1、TIASTANDARDFOTP-8Measurement of Splice or Connector Loss and Reflectance Using an OTDRTIA-455-8May 2000 TELECOMMUNICATIONS INDUSTRY ASSOCIATION ANSI/TIA/EIA-455-8-2000 Approved: April 25, 2000 Reaffirmed: April 21, 2008 NOTICETIA Engineering Standards and Publications are designed to serve the publi
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6、 limitations before its use. (From Standards Proposal No. 3-2761 formulated under the cognizance of the TIA FO-4 Fiber Optics, FO-4.3 Subcommittee on Passive Optical Devices and Components.) Published by TELECOMMUNICATIONS INDUSTRY ASSOCIATION Standards and Technology Department 2500 Wilson Boulevar
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22、 OF THE USE OF THE CONTENTS HEREOF, AND THESE CONTENTS WOULD NOT BE PUBLISHED BY TIA WITHOUT SUCH LIMITATIONS. TIA/EIA-455-8iFOTP-8Measurement of splice or connectorloss and reflectance using an OTDRContentsPageSectionContents iForeword iii1 Introduction 12 Normative References . 13 Apparatus . 24 S
23、ampling and specimens . 25 Procedure 26 Calculation or interpretation of results 67 Documentation 78 Specification information . 8Figure1 Schematic OTDR Trace for a fiber lengthcontaining various types of discontinuities 42 Schematic OTDR close-up trace fora reflective splice or connector . 4AnnexA
24、Features of an OTDR . 9B Comparison between FOTP-8and IEC and ITU requirements 12TIA/EIA-455-8ii This page left blank. TIA/EIA-455-8iiiFOTP-8Measurement of splice or connectorloss and reflectance using an OTDRForeword(This foreword is informative and is not a part of this standard.)This document com
25、es from TIA Standards Proposal No. 2828A, formulated under the cognizanceof TIA FO-6.3, Subcommittee on Fiber Optic Interconnecting Devices. It has not been previouslypublished.This FOTP is part of the series of test procedures included within Recommended StandardTIA/EIA-455.There are two Annexes, o
26、ne normative, the other informative.Key words: splice, connector, reflectance, OTDRTIA/EIA-455-8ivThis page left blank.TIA/EIA-455-81FOTP-8Measurement of splice or connectorloss and reflectance using an OTDR1 Introduction1.1 IntentThis procedure describes the use of an optical time-domain reflectome
27、ter (OTDR) to indirectlymeasure the loss and reflectance of a splice or connector.1.2 Other methodsLoss or reflectance measurements may be obtained also by using FOTP-34 or FOTP-107. Thelatter values will be accepted as correct in the event of a dispute.1.3 Trace defectsSome OTDR/fiber combinations
28、appear to give “noisy” traces that may be repeatable for a givenOTDR but not against other OTDRs with the same fiber. These appear to be related topolarization and coherence effects, and are being studied in FO-6.6. Some OTDR manufacturersoffer noise filters, internal or external to the OTDR, and ca
29、re shall be taken that these do not mask“true” artifacts of the trace. Moreover, parts of the trace that are noisy due to low signal-to-noiseratio shall not be used.2 Normative referencesFOTP-34 (TIA/EIA/-455-34A) Interconnection device insertion loss testFOTP-57 (TIA/EIA-455-57B) Optical fiber end
30、preparation and examinationFOTP-60 (TIA/EIA-455-60A) Measurement of fiber or cable length using an OTDRFOTP-77 (EIA/TIA-455-77) Fabricating and qualifying a higher-order mode filter forsingle-mode fiber measurementsTIA/EIA-455-82FOTP-78 (EIA/TIA-455-78A) Spectral attenuation cutback measurement for
31、single-modefibersFOTP-107 (EIA/TIA-455-107A) Return loss for fiber optic componentsIEC 86(Secretariat)49, revised Calibration of optical time-domain reflectometers3 ApparatusSee Annex A.4 Sampling and specimens4.1 Specimens are one or more splices or connectors within a fiber on a reel, within a cab
32、le,or under a condition specified in the Detail Specification. Care should be taken so that thewinding does not introduce artificial loss or reflection. The measurement may be performed in thefactory or in the field, upon either single or concatenated sections.4.2 Prepare a flat endface at the input
33、 end of the specimen as described in FOTP-57, or asotherwise directed by instructions from the OTDRs manufacturer.5 Procedure5.1 Calibration verificationFor U.S. Military applications, this step shall be performed daily (or as otherwise required) prior tomaking any specimen measurements. In all othe
34、r operations, recalibration should occur once peryear or per other duration depending upon usage, required accuracy, OTDR manufacturerrecommendations, or as required by a Detail Specification.Perform loss and reflectance measurements on splices or connectors that bracket the desiredmeasurement range
35、s, using the procedures of the remainder of clause 5 with an OTDR of knownaccuracy, or using FOTP-34 or FOTP-107, as appropriate. If necessary, perform severalmeasurements to reduce measurement variability by statistical analysis.TIA/EIA-455-83Determine the calibration state of the current OTDR by r
36、emeasuring the same splices orconnectors. If the difference between the measured values exceeds a predetermined limit (suchas 0.05 dB in loss and 0.5 dB in reflectance) based on the intended use of the component,recalibrate and reverify the OTDR.An extensive calibration procedure, not specifically a
37、ddressing discontinuities, is given in the IECdocument referred to in clause 2. A simpler procedure, suitable for daily calibration, can be doneusing well-characterized loss and reflection artifacts.5.2 Connect to OTDRConnect the fiber containing the specimen(s) to either the instrument or to one en
38、d of thedead-zone fiber (if used). Connect the other end of the dead-zone fiber (if used) to theinstrument.5.3 Group indexIf accurate distances to the splices or connectors are to be recorded, the group index1of the fiberor cable is required. If this value is not known, use FOTP-60 to determine it.5
39、.4 OTDR parametersEnter OTDR parameters such as source wavelength, pulse duration, length range, and signalaveraging into the instrument, along with the fiber or cable group index (if required by 5.3). Thevalues of some of these parameters may be preset in the instrument.5.5 Display signalAdjust the
40、 instrument to display a backscatter signal from the specimen. It may be advantageousto begin with coarse vertical and horizontal scaling to maximize the length displayed. An exampleis given in Figure 1.1Other terms used: refractive index (common but erroneous), group delay index, effective group in
41、dex,group velocity index, fiber indexTIA/EIA-455-84Distance zOTDR Signal(dB)P2HP1z4z3z1P4P3LDistance zOTDR Signal(dB)noiseinputreflectionend-facereflectionreflection,without lossreflection,with lossapparent loss,no reflectionapparent gain,no reflectionFigure 1Schematic OTDR trace for a fiber length
42、containing various types of discontinuitiesFigure 2Schematic OTDR close-up trace for a reflective splice or connectorTIA/EIA-455-855.6 Adjust display this may be done by attenuating the signal with an OTDR control, by an in-linevariable attenuator, or by introducing a loop prior to the splice or con
43、nector. (The loop should bepositioned a distance prior to the reflection at least equal to a pulse duration or an attenuationdead-zone as given by the manufacturer. This ensures that the reading for G011still lies on the fiberbaseline.) If the value of the heightG03G01G01=21(in dB)is constant as the
44、 attenuation is varied, then saturation is not occurring.5.6.3 Place the same or another cursor at the end of the feature at a point along the linearportion of the fiber following it. Obtain the power level G013and the distance coordinate G023. Thedistance ( )G02G0231 may be several times the width
45、of the pulse near its peak to avoid thenonlinear tail.5.6.4 Repeat this for another following point of power G014and position G024. The distance()G02G0243 is small enough to minimize any attenuation nonuniformity and large enough so thatnoise is insignificant.5.6.5 (optional) Repeat the procedures o
46、f 5.6.3 and 5.6.4 for points G023and G024even furtherfrom G021. This can help to validate the previous measurements.5.7 Other directionRepeat the measurement for a signal launched into the specimen in the opposite direction.5.8 Other wavelengthsIf required by the Detailed Specification, repeat the t
47、est at other wavelengths.TIA/EIA-455-865.9 Other pulse widthsIf required by the Detailed Specification, repeat the test at other pulse widths. This is sometimesuseful to verify a reflectance value.6 Calculations or interpretation of resultsPerform the calculations required in the Detail Specificatio
48、n.6.1 LossAn estimate of the loss (in dB) of the splice or connector is given by()().34134331zzzzPPPPL=(The formula takes the fiber attenuation between G021and G023into account.) By the conventionused here, a positive loss characterizes a drop in the OTDR trace. A negative value indicates a“false ga
49、in“ due to appropriate fiber backscatter differences on either side of the splice orconnector.6.2 2-Point the calculated reflectance results need not be averaged. This eliminates effects(such as apparent gain) of length-varying backscatter properties, so that more accurate estimatesresult. Some OTDRs can perform these calculations automatically.7 Documentation7.1 Report the following information with each test:7.1.1 Date of test.7.1.2 Sample or specimen identification.7.1.3 FOTP number.7.1.4 As required by the Detail Specification, the locatio
