1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI British StandardsWB9423_BSI_StandardColCov_noK_AW:BSI FRONT COVERS 5/9/08 12:55 Page 1Fibre optic interconnectingdevices and passive components Basic test and measurement procedures Part 3-43: Examin
2、ations and measurements Modetransfer function measurement for fibre optic sourcesBS EN 61300-3-43:2009National forewordThis British Standard is the UK implementation of EN 61300-3-43:2009. It isidentical to IEC 61300-3-43:2009. It supersedes DD IEC/PAS 61300-3-43:2006which is withdrawn.The UK partic
3、ipation in its preparation was entrusted by Technical CommitteeGEL/86, Fibre optics, to Subcommittee GEL/86/2, Fibre optic interconnectingdevices and passive components.A list of organizations represented on this committee can be obtained onrequest to its secretary.This publication does not purport
4、to include all the necessary provisions of acontract. Users are responsible for its correct application. BSI 2009ISBN 978 0 580 56660 8ICS 33.180.20Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of the Standards
5、Policy and Strategy Committee on 3 Ju 2009Amendments issued since publicationAmd. No. Date Text affectedBRITISH STANDARDBS EN 61300-3-43:2009ly1EUROPEAN STANDARD EN 61300-3-43 NORME EUROPENNE EUROPISCHE NORM April 2009 CENELEC European Committee for Electrotechnical Standardization Comit Europen de
6、Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Central Secretariat: avenue Marnix 17, B - 1000 Brussels 2009 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members. Ref. No. EN 61300-3-43:2009 E ICS 33.180.20 English
7、version Fibre optic interconnecting devices and passive components - Basic test and measurement procedures - Part 3-43: Examinations and measurements - Mode transfer function measurement for fibre optic sources (IEC 61300-3-43:2009) Dispositifs dinterconnexion et composants passifs fibres optiques -
8、 Mthodes fondamentales dessais et de mesures - Partie 3-43: Examens et mesures - Mesures de la fonction de transfert de modes pour les sources fibres optiques (CEI 61300-3-43:2009) Lichtwellenleiter -Verbindungselemente und passive Bauteile - Grundlegende Prf- und Messverfahren - Teil 3-43: Untersuc
9、hungen und Messungen - Messung der Moden-Transferfunktion bei Lichtwellenleiterquellen (IEC 61300-3-43:2009) This European Standard was approved by CENELEC on 2009-04-01. CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this Euro
10、pean 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 (Eng
11、lish, 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,
12、 Belgium, Bulgaria, Cyprus, the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. BS EN
13、 61300-3-43:2009EN 61300-3-43:2009 - 2 - Foreword The text of document 86B/2780/FDIS, future edition 1 of IEC 61300-3-43, prepared by SC 86B, Fibre optic interconnecting devices and passive components, of IEC TC 86, Fibre optics, was submitted to the IEC-CENELEC parallel vote and was approved by CEN
14、ELEC as EN 61300-3-43 on 2009-04-01. 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) 2010-01-01 latest date by which the national standards conflicting with the EN have to be
15、withdrawn (dow) 2012-04-01 Annex ZA has been added by CENELEC. _ Endorsement notice The text of the International Standard IEC 61300-3-43:2009 was approved by CENELEC as a European Standard without any modification. _ BS EN 61300-3-43:2009- 3 - EN 61300-3-43:2009 Annex ZA (normative) Normative refer
16、ences to international publications with their corresponding European publications The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (i
17、ncluding any amendments) applies. 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 60793-1-20 -1)Optical fibres - Part 1-20: Measurement methods and test procedures - Fibre geometry
18、 EN 60793-1-20 20022)IEC 61300-1 -1)Fibre optic interconnecting devices and passive components - Basic test and measurement procedures - Part 1: General and guidance EN 61300-1 20032)IEC 61300-3-4 -1)Fibre optic interconnecting devices and passive components - Basic test and measurement procedures -
19、 Part 3-4: Examinations and measurements - Attenuation EN 61300-3-4 20012)1)Undated reference. 2)Valid edition at date of issue. BS EN 61300-3-43:2009 2 61300-3-43 IEC:2009(E) CONTENTS 1 Scope.5 2 Normative references .5 3 General description 5 4 Theory5 4.1 Alternative method 7 4.2 Mode power distr
20、ibution 7 4.3 Constraints8 5 Apparatus.9 5.1 General .9 5.2 Test sample 9 5.3 Sample positioning device.9 5.4 Optical system.10 5.5 Camera .10 5.6 Video digitiser .10 5.7 Calibration.10 6 Procedure 11 6.1 Mounting and aligning the sample .11 6.2 Optimisation 11 6.3 Acquiring the data .11 7 Calculati
21、ons .11 7.1 Background level subtraction.11 7.2 Location of centroid of intensity profile 12 7.3 Differentiating the intensity profile .12 7.4 Computing the MTF.13 8 Results.14 Annex A (informative) .16 Bibliography18 Figure 1 Example of normalised MTF.7 Figure 2 Example of normalised MPD 8 Figure 3
22、 Schematic of measurement apparatus9 Figure 4 Location of fibre centre using symmetry computation .13 Figure A.1 Sensitivity of MTF and MPD to core diameter16 Figure A.2 Sensitivity of MTF and MPD to profile factor .17 BS EN 61300-3-43:200961300-3-43 IEC:2009(E) 5 FIBRE OPTIC INTERCONNECTING DEVICES
23、 AND PASSIVE COMPONENTS BASIC TEST AND MEASUREMENT PROCEDURES Part 3-43: Examinations and measurements Mode transfer function measurement for fibre optic sources 1 Scope This part of IEC 61300 describes the method for measuring the mode transfer function (MTF) to be used in characterising the launch
24、 conditions for measurements of attenuation and or return loss of multimode passive components. The MTF may be measured at the operational wavelengths. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edi
25、tion cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 61300-1, Fibre optic interconnecting devices and passive components Basic test and measurement procedures Part 1: General and guidance IEC 61300-3-4, Fibre optic intercon
26、necting devices and passive components Basic test and measurement procedures Part 3-4: Examination and measurements Attenuation IEC 60793-1-20, Optical fibres Part 1-20: Measurement methods and test procedures Fibre geometry 3 General description The modal distribution launched into multimode fibre
27、can vary widely with different light sources. This variation in launched modal distribution can result in significant differences in measured attenuation in the same component. The MTF test method gives information about the launched modal distribution (LMD) condition in a measured component. The MT
28、F test method is based on a measurement of the near-field intensity distribution in the fibre 1, 21. 4 Theory For a fibre with a power-law index profile n(r), given by, 50121,)(=arnrn 1ar(1) where a is the fibre core radius; is the profile factor ( = 2 for a parabolic profile); _ 1Figures in square
29、brackets refer to the Bibliography. BS EN 61300-3-43:2009 6 61300-3-43 IEC:2009(E) is the relative index difference, given by 2122212nnn = (2) where n1 is the index at fibre centre; n2is the cladding index. The near-field intensity profile in the fibre I(r) may be determined from an integration of t
30、he mode transfer function MTF() in the fibre, as follows (ignoring constants): ()=ardMTFrI )()( (3) where is the normalised propagation constant; r/a is the normalised radial position. Differentiating both sides gives the MTF as follows (ignoring constants): ()arrdrrdIMTF=11)()( (4) The MTF is usual
31、ly plotted as in terms of the principal mode number m divided by the maximum principal mode number M, where 2)2(2)2( +=arMm(5) The term (m/M) is usually referred to as the relative mode number, or the normalised mode number. The maximum principle mode number M, is given by += anM221(6) A typical nor
32、malised MTF plot is shown in Figure 1, where it can be seen, in this example, that normalised mode numbers up to about 0,6 are equally filled and higher order modes are progressively less well-filled. BS EN 61300-3-43:200961300-3-43 IEC:2009(E) 7 Normalised mode number 0,0 0,25 0,50 0,75 1,0 0,0 0,2
33、 0,4 0,6 0,8 1,0 Normalised MTF IEC 2371/08 Figure 1 Example of normalised MTF 4.1 Alternative method If the profile factor, , in Equation (4) is not known, then an alternative expression for MTF can be used. It is known 3 that in a fully-filled fibre (i.e. MTF=1 for all mode numbers) the near-field
34、 intensity profile, Io, is approximately the same shape as the square of the refractive index profile, n(r)2. Furthermore, the term r-1Equation (4) is equal (ignoring constants) to the differential of n(r)2and so Equation(4) can be rewritten as: ()21arodrrdIdrrdIMTF=)()()( (7) where a value of =2 ha
35、s been assumed in order to compute values for the normalised mode number. Thus the MTF is equal to the ratio of the derivative of the intensity profile under test to the derivative of the intensity profile of the same fibre under fully-filled conditions. 4.2 Mode power distribution For graded index
36、multimode fibre the number of discrete modes in a particular mode group is proportional to the principal mode number. Thus higher-order mode groups contain more modes and therefore will carry more light if all the modes are equally excited. This can be represented by the mode power distribution (MPD
37、), defined as: mmMTFmMPD = )()( (8) Because of this relationship of modes within mode groups, the MPD transform effectively displays the relative power in the mode groups. An example of a normalised MPD is shown in Figure 2, where it can be seen, in this case, that the peak power level occurs around
38、 0,65 normalised mode number. BS EN 61300-3-43:2009 8 61300-3-43 IEC:2009(E) Normalised mode number0,0 0,25 0,50 0,75 1,0 0,0 0,2 0,4 0,6 0,8 1,0 Normalised MPD IEC 2372/08 Figure 2 Example of normalised MPD 4.3 Constraints The MTF measurement method described herein is only valid under certain cond
39、itions, as follows: modes within a mode group carry the same power; there are random phases between the propagating modes. It has been found4 that both these conditions can be simultaneously met if the line-width of the source is sufficiently broad, leading to the so-called “mode-continuum approxima
40、tion“, given by: Na 02k(10) where is the optical wavelength; k0= 2/; N is the group index, given by ddnnN11= (11) Typically, for a 50 m core diameter fibre, with 0,21 numerical aperture, then 0,5 nm at 850 nm and 1,0 nm at 1 300 nm satisfy this condition. If the source line-width does not meet this
41、criterion then interference between propagating modes may take place, resulting in “speckle“ in the near-field image. The method can, however, still be applied to such sources by gently shaking, or somehow agitating, the fibre under test so as to cause a temporal averaging of the speckle pattern. In
42、 this case, it is important to ensure the near-field is azimuthally symmetric. This can be achieved by checking that the MTFs measured at 45 intervals around the fibre coincide with each other5. The peak of the MPD occurs at a normalised mode number of 0,8. BS EN 61300-3-43:200961300-3-43 IEC:2009(E
43、) 9 It is known that deviation of the measured near-field intensity profile I(r) from the power law profile in Equation (1), for fibres that are well-filled, may occur towards the core/cladding boundary. It is recommended that, in this case, the alternative method for the determination of MTF descri
44、bed in 4.1 is employed. 5 Apparatus 5.1 General The apparatus is essentially a video microscope where a near-field image of the end of the fibre under test is formed on the surface of a camera by an optical system. The camera image is then digitised by a video digitiser and transferred to a computer
45、 for analysis and data presentation. A schematic of a typical measurement configuration is shown in Figure 3. Fibre holder and XYZ manipulator Imaging lens Condensing lens Beamsplitter Optional neutral density filter Camera Computer LED source IEC 2373/08 Figure 3 Schematic of measurement apparatus
46、5.2 Test sample The test sample consists of a multimode patch cord attached to a light source. It should be recognised that the mode distribution at the output of the patch cord is a product of both the launch conditions of the source and of the patch cord itself. The resultant MTF is therefore not
47、a parameter of either the light source or the patch cord individually but rather of the combination, including the particular conditions under which the patch cord is disposed, such as bend radius. 5.3 Sample positioning device A positioning device is required to ensure that the end of the patch cor
48、d under test is located on the optical axis of the instrument and also in the correct axial position to give a well-focussed image on the camera. For this purpose, an XYZ manipulation stage may be used or, preferably, a suitable connector receptacle mounted axially with the optics. An example is a s
49、tandard 2,5 mm ferrule receptacle which is able to accommodate several connector types, BS EN 61300-3-43:2009 10 61300-3-43 IEC:2009(E) such as FC, ST and SC. In this case, the XY positioning of the patch cord is well-defined and only a focussing adjustment is required. 5.4 Optical system The optical syste
