components of the signal. For a sufficiently narrow band source, theeffect can be related to a differential group delay (DGD), ∆τ, between pairs of orthogonallypolarized principal states of polarization (PSP) at a given wavelength. For broadbandtransmission, the delays bifurcate and result in an output pulse that is spread out in the timedomain. In this case, the spreading can be related to the average of DGD values.In long fibre spans, DGD is random in both time and wavelength since it depends on thedetails of the birefringence along the entire fibre length. It is also sensitive to time-dependenttemperature and mechanical perturbations on the fibre. For this reason, a useful way tocharacterize PMD in long fibres is in terms of the expected value, <∆τ>, or the mean DGDover wavelength. In principle, the expected value <∆τ> does not undergo large changes for agiven fibre from day to day or from source to source, unlike the parameters δτ or ∆τ. Inaddition, <∆τ> is a useful predictor of lightwave system performance.The term “PMD” is used both in the general sense of two polarization modes having differentgroup velocities, and in the specific sense of the expected value <∆τ>. The DGD ∆τ or pulsebroadening δτ can be averaged over wavelength, yielding <∆τ>λ, or time, yielding <∆τ>t, ortemperature, yielding <∆τ>T. For most purposes, it is not necessary to distinguish betweenthese various options for obtaining <∆τ>.The coupling length lc is the length of fibre or cable at which appreciable coupling betweenthe two SOPs begins to occur. If the fibre length L satisfies the condition L << lc , mode-coupling is negligible and <∆τ> scales with fibre length. The corresponding PMD coefficient is“short-length” PMD coefficient = <∆τ>/L.(1)Fibres in practical systems are nearly always in the L >> lc , regime and mode-coupling israndom. If mode-coupling is found to be random, <∆τ> scales with the square root of fibrelength, and“long-length” PMD coefficient = <∆τ>/L(2)The text provides means for deciding when it is appropriate to use Equations (1) or (2) tocalculate the PMD coefficient. Typical units are ps for ∆τ, km for L, ps/km for short-lengthPMD, and ps/km for long-length PMD. See 5.1 and Annex H for more details on determiningthe mode-coupling regime.
60793-1-48 © IEC:2003– 13 –OPTICAL FIBRES –Part 1-48: Measurement methods and test procedures –Polarization mode dispersion1 ScopeThis part of IEC 60793 applies to three methods of measuring PMD, which are described inClause 3. It establishes uniform requirements for measuring the PMD of optical fibre, therebyassisting in the inspection of fibres and cables for commercial purposes.2 Normative referencesThe following referenced documents are indispensable for the application of this document.For dated references, only the edition cited applies. For undated references, the latest editionof the referenced document (including any amendments) applies.IEC 60793-1-1, Optical fibres – Part 1-1: Generic specification – GeneralIEC 60793-1-44:2001, Optical fibres – Part 1-44: Measurement methods and test procedures– Cut-off wavelengthIEC 60793-1-50:2001, Optical fibres – Part 1-50: Measurement methods and test procedures– Damp heat (steady state)IEC 60793-2-50:2002, Optical fibres – Part 2-50: Product specifications – Sectional specifi-cation for class B single-mode fibresIEC 60794-3:2001, Optical fibre cables – Part 3: Sectional specification – Outdoor cablesIEC 61280 (all parts), Fibre optic communication subsystem basic test proceduresIEC 61282-3:2002, Fibre optic communication system design guides – Part 3: Calculation ofpolarization mode dispersion in fibre optic systems3 GeneralThree methods are described for measuring PMD (see Annexes A, B and C for more details).The methods are listed below in the order of their introduction. For some methods, multipleapproaches of analysing the measured results are also provided.Method AFixed analyserExtrema counting (EC)Fourier transform (FT)
60793-1-48 © IEC:2003– 15 –Method BStokes parameter evaluationJones matrix eigenanalysis (JME)Poincaré sphere analysis (PSA)State of polarization (SOP)Method CInterferometryNegligible mode-couplingRandom mode-couplingAll these methods are suitable for laboratory measurements of factory lengths of optical fibreand optical fibre cable. For all methods, changes in the deployment of the specimen can alterthe results. For installed lengths, only Method C is appropriate for measurements of installedoptical fibre cable that may be moving or vibrating.All methods require light sources that are controlled at one or more SOPs. All methodsrequire injecting light across a broad spectral region (i.e. 50 nm to 200 nm wide) to obtaina PMD value that is characteristic of the region (i.e. 1 300 nm or 1 550 nm). The methodsdiffer ina) the wavelength characteristics of the source;b) the physical characteristics that are actually measured;c) the analysis methods.Method A measures PMD by measuring a response to a change of narrowband light across awavelength range. At the source, the light is linearly polarized at one or more states ofpolarization. For each state, the change in output power that is filtered through a fixedpolarization analyser, relative to the power detected without the analyser, is measured as afunction of wavelength. The resulting measured function can be analysed in one of two ways.• By counting the number of peaks and valleys (extrema counting) of the curve andapplication of a formula that has been shown [1]3 to agree with the average of DGDvalues. This analysis is considered as a frequency domain approach.• By taking the Fourier transform of the measured function. This transform is equivalent tothe pulse spreading obtained by the broadband transmission of Method C. Appropriatecharacterization of the width of the transform function agrees with the average of DGDvalues.Method B measures PMD by measuring a response to a change of narrowband light across awavelength range. At the source, the light is linearly polarized at one or more states ofpolarization. The Stokes vector of the output light is measured for each wavelength. Thechange of these Stokes vectors with angular optical frequency (wavelength), ω and with the(optional) change in input state of polarization yields the DGD as a function of wavelengththrough relationships that are based on the following definitions:()()()ωωΩωωss×=dd(3a)___________3
Figures in square brackets refer to the bibliography.
60793-1-48 © IEC:2003– 17 –()()ωΩωτ=∆(3b)wheresis the output Stokes vector;Ω is the polarization dispersion vector in the direction of the PSPs;∆τ is the DGD.For both the JME and PSA analysis approaches, three linear SOPs at nominally 0°, 45°, and90° (orthogonal on the Poincaré sphere) must be launched for each wavelength. For the SOPanalysis, only one input state is required.The JME approach is completed by transforming the output Stokes vectors to Jones matrices[2], appropriate combination of the matrices at adjacent wavelengths, and a calculation usingthe eigenvalues of the result to obtain the DGD, by application of an argument formula, at thebase frequency.The PSA approach is completed by doing matrix algebra on the normalized output Stokesvectors to infer the output Stokes vector associated with circular birefringence at two adjacentwavelengths, followed by the application of an arcsine formula to obtain the DGD.The SOP approach is based on a piecewise evaluation of Equation (3a) using the normalizedmeasured Stokes vectors.The JME and PSA approaches are mathematically equivalent for common assumptions. TheSOP approach yields valid results when the transit of the output Stokes vector is well-behaved (negligible mode-coupling) but can produce incorrect results when the output Stokesvector changes rapidly and randomly. The extra measurement time required for the threeinput states of polarization for JME and PSA result in a more robust measurement.Method C is based on a broadband light source that is linearly polarized. The cross-correlation of the emerging electromagnetic field is determined by the interference pattern ofthe output light. The characterization of this pattern is either done by computing the r.m.swidth for randomly mode-coupled specimens or by evaluation of the most extremeinterferogram “spike” for specimens with negligible mode-coupling. For random mode-coupledspecimens, the r.m.s width relates to the average DGD (PMD).Information common to all three methods is contained in Clauses 3 to 9, and requirementspertaining to each individual method appear in Annexes A, B, and C, respectively.3.1 Reference test methodMethod B, Stokes parameter evaluation (only JME and PSA approaches), is the reference testmethod (RTM), which shall be the one used to settle disputes.
60793-1-48 © IEC:2003– 19 –3.2 ApplicabilityPMD in fibre is a statistical parameter. IEC 60794-3 includes a statistical requirement on PMDthat is based on sampled measurements of optical fibre cable and calculations forconcatenated links. IEC 60793-2-50 includes an optional maximum for individual uncabledfibres for support of cabled results – provided that the relationship of measurements onuncabled fibre and cabled fibre have been demonstrated to be stable for a given cableconstruction.The fibre or cable deployment should be selected so externally induced mode-coupling isminimized. Sources of such external mode-coupling can be:a) excessive tension;b) excessive bending induced from‚‚‚‚fibre cross-overs on a shipping reel;‚‚‚‚crimping of fibre within a cable on a spool that is too small;‚‚‚‚too small a bend radius;c) excessive twist.Reproducibility of individual measurements should be evaluated after perturbing the fibre toallow sampling the full range of mode-coupling combinations. This can be done by, forexample, changing the temperature slightly or making small adjustments in the deployment.Annex D includes information on the inter-comparison of the methods based on round-robinstudies. Gisin [3] reported a fundamental reproducibility limit for measurements showing thatthe reproducibility increases as the PMD increases and as the spectral width of the sourceincreases. Annex E includes information on approaches to improving the precision.Guidelines for the calculation of PMD for systems that include other components such asdispersion compensators or optical amplifiers are given in IEC 61282-3. Test methods foroptical amplifiers are given in IEC 61280.4 ApparatusThe following apparatus is common to all three measurement methods. Annexes A, B, and Cinclude layout drawings and other equipment requirements for each of the three methods,respectively.4.1 Light source and polarizersSee Annexes A, B, and C for detailed options of the spectral characteristics of the lightsource. The source shall produce sufficient radiation at the intended wavelength(s) and bestable in intensity over a time period sufficient to perform the measurement.For all methods, the polarization of the light is required to be linearly polarized before it isinjected int
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