IEC TR 63484:2024

Guidance on fungus resistance of optical fibre cables

IEC TR 63484:2024 information about fungal growth on the outer sheath of optical fibre cables and on the inner components of the cable. It also provides guidance for specifying fungus resistance performance of optical cable outer sheath and internal cable components, including recommendations for fungus resistance test method as well as evaluation after test.
This document applies to optical fibre cables for use with telecommunication equipment and devices employing similar techniques, and to hybrid telecommunication cables having a combination of both optical fibres and electrical conductors.
Since conditions suitable for fungal growth include high relative humidity and a warm atmosphere, the document is applicable to optical cables intended for transportation, storage and use under such environment over certain period, for instance, some days at least.

General Information

• Status: Published
• Publication Date: 23-Sep-2024
• ICS: 33.180.10 - Fibres and cables
• Technical Committee: SC 86A - Fibres and cables
• Current Stage: PPUB - Publication issued
• Start Date: 24-Sep-2024
• Completion Date: 11-Oct-2024

Overview

IEC TR 63484:2024 – Guidance on Fungus Resistance of Optical Fibre Cables provides a comprehensive overview and targeted recommendations for managing fungal growth on optical fibre cable components. This technical report from the International Electrotechnical Commission (IEC) identifies the mechanisms of fungal infection, covers environmental conditions promoting fungal activity, and presents guidance on specifying, testing, and evaluating fungus resistance in optical fibre cables. The document is applicable to cables used in telecommunications and hybrid telecommunication cables that combine optical fibres and electrical conductors. It addresses the challenges posed by high humidity and warm conditions that commonly support fungal growth during the transportation, storage, and operational lifecycle of optical cables.

Key Topics

• Fungal Growth Mechanisms: Explains how fungal spores infect cable surfaces and the roles of environmental factors such as moisture, temperature, nutrients, and airflow in promoting fungal proliferation.
• Impacts on Cables: Lists the direct and indirect effects of fungal activity, including surface discoloration, degradation of sheath material, decreased insulation resistance, and potential performance failures.
• Prevention Strategies:
  • Physical methods: Emphasizes environmental controls and proper cable deployment.
  • Chemical methods: Recommends selecting fungus-resistant materials and adding mildew inhibitors or fungicides to cable sheaths or surfaces.
• Material and Design Considerations: Overviews common sheath materials such as polyethylene (PE), polyvinyl chloride (PVC), low-smoke zero-halogen (LSZH) polyolefins, and thermoplastic polyurethane (TPU), highlighting their respective vulnerability or resistance to fungal attack.
• Fungus Resistance Testing:
  • Details approaches for selecting, preparing, and conditioning cable samples.
  • Describes the use of recommended test fungi and outlines procedures for visual and physical assessment post-exposure.

Applications

IEC TR 63484:2024 is crucial for manufacturers, cable designers, and installers seeking to enhance the reliability and longevity of optical fibre cables in environments prone to fungal growth. Applications include:

• Telecommunication Networks: Ensures robust optical fibre performance in humid or warm climates, such as data centers, underground installations, or outdoor deployments.
• Hybrid Cables: Offers guidance for cables combining fibre optics and electrical conductors commonly used in utility, transportation, or industrial networks.
• Cable Storage and Transportation: Provides measures to mitigate microbiological risks during warehousing or shipping, particularly when cables are stored on wood drums susceptible to fungal infestation.
• Quality Assurance: Supports the development of specifications and validation procedures to meet customer or regulatory requirements regarding fungus-resistant cable designs.

Related Standards

For effective implementation and compliance with international best practices, the following related standards and test methods are referenced in IEC TR 63484:2024:

• IEC 60068-2-10: Environmental testing – Mould growth test methods.
• IEC 60793-1-31 and IEC 60793-1-32: Optical fibre tensile strength and coating strippability.
• IEC 60794 series: Generic specifications and optical cable test procedures.
• IEC 60811-501: Mechanical tests for insulating and sheathing compounds.
• IEC 61196-1-102: Electrical test methods for insulation resistance.
• ISO 846: Plastics – Evaluation of microorganisms' action.
• TIA-455-56-C: Evaluating fungus resistance of optical fibres and cables.
• ASTM G21: Determining resistance of synthetic polymeric materials to fungi.

Practical Value

By applying the guidance in IEC TR 63484:2024, stakeholders can:

• Reduce the risk of cable failure due to fungal degradation.
• Specify appropriate materials and design features for fungus resistance.
• Employ effective test methods to verify cable integrity under adverse environmental conditions.
• Sustain network reliability and minimize maintenance costs in challenging climates.

This standard is foundational for organizations committed to quality, durability, and risk mitigation in critical optical fibre infrastructure.

Standards Content (Sample)

IEC TR 63484 ®
Edition 1.0 2024-09
TECHNICAL
REPORT
Guidance on fungus resistance of optical fibre cables

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IEC TR 63484 ®
Edition 1.0 2024-09
TECHNICAL
REPORT
Guidance on fungus resistance of optical fibre cables

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 33.180.10  ISBN 978-2-8322-9719-3

– 2 – IEC TR 63484:2024 © IEC 2024
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Mechanisms of fungal infection and growth. 6
4.1 Mechanisms of fungal infection . 6
4.2 Environmental conditions for fungal growth . 7
5 Effects of fungal growth on optical cable . 7
5.1 General . 7
5.2 Main effects on optical cable . 8
6 Prevention of fungal growth . 8
6.1 General . 8
6.2 Cable sheath . 8
6.2.1 Physical methods . 8
6.2.2 Chemical methods . 8
6.3 Cable internal components . 9
6.4 Cable drum . 9
7 Sheath material selection and cable design principles . 9
7.1 Common sheath material . 9
7.2 Cable design principles . 11
8 Fungus resistance test method . 11
8.1 General consideration . 11
8.2 Objective . 11
8.3 Sample . 12
8.3.1 General . 12
8.3.2 Fibre samples . 12
8.3.3 Cable samples . 12
8.3.4 Material samples . 12
8.3.5 Biocide/Fungicide efficacy samples . 12
8.4 Apparatus . 12
8.5 Procedure . 13
8.5.1 General . 13
8.5.2 Conditioning . 13
8.5.3 Test fungi . 13
8.6 Assessment . 13
8.6.1 Visual inspection . 13
8.6.2 Evaluation of other properties . 13
8.7 Requirements . 14
8.8 Details to be specified . 14
Bibliography . 15

Figure 1 – Fungal growth on optical cable with PVC sheath . 10
Figure 2 – Fungal growth on optical cable with LSZH sheath . 10
Figure 3 – Fungal growth on optical cable with TPU sheath . 11

Table 1 – Test fungi . 13
Table 2 – Suggested test items (other than visual inspection) after exposure . 14

– 4 – IEC TR 63484:2024 © IEC 2024
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
GUIDANCE ON FUNGUS RESISTANCE OF OPTICAL FIBRE CABLES

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
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IEC TR 63484 has been prepared by subcommittee 86A: Fibres and cables, of IEC technical
committee 86: Fibre optics. It is a Technical Report.
The text of this Technical Report is based on the following documents:
Draft Report on voting
86A/2485/DTR 86A/2489/RVDTR
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this Technical Report is English.

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– 6 – IEC TR 63484:2024 © IEC 2024
GUIDANCE ON FUNGUS RESISTANCE OF OPTICAL FIBRE CABLES

1 Scope
This document provides information about fungal growth on the outer sheath of optical fibre
cables and on the inner components of the cable. It also provides guidance for specifying fungus
resistance performance of optical cable outer sheath and internal cable components, including
recommendations for fungus resistance test method as well as evaluation after test.
This document applies to optical fibre cables for use with telecommunication equipment and
devices employing similar techniques, and to hybrid telecommunication cables having a
combination of both optical fibres and electrical conductors.
Since conditions suitable for fungal growth include high relative humidity and a warm
atmosphere, the document is applicable to optical cables intended for transportation, storage
and use under such environment over certain period, for instance, some days at least.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
4 Mechanisms of fungal infection and growth
4.1 Mechanisms of fungal infection
Fungi grow in or on many types of common materials. They propagate by producing spores.
These spores are very small (1 μm to 10 μm) and easily carried in moving air. They also adhere
to dust particles and various surfaces.
Thus, the cable surface and the cable end into which air penetrates can be infected with spores.
The infection can also occur during handling, for example, spores can be transferred by touch.

4.2 Environmental conditions for fungal growth
There are various factors which affect the germination and growth of spores. But the key factors
are shown as follows:
a) Moisture
Adequate moisture is necessary for spore growth and propagation. 65 % humidity is the
threshold for fungal growth, whereas explosive growth occurs in excess of 90 %.
Fungal spores can survive for an extended period of time in a state of hibernation when
humidity levels are below 65 %. Once adequate moisture becomes available, these spores
will activate and start growing.
Water-absorption products on cable surfaces will accelerate fungal spore growth. These
materials will absorb water from the atmosphere and fungi can access that water for
metabolic use.
b) Temperature
Most fungi require temperatures between 10 °C to 35 °C, with some exceptions based on
fungal species. Within this range, the closer to 35 °C, more growth will occur. Almost no
fungi types grow below 0 °C or above 40 °C.
Fungal spores do not die when exposed to extreme temperatures, rather they go into a
hibernation state. Once temperatures return to a suitable level, they will activate and start
growing again.
c) Nutrient
Fungi require certain essential nutrients for growth including nitrogen, potassium,
phosphorus, and sulphur, amongst others from a nutrient base for energy. Generally,
nutrients can include inorganic salts and a carbon source. Basic plastic resins do not
typically serve as carbon sources for fungal growth, but other components such as
plasticizers, stabilizers, colorants, lubricants, and cellulosics can be responsible for fungal
attack.
d) Airflow
Airflow also has an effect on the rate of fungal growth. High airflow can limit the growth and
propagation of fungi. Stagnant air spaces and lack of ventilation can encourage fungal
growth. In vacuum conditions, fungi cannot grow.
In addition, pH value, sunlight, surface roughness, interaction of organisms, exposure time
and so on can affect fungal growth as well.
5 Effects of fungal growth on optical cable
5.1 General
Organic materials are commonly used in optical cable production, such as the sheath, buffer,
filling/flooding compound, strength member, conductor insulation and fibre coating.
Fungi can live on most organic materials. They decompo
...