IEC 61755-2-2:2022

IEC 61755-2-2
®

Edition 2.0 2022-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside


Fibre optic interconnecting devices and passive components – Connector
optical interfaces for single-mode fibres –
Part 2-2: Connection parameters of dispersion unshifted physically contacting
fibres – Angled

Dispositifs d’interconnexion et composants passifs fibroniques – Interfaces
optiques des connecteurs pour fibres unimodales –
Partie 2-2: Paramètres de connexion des fibres en contact physique à dispersion
non décalée – avec angle

IEC 61755-2-2:2022-09(en-fr)

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IEC 61755-2-2

®


Edition 2.0 2022-09




INTERNATIONAL



STANDARD




NORME



INTERNATIONALE
colour

inside










Fibre optic interconnecting devices and passive components – Connector optical

interfaces for single-mode fibres –

Part 2-2: Connection parameters of dispersion unshifted physically contacting


fibres – Angled



Dispositifs d’interconnexion et composants passifs fibroniques – Interfaces


optiques des connecteurs pour fibres unimodales –

Partie 2-2: Paramètres de connexion des fibres en contact physique à dispersion

non décalée – avec angle










INTERNATIONAL

ELECTROTECHNICAL

COMMISSION


COMMISSION

ELECTROTECHNIQUE


INTERNATIONALE




ICS 33.180.20 ISBN 978-2-8322-5698-5




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

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® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale

---------------------- Page: 3 ----------------------
– 2 – IEC 61755-2-2:2022 © IEC 2022
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Attenuation and return loss grades . 6
5 Criteria for a fit within attenuation and return loss grades . 6
5.1 General . 6
5.2 Attenuation grades and criteria . 7
5.3 Visual requirements for return loss grades . 8
Annex A (informative) Return loss model on angled connections . 10
Bibliography . 11

Figure 1 – Lateral offset and angular offset versus attenuation, η , for single-
combined
mode fibre with 8,9 µm MFD at 1 310 nm . 8

Table 1 – Single-mode random mate attenuation grades . 6
Table 2 – Single-mode return loss grades for APC (8°) . 6
Table 3 – MFD and fibre core nominal index of refraction . 7
Table 4 – Visual requirements for single-mode angle polished (APC) fibres
SM APC (RL ≥ 60 dB) . 9

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IEC 61755-2-2:2022 © IEC 2022 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

FIBRE OPTIC INTERCONNECTING
DEVICES AND PASSIVE COMPONENTS –
CONNECTOR OPTICAL INTERFACES FOR SINGLE-MODE FIBRES –

Part 2-2: Connection parameters of dispersion
unshifted physically contacting fibres – Angled

FOREWORD
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rights. IEC shall not be held responsible for identifying any or all such patent rights.
IEC 61755-2-2 has been prepared by subcommittee 86B: Fibre optic interconnecting devices
and passive components, of IEC technical committee 86: Fibre optics. It is an International
Standard.
This second edition cancels and replaces the first edition published in 2006. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) addition of normative references and visual requirements;
b) reconsideration of the whole parts of the text to avoid misuse of the standard.

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– 4 – IEC 61755-2-2:2022 © IEC 2022
The text of this International Standard is based on the following documents:
Draft Report on voting
86B/4640/FDIS 86B/4661/RVD

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/standardsdev/publications.
A list of all parts in the IEC 61755 series, published under the general title Fibre optic
interconnecting devices and passive components – Connector optical interfaces for single-
mode fibres, can be found on the IEC website.
Future documents in this series will carry the new general title as cited above. Titles of existing
documents in this series will be updated at the time of the next edition.
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.

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IEC 61755-2-2:2022 © IEC 2022 – 5 –
FIBRE OPTIC INTERCONNECTING
DEVICES AND PASSIVE COMPONENTS –
CONNECTOR OPTICAL INTERFACES FOR SINGLE-MODE FIBRES –

Part 2-2: Connection parameters of dispersion
unshifted physically contacting fibres – Angled



1 Scope
This part of IEC 61755 defines a set of prescribed conditions for a single-mode fibre optic
connection that is maintained in order to satisfy the requirements of attenuation and return loss
(RL) performance in a randomly mated pair of angled polished physically contacting (APC)
fibres. The model uses a Gaussian distribution of light intensity over the specified mode field
diameter (MFD) for determination of attenuation performance grades, based on MFD mismatch
and the amount of lateral and angular fibre core offsets. Attenuation and RL performance grades
are defined in IEC 61755-1.
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 60793-2-50, Optical fibres – Part 2-50: Product specifications – Sectional specification for
class B single-mode fibres
IEC 61300-3-6, Fibre optic interconnecting devices and passive components – Basic test and
measurement procedures – Part 3-6: Examinations and measurements – Return loss
IEC 61300-3-34, Fibre optic interconnecting devices and passive components – Basic test and
measurement procedures – Part 3-34: Examinations and measurements – Attenuation of
random mated connectors
IEC 61300-3-35, Fibre optic interconnecting devices and passive components – Basic test and
measurement procedures – Part 3-35: Examinations and measurements – Visual inspection of
fibre optic connectors and fibre-stub transceivers
IEC 61300-3-45, Fibre optic interconnecting devices and passive components – Basic test and
measurement procedures – Part 3-45: Examinations and measurements – Attenuation of
random mated multi-fibre connectors
IEC 61755-1, Fibre optic interconnecting devices and passive components – Connector optical
interfaces for single-mode fibres – Part 1: Optical interfaces for dispersion unshifted fibres –
General and guidance
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 61755-1 and the
following apply.

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– 6 – IEC 61755-2-2:2022 © IEC 2022
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
defect size
diameter of the smallest circle that can encompass the entire defect
4 Attenuation and return loss grades
Attenuation and return loss grades for APC polished connections are given in Table 1 and
Table 2 according to IEC 61755-1. The return loss grade is for angled contacting fibres only.
The grades that shall be used for non-angled polished PC connections are given separately in
IEC 61755-2-1.
Table 1 – Single-mode random mate attenuation grades
a
Attenuation
Attenuation grade Attenuation mean Notes
b
≥ 97 %
dB dB
A  Reserved for future application
B ≤ 0,12 ≤ 0,25
C ≤ 0,25 ≤ 0,50
D ≤ 0,50 ≤ 1,0
a
Attenuation shall be measured by IEC 61300-3-34 for single-fibre connectors and IEC 61300-3-45 for multi-
fibre connectors.
b
The probability of a randomly mated connection set meeting the specified attenuation requirement will be
≥ 97 %. This performance is reached by means of a statistical distribution of connection parameters (MFD
mismatch, lateral offset and angular offset) using a nominal value for wavelength of 1 310 nm.

Table 2 – Single-mode return loss grades for APC (8°)
a
Return loss grade Return loss (unmated)
Return loss (mated)
dB dB
1 ≥ 60 ≥ 55
a
The test shall be carried out according to IEC 61300-3-6.

Single-mode attenuation and return loss grades are applicable for the wavelengths from
1 310 nm to 1 625 nm.
5 Criteria for a fit within attenuation and return loss grades
5.1 General
Figure 1, Table 3 and Table 4 give the criteria for meeting the attenuation and return loss
grades listed in Table 1 and Table 2. The parameters chosen for the criteria definition are based
on the degree of significance by which they affect the performance under test. The criteria
selected are based on the theoretical model in 5.2 and 5.3 as well as experimental results.

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IEC 61755-2-2:2022 © IEC 2022 – 7 –
5.2 Attenuation grades and criteria
Using a Gaussian distribution for the incident light, the attenuation of the joint between two
dispersion unshifted single-mode optical fibres defined by IEC 60793-2-50 category B is given
by Formula (1). Attenuation is also referred to as insertion loss (IL), or coupling efficiency of
the fibres.
The range of the nominal MFD and index of refraction (n ) of the fibre cores are given in Table 3.
0
Table 3 – MFD and fibre core nominal index of refraction
Fibre sub-category Nominal wavelength Nominal MFD n (core)
0
nm µm
IEC 60793-2-50 fibres 1 310 8,6 to 9,2 1,452 0

These attenuation grades are based on a statistical approach defining parameter values of
connection populations to reach the attenuation to be less than or equal to the given value in
97 % of the connections. This performance is assumed at the nominal wavelength with fibre
MFD in the range defined in IEC 60793-2-50 family specification for single-mode dispersion
unshifted fibres category B.
Populations of lateral and angular offset of the random mated connections are assumed to be
statistically distributed within the specific ranges of parameter values d and θ in Formula (1).
Each curve given in Figure 1 represents maximum allowable combinations of lateral offset and
angular offset so as not to exceed the specified attenuation of any single connection, without
the contribution from fibre MFD mismatch. Additional attenuation due to mismatch of the MFD
from the randomly selected fibres is included in Formula (1).
Formula (1) is applicable to wavelengths from the range between 1 310 nm and 1 625 nm, using
the parameters for these wavelengths. The curves in Figure 1 are only shown at 1 310 nm
wavelength.

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– 8 – IEC 61755-2-2:2022 © IEC 2022

Figure 1 – Lateral offset and angular offset versus attenuation, η ,
combined
for single-mode fibre with 8,9 µm MFD at 1 310 nm
Attenuation η is expressed in Formula (1) below:
combined
 
22

2
2 2
ω ω
( 21 )
 (2ωω ) 
−2⋅d n
21
220
η =−−10log exp 2πθsin
( ) (1)
 
combined 10
2 22 2
22
22
ωω+ λ
ωω+
 21 
( 21 )
ωω+

( )
21

 

where
d is the total lateral offset between two fibres;
θ is the angular offset between fibre core axes;
λ is the wavelength of transmitted light in vacuum;
n is the index of refraction of the fibre core;
0
ω is the transmit fibre mode field radius;
1
ω is the receive fibre mode field radius.
2
5.3 Visual requirements for return loss grades
Without considering any contamination or defect on the end face, the intrinsic return loss for
angled polished physical contacting fibres is primarily governed by the polishing angle (see
Annex A). The appropriate polishing method shall be applied to obtain the return loss grade in
Table 2. The quality of the end face shall be inspected using IEC 61300-3-35. The visual
requirements for single-mode APC polished end faces in fibre core zone (zone A), and fibre
cladding zone (zone B) based on defect size, scratch width, and their respective quantities are
shown in Table 4.

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IEC 61755-2-2:2022 © IEC 2022 – 9 –
Table 4 – Visual requirements for single-mode angle
polished (APC) fibres SM APC (RL ≥ 60 dB)
Zone Defects Scratches
(diameter) (diameter) (width)
No limit < 2 µm No limit < 3 µm
A: core
Maximum 1 ≥ 2 µm and ≤ 3 µm Maximum 4 ≥ 3 µm and ≤ 4 µm
25 µm
None > 3 µm None > 4 µm
B: cladding No limit ≤ 25 µm
No limit
25 µm to 110 µm None > 25 µm

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– 10 – IEC 61755-2-2:2022 © IEC 2022
Annex A
(informative)

Return loss model on angled connections
For connections with angled polished end faces, the intrinsic return loss can be calculated as
RL in Formula (A.1):
2
(π⋅𝑛𝑛 ⋅𝜔𝜔 )
1 1
2
(A.1)
𝑅𝑅𝑅𝑅(𝜏𝜏̂) = 10⋅ ⋅log (e)⋅(2⋅𝜏𝜏̂) +𝑅𝑅𝑅𝑅
10 0
2
𝜆𝜆
2

 
nn−
12


RL =−10⋅log
  (A.2)
0 10
nn+
 12 


where
RL is the return loss as a function of polishing angle τ (for τ < 10°) (dB);

τ is the polishing angle (rad);
ω is the mode field radius of transmitting fibre (µm);
1
n is the nominal index of refraction for transmitting fibre;

1
n is the nominal index of refraction for receiving medium (= 1 for unmated interface);
2
λ is the wavelength of transmitted light in vacuum (μm);
RL is the calculation for return loss from Fresnel reflection at the interface with normal
0
incidence, assuming negligible effect from other factors, such as damaged surface layer
from polishing.

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IEC 61755-2-2:2022 © IEC 2022 – 11 –
Bibliography
IEC 61755-2-1, Fibre optic interconnecting devices and passive components – Connector
optical interfaces for single-mode fibres – Part 2-1: Connection parameters of dispersion
unshifted physically contacting fibres – Non-angled
IEC 61755-3-2, Fibre optic interconnecting devices and passive components – Connector
optical interfaces for single-mode fibres – Part 3-2: Connector parameters of dispersion
unshifted physically contacting fibres – Angled cylindrical full zirconia ferrules
IEC 61755-3-31, Fibre optic interconnecting devices and passive components – Connector
optical interfaces – Part 3-31: Connector parameters of non-dispersion shifted single mode
physically contacting fibres – Angled polyphenylene sulphide rectangular ferrules

___________

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– 12 – IEC 61755-2-2:2022 © IEC 2022
SOMMAIRE
AVANT-PROPOS . 13
1 Domaine d’application . 15
2 Références normatives . 15
3 Termes et définitions . 16
4 Classes d’affaiblissement et d’affaiblissement de réflexion . 16
5 Critères d’ajustement dans les classes d’affaiblissement et d’affaiblissement de
réflexion . 17
5.1 Généralités . 17
5.2 Classes d’affaiblissement et critères . 17
5.3 Exigences visuelles pour les classes d’affaiblissement de réflexion . 18
Annexe A (informative) Modèle d’affaiblissement de réflexion sur les connexions avec
angle . 20
Bibliographie . 21

Figure 1 – Décalage latéral et décalage angulaire en fonction de l’affaiblissement,
η , pour les fibres unimodales de MFD 8,9 µm à 1 310 nm . 18
combined

Tableau 1 – Classes d’affaiblissement en unimodal et accouplement sans choix
préalable . 16
Tableau 2 – Classes d’affaiblissement de réflexion en unimodal pour APC (8°) . 16
Tableau 3 – MFD et indice de réfraction nominal du cœur de fibre . 17
Tableau 4 – Exigences visuelles pour les fibres polies avec angle (APC) en unimodal -
Unimodal APC (RL ≥ 60 dB) . 19

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IEC 61755-2-2:2022 © IEC 2022 – 13 –
COMMISSION ÉLECTROTECHNIQUE INTERNATIONALE
____________

DISPOSITIFS D’INTERCONNEXION ET
COMPOSANTS PASSIFS FIBRONIQUES – INTERFACES
OPTIQUES DES CONNECTEURS POUR FIBRES UNIMODALES –

Partie 2-2: Paramètres de connexion des fibres en contact
physique à dispersion non décalée – avec angle

AVANT-PROPOS
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