Guidance of measurement methods and test procedures - Basic tests for polarization-maintaining optical fibres

IEC TR 62349:2014(E) applies to polarization-maintaining (PM) optical fibres. The object of this report is to define test procedures to be used in establishing uniform requirements for the geometrical and transmission properties of PM fibres. This second edition cancels and replaces the first edition published in 2005. It constitutes a technical revision. In this edition, guidance of measurement methods and test procedures for dimensional characteristics, cut-off wavelength, mode field diameter and beat length of polarization-maintaining optical fibres have been added. Thus, the title of the technical report is changed to "Guidance of measurement methods and test procedures - Basic tests for polarization-maintaining optical fibres" from "Guidance for polarization crosstalk measurement of optical fibre". Keywords: polarization-maintaining (PM) optical fibres, geometrical and transmission properties

General Information

Status
Published
Publication Date
29-Jun-2020
Technical Committee
Current Stage
WPUB - Publication withdrawn
Completion Date
30-Jun-2020
Ref Project

Buy Standard

Technical report
IEC TR 62349:2014 - Guidance of measurement methods and test procedures - Basic tests for polarization-maintaining optical fibres
English language
23 pages
sale 15% off
Preview
sale 15% off
Preview

Standards Content (sample)

IEC TR 62349
Edition 2.0 2014-02
TECHNICAL
REPORT
colour
inside
Guidance of measurement methods and test procedures – Basic tests for
polarization-maintaining optical fibres
IEC TR 62349:2014-02(EN)
---------------------- Page: 1 ----------------------
THIS PUBLICATION IS COPYRIGHT PROTECTED
Copyright © 2014 IEC, Geneva, Switzerland

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form

or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from

either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC

copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or

your local IEC member National Committee for further information.
IEC Central Office Tel.: +41 22 919 02 11
3, rue de Varembé Fax: +41 22 919 03 00
CH-1211 Geneva 20 info@iec.ch
Switzerland www.iec.ch
About the IEC

The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes

International Standards for all electrical, electronic and related technologies.
About IEC publications

The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the

latest edition, a corrigenda or an amendment might have been published.
IEC Catalogue - webstore.iec.ch/catalogue Electropedia - www.electropedia.org

The stand-alone application for consulting the entire The world's leading online dictionary of electronic and

bibliographical information on IEC International Standards, electrical terms containing more than 30 000 terms and

Technical Specifications, Technical Reports and other definitions in English and French, with equivalent terms in 14

documents. Available for PC, Mac OS, Android Tablets and additional languages. Also known as the International

iPad. Electrotechnical Vocabulary (IEV) online.

IEC publications search - www.iec.ch/searchpub IEC Glossary - std.iec.ch/glossary

The advanced search enables to find IEC publications by a More than 55 000 electrotechnical terminology entries in

variety of criteria (reference number, text, technical English and French extracted from the Terms and Definitions

committee,…). It also gives information on projects, replaced clause of IEC publications issued since 2002. Some entries

and withdrawn publications. have been collected from earlier publications of IEC TC 37,

77, 86 and CISPR.
IEC Just Published - webstore.iec.ch/justpublished

Stay up to date on all new IEC publications. Just Published IEC Customer Service Centre - webstore.iec.ch/csc

details all new publications released. Available online and If you wish to give us your feedback on this publication or

also once a month by email. need further assistance, please contact the Customer Service

Centre: csc@iec.ch.
---------------------- Page: 2 ----------------------
IEC TR 62349
Edition 2.0 2014-02
TECHNICAL
REPORT
colour
inside
Guidance of measurement methods and test procedures – Basic tests for
polarization-maintaining optical fibres
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
ICS 33.180.10 ISBN 978-2-8322-1396-4

Warning! Make sure that you obtained this publication from an authorized distributor.

® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 3 ----------------------
– 2 – TR 62349 © IEC:2014(E)
CONTENTS

FOREWORD ........................................................................................................................... 4

1 Scope and object ............................................................................................................. 6

2 Normative references ...................................................................................................... 6

3 Terms and definitions ...................................................................................................... 6

4 Testing conditions ........................................................................................................... 7

5 Guidance for dimensional characteristics measurement of polarization-maintaining

optical fibres .................................................................................................................... 7

5.1 Object ................................................................................................................ 7

5.2 Overview of method ........................................................................................... 7

5.3 Reference test method ....................................................................................... 8

6 Guidance for cut-off wavelength measurement of polarization-maintaining optical

fibres ............................................................................................................................... 8

6.1 Object ................................................................................................................ 8

6.2 Overview of method ........................................................................................... 8

7 Guidance for mode field diameter measurement of polarization-maintaining optical

fibres ............................................................................................................................... 8

7.1 Object ................................................................................................................ 8

7.2 Overview of method ........................................................................................... 8

8 Guidance for beat length measurement of polarization-maintaining optical fibres ............. 9

8.1 Object ................................................................................................................ 9

8.2 Overview of methods ......................................................................................... 9

8.3 Reference test method ....................................................................................... 9

8.4 Specimen ........................................................................................................... 9

8.5 Beat length measuring method ........................................................................... 9

8.5.1 Method A: Phase beat length measurement method ......................... 9
8.5.2 Method B: Group beat length measurement method ....................... 12

8.6 Results ............................................................................................................ 12

8.6.1 Information available with each measurement ................................. 12

8.6.2 Information available upon request ................................................. 13

9 Guidance for polarization crosstalk measurement of polarization-maintaining

optical fibres .................................................................................................................. 13

9.1 Object .............................................................................................................. 13

9.2 Polarization crosstalk measuring method ......................................................... 13

9.2.1 General .......................................................................................... 13

9.2.2 Method A: Power ratio method ........................................................ 13

9.2.3 Method B: In-line polarimetric method ............................................. 15

Annex A (informative) Cut-off wavelength of PM fibre and SM fibre – Profiles and bend

dependence of cut-off wavelength ................................................................................. 17

Annex B (informative) Difference of beat length by measurement method ............................ 19

B.1 Modal birefringence and beat length ................................................................ 19

B.2 Beat length defined by Method B ..................................................................... 19

Annex C (informative) Electromagnet for Faraday rotation ................................................... 22

Bibliography .......................................................................................................................... 23

---------------------- Page: 4 ----------------------
TR 62349 © IEC:2014(E) – 3 –

Figure 1 – Apparatus of beat length measurement – Method A ............................................. 10

Figure 2 – Example of measurement profile by electro magnet ............................................. 11

Figure 3 – Example of test apparatus for polarization crosstalk measurement (power

ratio method) ........................................................................................................................ 14

Figure 4a – Front view of data arc and fitted circle ................................................................ 16

Figure 4b – 90° – Rotated cutaway view defining the geometrical relationships .................... 16

Figure 4 – Poincaré sphere representations for Method B ..................................................... 16

Figure A. 1 – Cut-off wavelength profiles of PM fibre and SM fibre ........................................ 17

Figure A. 2 – Cut-off wavelength profile of PM fibre with extra bending ................................. 17

Figure C. 1 – A schematic of the electromagnet .................................................................... 22

---------------------- Page: 5 ----------------------
– 4 – TR 62349 © IEC:2014(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
GUIDANCE OF MEASUREMENT METHODS AND TEST PROCEDURES –
BASIC TESTS FOR POLARIZATION-MAINTAINING OPTICAL FIBRES
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.

7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and

members of its technical committees and IEC National Committees for any personal injury, property damage or

other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and

expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC

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.

The main task of IEC technical committees is to prepare International Standards. However, a

technical committee may propose the publication of a technical report when it has collected

data of a different kind from that which is normally published as an International Standard, for

example "state of the art".

IEC/TR 62349, which is a technical report, has been prepared by subcommittee 86A: Fibres

and cables, of IEC technical committee 86: Fibre optics.

This second edition cancels and replaces the first edition published in 2005. It constitutes a

technical revision.

In this edition, guidance of measurement methods and test procedures for dimensional

characteristics, cut-off wavelength, mode field diameter and beat length of polarization-

maintaining optical fibres have been added. Thus, the title of the technical report is changed

to “Guidance of measurement methods and test procedures – Basic tests for polarization-

maintaining optical fibres” from “Guidance for polarization crosstalk measurement of optical

fibre”.
---------------------- Page: 6 ----------------------
TR 62349 © IEC:2014(E) – 5 –
The text of this technical report is based on the following documents:
Enquiry draft Report on voting
86A/1488/DTR 86A/1507/RVC

Full information on the voting for the approval of this technical report can be found in the

report on voting indicated in the above table.

This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

The committee has decided that the contents of this publication will remain unchanged until

the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data

related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

IMPORTANT – The “colour inside” logo on the cover page of this publication indicates

that it contains colours which are considered to be useful for the correct understanding

of its contents. Users should therefore print this publication using a colour printer.

---------------------- Page: 7 ----------------------
– 6 – TR 62349 © IEC:2014(E)
GUIDANCE OF MEASUREMENT METHODS AND TEST PROCEDURES –
BASIC TESTS FOR POLARIZATION-MAINTAINING OPTICAL FIBRES
1 Scope and object
This technical report applies to polarization-maintaining (PM) optical fibres.

The object of this report is to define test procedures to be used in establishing uniform

requirements for the geometrical and transmission properties of PM fibres.
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and

are indispensable for its application. 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 60793-1-20:2001, Optical fibres – Part 1-20: Measurement methods and test procedures

– Fibre geometry

IEC 60793-1-44, Optical fibres – Part 1-44: Measurement methods and test procedures – Cut-

off wavelength

IEC 60793-1-45:2001, Optical fibres – Part 1-45: Measurement methods and test procedures

– Mode field diameter

IEC 60793-1-48, Optical fibres – Part 1-48: Measurement methods and test procedures –

Polarization mode dispersion
3 Terms and definitions
For the purposes of this document, the following ters and definitions apply.
NOTE IEC 60793-1-1[1] provides general definitions for testing.
3.1
polarization-maintaining optical fibre
PM fibre

optical fibre capable of transmitting, under external perturbations such as bending or lateral

X Y

pressure, both independently of or either of the polarization modes HE and HE whose

11 11

directions of electric field vector intersect orthogonally with each other and which have

different propagation constants
___________
Numbers in square brackets refer to the bibliography.
---------------------- Page: 8 ----------------------
TR 62349 © IEC:2014(E) – 7 –
3.2
phase beat length

one cycle of the periodical coupled polarization state by the phase difference of two linear-

polarization modes intersecting orthogonally in the PM fibre

Note 1 to entry: Small beat length results in high polarization maintaining capability

3.3
group beat length

one cycle of the periodical coupled polarization state by the group delay difference of two

linear-polarization modes intersecting orthogonally in the PM fibre

Note 1 to entry: Small beat length results in high polarization maintaining capability.

3.4
polarization crosstalk

strength of coupling of the two polarization modes intersecting orthogonally with each other

within a polarization-maintaining optical fibre, representing the ratio in optical strength exiting

the fibre of one polarization mode launched at the input end to the optical power of the other

polarization mode exiting the fibre when only the former polarization mode is excited (see also

9.2.2.4.2)
4 Testing conditions

Unless otherwise specified, the test is conducted under the standard conditions specified in

IEC 60068-1. However, when it is difficult to make measurements in the standard conditions,

the test can be conducted in conditions other than the standard conditions provided that no

doubts will arise about judgments.
5 Guidance for dimensional characteristics measurement of polarization-
maintaining optical fibres
5.1 Object
Clause 5 describes measurement methods and test procedures for the dimensional
characteristics of uncoated PM optical fibres.
5.2 Overview of method

This technical report gives measurement methods for dimensional characteristics of PM fibre

which are given in terms of the following parameters:
• cladding diameter;
• cladding non-circularity;
• core concentricity error.
Two methods are described for measuring dimensional characteristics of PM fibre:
• Method A: Refracted near-field;
• Method B: Grey-scale technique of near-field light distribution.

Information pertaining to each individual method is given in Annexes A and C of IEC 60793-1-

20:2001. Only notes for PM fibre are described below.

For a general optical fibre, a circle-fitting is used to determine the core centre. However, as

for the PM fibre, in particular the elliptical core PM fibre, the core centre cannot be

determined if an ellipse-fitting is not used, because the fibre has an oval core.

---------------------- Page: 9 ----------------------
– 8 – TR 62349 © IEC:2014(E)
5.3 Reference test method

Method B is the reference test method (RTM), which is the one used to settle disputes.

6 Guidance for cut-off wavelength measurement of polarization-maintaining
optical fibres
6.1 Object

Clause 6 describes a measurement method and a test procedure for the cut-off wavelength,

λ of PM fibres.
6.2 Overview of method

The measurement method in this technical report describes procedures for determining the

cut-off wavelength of a sample fibre in a short length, uncabled and primary coated condition

(λ ).

Information pertaining to each individual method is given in IEC 60793-1-44. Only notes for

PM fibre are described below.

As shown in Annex A, the cut-off wavelength of the PM fibre is measured paying attention to

excite a LP mode sufficiently and not to impose an extra, small bending more carefully than

the cut-off wavelength measurement of a single-mode (SM) optical fibre.

The recommended deployment configuration of the sample fibre is as defined for the fibre cut-

off wavelength in IEC 60793-1-44.
7 Guidance for mode field diameter measurement of polarization-maintaining
optical fibres
7.1 Object

Clause 7 describes measurement methods and test procedures for the mode field diameter

(MFD) of PM fibres.
7.2 Overview of method
Three methods are described for measuring the MFD of the PM fibre:
• Method A: direct far-field scan;
• Method B: variable aperture in the far field;
• Method C: near-field scan.

Information pertaining to each individual method is given in Annexes A, B and C of

IEC 60793-1-45:2001. Only notes for PM fibre are described below.

The MFD of the PM fibre is non-axisymmetric in principle. The MFD is measured in the same

directions by rotating the fibre around the axis properly. The azimuthal dependence of the

MFD of a stress induced PM fibre and an elliptical sheath PM fibre are relatively small. On the

other hand, the azimuthal dependence of the MFD of an elliptical core PM fibre is relatively

large. The MFD of a stress induced fibre and an elliptical sheath PM fibre may be measured

without rotating the fibre complying with the demand of a required accuracy of the customer

depending on the measurement method.
---------------------- Page: 10 ----------------------
TR 62349 © IEC:2014(E) – 9 –

In Method A, the MFD of a stress induced PM fibre and an elliptical sheath PM fibre may be

measured without rotating the fibre complying with the demand of a required accuracy by the

customer.

In Method B, the MFD of a stress induced PM fibre and an elliptical sheath PM fibre may be

measured complying with the demand of a required accuracy of the customer. The MFD is

measured as an axisymmetric electromagnetic field in Method B. Therefore, the MFD of the

PM fibre cannot be measured in Method B. However, the MFD of a stress induced PM fibre

and an elliptical sheath PM fibre may be measured in Method B because of the relatively

small azimuthal dependence of the MFD. Method B cannot be used to measure the MFD of an

elliptical core PM fibre.

In Method C, a two-dimensional detector is used. The fibre is rotated around the axis properly

on measurement with a one dimensional detector.
8 Guidance for beat length measurement of polarization-maintaining optical
fibres
8.1 Object

Clause 8 describes measurement methods and test procedures for the beat length of PM

fibres.
8.2 Overview of methods

This technical report gives two methods for measuring the beat length of the PM fibre:

• Method A: Phase beat length measurement method (Direct measurement method);
• Method B: Group beat length measurement methods (Indirect measurement method).
Phase beat length, L and group beat length, L are measured in Method A and
B (phase) B (group)

B, respectively. As shown in Annex B, the beat lengths obtained by Methods A and B are

based on different definitions, and will often give different results depending on the type of PM

fibre. Differences of more than 100 % have been reported [2]. Therefore, the definition of the

measured beat length parameter (phase or group) and the measurement method need to be

stated in the measurement result of beat length. Mentioning of the measurement method may

be excluded according to an agreement between the customer and the supplier.
8.3 Reference test method

Method A is the reference test method (RTM), which is the one used to settle disputes.

8.4 Specimen

A specimen length is the minimum necessary to set up the test apparatus. If the specimen is

extra long, care shall be taken that no stresses will be induced in the specimen.

8.5 Beat length measuring method
8.5.1 Method A: Phase beat length measurement method
8.5.1.1 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 SOP at one wavelength versus travel distance.
The perturbation can either be a lateral force or an electromagnet.
---------------------- Page: 11 ----------------------
– 10 – TR 62349 © IEC:2014(E)

In this technical report, the test method using an electromagnet and the monitoring of output

power versus travel distance is described in detail. Examples of other test methods expected

to give similar measurement results are described e.g. in [3], [4] and [5].
8.5.1.2 Apparatus
a) 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.

IEC 0416/14
Figure 1 – Apparatus of beat length measurement – Method A
b) Light source

A light source, which has a narrow spectrum line-width, such as a DFB laser, is used.

c) Retardation plate

A retardation plate is 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.
d) Polarizer and analyser

A polarizer and an analyser are capable of outputting linearly polarized light having a

certain direction of electric field vector when they have received light in a state of

polarization.
e) Detector

A detector to be used is recommended to have a light receiving area that can detect all

the optical power emitted from the output end of the optical fibre.
f) Electromagnet for Faraday rotation

An electromagnet for Faraday rotation rotates the polarization of the light in the fibre by

applying an electromagnetical field along the fibre longitudinal axis. The polarization

rotation is modulated by an electrical signal from outside to improve measurement

sensitivity. See Annex C.
g) Pulse stage

A pulse stage needs to be able to move the electromagnet along the fibre longitudinal

axis. The pulse stage has the moving range and pitch which are sufficient to measuring

the beat length of the sample fibre.
h) Lock-in amplifier

A lock-in amplifier is used to improve measurement sensitivity. The lock-in amplifier has

response time enough to respond the modulation speed of the electromagnet.
i) Signal generator
---------------------- Page: 12 ----------------------
TR 62349 © IEC:2014(E) – 11 –
A signal generator provides modulated signal to the lock-in amplifier and the
electromagnet.
j) Power amplifier

A power amplifier may be used as necessary. The power amplifier provides enough power

for the electromagnet.
k) Computer

A computer controls the pulse stage and processes the output signal from the lock-in

amplifier.
l) 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 for example

on a plotter.
8.5.1.3 Procedure
a) 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 using the V-groove. 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.

b) 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 the travel distance ΔZ which is a half

period of the sequence of V.
60
ΔZ ΔZ ΔZ ΔZ ΔZ
1 2 3 4 5
40
20
−20
−40
−60
0 10 20 30 40
Travel distance of stage (mm)
IEC 0417/14
Figure 2 – Example of measurement profile by electro magnet
8.5.1.4 Calculation
The phase beat length L is given by:
B (phase)
Lock in amplifier output (mV)
---------------------- Page: 13 ----------------------
– 12 – TR 62349 © IEC:2014(E)
2 ΔZ
∑ i
i=1
L = (1)
B(phase)
where
L is the phase beat length;
B (phase)

ΔZ is the travel distance of the stage where the lock-in amplifier output changes by

the half period;
N is the number of the half period.
8.5.2 Method B: Group beat length measurement method
8.5.2.1 Apparatus and procedure

In this method, differential group delay (DGD) or group modal birefringence is utilized for

calculation of beat length. It is 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 is given in IEC 60793-1-48.

8.5.2.2 Calculation
A group beat length can be calculated from r
...

Questions, Comments and Discussion

Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.