1、 TIA/EIA STANDARD FOTP-132 Measurement of the Effective Area of Single-Mode Optical Fiber TIA/EIA-455-132A (Revision of TIA/EIA-455-132) JUNE 2001 TELECOMMUNICATIONS INDUSTRY ASSOCIATION The Telecommunications Industry Association represents the Communications Sector of ANSI/TIA/EIA-455-132A-2001 Ap
2、proved: May 16, 2001 TIA/EIA-455-132ANOTICE TIA/EIA Engineering Standards and Publications are designed to serve the public interest through eliminating misunderstandings between manufacturers and purchasers, facilitating interchangeability and improvement of products, and assisting the purchaser in
3、 selecting and obtaining with minimum delay the proper product for his particular need. Existence of such Standards and Publications shall not in any respect preclude any member or nonmember of TIA/EIA from manufacturing or selling products not conforming to such Standards and Publications, nor shal
4、l the existence of such Standards and Publications preclude their voluntary use by those other than TIA/EIA members, whether the standard is to be used either domestically or internationally. Standards and Publications are adopted by TIA/EIA in accordance with the American National Standards Institu
5、te (ANSI) patent policy. By such action, TIA/EIA does not assume any liability to any patent owner, nor does it assume any obligation whatever to parties adopting the Standard or Publication. This Standard does not purport to address all safety problems associated with its use or all applicable regu
6、latory requirements. It is the responsibility of the user of this Standard to establish appropriate safety and health practices and to determine the applicability of regulatory limitations before its use. (From Standards Proposal No. 4835, formulated under the cognizance of the TIA FO-6.6 Subcommitt
7、ee on Fibers and Materials.) Published by TELECOMMUNICATIONS INDUSTRY ASSOCIATION 2001 Standards and Technology Department 2500 Wilson Boulevard Arlington, VA 22201 PRICE: Please refer to current Catalog of EIA ELECTRONIC INDUSTRIES ALLIANCE STANDARDS and ENGINEERING PUBLICATIONS or call Global Engi
8、neering Documents, USA and Canada (1-800-854-7179) International (303-397-7956) All rights reserved Printed in U.S.A. PLEASE! DONT VIOLATE THE LAW! This document is copyrighted by the TIA and may not be reproduced without permission. Organizations may obtain permission to reproduce a limited number
9、of copies through entering into a license agreement. For information, contact: Global Engineering Documents 15 Inverness Way East Englewood, CO 80112-5704 or call U.S.A. and Canada 1-800-854-7179, International (303) 397-7956 iFOTP-132Measurement of the effective area of single-mode optical fiberCon
10、tents Page1 Introduction .12 Normative references . 23 Apparatus .34 Sampling and specimens .45 Procedure .46 Calculations or interpretation of results . 47 Documentation .58 Specification information . 6Annex A Direct far-field method measurement specifics .7Annex B Variable aperture in the far-fie
11、ld measurement specifics . 12Annex C Near-field method measurement specifics 17Annex D Sample data and calculations .20Annex E Comparison between this method and IEC or ITU Standards 23Annex F Treatment of side lobes in Far-Field Data 24Annex G A Method for Computing Effective Area from VariableAper
12、ture Data. 25TIA/EIA-455-132AiiThis page left blank.TIA/EIA-455-132AiiiFOTP-132Measurement of the effective area of single-mode optical fiberForewordThis document comes from TIA Project No. 3631, and was formulated under thecognizance of TIA FO-6.6, Subcommittee on Optical Fibers and Materials.This
13、FOTP is part of the series of test procedures included within RecommendedStandard EIA/TIA-455.There are three normative annexes and two informative annexes.Key words: Nonlinear refractive index, effective areaTIA/EIA-455-132AivThis page left blank.1FOTP-132Measurement of effective area of single-mod
14、e optical fiber1 Introduction1.1 IntentThis is intended to document the methods for measuring the effective area (Aeff) ofsingle-mode fiber.1.2 ScopeThis document defines three methods of measuring Aeff. Information common to all themethods is found in the body of this document. Information specific
15、 to each method isfound in a normative annex. The three methods are:A Direct far-field (DFF)B Variable aperture in the far-field (VAMFF)C Near-field (NF)The reference method, used to resolve disputes, is Method A, direct far-field.1.3 BackgroundEffective area is an optical attribute that is specifie
16、d for single-mode fibers and used insystem designs that may be affected by the nonlinear refractive index coefficient, n2.There is agreement in both national and international Standards bodies for thedefinition used in this document. Methods A, B, and C have been recognized asproviding equivalent re
17、sults, provided that good engineering is used in implementation.The direct far-field is the reference method because it is the most direct method and isnamed as the reference method for mode field diameter in the ITU.1.4 MappingA mapping function is a formula by which the measured results of one att
18、ribute are used topredict the value of another attribute on a given fiber. For a given fiber type and design, themode field diameter (MFD) can be used to predict the effective area with a mappingfunction. A mapping function is specific to a particular fiber type and design. Mappingfunctions are gene
19、rated by doing an experiment in which a sample of fiber is chosen torepresent the spectrum of values of both MFD and for the fiber type and in which the fibersTIA/EIA-455-132A2in the sample are measured for both MFD and Aeff. Linear regression can be used todetermine the fitting coefficient, k, as d
20、efined by the following:AkMFDeff=Ge6Ge8Ge7Gf6Gf8Gf722(1)Note: Other mathematical models may be used if they are more generally accurate.2 Normative referencesFOTP-57 (TIA/EIA-455-57B) Preparation and Examination of Optical Fiber Endfacefor Testing PurposesFOTP-59 (TIA/EIA-455-59A), Measurement of Fi
21、ber Point Discontinuities using an OTDRFOTP-61 (TIA/EIA-455-61A), Measurement of Fiber or Cable Attenuation using an OTDRFOTP-77 (TIA/EIA-455-77), Procedures to Qualify a Higher-Order Mode Filter forMeasurements on Single-Mode FiberFOTP-80 (TIA/EIA-455-80), Measurement of Cutoff Wavelength of Uncabl
22、ed Single-Mode Fiber by Transmitted PowerFOTP-170 (TIA/EIA-455-170), Cable Cutoff Wavelength of Single-Mode Fiber by Transmitted PowerTIA/EIA-455-132A33. ApparatusAnnexes A, B, and C include schematics for each method.3.1 Light sourceUse a suitable coherent or noncoherent light source, such as a sem
23、iconductor laser ora sufficiently powerful filtered white light or LED source. The source shall be stable inintensity and wavelength over a time period sufficient to perform the measurement.The wavelength of the source shall be specified in the Detail Specification. Unlessotherwise specified in the
24、Detail Specification, the spectral line width shall be less thanor equal to 10 nm Full Width at Half-Maximum (FWHM).3.2 Input opticsUse an optical lens system or fiber pigtail to excite the test fiber. Couple the power intothe test fiber so it is insensitive to the position of the input end face. Th
25、is can be donewith a launch beam that spatially and angularly overfills the test fiber. If a butt splice isused, use index matching fluid to avoid interference effects. The coupling shall bestable for the duration of the test.3.3 Cladding mode stripperUse a device that extracts cladding modes. The f
26、iber coating will typically perform thisfunction.3.4 High order mode filterUse a method to remove higher order modes whenever they are capable ofpropagating. (Refer to the procedures in FOTP-77 for guidance). For example, a one-turn bend of diameter 30 mm in the test fiber is generally sufficient.3.
27、5 ComputerOptionally, use a computer to control the apparatus, take intensity measurements, andcompute the final result.TIA/EIA-455-132A44 Sampling and specimens4.1 Specimen lengthPrepare the single-mode fiber test specimen to a length of, typically, 2.0 0.2 m.4.2 Specimen end facesPrepare flat end
28、faces at the input and output ends of the specimen, as described inFOTP-57.For the input end, any of the conditions in table 1 of FOTP-57 are acceptable. For theoutput end, “Always Acceptable” or “Usually Acceptable” are acceptable (except for1G). Poor output end quality can produce erroneous measur
29、ements.5. ProcedureSee annexes A, B, or C for methods A, B, and C, respectively.6. Calculation or interpretation of resultsThe following equations define the Aefffor the methods in terms of the electromagneticfield emitted from the end of the specimen. Calculation procedures are given in theannexes.
30、6.1 Near-fieldEffective area, Aeff, is defined from the near-field intensity distribution, I(r), r being theradial distance from the center of the mode field profile, through the following equation:()()AIrrdrIr rdreff=Ge9GebGeaGeaGf9GfbGfaGfaGf2Gf220220(2)TIA/EIA-455-132A56.2 Direct far-fieldThe zer
31、o-order Bessel function, J0, is used to determine the near-field intensitydistribution pattern, I(r), from the far-field power distribution, ()Pff :() ()()()202/1sinsin2)(GfaGfaGfbGf9GeaGeaGebGe9Gf7Gf8Gf6Ge7Ge8Ge6=Gf2 drJPrIff(3)Note - The units of the measured wavelength, , shall be the same as tho
32、se ofthe radial coordinate, r. Typically these are measured in m.Note If side lobes are observed, odd lobes are to be changed in sign(reference to sign in equation) before integration. (See Annex F for moreinformation).The resultant near-field intensity distribution derived from Equation 3 is then u
33、sed withequation 2 to determine Aeff.6.3 Variable aperture in the far-fieldThe power detected through an aperture of radius v is ()Pvv. The direct far field poweris related to the aperture power as:=Ge6Ge8Ge7Gf6Gf8Gf7tan1vD; () sin2= (4)()ddPPvff2)(= (5)Use equation 5 to convert )(vPvto ()ffP . Use
34、equation 3 to convert to the near-fieldintensity pattern and then equation 2 to calculate the effective area.7. Documentation7.1 Report the following with each measurement:7.1.1 The FOTP number used.TIA/EIA-455-132A67.1.2 Identification for each test specimen7.1.3 Effective area (Aeff), in squared m
35、icrometers (m2)7.1.4 Wavelength7.2 The following information shall be available upon request:7.2.1 Test method7.2.2 Description of the test equipment including: light sources, scanning or translationmethod, launch optics, cladding mode stripper, detection optics, and recordingtechniques.7.2.3 Date a
36、nd results for the most recent instrument calibration.7.2.4 Data on measurement reproducibility.7.3 United States military applications require that the following information also bereported for each test. For other (nonmilitary) applications, this information need not bereported for each test.7.3.1
37、 Name(s) of test personnel.7.3.2 Test equipment and date of latest calibration.8 Specification informationThe following shall be part of the Detail Specification:8.1 Fiber type8.2 This FOTP (FOTP-132)8.3 Nominal measurement wavelength8.4 Failure or acceptance criteriaTIA/EIA-455-132A7Annex A (normat
38、ive)Annex A - Direct far-field method measurement specificsThis annex documents the apparatus, procedure, and calculation for the direct far-fieldmethod.A.1 ApparatusA schematic of the apparatus is given in figure 1.XLight SourcePigtailTest FiberJointRotation StagePIN DetectorLock-inAmplifierCompute
39、rReferenceFigure 1 - Test set-up for the direct far-field measurementA.1.1 Detector and apertureUse a detector, such as a PIN diode, that has enough dynamic range, i.e, 50 dB downfrom the maximum power at zero degrees, and that is linear over the range ofintensities that are encountered. The “detect
40、ion floor” or “baseline noise” of thedetector should be minimized so as to maximize the usable dynamic range of thesystem. A minimum of 50 dB of usable dynamic range is recommended. The detectorshall be placed a distance of at least 100 2wfrom the test fiber end face, where 2w isthe nominal mode fie
41、ld diameter of the test fiber and is the nominal measurementwavelength. The angle subtended by the aperture in front of the detector shall be lessthan or equal to 0.5 degree in either dimension.TIA/EIA-455-132A8A.1.2 Scanning apparatusEither scan the far-field radiation pattern by rotating the detec
42、tor about an arc that iscentered on the fiber end face or by rotating the fiber end face before a fixed detector.The scanning apparatus shall be capable of steps of 0.5 degree or finer. The scan shallcover an entire diameter of the far-field pattern. Typically, the scanning apparatusshould be capabl
43、e of scanning an arc radius of at least 23.5 degrees.Note: Multiple measurements, with the fiber rotated relative to the scanning plane willresult in improved accuracy.Note: Maximum scan angle in combination with the integration limits, for a given fiber,should be set at the point at which signal ha
44、s routinely dropped to the level of the“detection floor“ or “baseline noise.“ Scanning to a smaller angle will truncate the far-field pattern and give a result that is too large. Scanning to larger angles, much beyondthis point, will include noise as signal and will lead to a measured value that is
45、toosmall.A.2 ProcedureA.2.1 Prepare the test fiberPrepare the test fiber and align it in the system so the power on the centered detector(angle = 0) is maximum.A.2.2 Scan the detectorScan the detector over the arc radius specified in A.1.2, in increments of equal angle.For each position, i, record t
46、he detected power, ()Pi . The maximum detector angleused is maxat index i=n, the number of positive angular positions. For 0, theindex, i, is defined with negative values. Note: 00= .A.2.3 Complete calculationsComplete the calculations defined in A.3 to determine the effective area.A.3 CalculationsT
47、he following calculations are one means of completing the integrations of 6. Othermethods may be used if they are at least as accurate as the following. Instead offolding the data, for example, a separate MFD calculation for positive and negativeangular data sets can be completed and then averaged f
48、or the final result.A.3.1 Fold the far-field radiation power dataTIA/EIA-455-132A9Let P(i) be the measured power as a function of angular position, i indexed by i. Thefolded power curve, Pf(i), for 0 i maxis:2)()()(iiifPPP+= (A1)If the far-field data is not centered about = 0, then the data around t
49、his point willcause errors to occur. The table below presents estimates of the error resulting fromfolding around =0 of non centered data.Center ofSymmetry error AeffError(degrees) (m2)00.0%0.2 -0.4%0.4 -1.7%To avoid this folding error, the far-field data can be folded around the centroid of thefar-filed pattern:Calculate the centroid of the peak region of the far-field data by the following equation:()()Gf2Gf2=rightleftrightleftcentroiddPdPii(A2)Where left is the angle that corresponds to t
