IEC 61746-2:2010

IEC 61746-2 ®
Edition 1.0 2010-06
INTERNATIONAL
STANDARD
Calibration of optical time-domain reflectometers (OTDR) –
Part 2: OTDR for multimode fibres

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IEC 61746-2 ®
Edition 1.0 2010-06
INTERNATIONAL
STANDARD
Calibration of optical time-domain reflectometers (OTDR) –
Part 2: OTDR for multimode fibres

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
X
ICS 33.180.01 ISBN 978-2-88912-026-0
– 2 – 61746-2 © IEC:2010(E)
CONTENTS
FOREWORD.4
INTRODUCTION.6
1 Scope.7
2 Normative references.7
3 Terms, definitions and symbols .7
4 Preparation for calibration.13
4.1 Organization .13
4.2 Traceability.13
4.3 Preparation.13
4.4 Test conditions .13
4.5 Documentation .13
5 Distance calibration – General .14
5.1 General .14
5.2 Location deviation model .14
5.3 Using the calibration results.16
5.4 Measuring fibre length .17
6 Distance calibration methods .17
6.1 General .17
6.2 External source method .17
6.2.1 Short description and advantage .17
6.2.2 Equipment .17
6.2.3 Calibration of the equipment .19
6.2.4 Measurement procedure .20
6.2.5 Calculations and results .20
6.2.6 Uncertainties .21
6.3 Concatenated fibre method (using multimode fibres) .23
6.3.1 Short description and advantages .23
6.3.2 Equipment .23
6.3.3 Measurement procedures.24
6.3.4 Calculations and results .24
6.3.5 Uncertainties .25
6.4 Recirculating delay line method.26
6.4.1 Short description and advantages .26
6.4.2 Equipment .27
6.4.3 Measurement procedure .28
6.4.4 Calculations and results .28
6.4.5 Uncertainties .29
7 Vertical scale calibration – General .30
7.1 General .30
7.2 Loss difference calibration .31
7.2.1 Determination of the displayed power level F.31
7.2.2 Development of a test plan.31
7.3 Characterization of the OTDR source near field .33
7.3.1 Objectives and references .33
7.3.2 Procedure.33
8 Loss difference calibration method.34

61746-2 © IEC:2010(E) – 3 –
8.1 General .34
8.2 Long fibre method.34
8.2.1 Short description.34
8.2.2 Equipment .34
8.2.3 Measurement procedure .36
8.2.4 Calculation and results.36
Annex A (normative) Multimode recirculating delay line for distance calibration.37
Annex B (normative) Mathematical basis .41
Bibliography .44

Figure 1 – Definition of attenuation dead zone .8
Figure 2 – Representation of the location deviation ΔL(L).15
Figure 3 – Equipment for calibration of the distance scale – External source method .18
Figure 4 – Set-up for calibrating the system insertion delay.19
Figure 5 – Concatenated fibres used for calibration of the distance scale.23
Figure 6 – Distance calibration with a recirculating delay line .27
Figure 7 – OTDR trace produced by recirculating delay line .28
Figure 8 – Determining the reference level and the displayed power level .31
Figure 9 – Region A, the recommended region for loss measurement samples .32
Figure 10 – Possible placement of sample points within region A .33
Figure 11 – Linearity measurement with a long fibre .35
Figure 12 – Placing the beginning of section D outside the attenuation dead zone .35
Figure A.1 – Recirculating delay line.37
Figure A.2 – Measurement set-up for loop transit time T .38
b
Figure A.3 – Calibration set-up for lead-in transit time T .39
a
Table 1 – Additional distance uncertainty.16
Table 2 – Attenuation coefficients defining region A.32

– 4 – 61746-2 © IEC:2010(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
CALIBRATION OF OPTICAL TIME-DOMAIN
REFLECTOMETERS (OTDR) –
Part 2: OTDR for multimode fibres

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International Standard IEC 61746-2 has been
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