SIST IEC 61000-3-8:2004

SLOVENSKI SIST IEC 61000-3-8:2004

STANDARD
april 2004
Electromagnetic compatibility (EMC) - Part 3: Limits - Section 8: Signalling on low-
voltage electrical installations - Emission levels, frequency bands and
electromagnetic disturbance levels
ICS 33.100.10 Referenčna številka
SIST IEC 61000-3-8:2004(en)
©  Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno

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NORME
CEI
INTERNATIONALE
IEC
61000-3-8
INTERNATIONAL
Première édition
STANDARD
First edition
1997-08
Compatibilité électromagnétique (CEM) –
Partie 3:
Limites –
Section 8: Transmission de signaux dans
les installations électriques à basse tension –
Niveaux d’émission, bandes de fréquences
et niveaux de perturbations électromagnétiques
Electromagnetic compatibility (EMC) –
Part 3:
Limits –
Section 8: Signalling on low-voltage electrical
installations – Emission levels, frequency bands
and electromagnetic disturbance levels
 IEC 1997 Droits de reproduction réservés  Copyright - all rights reserved
Aucune partie de cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized in
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procédé, électronique ou mécanique, y compris la photo- including photocopying and microfilm, without permission in
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International Electrotechnical Commission
Pour prix, voir catalogue en vigueur
For price, see current catalogue

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61000-3-8 © IEC:1997 – 3 –
CONTENTS
Page
FOREWORD . 5
INTRODUCTION. 7
Clause
1 Scope. 9
2 Normative references. 9
3 General. 11
4 Definitions. 13
5 Frequency bands (ITU region 1 only). 13
6 Transmitter output signal voltage .13
7 Disturbance and interference limits. 17
8 Test conditions. 21
9 Inadvertent operation. 23
Tables
1 Limits of mains terminal interference voltage in the frequency range 0,15 MHz to 30 MHz . 19
2 Limits of radiated interference field strength in the frequency range 30 MHz
to 1 000 MHz at a test distance of 10 m. 19
3 Limits of disturbance . 21
Figures
1 Measurement of output levels in the band 3 kHz to 9 kHz (differential mode) . 25
2 Measurement of output levels in the band 3 kHz to 9 kHz (common mode) . 27
3 Measurement of spectral bandwidth . 29
4 Measuring arrangement for equipment whose operation is dependent on the
transmitter being in circuit . 31
5 Artificial mains network 3 kHz to 9 kHz . 33
6 Idealized equivalent circuit model – DUT port impedance . 35
Annexes
A Measurement of output signal levels and conducted interference levels
(3 kHz to 30 MHz) . 37
B Basis of the artificial mains network for the measurement of output signals at
frequencies below 9 kHz . 39

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61000-3-8 © IEC:1997 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
_________
ELECTROMAGNETIC COMPATIBILITY (EMC) –
Part 3: Limits –
Section 8: Signalling on low-voltage electrical installations –
Emission levels, frequency bands and electromagnetic disturbance levels
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of the IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, the IEC publishes International Standards. Their preparation is
entrusted to technical committees; any IEC National Committee interested in the subject dealt with may
participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. The IEC collaborates closely with the International Organization
for Standardization (ISO) in accordance with conditions determined by agreement between the two
organizations.
2) The formal decisions or agreements of the IEC on technical matters express, as nearly as possible, an
international consensus of opinion on the relevant subjects since each technical committee has representation
from all interested National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form
of standards, technical reports or guides and they are accepted by the National Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject
of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
International standard IEC 61000-3-8 has been prepared by subcommittee 77B: High-frequency
phenomena, of IEC technical committee 77: Electromagnetic compatibility.
The text of this standard is based on the following documents:
FDIS Report on voting
77B/187/FDIS 77B/202/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
Annex A forms an integral part of the standard.
Annex B is for information only.

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61000-3-8 © IEC:1997 – 7 –
INTRODUCTION
This standard is part of the IEC 61000 series, according to the following structure:
Part 1: General
General consideration (introduction, fundamental principles)
Definitions, terminology
Part 2: Environment
Description of the environment
Classification of the environment
Compatibility levels
Part 3: Limits
Emission limits
Immunity limits (in so far as they do not fall under the responsibility of the product committees)
Part 4: Testing and measurement techniques
Measurement techniques
Testing techniques
Part 5: Installation and mitigation guidelines
Installation guidelines
Mitigation methods and devices
Part 6: Generic standards
Part 9: Miscellaneous
Each part is further subdivided into sections which are to be published either as international
standards or as technical reports.
This section is an international standard which gives requirements related to emission levels,
frequency bands and electromagnetic disturbance levels for signalling on low-voltage electrical
installations.

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61000-3-8 © IEC:1997 – 9 –
ELECTROMAGNETIC COMPATIBILITY (EMC) –
Part 3: Limits –
Section 8: Signalling on low-voltage electrical installations –
Emission levels, frequency bands and electromagnetic disturbance levels
1 Scope
This section of IEC 61000-3 applies to electrical equipment using signals in the frequency
range from 3 kHz up to 525 kHz to transmit information on low-voltage electrical installations,
either on the public supply system or within customers' premises.
It specifies frequency bands allocated to different applications (where appropriate), limits for
the terminal output voltage in the operating band and limits for conducted and radiated
disturbance. It also gives the methods of measurement.
It specifies disturbance limits in the frequency range from 3 kHz up to 400 GHz.
It does not specify the signal modulation methods nor the coding methods, nor functional
features.
Environmental requirements and tests are not included.
NOTE – Compliance with this standard does not imply permission to establish communications with locations
outside the customer's installation or with other customers through the public supply system where this would
otherwise not be allowed.
2 Normative references1
The following normative documents contain provisions which, through reference in this text,
constitute provisions of this section of IEC 61000-3. At the time of publication, the editions
indicated were valid. All normative documents are subject to revision, and parties to
agreements based on this section of IEC 61000-3 are encouraged to investigate the
possibility of applying the most recent editions of the normative documents indicated below.
Members of IEC and ISO maintain registers of currently valid International Standards.
IEC 60050(60): 1970, International Electrotechnical Vocabulary (IEV) – Chapter 60: Radio-
communications
IEC 60050(161): 1990, International Electrotechnical Vocabulary (IEV) – Chapter 161: Electro-
magnetic compatibility
CISPR 14: 1993, Limits and methods of measurement of radio disturbance characteristics of
electrical motor-operated and thermal appliances for household and similar purposes, electric
tools and electric apparatus
CISPR 16-1: 1993, Specification for radio disturbance and immunity measuring apparatus and
methods – Part 1: Radio disturbance and immunity measuring apparatus
CISPR 16-2: 1996, Specification for radio disturbance and immunity measuring apparatus and
methods – Part 2: Méthods of measurement of disturbances and immunity
CISPR 22: 1993, Limits and methods of measurement of radio disturbance characteristics of
information technology equipment

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61000-3-8 © IEC:1997 – 11 –
3 General
The objects of this section are twofold:
– to prevent interference by mains signalling equipment to radiocommunications services
and other equipment connected to the network;
– to limit mutual interference between differing mains signalling equipments connected to
the same electrical network.
With regard to the former object and above 150 kHz, limits for maximum output terminal
voltage for household equipment are given in CISPR 14, and for information technology
equipment are given in CISPR 22. Neither of these specifically apply to mains signalling
equipment, but they have been used as guidance for the maximum output levels specified in
this section. However, it should be pointed out that the CISPR is concerned with involuntary
emissions whereas mains signalling is deliberate emission and, with some methods of
signalling, the signal level needs to be above the possible noise level in order to achieve
signalling success.
Below 150 kHz, there is no guidance and the values specified are considered appropriate and
consistent with the CISPR principles. Another factor at any frequency band is that there may
be, in some countries, regulatory guidelines for maximum emission levels for signalling which
must be observed.
With regard to the latter object, three classes of technique may be used to limit mutual
interference between different signalling systems:
a) physical separation, separation by means of filters to limit interchange of emissions, or
differential signal injection systems;
b) separation by frequency bands allocated to different types of application;
c) agreement to a common protocol, with identified and separate addressing mechanisms
for different applications to avoid contention.
The general rules for the assignment and use of frequencies in the range from 9 kHz to
400 GHz by radiocommunication services and definitions of these services are specified in
the ITU radio regulations which contain a table of frequency allocations. This standard takes
these allocations into account where it defines frequency bands for different applications, in
order to avoid disturbances to radiotelecommunications services. However, in the event of
actual disturbance being caused, then additional precautions will need to be applied. The ITU
regulations specify three regions, and frequency allocations vary between these regions.
Where requirements in specific regions having equipment within the scope of this section are
known to differ from values stated, this is recorded by means of a note (as in clause 7).
However, omission of such a note does not imply that frequency bands, output voltages, or
conducted or radiated disturbance values stated are necessarily acceptable in these regions.
In ITU region 1, AM broadcasting bands begin above 148,5 kHz, and to optimise the use of the
range in which mains signalling is allowed, and taking into account that there is no protocol
common to electricity supplier and customer applications, the CENELEC countries have
adopted the approach of b) and have agreed separate frequency bands for supplier/customer
use. All clauses of this section therefore apply, and care is required with out of band emissions
within the band(s) available for other equipment in order to limit the possibility of mutual
interference.

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61000-3-8 © IEC:1997 – 13 –
In ITU regions 2 and 3, AM broadcasting begins at 525 kHz and 526,5 kHz respectively.
Frequency band allocation for mains signalling is not employed and the methods used to limit
mutual interference may fall outside the scope of this section, particularly where protocols need
to be defined. In these regions, clause 5 will not apply and, as regards clause 7, out of band
emissions within the band available for mains signalling may not be relevant in that they cannot
interfere with radiocommunications services. However, consideration shall be given to possible
interference with other equipment connected to the mains, and the relevant values given in
clause 6 should be observed.
NOTE – In the United States, the Federal Communications Commission is to allow mains signalling at
frequencies above which AM broadcasting begins (in the band 535 kHz to 1 705 kHz), albeit with restrictions on
maximum output levels. This is a special case and is not covered by this section.
Common-mode injection shall not be used unless otherwise explicitly allowed in local
regulations (see also clause 9).
4 Definitions
For the purpose of this section, the definitions of IEC 60050(60) and IEC 60050(161) apply.
5 Frequency bands (ITU region 1 only)
Under consideration in ITU region 3.
5.1 Band 3 kHz up to 9 kHz
The use of frequencies in
...

IEC 60793-1-60
®

Edition 1.0 2017-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside


Optical fibres –
Part 1-60: Measurement methods and test procedures – Beat length

Fibres optiques –
Partie 1-60: Méthodes de mesure et procédures d’essai – Longueur de battement

IEC 60793-1-60:2017-02(en-fr)

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IEC 60793-1-60

®


Edition 1.0 2017-02




INTERNATIONAL



STANDARD




NORME


INTERNATIONALE
colour

inside










Optical fibres –

Part 1-60: Measurement methods and test procedures – Beat length



Fibres optiques –

Partie 1-60: Méthodes de mesure et procédures d’essai – Longueur de battement
















INTERNATIONAL

ELECTROTECHNICAL

COMMISSION


COMMISSION

ELECTROTECHNIQUE


INTERNATIONALE




ICS 33.180.10 ISBN 978-2-8322-9363-8




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® Registered trademark of the International Electrotechnical Commission
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– 2 – IEC 60793-1-60:2017 © IEC 2017
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Testing conditions . 6
5 Reference test method . 6
6 Specimen . 6
7 Test methods . 6
7.1 Phase beat length measurement methods . 6
7.1.1 General . 6
7.1.2 Monitoring of output power using an electromagnet . 6
7.1.3 Monitoring of SOP using a lateral force . 9
7.2 Group beat length measurement method . 11
7.2.1 General . 11
7.2.2 Apparatus and procedure. 12
7.2.3 Calculation . 12
8 Results . 12
8.1 Information available with each measurement . 12
8.2 Information available upon request . 13
Annex A (informative) Difference of beat lengths by measurement method (phase beat
length and group beat length) . 14
A.1 Phase modal birefringence and phase beat length . 14
A.2 Group modal birefringence and group beat length . 14
Annex B (informative) Correlation between results obtained by the two methods
(phase beat length and group beat length) . 17
B.1 General . 17
B.2 Example of correlation between phase and group beat lengths in the case of
PANDA fibres . 17
B.3 Example of correlation between phase and group beat lengths in the case of
elliptical core fibres . 18
Annex C (informative) Electromagnet for Faraday rotation . 19
Bibliography . 20

Figure 1 – Apparatus of phase beat length measurement using an electromagnet . 7
Figure 2 – Example of measurement profile by electromagnet . 9
Figure 3 – Set-up for measuring L when monitoring SOP together with a
B(phase)
moving lateral force . 9
Figure 4 – SOP measured at different levels of lateral force . 11
Figure 5 – Example of SOP evolution and normalized Stokes vector components . 11
Figure B.1 – Wavelength dependence of B /B [3] . 17
group phase
Figure C.1 – Schematic of the electromagnet . 19

Table B.1 – B /B of elliptical core fibres . 18
group phase

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IEC 60793-1-60:2017 © IEC 2017 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

OPTICAL FIBRES –

Part 1-60: Measurement methods and test procedures –
Beat length

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
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Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60793-1-60 has been prepared by subcommittee 86A: Fibres and
cables, of IEC technical committee 86: Fibre optics.
The text of this International Standard is based on the following documents:
CDV Report on voting
86A/1737/CDV 86A/1782/RVC

Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 60793 series, published under the general title Optical fibres, can
be found on the IEC website.

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– 4 – IEC 60793-1-60:2017 © IEC 2017
The committee has decided that the contents of this document will remain unchanged until the
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the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.

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colour printer.

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IEC 60793-1-60:2017 © IEC 2017 – 5 –
OPTICAL FIBRES –

Part 1-60: Measurement methods and test procedures –
Beat length



1 Scope
This part of IEC 60793 defines test methods for both the phase beat length, and the group
beat length. These two parameters are defined differently, and will give different results
depending on the type of polarization-maintaining (PM) fibre.
The phase beat length is the relevant parameter for the fibres ability to maintain a high
extinction ratio. This is described in more details in Annexes A and B.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements of this document. For dated references, only the edition
cited applies. For undated references, the latest edition of the referenced document (including
any amendments) applies.
IEC 60068-1, Environmental testing – Part 1: General and guidance
IEC 60793-1-1, Optical fibres – Part 1-1: Measurement methods and test procedures –
General and guidance
IEC 60793-1-48, Optical fibres – Part 1-48: Measurement methods and test procedures –
Polarization mode dispersion
1
IEC 60793-2-70 , Optical fibres – Part 2-70: Product specifications – Sectional specifications
for polarization-maintaining fibres
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60793-1-1 and the
following apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
phase beat length
L
B(phase)
distance over which two orthogonal polarization modes are delayed by one cycle (2 )
π
___________
1
Under preparation. Stage at the time of publication: IEC CCDV 60793-2-70:2017.

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– 6 – IEC 60793-1-60:2017 © IEC 2017
3.2
group beat length
L
B(group)
distance over which the group delay difference is one cycle (2 )
π
Note 1 to entry A group delay is based on group refractive index.
4 Testing conditions
Unless otherwise specified, the test shall be conducted under the standard conditions
specified in IEC 60068-1. However, when it is difficult to make measurements in the standard
conditions, the test may be conducted in conditions other than the standard conditions
provided that no doubts will arise about judgments.
5 Reference test method
Since the phase beat length is the parameter specified in the product specification,
IEC 60793-2-70, both phase beat length test methods described in 7.1 are defined as the
reference test method (RTM). Test method for group beat length described in 7.2 can be used
as an alternative test method (ATM) when the correlation between phase and group beat
lengths is confirmed in advance (as shown in Annex B).
6 Specimen
A specimen length should be the minimum necessary to set up the test apparatus. If the
specimen is extra long, take care that no stresses will be induced in the specimen.
7 Test methods
7.1 Phase beat length measurement methods
7.1.1 General
The phase beat length measurement method is based on applying a point-like perturbation
along a short length of the fibre under test, and either monitor the changes in output power, or
monitor changes in output state of polarization (SOP) at one wavelength versus travel
distance.
The perturbation can either be a lateral force or an electromagnet.
In this document, the test methods where output power is monitored using an electromagnet,
and where SOP is monitored using a lateral force, are both described.
7.1.2 Monitoring of output power using an electromagnet
7.1.2.1 Apparatus
7.1.2.1.1 General apparatus
See Figure 1 for a diagram of the test set-up.
An electromagnet is moved along the optical fibre longitudinal axis for Faraday rotation.

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IEC 60793-1-60:2017 © IEC 2017 – 7 –
Driving
Reference
modulation
Electromagnet
signal
oscillation Power
Signal
amplifier
generator
Retardation
plate
Lens Polarizer Analyzer
Light Lock-in
Detector
source amplifier
Translation stage
Mesurement
Sample fibre
Control signal signal
Computer
Output
device

IEC
Figure 1 – Apparatus of phase beat length measurement
using an electromagnet
7.1.2.1.2 Light source
A light source which has a narrow spectrum line-width such as a DFB laser shall be used.
7.1.2.1.3 Retardation plate
A retardation plate (λ/4 retarder) shall be provided to enable the input of certain level of
optical power into the fibre even when the polarizer is rotated. The retardation plate converts
the polarization of incident light from linear polarization into circular polarization.
7.1.2.1.4 Polarizer and analyser
A polarizer and an analyser shall be capable of outputting linearly polarized light having a
certain direction of electric field vector when they have received light in a state of polarization.
7.1.2.1.5 Detector
A detector to be used shall have a light receiving area that can detect all the optical power
emitted from the output end of the optical fibre.
7.1.2.1.6 Electromagnet for Faraday rotation
An electromagnet for Faraday rotation rotates the polarization of the light in a fibre by
applying an electromagnetical field along the fibre longitudinal axis. The polarization rotation
shall be modulated by an electrical signal from outside to improve measurement sensitivity.
The interaction length should be smaller than the specified beat length (for example, around
1 mm) enough for detecting the beat length with appropriate accuracy. The applied
electromagnetical field should be large enough for detecting the beat length with appropriate
accuracy. Annex C describes the examples of electromagnet equipment for Faraday rotation.
7.1.2.1.7 Translation stage
A translation stage shall be able to move the electromagnet along the fibre longitudinal axis.
The translation stage shall have the moving range and pitch which are sufficient to measuring
the beat length of the sample fibre.

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7.1.2.1.8 Lock-in amplifier
A lock-in amplifier shall be used to improve measurement sensitivity. The lock-in amplifier
shall have response time enough to respond to the modulation speed of the electromagnet.
7.1.2.1.9 Signal generator
A signal generator provides modulated signal to the lock-in amplifier and the electromagnet.
7.1.2.1.10 Power amplifier
A power amplifier may be used as necessary. The power amplifier shall provide enough power
for the electromagnet.
7.1.2.1.11 Computer
A computer should control the pulse stage and process the output signal from the lock-in
amplifier.
7.1.2.1.12 Output device
An output device is used to output a measurement profile processed by the computer. The
output device may directly output the signal level of the lock-in amplifier by such as a plotter.
7.1.2.2 Procedure
7.1.2.2.1 Preparation and adjustment
Prepare a V-groove or bare fibre adapter to connect the sample fibre under test to the
polarizer and analyser. Remove the primary coating from both ends of the fibre under test,
and cleave the ends into mirror surfaces perpendicular to the axis of the fibre. Connect one
end of the fibre to the polarizer, either the V-groove or the bare fibre adapter. Connect the
other end of the fibre to the analyser, and connect the analyser with the detector, so that all
the input light can be received.
Rotate the polarizer and analyser to minimize the optical output power through the analyser.
Next, adjust the analyser to maximize the output voltage of the lock-in amplifier.
7.1.2.2.2 Measurement
Move the electromagnet by driving the pulse stage. Memorize a relationship between the
electromagnet travel distance Z and the lock-in amplifier output V. The relationship as shown
in Figure 2 can be obtained. Measure N times of the travel distances, ∆Z which is a half
i
period of the sequence of V.

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IEC 60793-1-60:2017 © IEC 2017 – 9 –
60
∆Z ∆Z ∆Z ∆Z ∆Z
1 2 3 4 5
40
20
0
–20
–40
–60
0 10 20 30 40
Travel distance of stage (mm)

IEC
Figure 2 – Example of measurement profile by electromagnet
7.1.2.3 Calculation
The phase beat length L is given by:
B(phase)
N
2 ∆Z
∑ i
i =1
L =
B(phase)
 (1)
N
where
L is the phase beat length;
B(phase)
∆Z is the travel distance of the stage where the lock-in amplifier output changes by the
i
half period;
N is the number of the half period.
7.1.3 Monitoring of SOP using a lateral force
7.1.3.1 Apparatus
7.1.3.1.1 General apparatus
See Figure 3 for a diagram of the test set-up.
By applying a lateral force at a point that moves along the fibre axis and simultaneously
measure the SOP, the L can be obtained.
B(phase)
L
Point force
Polarization
Polarized
analyser
Computer
laser
(polarimeter)
FUT
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Figure 3 – Set-up for measuring L when monitoring SOP
B(phase)
together with a moving lateral force
Lock-in amplifier output (mV)

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7.1.3.1.2 Light source
A polarized laser source with a narrow spectrum line-width, such as a distributed feedback
laser (DFB) shall be used.
7.1.3.1.3 Polarization analyser
Any commercial available polarization analyser (polarimeter) can be used.
7.1.3.1.4 Translation stage
A translation stage shall be able to move the lateral force along the fibre longitudinal axis.
The translation stage shall have the sufficient moving range to measure the beat length of the
sample fibre. It is recommended to have a range long enough to ensure five to ten periods in
order to average the result.
The length of interaction between the lateral force and the sample fibre should be significantly
smaller than the specified beat length (e.g. 1/10).
7.1.3.1.5 Computer
A computer should be used to combine the SOP data and the displacement data.
7.1.3.2 Procedure
7.1.3.2.1 Preparation and adjustment
The fibre sample shall be placed straight on a flat and smooth surface. It is important to avoid
any twisting of the fibre sample.
2
Since a specific input SOP is not needed (or needs to be known) [1] , the input end of the
fibre sample can be spliced to any type of pigtail fibre connected to the light source.
The output end of the sample fibre can be connected directly to the polarization analyser by
using for example a bare fibre adapter.
7.1.3.2.2 Measurement
Move the lateral force to one end of the fibre sample and lower it onto the fibre sample.
Then move the lateral force slowly along the length of the fibre sample.
Observe the SOP on the polarization analyser. One full circle corresponds to one period.
The diameter of the circle showed on the Poincaré sphere gets larger for increasing lateral
force (see Figure 4 below).
___________
2
 Numbers in square brackets refer to the Bibliography.

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Figure 4 – SOP measured at different levels of lateral force
7.1.3.3 Calculation
The phase beat length is obtained from the periodic variation of the SOP. Examples of SOP
evolution on the Poincaré sphere (left) and the three normalized Stokes vector components as
function of displacement length from which the L is determined (right) are shown in
B (phase)
Figure 5.
1
+S
3
RCP
1
0,5
+S
2
S1
0
S2
0
L
S3
B(phase)
+S
–0,5
1
–1
–1
1 –1
–0,5
0,5
0 20 40 60 80 100
0
0
0,5
–0,5
Displacement length (mm)
–1
1
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Figure 5 – Example of SOP evolution and normalized
Stokes vector components
7.2 Group beat length measurement method
7.2.1 General
In principle, polarization mode dispersion is measured with the group beat length
measurement method. A modal birefringence and a beat length are measured by this method,
which are defined on the basis of a differential group refractive index, and are different from a
modal birefringence and a beat length measured by the methods in 7.1. See Annex A.
As shown in Annex B, there is a correlation between results obtained by the methods in 7.1
and 7.2 in some types of polarization maintaining fibre. If the correlation between both
methods is confirmed in advance (as shown in Annex B), the measurement method in 7.2 can
be used as an alternative easy-to-use measurement method (ATM), instead of 7.1 (RTM) for
phase beat length measurement, with an appropriate correlation factor.
Normalized stokes vector components

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7.2.2 Apparatus and procedure
In the group beat length measurement method, differential group delay (DGD) or group modal
birefringence is utilized for calculation of beat length. It should be measured by a method of
polarization mode dispersion measurement (i.e. fixed analyser or wavelength scanning,
Stokes parameter evaluation, Interferometry). Information pertaining to each individual
method appears in IEC 60793-1-48.
7.2.3 Calculation
A group beat length can be calculated from results in method of IEC 60793-1-48.
The group beat length L is given by:
B(group)
λ
L =
B(group) (2)
B
group
where
L is the group beat length;
B (group)
B is the group modal birefringence in 7.2;
group
λ is the wavelength.
is given by:
The group modal birefringence B
group
c
B = ⋅Δτ
 (3)
group
L
where
c is the velocity of light in vacuum [m/s];
L is the fibre length [m];
∆τ is the differential group delay (DGD) [s].
8 Results
8.1 Information available with each measurement
Report the following information on each measurement:
– date and title of measurement;
– length of specimen;
– identification of specimen;
– measurement wavelength;
– beat length;
– measurement method.

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8.2 Information available upon request
The following information shall be available upon request:
– description of measurement apparatus
...