IEC 62783-2:2025

IEC 62783-2 ®
Edition 2.0 2025-10
INTERNATIONAL
STANDARD
REDLINE VERSION
Twinax cables for digital communications -
Part 2: Family specification - Cable for Ethernet-over-twinax physical interfaces
ICS 33.120.20 ISBN 978-2-8327-0782-1

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 Secretariat Tel.: +41 22 919 02 11
3, rue de Varembé info@iec.ch
CH-1211 Geneva 20 www.iec.ch
Switzerland
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 corrigendum or an amendment might have been published.

IEC publications search - IEC Products & Services Portal - products.iec.ch
webstore.iec.ch/advsearchform Discover our powerful search engine and read freely all the
The advanced search enables to find IEC publications by a publications previews, graphical symbols and the glossary.
variety of criteria (reference number, text, technical With a subscription you will always have access to up to date
committee, …). It also gives information on projects, content tailored to your needs.
replaced and withdrawn publications.
Electropedia - www.electropedia.org
The world's leading online dictionary on electrotechnology,
IEC Just Published - webstore.iec.ch/justpublished
Stay up to date on all new IEC publications. Just Published containing more than 22 500 terminological entries in English
details all new publications released. Available online and and French, with equivalent terms in 25 additional languages.
once a month by email. Also known as the International Electrotechnical Vocabulary
(IEV) online.
IEC Customer Service Centre - webstore.iec.ch/csc
If you wish to give us your feedback on this publication or
need further assistance, please contact the Customer
Service Centre: sales@iec.ch.
CONTENTS
FOREWORD . 3
INTRODUCTION . 1
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Requirements for cables construction . 7
4.1 General remarks . 7
4.2 Cable construction . 7
4.2.1 General . 7
4.2.2 Conductor . 7
4.2.3 Insulation . 7
4.2.4 Colour code . 7
4.2.5 Drain wire . 7
4.2.6 Screening of cable assembly element . 7
4.2.7 Cable make-up . 7
4.2.8 Screening of the cable core . 7
4.2.9 Sheath . 8
4.2.10 Colour of sheath . 8
4.2.11 Identification . 8
4.2.12 Finished cable . 8
5 Requirements and test methods . 8
5.1 General remarks . 8
5.2 Electrical tests . 9
5.2.1 Conductor resistance . 9
5.2.2 Resistance unbalance. 9
5.2.3 Dielectric strength . 9
5.2.4 Insulation resistance . 9
5.2.5 Mutual capacitance .
5.2.5 Surface transfer impedance . 9
5.2.6 Coupling attenuation . 10
5.3 Transmission requirements and tests . 10
5.3.1 General . 10
5.3.2 Characteristic impedance . 10
5.3.3 Return loss . 10
5.3.4 Attenuation . 10
5.3.5 Propagation delay, inter-element delay pair skew, and intra-element delay
pair skew . 10
5.3.6 Near-end crosstalk (NEXT) . 10
5.3.7 Attenuation to crosstalk ratio far-end (ACR-F)
5.3.7 Far-end crosstalk (FEXT) . 10
5.3.8 Transverse conversion loss (TCL) .
5.3.8 Differential-mode to common-mode conversion (S ) . 10
cd21
5.3.9 Equal level transverse conversion transfer loss (ELTCTL)
(S – S ) . 10
cd21 dd21
5.3.10 Screening attenuation .
5.4 Mechanical and dimensional requirements and test methods . 11
5.4.1 General . 11
5.4.2 Measurement of dimensions . 11
5.4.3 Elongation at break of the conductor. 11
5.4.4 Tensile strength of the insulation . 11
5.4.5 Elongation at break of the sheath . 11
5.4.6 Tensile strength of the sheath . 11
5.4.7 Crush test of the cable . 11
5.4.8 Cold impact test of the cable . 11
5.4.9 Repeated bending of the cable . 11
5.4.10 Tensile performance of the cable . 11
5.4.11 Vibration test of the cable . 11
5.5 Environmental tests . 12
5.5.1 Shrinkage of the insulation . 12
5.5.2 Wrapping test of the insulation after thermal ageing . 12
5.5.3 Bending test of the insulation at low temperature . 12
5.5.4 Tensile strength and elongation of the sheath after ageing . 12
5.5.5 Sheath pressure test at high temperature . 12
5.5.6 Cold bend test of the cable . 12
5.5.7 Heat shock test . 12
5.5.8 Damp heat steady state . 12
5.5.9 Salt mist . 12
5.5.10 Flame propagation characteristics of a single cable . 12
5.5.11 Flame propagation characteristics of bunched cables . 12
5.5.12 Smoke generation . 12
5.5.13 Halogen-free compounds test . 13
Annex A (informative) Supported ISO/IEC/IEEE 8802-3 Ethernet-over-twinax PHYs . 14
A.1 General . 14
A.2 Ethernet-over-twinax PHY transmission specifications . 14
Bibliography . 15

Table 1 – Supported IEEE 802.3 Ethernet-over-twinax implementations, configurations
Table 2 – Supported IEEE 802.3 Ethernet-over-twinax implementations,
transmission requirements .
Table 1 – Supported ISO/IEC/IEEE 8802-3 Ethernet over twinax PHY link segment
specifications . 8
Table A.1 – Supported ISO/IEC/IEEE 8802-3 Ethernet-over-twinax PHY transmission
specifications . 14

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
Twinax cables for digital communications -
Part 2: Family specification -
Cable for Ethernet-over-twinax physical interfaces

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) IEC draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). IEC takes no position concerning the evidence, validity or applicability of any claimed patent rights in
respect thereof. As of the date of publication of this document, IEC had not received notice of (a) patent(s), which
may be required to implement this document. However, implementers are cautioned that this may not represent
the latest information, which may be obtained from the patent database available at https://patents.iec.ch. IEC
shall not be held responsible for identifying any or all such patent rights.
This redline version of the official IEC Standard allows the user to identify the changes made
to the previous edition IEC 62783-2:2019. A vertical bar appears in the margin wherever a
change has been made. Additions are in green text, deletions are in strikethrough red text.

IEC 62783-2 has been prepared by subcommittee 46C: Wires and symmetric cables, of IEC
technical committee 46: Cables, wires, waveguides, RF connectors, RF and microwave passive
components and accessories. It is an International Standard.
This second edition cancels and replaces the first edition published in 2019. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) updating according to the revised generic twinax cable requirements given in
IEC 62783-1:2023;
b) updating according to new twinax link segment specifications recently added to
ISO/IEC/IEEE 8802-3 Ethernet physical interfaces.
The text of this International Standard is based on the following documents:
Draft Report on voting
46C/1309/CDV 46C/1318/RVC
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 International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
This International Standard is to be used in conjunction with IEC 62783-1.
A list of all parts in the IEC 62783 series, published under the general title Twinax cables for
digital communications, can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
– reconfirmed,
– withdrawn, or
– revised.
INTRODUCTION
This document is a family specification. It constitutes Part 2 of the IEC 62783 series, which
covers specific characteristics of twinax cables.
This document describes cables that are in compliance with the generic twinax cable
requirements given in IEC 62783-1.
The family of twinax cables covered in this document are specifically intended for
interconnection of Ethernet links over twinax cables, which are implemented using twinax link
segments specifications in accordance with IEEE Std 802.3™ ISO/IEC/IEEE 8802-3 Ethernet
physical interfaces, for example, including 10GBASE-CX4, 10GBASE-CX, 25GBASE-CR,
50GBASE-CR1, and 100GBASE-CR1.
1 Scope
This part of IEC 62783 covers indoor cables and specifies the definitions and requirements of
twin-axial (twinax) cables used in digital communication systems.
This document, which is a family specification, gives additional requirements for twinax cables
for use in IEEE Std 802.3 Ethernet physical interfaces.
This document covers twinax cable intended to be used indoors. The specifications are intended
to support the twinax link segment specifications of the ISO/IEC/IEEE 8802-3 Ethernet over
twinax physical layer (PHY) specifications.
This document gives requirements and transmission characteristics for a single twinax elements
as well as for multiple twinax elements within the same sheath, i.e. "twinax cable".
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 TR 61156-1-2 :2009, Multicore and symmetrical pair/quad cables for digital communications
– Part 1-2: Electrical transmission characteristics and test methods of symmetrical pair/quad
cables
IEC TR 61156-1-2:2009/AMD1:2014
IEC 60811-401, Electric and optical fibre cables - Test methods for non-metallic materials -
Part 401: Miscellaneous tests - Thermal ageing methods - Ageing in an air oven
IEC 60811-501, Electric and optical fibre cables - Test methods for non-metallic materials -
Part 501: Mechanical tests - Tests for determining the mechanical properties of insulating and
sheathing compounds
IEC 62783-1:— 2023, Twinax cables for digital communications - Part 1: Generic specification
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 62783-1 apply.
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
___________
A consolidated version of this publication exists, comprising IEC TR 61156-1-2:2009 and
IEC TR 61156-1-2:2009/AMD 1:2014.
Under preparation. Stage at the time of publication: IEC FDIS 62783-1:2018.
4 Requirements for cables construction
4.1 General remarks
Twinax cables' characteristic impedance is 100 Ω. Twinax cable configurations range from 2 to
20 twinax elements, depending on the specific Ethernet implementation. Conductor size may
range from 0,2 mm to 0,6 mm (32 AWG to 22 AWG).
4.2 Cable construction
4.2.1 General
The cable element and the cable shall be constructed according to IEC 62783-1 and to this
document.
4.2.2 Conductor
The conductor shall conform to IEC 62783-1 and to the detail specifications.
4.2.3 Insulation
The insulation shall conform to IEC 62783-1 and to the detail specifications.
4.2.4 Colour code
The colour code shall conform to the detail specifications.
4.2.5 Drain wire
The drain wire shall conform to IEC 62783-1 and to the detail specifications.
4.2.6 Screening of cable assembly element
The cable element screen shall conform to IEC 62783-1 and to the detail specifications.
4.2.7 Cable make-up
The twinax cable consisting of 2 to 20 twinax elements as specified in Table 1 shall conform to
IEC 62783-1 and to the detail specifications.
Table 1 – Supported IEEE 802.3 Ethernet-over-twinax implementations, configurations
Application IEEE 802.3:2015 Nominal Number Long Short
(reference) frequency of lanes reach reach
m m
1000BASE-CX Clause 39 625 MHz 2 10 5
10GBASE-CX4 Clause 54 1,562 5 GHz 8 7 3
100GBASE-CR10 Clause 85 5,156 25 GHz 20 3 1
40GBASE-CR4 Clause 85 5,156 25 GHz 8 3 1
100GBASE-CR4 Clause 92 12,890 6 GHz 8 3 1
a
25GBASE-CR 12,890 6 GHz 2 3 1
a
Clause 110 to be published in IEEE 802.3:2018.

Table 1 – Supported ISO/IEC/IEEE 8802-3 Ethernet
over twinax PHY link segment specifications
Number of Standard
ISO/IEC/IEEE 8802-3 ISO/IEC/IEEE 8802-3 Nominal frequency
simplex lanes reach
PHY PHY
Name Designation
GHz m
10GBASE-CX4 ak 1,562 5 8 15
(4 × 2,5 Gbps)
40GBASE-CX4 ba 5,156 25 8 7
100GBASE-CX10 ba 5,156 25 20 7
25GBASE-CR by 12,890 6 2 5
100GBASE-CR bj 12,890 6 8 5
50GBASE-CR1 cd 13,281 25 2 3
100GBASE-CR4 cd 13,281 25 4 3
200GBASE-CR8 cd 13,281 25 8 3
100GBASE-CR1 ck 26,56 2 2
200GBASE-CR4 ck 26,56 4 2
400GBASE-CR8 ck 26,56 8 2
4.2.8 Screening of the cable core
The cable core screening shall conform to IEC 62783-1 and to the detail specifications.
4.2.9 Sheath
The finished cable sheath shall conform to IEC 62783-1 and to the detail specifications.
4.2.10 Colour of sheath
The colour of the finished cable sheath may be specified in the detail specifications.
4.2.11 Identification
4.2.11.1 Cable marking
The cable shall be marked as specified in the detail specifications.
4.2.11.2 Labelling
The cable shall be labelled as specified in the detail specifications.
4.2.12 Finished cable
Finished cable shall be packaged as specified in the detail specifications.
5 Requirements and test methods
5.1 General remarks
Unless otherwise specified, All tests and measurements shall conform to IEC 62783-1 and to
the detail specifications.
These transmission requirements given in Table 2 are based on IEEE 802.3 Ethernet -over
-twinax link segment requirements, which are given for information.
Cable transmission specifications, based on ISO/IEC/IEEE 8802-3 Ethernet over twinax PHY
link segment transmission specifications, are given in Annex A for information.
Table 2 – Supported IEEE 802.3 Ethernet-over-twinax implementations,
transmission requirements
Application IEEE Nominal Frequency IL max. RL min. ACR-F max.
802.3:2015 frequency range (at nominal (at nominal (at nominal
frequency) frequency) frequency)
1000BASE- Clause 39 625 MHz 10 MHz to 8,8 dB See detail See detail
CX 1 GHz specifications specifications
10GBASE- 100 MHz See detail
Clause 54 1,562 5 GHz 16,0 dB 12 dB
CX4 to 2 GHz specifications
100GBASE- Clause 85 5,156 25 GHz 50 MHz to 17,04 dB 6,66 dB See detail
CR10, 10 GHz specifications
40GBASE- Clause 85 5,156 25 GHz 50 MHz to 17,04 dB 6,66 dB See detail
CR4 10 GHz specifications
100GBASE- Clause 92 12,890 6 GHz 50 MHz to 22,48 dB 6 dB See detail
CR4 19 GHz specifications
a
25GBASE-CR 12,890 6 GHz 50 MHz to 22,48 dB 6 dB See detail
19 GHz specifications
a
Clause 110 to be published in IEEE 802.3:2018.
NOTE Near-end crosstalk (NEXT) is not specified for this application.

5.2 Electrical tests
5.2.1 Conductor resistance
The conductor resistance shall conform to IEC 62783-1 and to the detail specifications.
5.2.2 Resistance unbalance
The resistance unbalance shall conform to IEC 62783-1 and to the detail specifications.
5.2.3 Dielectric strength
Dielectric strength shall conform to IEC 62783-1 and to the detail specifications.
5.2.4 Insulation resistance
Insulation resistance shall conform to IEC 62783-1 and to the detail specifications.
5.2.5 Mutual capacitance
Mutual capacitance shall conform to IEC 62783-1 and to the detail specifications.
5.2.5 Surface transfer impedance
Surface transfer impedance of the screen shall conform to IEC 62783-1 and to the detail
specifications.
5.2.6 Coupling attenuation
Coupling attenuation shall conform to IEC 62783-1 and to the detail specifications.
Alternatively, coupling attenuation may be verified by the combination of ELTCTL and screening
attenuation verification.
5.3 Transmission requirements and tests
5.3.1 General
Transmission requirements shall conform to IEC 62783-1 and to the detail specifications, over
the frequency range specified in the detail specifications.
Transmission requirements' conformance is determined in accordance with IEC 62783-1 using
test procedures according to IEC TR 61156-1-2:2009/AMD1:2014.
5.3.2 Characteristic impedance
The nominal characteristic impedance, 100 Ω, shall conform to IEC 62783-1 and to the detail
specifications.
5.3.3 Return loss
The return loss shall conform to IEC 62783-1 and to the detail specifications.
5.3.4 Attenuation
The attenuation shall conform to IEC 62783-1 and to the detail specifications.
5.3.5 Propagation delay, inter-element delay pair skew, and intra-element delay pair
skew
Propagation delay, inter-element delay pair skew, and intra-element delay pair skew shall
conform to IEC 62783-1 and to the detail specifications.
5.3.6 Near-end crosstalk (NEXT)
If required, the near-end crosstalk (NEXT) loss shall conform to IEC 62783-1 and to the detail
specifications.
5.3.7 Attenuation to crosstalk ratio far-end (ACR-F)
The ACR-F loss shall conform to IEC 62783-1 and to the detail specifications.
5.3.8 Transverse conversion loss (TCL)
TCL shall conform to IEC 62783-1 and to the detail specifications.
5.3.7 Far-end crosstalk (FEXT)
If required, the near-end crosstalk (FEXT) loss shall conform to IEC 62783-1 and to the detail
specifications.
5.3.8 Differential-mode to common-mode conversion (S )
cd21
Differential-mode to common-mode conversion (S ) shall conform to IEC 62783-1 and to the
cd11
detail specifications.
5.3.9 Equal level transverse conversion transfer loss (ELTCTL) (S – S )
cd21 dd21
Transverse conversion transfer loss (TCTL) ELTCTL (S -S ) shall conform to IEC 62783-
cd21 dd21
1 and to the detail specifications. ELTCTL S -S is derived from TCTL (S ) and IL
cd21 dd21 cd21
(S ) measurements by deducting subtracting IL from TCTL.
dd21
5.3.10 Screening attenuation
Screening attenuation shall conform to IEC 62783-1 and to the detail specifications.
5.4 Mechanical and dimensional requirements and test methods
5.4.1 General
Mechanical and dimensional requirements shall be as specified in the detail specifications.
5.4.2 Measurement of dimensions
The measurement of dimensions shall conform to IEC 62783-1 and to the detail specifications.
5.4.3 Elongation at break of the conductor
The elongation at break of the conductor shall conform to IEC 62783-1 and to the detail
specifications.
5.4.4 Tensile strength of the insulation
The tensile strength of the insulation shall conform to IEC 62783-1 and to the detail
specifications.
5.4.5 Elongation at break of the sheath
The elongation at break of the sheath shall conform to IEC 62783-1 and to the detail
specifications.
5.4.6 Tensile strength of the sheath
The tensile strength of the sheath shall conform to IEC 62783-1 and to the detail specifications.
5.4.7 Crush test of the cable
The crush resistance of the cable shall conform to IEC 62783-1 and to the detail specifications.
5.4.8 Cold impact test of the cable
The impact resistance of the cable shall conform to IEC 62783-1 and to the detail specifications.
5.4.9 Repeated bending of the cable
The resistance to repeated bending shall conform to IEC 62783-1 and to the detail
specifications.
5.4.10 Tensile performance of the cable
The tensile performance shall conform to IEC 62783-1 and to the detail specifications.
5.4.11 Vibration test of the cable
Vibration test of the cable shall conform to IEC 62783-1 and to the detail specifications.
5.5 Environmental tests
5.5.1 Shrinkage of the insulation
The shrinkage of the insulation shall conform to IEC 62783-1 and to the detail specifications.
5.5.2 Wrapping test of the insulation after thermal ageing
The ageing performance of the insulation shall conform to IEC 62783-1 and to the detail
specifications.
5.5.3 Bending test of the insulation at low temperature
The cold bend test performance shall conform to IEC 62783-1 and to the detail specifications.
5.5.4 Tensile strength and elongation of the sheath after ageing
The tensile strength and elongation at break of the sheath after ageing test performance shall
conform to IEC 62783-1 and to the detail specifications.
As required by IEC 62783-1, samples of sheath are prepared and tested in accordance with
IEC 60811-501, af
...