IEC TR 62000:2021

IEC TR 62000 ®
Edition 3.0 2021-09
REDLINE VERSION
TECHNICAL
REPORT
colour
inside
Guidelines for combining different single-mode fibres types fibre sub-categories

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IEC TR 62000 ®
Edition 3.0 2021-09
REDLINE VERSION
TECHNICAL
REPORT
colour
inside
Guidelines for combining different single-mode fibres types fibre sub-categories
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 33.180.10 ISBN 978-2-8322-4528-6
– 2 – IEC TR 62000:2021 RLV © IEC 2021
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references. 7
3 Abbreviated terms . 7
4 System issues . 7
5 Optical fibre issues . 8
5.1 General . 8
5.2 Cut-off wavelength . 8
5.3 Splicing issues . 8
5.4 Combination of fibre parameters: chromatic dispersion coefficient and slope,
polarization mode dispersion (PMD) . 9
5.5 Non-linear effects . 9
6 Launch fibres, pigtails, patch-cords and jumper cables . 10
7 Attenuation . 10
8 Summary . 10
Bibliography . 14

Table 1 – Correspondence table of various single-mode fibres . 5
Table 2 – Suggested level of attention to be dedicated to each issue when connecting
fibre types . 11

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
GUIDELINES FOR COMBINING DIFFERENT SINGLE‑MODE FIBRES TYPES
FIBRE SUB‑CATEGORIES
FOREWORD
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This redline version of the official IEC Standard allows the user to identify the changes made to
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has been made. Additions are in green text, deletions are in strikethrough red text.

– 4 – IEC TR 62000:2021 RLV © IEC 2021
IEC TR 62000 has been prepared by subcommittee 86A: Fibres and cables, of IEC technical
committee 86: Fibre optics. It is a Technical Report.
This third edition cancels and replaces the second edition published in 2010. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) global uniformity of terminology concerning fibre classes, categories and sub-categories
throughout the document;
b) updating and aligning to the new naming convention of IEC 60793-2-50 for class B fibre
categories and sub-categories;
c) updating and aligning with IEC 60793-2-50 as per supported fibre sub-categories;
d) additional guidelines concerning combination of fibre parameters: chromatic dispersion and
slope, polarization mode dispersion;
e) additional guidelines concerning non-linear affects;
f) updating of bibliographical references.
The text of this Technical Report is based on the following documents:
Draft Report on voting
86A/2114/DTR 86A/2129/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.
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/standardsdev/publications.
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,
• replaced by a revised edition, or
• amended.
IMPORTANT – The "colour inside" logo on the cover page of this document 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.

GUIDELINES FOR COMBINING DIFFERENT SINGLE‑MODE FIBRES TYPES
FIBRE SUB‑CATEGORIES
1 Scope
This document provides guidelines concerning single-mode fibre inter-compatibility.
A given type category of single-mode fibre, for example B4 B-655, may can have different
implementations by suitably optimising several of the following parameters: mode field diameter
(hence effective area), chromatic dispersion coefficient, slope of the chromatic dispersion
curve, cable cut-off wavelength.
These guidelines indicate the items that should be are taken into account when planning to
connect
1) different implementations of single-mode fibres of the same type category, for example
different implementations of type Class B single-mode fibres, and
2) single-mode fibres of different types sub-categories, for example B1.1 B-652.B with B4 B-
655.C.
See IEC 60793-2-50 for the attributes and definitions of single-mode fibre. The attributes and
definitions of fibres covered in this document are given in Table 1.
Table 1 – Correspondence table of various single-mode fibres
ITU-T
Common name IEC Class
Use (IEC 6079-2-50)
Recommendation
Dispersion B1.1 G.652 A, B
Optimised for use in the 1 310 nm region but can
be used in the 1 550 nm region
unshifted single-
mode fibre
Cut-off shifted B1.2 G.654
Optimised for low loss in the 1 550 nm region,
single-mode fibre
with cut off wavelength shifted above the 1 310
nm region
Extended band B1.3 G.652 C, D
Optimised for use in the 1 310 nm region but can
dispersion unshifted
be used in the O, E, S, C and L-band (i.e.
single-mode fibre
throughout the 1 260 nm to 1 625 nm range).

Dispersion shifted B.2 G.653
Optimised for single channel transmission in the
single-mode fibre
1 550 nm region. Multiple channels can only be

transmitted if care is taken to avoid the effects of

four wave mixing by, for example, moderating the
power levels or appropriate spacing or placement
of the channels
Non-zero B4 G.655
Optimised for multiple channel transmission in
dispersion-shifted
the 1 550 nm region with a cut off wavelength

single-mode fibre
that may be shifted above the 1 310 nm region

Wideband non-zero B5 G.656
Optimised for multiple channel transmission in
dispersion-shifted
the wavelength range of 1 460 to 1 625 nm with

single-mode fibre
the positive value of the chromatic dispersion

– 6 – IEC TR 62000:2021 RLV © IEC 2021
ITU-T
Common name IEC Class
Use (IEC 6079-2-50) Recommendation
coefficient that is greater than some non-zero
value over the same wavelength range.
Bend loss optimised B6_a G.657.A
Bending loss insensitive single-mode fibre
suitable for use in the access networks, including

inside buildings at the end of these networks.
B6_a fibres are suitable to be used in the O, E,
S, C and L-band (i.e. throughout the 1 260 nm to
1 625 nm range) and meet the requirements of
B1.3 fibres.
B6_b G.657.B
Bending loss insensitive single-mode fibre
suitable for use in the access networks, including
inside buildings at the end of these networks.
B6_b fibres are suitable for transmission at 1 310
nm, 1 550 nm, and 1 625 nm for restricted
distances that are associated with in-building
transport of signals.
Common name Use (IEC 60793-2-50) IEC sub‑category ITU-T
Recommendation
Dispersion Optimised for use in the 1 310 nm region but B-652.B G.652.B
unshifted fibre can be used in the 1 550 nm region.
Extended band Optimised for use in the 1 310 nm region but B-652.D G.652.D
dispersion can be used in the O, E, S, C and L-band (i.e.
unshifted fibre throughout the 1 260 nm to 1 625 nm range).
Dispersion Optimised for single channel transmission in B-653.A G.653.A
shifted fibre the 1 550 nm region. Multiple channels can
only be transmitted if care is taken to avoid
non-linear effects such as four wave mixing by,
B-653.B G.653.B
for example, moderating the power levels or
appropriate spacing or placement of the
channels.
Cut-off shifted Optimised for low loss in the 1 550 nm region, B-654.A G.654.A
fibre with cut off wavelength shifted above the
B-654.B G.654.B
1 310 nm region.
B-654.C G.654.C
B-654.D G.654.D
B-654.E G.654.E
Non-zero Optimised for multiple channel transmission in B-655.C G.655.C
dispersion- the 1 530 to 1 625 nm region with a positive or
B-655.D G.655.D
shifted fibre negative, non-zero chromatic dispersion and a
cut off wavelength that can be shifted above
B-655.E G.655.E
the 1 310 nm region.
Wideband non- Optimised for multiple channel transmission in B-656 G.656
zero dispersion- the wavelength range of 1 460 nm to 1 625 nm
shifted fibre with the positive value of the chromatic
dispersion coefficient that is greater than some
non-zero value over the same wavelength
range.
Common name Use (IEC 60793-2-50) IEC sub‑category ITU-T
Recommendation
Bending loss Bending loss insensitive single-mode fibre B-657.A1 G.657.A1
insensitive fibre suitable for use in the access networks,
including inside buildings at the end of these
B-657.A2 G.657.A2
networks.
They are suitable to be used in the O, E, S, C
B-657.B2 G.657.B2
and L-band (i.e. throughout the 1 260 nm to
1 625 nm range) and, in the case of
B‑657.A1 and B-657.A2, meet the requirements
B-657.B3 G.657.B3
of B-652.D fibres.
Subcategories B-657.B2 and B-657.B3 fibres
are intended to be used for restricted distances
(less than 1 000 m) at the end of access
networks, in particular inside buildings
or near buildings (e.g. outside building riser
cabling).
This document does not consider the connection of fibres with the same implementation
category from different manufacturers, which is already considered by the standardisation
procedure.
2 Normative references
There are no normative references in this document.
3 Abbreviated terms
OTDR optical time domain reflectometer
PMD polarization mode dispersion
DWDM dense wavelength division multiplexing
NRZ non return to zero
RZ return to zero
4 System issues
The different characteristics of class B type optical fibres can be explicitly combined to optimise
system performance in terms of the dispersion characteristic (global dispersion coefficients,
slope) of the link. It is in fact possible to combine fibres with opposite signs of the dispersion
coefficient in a given wavelength range to bring the total link dispersion to near-zero in that
range. The final result will however depend on the accuracy of individual fibre dispersion
measurements and the ability to match lengths.
The process of combining fibres with different dispersion coefficient characteristics can be one
of the ways to make dispersion management in a transmission line (the most common one being
the periodical insertion of dispersion compensating modules).
Combining fibres with different effective areas is also a possible way to minimise the overall
impact of non-linear effects. For instance, it is possible to place large effective area fibres in
the initial section of a link, where the propagating power is relatively large. In this case, the
large core reduces the associated non-linear effects. For link sections away from the source,
where power levels are reduced, fibres with smaller effective area may can be used, to take
advantage of a possible reduction of the dispersion slope or to increase the efficiency of Raman
amplification. The relative size and placement of fibres with large effective area versus fibres
with smaller effective area are can be critical issues in system design of the highest performing
optical networks.
– 8 – IEC TR 62000:2021 RLV © IEC 2021
Splice loss considerations (see 5.3) should can also be taken into account when fibres with
different effective areas or mode field diameter are combined.
5 Optical fibre issues
5.1 General
Most fibre characteristics are wavelength dependent: the actual operating wavelengths of the
system shall need therefore to be taken into account when considering the following comments
and suggestions.
The compatibility between fibre specified characteristics (e.g. attenuation and dispersion) and
the system operating wavelength must needs to be considered.
5.2 Cut-off wavelength
Different fibres have been historically developed for operation in different wavelength ranges:
they can therefore have different cut-off wavelengths. If the source wavelength is below the cut-
off wavelength, undesirable multi-modal propagation and modal noise could occur.
It should however be considered that The cut-off wavelength is however reduced after cabling
and installation. The amount of the reduction depends on the refractive index profile, i.e. on the
fibre type. If fibre cut-off wavelength is specified, it can be assumed that, after cabling and
installation, the cut-off will be down-shifted by several tens of nanometres (depending on the
fibre type). Cable cut-off wavelength is therefore specified in international standards. See
IEC 60793-2-50 and IEC 60793-1-44.
These considerations should need to be applied when connecting different fibre types
categories, for example type B4 with B1 B-655 with B-652, in order to avoid multimodal
operation and noise, which could affect the system performance, depending on the source
wavelength. A launch from another single-mode fibre will typically serve as a mode filter which
can significantly reduce or eliminate the potential for multimode transmission.
5.3 Splicing issues
The very different mode field diameter ranges, typical of the several fibre families, have an
effect on splice losses when fibres of different categories are spliced together. Care must needs
to be taken to properly adjust splicing equipment and to correctly evaluate the splicing losses
among different fibre families categories, which can show increases in comparison with
conventional same-category splice losses.
The optimal set-up parameters of fusion splicers are not the same for the different types
categories of fibre (e.g. B1 B-652 versus B6 B-657 fibres) or combinations of different
implementations categories of fibres.
Some B6_b B-657.B3 fibres may can cause difficulties with the core alignment systems of some
fusion splicing machines because the characteristics that provide improved bend loss
performance can interact with the splicer alignment field of view. Amended splice programs or
specialist fusion splicing technology has eliminated this problem on many fusion splicers. An
alternative and recommended approach is to use an outside diameter (OD) or cladding
alignment fusion splicing program as is generally used with multimode optical fibres. Since
recent advances in fibre manufacturing technology have resulted in improved fibre geometry –
with fibre core concentricity errors typically less than 0,5 µm –, the splice losses encountered
are usually < ~ less than 0,1 dB.
Another factor that has to be taken into account when using an OTDR to measure the splice
loss across fibres with different mode field diameters is that the bidirectional method is strictly
required. The mismatch of mode fields can make a splice appear to have much more loss from

one direction than the other. Negative loss or "gain" can also be apparent with uni-directional
OTDR measurements. See IEC TR 62316 for more information.
When using an OTDR to measure the distance between splices of various sections of fibre with
different mode field diameters, the apparent distance can be different than the actual distance
because it is possible the group velocity for the different fibres may is not be the same. For
accurate length measurements, the OTDR length calibration setting must needs to be adjusted
according to the section and type of fibre that is present.
Most of the previous considerations also apply to mechanical (temporary or permanent)
connections.
5.4 Combination of fibre parameters: chromatic dispersion coefficient and slope,
polarization mode dispersion (PMD)
The chromatic dispersion coefficients of two fibres combine linearly on a length-weighted basis.
It is possible to combine different fibres or dispersion compensation devices to achieve the
desired overall system chromatic dispersion values.
When different fibre families are combined, it is recommended important that the calculations
for the overall chromatic dispersion be completed by using the chromatic dispersion of each
section, in ps/nm, rather than considering the combination of possibly misleading descriptive
parameters such as the zero-dispersion wavelength or slope. In fact, zero-dispersion
wavelength and slope are not defined for some fibre families.
Sometimes, the term "slope compensation" is found, referring to a situation where fibres with
different wavelength-dependence of the chromatic dispersion coefficient are combined: the
resulting dispersion vs. wavelength curve will be the linear combination (on a length weighted
basis) of the two original curves.
Details on dispersion accommodation and compensation and on slope compensation can be
found in IEC TR 61282-5.
For polarization mode dispersion (PMD), the PMD values combine in quadrature (square root
of sum of squares) rather than in the linear fashion that is appropriate for chromatic dispersion.
Because PMD is a stochastic attribute, the link characteristics are defined statistically. See
IEC 60794-3 for information on the calculations for concatenations of cables and
IEC TR 61282-3 for information on the calculation for the combined link, including the effects
of other link components such as amplifiers. See IEC TR 61282-9 for more information on PMD
generalities and theory.
5.5 Non-linear effects
Non-linear effects come from the interactions of the propagating pulse with the transmission
medium that make the propagation sensitive to the channel optical power. They are generated
with an efficiency, which is dependent on the concentration of energy in the fibre core (therefore
proportional to optical power and inversely proportional to effective area), and on the distance
over which the light is propagated.
The local chromatic dispersion of the fibre also has an effect on the impairment due to non-
linear effects, depending on, for example, the channel density, bit rate, and modulation format.
See IEC TR 61282-4 for more information.
For high power DWDM systems operating at 10 Gb/s and higher, the local fibre chromatic
dispersion shall needs to be different than zero by an amount that is dependent on the details
of the system. The actual values of the optimal chromatic dispersion coefficient and effective
area for a given link section are a trade-off depending on the number of optical channels, the
powers of the channels in the section, the bit rate, and the modulation format (NRZ versus RZ).

– 10 – IEC TR 62000:2021 RLV © IEC 2021
The global characteristic of hybrid links, obtained by the combination of different fibre families
categories, shall need to be consistent with the initial link design considerations that take into
account the effects of overall distortion, optical signal to noise ratio and receiver sensitivity.
6 Launch fibres, pigtails, patch-cords and jumper cables
Generally, it is not necessary to adopt the same fibre type sub-category in the pigtail as in the
fibre to be measured or connected into a system, for example taking attenuation, dispersion, or
PMD into account, B1.3 B-652.D fibre may can well be used for pigtails and patch-cords in a
network with B4 B-655.E or B5 B-656 fibre, even though,
• in some situations, more care may can be necessary to obtain the desired patch cord/fibre
interface performance, and
• regardless of the fibre types that are connected, the back-reflected light from a connection
point may can affect system performance and should needs be considered in advance, see
IEC TR 62316.
7 Attenuation
Different fibre types have been designed to operate preferably at specific wavelengths and in
specific deployment conditions (e.g. stored fibres or bends of installed cabled fibres): their
attenuation performances can vary when used at different wavelengths. For instance: a B1.1
B-652.B fibre is optimized for use in the 1 310 nm region, with some characteristics higher
attenuation in the 1 383 nm region which are not the same as B1.3 fibres; a link obtained by
combining several fibre types would have consequently a 1 383 nm attenuation performance
depending on their length-weighted composition, although they belong to the same sectional
specification.
8 Summary
Table 2 summarises the suggested level of attention which should can be dedicated to each
issue when connecting fibre types in the first and second column. It is not intended to give
guidance on the preferred combination: some of these combinations are not preferred from the
fibre view point, but may can be dictated by the existing link architecture and/or by system
design considerations. The ranking is as follows.
1 = low – means that the parameter should needs to be considered properly (as suggested in
the referenced clauses/subclauses), although it is not expected to cause system related issues,
provided the operating wavelength(s) is compatible with the characteristics of both fibre types.
2 = medium – means that the parameter should needs to be considered properly (as suggested
in the referenced clauses/subclauses); if all aspects of the two fibre types (with respect to the
system design), with reference to the specific parameter, are taken into account, then the
combination is not expected to cause system related issues, provided the operating
wavelength(s) is compatible with the characteristics of both fibre types.
3 = high – means that the parameter should needs to be considered carefully (as suggested in
the referenced clauses/subclauses); in some situations, system performances can be severely
degraded by the indicated combination; it is important users are recommended to carefully
consider the characteristics of the two fibre types with respect to that parameter, taking also
into account the actual operating wavelength of the system and its compatibility with both fibre
types.
Table 2 – Suggested level of attention to be dedicated to each issue
when connecting fibre types
a
Fibre With fibre Attenuation Dispersion Cable cut off Splice or
c
type type & dispersion considerations connection
b d
slope loss
B1.1 B1.1 1 1 1 1
B1.2 1 2 3 3
B1.3 2 1 1 1
B2 1 3 1 2
B4 1 3 3 2
B5 1 3 3 2
B6_a 1 1 1 1
B6_b 2 2 1 2
B1.2 B1.2 1 1 1 1
B1.3 1 2 3 3
B2 1 3 3 3
B4 1 3 3 3
B5 1 3 3 3
B6_a 1 2 3 3
B6_b 1 3 3 3
B1.3 B1.3 1 1 1 1
B2 1 3 1 2
B4 1 3 3 2
B5 1 3 3 2
B6_a 1 1 1 1
B6_b 2 2 1 2
B2 B2 1 1 1 1
B4 1 3 3 2
B5 1 3 3 2
B6_a 1 3 1 2
B6_b 1 3 1 2
B4 B4 1 2 1 2
– 12 – IE
...