Amendment 1 - Optical fibre cables - Part 1-21: Generic specification - Basic optical cable test procedures - Mechanical tests methods

Amendement 1 - Câbles à fibres optiques - Partie 1-21: Spécification générique - Procédures fondamentales d’essais des câbles optiques - Méthodes d’essai mécanique

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Published
Publication Date
04-Mar-2020
Technical Committee
Current Stage
PPUB - Publication issued
Completion Date
05-Mar-2020
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IEC 60794-1-21:2015/AMD1:2020 - Amendment 1 - Optical fibre cables - Part 1-21: Generic specification - Basic optical cable test procedures - Mechanical tests methods
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IEC 60794-1-21
Edition 1.0 2020-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
A MENDMENT 1
AM ENDEMENT 1
Optical fibre cables –
Part 1-21: Generic specification – Basic optical cable test procedures –
Mechanical test methods
Câbles à fibres optiques –
Partie 1-21: Spécification générique – Procédures fondamentales d'essais
des câbles optiques – Méthodes d'essai mécanique
IEC 60794-1-21:2015-03/AMD1:2020-03(en-fr)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 60794-1-21
Edition 1.0 2020-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
A MENDMENT 1
AM ENDEMENT 1
Optical fibre cables –
Part 1-21: Generic specification – Basic optical cable test procedures –
Mechanical test methods
Câbles à fibres optiques –
Partie 1-21: Spécification générique – Procédures fondamentales d'essais
des câbles optiques – Méthodes d'essai mécanique
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 33.180.10 ISBN 978-2-8322-7896-3

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® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 2 – IEC 60794-1-21:2015/AMD1:2020
 IEC 2020
FOREWORD

This amendment has been prepared by subcommittee SC 86A: Fibre optics, of IEC technical

committee TC 86: Fibres and cables.
The text of this amendment is based on the following documents:
FDIS Report on voting
86A/1975/FDIS 86A/1990/RVD

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

voting indicated in the above table.

The committee has decided that the contents of this amendment and the base publication will

remain unchanged until the stability date indicated on the IEC website 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.

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 document using a colour printer.

_____________
INTRODUCTION to Amendment

This Amendment adds new test methods and revises existing ones in a timely fashion until the

next full revision of IEC 60794-1-21:2015.

Both the E-series numbering of the test methods, clause numbers, figures and equations of the

technical section are aligned with IEC 60794-1-21:2015.

As part of the ongoing rationalization of the test methods specification set, several tests of

IEC 60794-1-21 were determined to be more properly aligned with others of the set and have

been moved. To that end, the proposed text to affect these moves has been inserted in this

document.

Clause 7 has been redesignated as a cable element test method. It has been moved to

IEC 60794-1-23 Ed2 and given the test method number G10A.

Clause 8 has been redesignated as a cable element test method. It has been moved to

IEC 60794-1-23 Ed2 and given the test method number G10B.
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IEC 60794-1-21:2015/AMD1:2020 – 3 –
 IEC 2020

Clause 18 has been redesignated as an environmental test method. It has been moved to

IEC 60794-1-22 Ed2 and given the test method number F16.

Clause 19 has been redesignated as a cable element test method. It has been moved to

IEC 60794-1-23 Ed2 and given the test method number G9.
1 Scope and object
Replace the existing last paragraph by the following new paragraph:

See IEC 60794-1-2 for general requirements and definitions and for a complete reference guide

to test methods of all types.
7 Method E5A: Stripping force stability of cabled optical fibres
Delete the entire clause, including its title.
8 Method E5B: Strippability of optical fibre ribbons
Delete the entire clause, including its title.
18 Method E14: Compound flow (drip)
Delete the entire clause, including its title.
19 Method E15: Bleeding and evaporation
Delete the entire clause, including its title.
32 Method E27: Indoor simulated installation test
Replace the existing text by the following new text:
32.1 Object

This test is designed to simulate an installation of an indoor cable where tight corners,

attachment points and cable storage may occur. This test is intended to demonstrate a level of

robustness of the cable tested which is more severe than traditional installation practices.

NOTE This test is primarily intended to evaluate the performance of cables containing bending loss insensitive

fibres. Indoor cables containing other fibre types are not assumed to fulfil the requirements associated with this test.

32.2 Sample

The cable sample shall be of sufficient length to accommodate the route necessary to

accomplish the steps of the procedure defined in 32.4 and to allow the specified optical testing.

A minimum length of 100 m is recommended.
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 IEC 2020
32.3 Apparatus

The apparatus shall be made of a material as specified in the detail specification. In general,

the apparatus is a building wall "stud" or other substrate of sufficient length to accommodate

the required wraps and attachment points. The test fixtures (see Figures 34 and 36) are

intended to simulate installation around a door or a window as well as cable that skirts around

obstacles using staples or other attachment methods as specified.
Key
Test sequence number
1 multiple corner bends
2 corner bend, 2 kg load
3 corner bend, residual load
4 mandrel wrap
5 attachments, serial
M optical measurement
F.D. cable fixing device, as in method E28, for example
r 1 mm corner radius
D 10 mm mandrel diameter
F 2 kg load
F residual load for cable specified
The test sequences correspond to the numbered items of 32.4.
Figure 34 – Indoor installation simulation apparatus
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IEC 60794-1-21:2015/AMD1:2020 – 5 –
 IEC 2020
Figure 36 – Stapling and bending test fixture

The apparatus of Figure 36 may be used for the multiple corner bends section (1) and the serial

attachment section (5) of Figure 34 with results that are comparable.

NOTE The material and attachment methods are significantly affected by local building practices. Many areas use

a wooden stud; steel, composite materials, etc. are also common.
32.4 Procedure

A continuous length of cable shall progress through each of the following conditions. See Figure

34.

1) Fourteen or fifteen 90° corner bends (1 mm radius), as appropriate for the fixture, with

minimal manual tension, sufficient to wrap the cable around the fixture.

Use of a wood device for corner bends can result in indentation in the device that could

produce incorrect bending and test results. The use of metallic materials for the device or

for the corners is recommended.

NOTE The specified bend radius is that of the apparatus corner. The cable is not presumed to assume the

1 mm radius bend. The structure of a cable under load, as specified, will result in a cable bend radius that is

characteristic of the cable structure, thus determining whether said cable can operate when bent around the

corners and mandrel of the specified apparatus.
2) One 90° corner bend (1 mm radius) with a 2 kg load.
3) One 90° corner bend (1 mm radius) with rated residual load.
4) Two 10 mm diameter mandrel wraps.
5) Thirty attachment points, as specified in the detail specification.

Many fastening methods for cables can be considered, including appropriate staples,

adhesives, and cable ties. Methods shall be compatible with the substrate used and local

practices.

In the case of stapling, only crowned (round) staples of dimensions compatible with the size

of the cable are allowed. Staple according to the state of the art. Follow the procedures

recommended by the manufacturer.

6) Test the cable for a period of time sufficient for any attenuation change to become stable.

32.5 Requirements

The acceptance criteria for the test shall be stated in the detail specification. Typical failure

modes include damage to the cable or cable elements, residual degradation of optical

performance beyond the specified level, or loss of continuity.

It is recommended that the attenuation due to the stapling should not be greater than

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– 6 – IEC 60794-1-21:2015/AMD1:2020
 IEC 2020
– 0,20 dB at 1 550 nm for single-mode fibre, or
– 0,40 dB at 1 300 nm for multimode fibre.
32.6 Details to be specified
The following shall be specified in the detail specification:
– cable type to be tested;
– type of substrate;

– number of 90° corner bends under minimal manual tension, if different from 32.4;

– number of 90° corner bends under load, if different from 32.4;
– the radius of the sharp corner, if different from 32.4;

– type of attachment; method and distance separating the attachment points, if required;

– tension for 32.4, 2), if different from 32.4;
– cable rated residual load;
– test temperature;
– acceptance criteria (see 32.5).
Add, after the existing Clause 33, the following new clauses:
34 Method E29: Straight midspan access to optical elements
34.1 Object

This test is to evaluate if a core optical element can be effectively removed from a cable by

midspan access. A substantially straight cable being tested is subjected to two types of

controlled minor bends for the test. This test is intended to evaluate a cable type which is

designed for easy withdrawal of cable elements, midspan, for external connection, as in MDU

retractable cable.

NOTE The optical elements can be a fibre, a cord, a ribbon, a micro-module, or other, as appropriate.

34.2 Apparatus

An apparatus shall be constructed to test a cable according to either procedure 1 or procedure

2 described in 34.4.2 and 34.4.3 respectively. The apparatus shall conform to the conceptual

description of the test below, using the variations described in procedures 1 and 2.

The concept of the test is as follows (refer to Figure 37).

– A part of the cable sheath is removed (window 2) to have access to the optical elements.

– Depending on need, one or several elements are cut in window 2.
– A second window (window 1) is made on the cable.
– Elements cut in window 2 can be removed from window 1.
Figure 37 – Concept of straight midspan access
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IEC 60794-1-21:2015/AMD1:2020 – 7 –
 IEC 2020
The apparatus shall consist of the following.

– Positions for opening windows 1 and 2 (Figure 37), with space between. The space shall be

6 m, unless otherwise specified.
– Fixturing between the window positions to route the cable as specified:
• straight, per Figure 37, if required;
• two controlled bends, per Figure 38 a) and 38 b); and
• one S-bend, per Figure 39.

– Appropriate clamping fixtures to secure the cable for the test without compressing the cable

or imparting increased attenuation.
34.3 Sample

A single cable sample, 50 m in length, shall be used. Alternatively, two samples from like cables,

each 20 m, may be used. Other lengths may be used, as specified.
34.4 Procedure
34.4.1 General

The manufacturer shall propose methods and tools to open windows of 80 mm length in the

cable without risk to damage elements or fibres. The manufacturer shall propose methods to

avoid risk of tight bends (below the minimum bend radius) or kinking of elements during the

removal from the cable.

Remove a length of one of two adjacent elements (microbundle or buffer) using one or both of

the two procedures below, as specified.

The attenuation of cable elements not removed shall be monitored during the test. The number

of fibres monitored shall be specified by the detail specification.
34.4.2 Procedure 1

– A section of a cable sample, approximately 15 m from an end, shall be laid according to the

configurations described in Figure 37, having two bends, preferentially in a vertical position.

The size and locations of the bends shall meet the following criteria:
• ≥ 4 core lay length twists between the bends (Figure 38 a));

• 2 bends produced using the criteria below, per Figure 38 b), and separated by 3 m

(Figure 38 a)):
i) 3 mandrels: 30 mm in diameter;
ii) depth: 100 mm;
iii) length: 200 mm.
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– 8 – IEC 60794-1-21:2015/AMD1:2020
 IEC 2020
a) Location of bends
Dimensions in millimetres
b) Details of bend
Figure 38 – Straight midspan access – Procedure 1

– Block elements of the cable at each end of the cable, beyond the window locations, by

folding them or coiling the cable.
– Monitor the attenuation of the non-removed elements, as specified.

– Open two windows, separated by 6 m, according to the manufacturer’s method, to provide

access to elements. Verify the integrity of the elements after this operation.
– Cut two adjacent elements at window 2.
– From window 1, remove one of the two elements, according to the manufacturer’s
procedure.
• Measure the tensile stress needed with a dynamometer, if required.
• Measure any displacement of the other cut element.
34.4.3 Procedure 2

At a position in the sample approximately 15 m from the site of procedure 1, make two windows,

separated by 6 m, as in Procedure 1. Block the fibres at the ends, as in procedure 1.

Between these two windows, make two right angles, bent at the minimum bend radius of the

cable under test. The two bends shall be immediately adjacent to each other. See Figure 39.

---------------------- Page: 10 ----------------------
IEC 60794-1-21:2015/AMD1:2020 – 9 –
 IEC 2020
Figure 39 – Straight midspan access – Procedure 2

Perform procedure 2 in the same manner as the procedure 1. The key functional parts of the

procedure are the following.
– Cut two adjoining elements in window 1.
– Remove one element from window 2.
• Measure the tensile stress needed to remove it, if required.
• Measure the displacement of the other cut element.
34.4.4 Overview

Accomplish procedures 1 and 2 successively. At the end of each procedure, visually examine

the removed and non-removed elements and any fibres within to assess any abrasion of fibre

and elements.
34.5 Requirements
Acceptance criteria in the detail specification may include
– no abrasion or perforation of the elements or fibres,
– no broken fibres in either the removed or non-removed elements,
– maximum allowed attenuation increase,
– maximum allowed sliding distance of the non-removed element, and
– maximum allowed tensile stress.
34.6 Details to be specified
The following shall be specified in the detail specification:
– cable type to be tested;
– if the tensile stress to remove the elements is to be measured;
– the maximum tensile stress to remove an element, if required.
35 Method E30: Coefficient of friction between cables
35.1 Object

The object of this test is to ensure that the coefficient of friction of the sheathing material of a

specified cable against another specified cable is less than the value specified. Coefficient of

friction between two cables is an important parameter for installation of a cable in a duct or tray

having previously installed cable.
---------------------- Page: 11 ----------------------
– 10 – IEC 60794-1-21:2015/AMD1:2020
 IEC 2020
35.2 Sample

Two cables, which may be of the same type and size, or different, as specified, are selected.

The first cable shall be of sufficient length to make 2, or more (as specified), turns on the test

sheave. The second cable shall be of sufficient length of make 1/2 turn about the test sheave

holding the first cable, plus length sufficient for pulling and for attaching the pulling apparatus

and the snubbing force apparatus on the ends.
35.3 Apparatus
The apparatus, illustrated in Figure 40, shall consist of the following.

– A sheave: the sheave root diameter, D , shall be 20 to 25 times the second cable diameter

(but not less than the minimum bend diameter of that cable), with a circular groove formed

by a radius, R, of a minimum of 5 times the second cable diameter.
For cables that are not round, use the minimum dimension.

– A weight for attachment to one end of the second cable, sufficient to apply a snubbing force

tension so that the second cable contours the sheave: 1 N is generally sufficient, or it may

be as specified.
– An apparatus to apply a pulling force to one end of the second cable.
– A tensile measuring apparatus attached to the sheave.
---------------------- Page: 12 ----------------------
IEC 60794-1-21:2015/AMD1:2020 – 11 –
 IEC 2020
Key

F snubbing force, generally a weight, sufficient to make cable contour the sheave

F pulling force, sufficient to move the cable, but not specified or measured
F measured reaction force on the mandrel
D sheave root diameter, 20 to 25 × d, or as specified
R sheave face radius, min. 5 × d, or as specified
Figure 40 – Coefficient of friction test apparatus (drum test)
35.4 Procedure

– Wind the first cable sample on the sheave using 2, or more (as specified), adjacent turns.

Fix this coil in place.

– Wind the second cable sample in a half-turn on top of the coil. Alternatively, for thin cords,

wind the second cable sample in a quarter-turn on top of the coil.

– Apply a snubbing force (weight in 35.3), F , to one end of the second cable and a tensile

pulling force, F , to the other end of that sample, so as to move it on to the coil at a constant

speed of 3 mm/min. The force F is not measured.

– Using the tensile measuring apparatus, measure the reaction force, F, on the sheave while

the second cable is moving. The value of F used in Equation (17) and Equation (18) shall

be the average of the peak forces observed during the test.

– Calculate the coefficient of friction using Equation (17) for the half-turn case or Equation (18)

for the quarter-turn case.
---------------------- Page: 13 ----------------------
– 12 – IEC 60794-1-21:2015/AMD1:2020
 IEC 2020
1 FF−
μ= ln (17)
π F
1 FF−
(18)
μ= ln
π/ 2 F
35.5 Requirement
The calculated coefficient of friction shall be less that the value specified.
35.6 Details to be specified
The detail specification shall include the following:
– cables to be tested;
– turns on the sheave, if different from 2;
– mandrel root diameter (D ), if different than 20 × d;
– sheave face radius, if different from 5 × d;
– snubbing force, F , if different from the default
36 Method E31: Microduct inner clearance test: under consideration
37 Method E32: Creep behaviour tension test (for ADSS)
37.1 Object

This test method applies to all-dielectric self-supported (ADSS) optical fibre cables. The object

is to predict the increase of cable length due to permanent, cyclic load throughout the

operational life of cable. It provides means for engineering data useful to predict the long-term

cable sag of dielectric cables installed on overhead power lines. The test method evaluates

cable creep behaviour while requiring a reduced period of time for execution. There is no optical

requirement, nor pass fail criteria for this test.

NOTE 1 Results obtained by alternative methods (e.g. IEC 61395), as agreed between customer and supplier, can

also be used.

Instead of applying a constant load for an extended period of time, it simulates the variable

loads an ADSS cable is expected to experience during its operational lifetime. Low – high – low

tension cycles are applied to the sample and the cable strain values are registered for each

condition. As the number of applied load cycles increases, the cable strain values will show a

trend value that can be related to long-term strain or creep prediction.

NOTE 2 This test method was developed by WG 3 of SC 86A, considering for low load level the value recommended

by manufacturer as installation (sagging) limit (MIT) and for high load the specified maximal tension (MAT). A round

robin test showed that, for low-tension cables, the resultant strain was not detectable in some laboratories, due to

high incertitude in measurements; additional round-robin tests with 50 % increase in load values showed adequate

results. This procedure is focused on mechanical behaviour, with no optical requirement; during evaluation, the

declared maximal tension recommended for the cable operation can be exceeded in order to improve readings noting

that high load level is not close to the cable breaking load limit.
37.2 Sample

The sample length under tension shall be ≥ 15 m unless otherwise defined in the relevant

specification. Shorter lengths will adversely affect the accuracy of the measurement.

Total sample length will be longer than the length under tension to allow for clamping and

connection to test equipment.
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IEC 60794-1-21:2015/AMD1:2020 – 13 –
 IEC 2020
37.3 Apparatus
The apparatus, illustrated in Figure 41, consists of the following.

a) A tensile strength measuring apparatus which is able to axially accommodate the cable

length to be tested.
b) A load cell with a maximum error of ±2 % of its maximum range.

c) A clamping device to secure all cable components at the ends of the length under test. Care

should be taken that the specific method of securing the cable components does not affect

the results. Pre-formed dead-ends used in field operation are considered adequate for fixing

the ends of the cable.

The attaching points on the equipment shall be rigid and of enough mechanical resistance

to not be deformed while load cycles application.

The use of length extensions from the clamps on cable to the fixing points in the equipment

shall not be used as this would result in negative influence on the cable strain readings.

d) A mechanical or electrical means for measuring the cable load and elongation on a

controlled length of cable. The cable elongation measurements should be taken with

minimum accuracy of 0,10 mm.

e) A rod of 10,00 m length to delimit the control length of the sample under test. This rod will

be attached parallel to the sample under test to be used as the base length to calculate the

cable elongation. A dielectric rigid material is recommended in order to minimize errors on

the strain measurement due to temperature variations.
NOTE The term "strain" is used to indicate cable elongation.
Figure 41 – Tensile cycling test apparatus
37.4 Procedure
37.4.1 General procedure requirements

a) The test sample should be attached to the test equipment. A rigid rod should be clamped to

the sample under test to define the control length; one end of the rod should be fixed to the

cable and the other end should be loose to allow free movement.

b) Load the cable and secure it at both ends of the tensile rig. A method of securing the cable

shall be used, which uniformly locks the cable so that all components of the cable, including

fibres, are restricted in their movement to prevent the fibres from slipping.

c) Apply initial load to straighten the sample. Typically a 20 kg. load is sufficient. If necessary,

use attaching means along the 10,00 m control length, in order to avoid a catenary effect

and keep the sample straight under this tension. See Figure 42.

d) The tension shall be continuously increased to the required values indicated in the steps

detailed in 37.4.2.

e) The strain readings shall be taken at the end of the time periods stated in 37.4.2.

f) When changing the tension level on cable, the rate change shall be continuous and

homogenous. The target tension shall be reached maximum within a 3 min period of time.

g) If interruptions greater than 30 min occur while applying the sequence of tension cycles, the

sample should remain loaded at MAT.
---------------------- Page: 15 ----------------------
– 14 – IEC 60794-1-21:2015/AMD1:2020
 IEC 2020

NOTE Attenuation reading can be made while the load is between MIT and MAT values in order to verify that the

cable meets tension specification, although this is not correlated to creep determination.

Figure 42 – Control cable length arrangement
37.4.2 Procedure steps

1) Apply the maximum installation tension (MIT) specified by the manufacturer and, without

any further tension adjustment in the apparatus, maintain for 60 min (i.e. the applied load

does not need to
...

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