1、BRITISH STANDARDBS EN 60793-1-49: 2006Optical fibres Part 1-49: Measurement methods and test procedures Differential mode delayThe European Standard EN 60793-1-49:2006 has the status of a British StandardICS 33.180.10g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54
2、g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58BS EN 60793-1-49:2006This British Standard was published under the authority of the Standards Policy and Strategy Committeeon 29 September 2006 BSI 2006ISBN 0 580 49288 5National fore
3、wordThis British Standard was published by BSI. It is the UK implementation of EN 60793-1-49:2006. It is identical with IEC 60793-1-49:2006. It supersedes BS EN 60793-1-49:2003 which is withdrawn.The UK participation in its preparation was entrusted by Technical Committee GEL/86, Fibre optics, to Su
4、bcommittee GEL/86/1, Optical fibres and cables.A list of organizations represented on GEL/86/1 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 Brit
5、ish Standard cannot confer immunity from legal obligations.Amendments issued since publicationAmd. No. Date CommentsEUROPEAN STANDARD EN 60793-1-49 NORME EUROPENNE EUROPISCHE NORM July 2006 CENELEC European Committee for Electrotechnical Standardization Comit Europen de Normalisation Electrotechniqu
6、e Europisches Komitee fr Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B - 1050 Brussels 2006 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members. Ref. No. EN 60793-1-49:2006 E ICS 33.180.10 Supersedes EN 60793-1-49:2003Englis
7、h version Optical fibres Part 1-49: Measurement methods and test procedures - Differential mode delay (IEC 60793-1-49:2006) Fibres optiques Partie 1-49: Mthodes de mesure et procdures dessai - Retard diffrentiel de mode (CEI 60793-1-49:2006) Lichtwellenleiter Teil 1-49: Messmethoden und Prfverfahren
8、 - Gruppenlaufzeitdifferenz (IEC 60793-1-49:2006) This European Standard was approved by CENELEC on 2006-07-01. 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
9、 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
10、 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, Cyprus, the Czech Republic, Denmark, Estonia, Fin
11、land, 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. 2 Foreword The text of document 86A/1061/FDIS, future edition 2 of IEC 607
12、93-1-49, 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 60793-1-49 on 2006-07-01. This European Standard supersedes EN 60793-1-49:2003. It adds minimum calculated effective modal bandwidth (EMBc) to
13、the test procedures, supporting EN 60793-2-10. This standard is to be read in conjunction with EN 60793-1-1 and EN 60793-2-10. 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)
14、2007-04-01 latest date by which the national standards conflicting with the EN have to be withdrawn (dow) 2009-07-01 Annex ZA has been added by CENELEC. _ Endorsement notice The text of the International Standard IEC 60793-1-49:2006 was approved by CENELEC as a European Standard without any modifica
15、tion. _ EN 60793-1-49:2006 3 CONTENTS 1 Scope.4 2 Normative references .4 3 Terms and definitions .5 4 Apparatus.6 4.1 Optical source .6 4.2 Stability.6 4.3 Launch system 6 4.4 Detection system.7 4.5 Computational equipment8 5 Sampling and specimens8 5.1 Test sample 8 5.2 Specimen endfaces .8 5.3 Sp
16、ecimen length8 5.4 Specimen packaging .8 5.5 Specimen positioning 8 6 Procedure 8 6.1 Adjust and measure system response .8 6.2 Adjust detection system.9 6.3 Measure the test sample .9 7 Calculations and interpretation of results10 7.1 Differential mode delay (DMD) 10 7.2 Minimum calculated effectiv
17、e modal bandwidth .10 7.3 Length normalization .12 8 Documentation .12 8.1 Report the following information for each test:.12 8.2 The following information shall be available upon request: 12 9 Specification information 12 Annex A (normative) Source spectral width limitation.14 Annex B (informative)
18、 Discussion of measurement details .17 Annex C (informative) Determining DMD weights for EMBc calculation 21 Annex D (informative) EMBc calculation information .24 Annex E (informative) Comparison between this standard and ITU recommendations.27 Bibliography28 Figure B.1 Idealized DMD data 17 Table
19、A.1 Highest expected dispersion for any of the commercially available Category A1 fibres 16 Table D.1 DMD weightings Example set 1.24 Table D.2 DMD weightings Example set 2.25 EN 60793-1-49:2006OPTICAL FIBRES Part 1-49: Measurement methods and test procedures Differential mode delay 1 Scope This par
20、t of IEC 60793 applies only to multimode, graded-index glass-core (category A1) fibres. The test method is commonly used in production and research facilities, but is not easily accomplished in the field. This standard describes a method for characterizing the modal structure of a graded-index multi
21、mode fibre. This information is useful for assessing the bandwidth performance of a fibre especially when the fibre is intended to support a variety of launch conditions such as those produced by standardized laser transmitters. With this method, the output from a fibre that is single-mode at the te
22、st wavelength excites the multimode fibre under test. The probe spot is scanned across the endface of the fibre under test, and the optical pulse delay is determined at specified offset positions. Two results can be produced from the same data. First, the difference in optical pulse delay time betwe
23、en the fastest and slowest mode groups of the fibre under test can be determined. The user specifies the upper and lower limits of radial offset positions over which the probe fibre is scanned in order to specify desired limits of modal structure. The DMD data is then compared to DMD specifications
24、that have been determined by modeling and experimentation to correspond to a minimum EMB for a range of transmitters. Second, the optical pulse shapes can be combined using specific weights to determine a calculated effective modal bandwidth (EMBc), and by calculating a sequence of EMBc values with
25、different sets of weights, a minimum EMBc can be calculated, corresponding to a range of transmitters. The test quantifies the effects of interactions of the fibre modal structure and the source modal characteristics excluding the source spectral interactions with fibre chromatic dispersion. Adding
26、the effects of chromatic dispersion and source spectral width will reduce the overall transmission bandwidth, but this is a separate calculation in most transmission models. In this test, the effects of non-zero spectral width are minimized but any residual effects will tend to increase the DMD valu
27、e and decrease the EMBc value. 2 Normative references 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 (including any amendments) appl
28、ies. EN 60793-1-49:2006 4 IEC 60793-1-1: Optical fibres Part 1: Measurement methods and test procedures - General and guidance IEC 60793-1-22: Optical fibres Part 1-22: Measurement methods and test procedures Length measurement IEC 60793-1-41: Optical fibres Part 1-41: Measurement methods and test p
29、rocedures Bandwidth. IEC 60793-1-42: Optical fibres Part 1-42: Measurement methods and test procedures Chromatic dispersion IEC 60793-1-45: Optical fibres Part 1-45: Measurement methods and test procedures - Mode field diameter IEC 60793-2-10: Optical fibres Part 2-10: Product specifications Section
30、al specification for category A1 multimode fibres IEC 61280-1-4: Fibre optic communication subsystem test procedures Part 1-4: General communication subsystems Collection and reduction of two-dimensional nearfield data for multimode fibre laser transmitters 3 Terms and definitions For the purposes o
31、f this document, the following terms and definitions apply. NOTE The user of this standard specifies either the maximum DMD for the outer (ROUTER) and inner (RINNER) limits of radial offset position over which the probe spot is scanned, or the minimum EMBc among the EMBc values calculated from a seq
32、uence of DMD weightings. 3.1 differential mode delay DMD the estimated difference in optical pulse delay time between the fastest and slowest modes excited for all radial offset positions between and including RINNERand ROUTER 3.2 effective modal bandwith bandwidth associated with the transfer funct
33、ion, H(f), of a particular laser/fibre combination 3.3 inner limit RINNERouter limit ROUTERlimits of radial offset positions on the endface of the fibre under test over which the probe spot is scanned EN 60793-1-49:2006 5 4 Apparatus 4.1 Optical source Use an optical source that introduces short dur
34、ation, narrow spectral width pulses into the probe fibre. The temporal duration of the optical pulse shall be short enough to measure the intended differential delay time. The maximum duration allowed for the optical pulse, characterized as full width at 25 % of maximum amplitude, will depend both o
35、n the value of DMD to be determined and the sample length. For example, if the desired length-normalized DMD limit is 0,20 ps/m over a sample of length 500 m, the DMD to be measured is 100 ps, and a pulse of duration less than 110 ps is needed. Testing to the same DMD limit in a 10 000 m length of f
36、ibre requires measuring a DMD of 2 000 ps, and a pulse a wide as 2 200 ps may be used. Detailed limits are given in 6.1, and may depend on the source spectral width. Chromatic dispersion induced broadening resulting from source spectral width shall be within the limits indicated in Annex A. The requ
37、irement on spectral width may be met either by using a spectrally narrow source, or alternatively by the use of appropriate optical filtering at either the source or detection end. The centre wavelength shall be within 10 nm of the nominal specified wavelength. A mode locked titanium-sapphire laser
38、is an example of a source usable for this application. 4.2 Stability Devices shall be available to position the input and output ends of the test specimen with sufficient stability and reproducibility to meet the conditions of 4.3 and 4.4. 4.3 Launch system The probe fibre between the light source a
39、nd test sample shall propagate only a single mode at the measurement wavelength. The mode field diameter of the probe fibre at shall be (8,7 2,39) 0,5 m, where is the measurement wavelength in micrometers, and the mode field diameter is determined using IEC 60793-1-45. This equation produces a mode
40、field diameter of 5 m at 850 nm and 9 m at 1 310 nm, which corresponds to commercially available single-mode fibres. Ensure that the output of the probe fibre is single-mode. One method to do this is to strip higher order modes by wrapping the probe fibre three turns around a 25-mm diameter mandrel.
41、 The output spot of the probe fibre shall be scanned across the endface of the test sample with a positional accuracy less than or equal to 0,5 m. The output beam from the probe fibre shall be perpendicular to the endface of the test sample to within an angular tolerance of less than or equal to 1,0
42、 degree. The launch system shall be capable of reproducibly centring the output spot of the probe fibre to within 1,0 m. EN 60793-1-49:2006 6 If directly coupled to the test sample, the gap between the output end of the probe fibre and the endface of the test sample shall be no more than 10 m. A fre
43、e space optics system of lenses or mirrors may be used to image the output spot of the probe fibre onto the endface of the test sample. When using this type of launch system, care should be taken to ensure that substantially the same modes are excited in the test fibre as would be if the beam were c
44、oupled directly from the output of the single-mode probe fibre. For example, a system of lenses or mirrors may be used to image the output of a single-mode fibre onto the end face of the test sample. Provide means to remove cladding light from the test sample. Often the fibre coating is sufficient t
45、o perform this function. Otherwise, use cladding mode strippers near both ends of the test sample. If the fibre is retained on the cladding mode stripper(s) with small weights, care shall be taken to avoid microbending at these sites. 4.4 Detection system Use an optical detection apparatus suitable
46、for the test wavelength. The detection apparatus shall couple all of the guided modes from the test sample onto the detectors active area, such that the detection sensitivity is not significantly mode dependent. The detector, along with any signal preamplifier, shall respond linearly (within 5 %) ov
47、er the range of power detected. The temporal response of the detector system, including any optional optical attenuator, shall not be significantly mode dependent. A specific test for mode dependence is given in 6.1. Alternatively, the detectors temporal response may be a function of offset as long
48、as it is stable over the course of the measurement (i.e. TPULSE(r) shall fulfil the 5 % requirement of 6.1). Ringing of the detector system shall be limited such that maximum overshoot or undershoot shall be less than 5 % of the peak amplitude of the detected optical signal as measured on the refere
49、nce. The waveform of the detected optical signal shall be recorded and displayed on a suitable instrument, such as a high-speed sampling oscilloscope with calibrated time sweep. The recording system should be capable of averaging the detected waveform for multiple optical pulses. Use a delay device, such as a digital delay generator, to provide a means of triggering the detection electronics at the correct time. The delay device may trigger the optical source, or be trigger
