SIST EN 61280-4-1:2010

Fibre optic communication subsystem test procedures - Part 4-1: Installed cable plant - Multimode attenuation measurement (IEC 61280-4-1:2009)

This part of IEC 61280-4 is applicable to the measurement of attenuation of installed fibreoptic cabling using multimode fibre, typically in lengths of up to 2 000 m. This cabling can include multimode fibres, connectors, adapters and splices. Cabling design standards such as ISO/IEC 11801, ISO/IEC 24702 and ISO/IEC 24764 contain specifications for this type of cabling. ISO/IEC 14763-3, which supports these design standards, makes reference to the test methods of this standard. In this standard, the fibre types that are addressed include category A1a (50/125 μm) and A1b (62,5/125 μm) multimode fibres, as specified in IEC 60793-2-10. The attenuation measurements of the other multimode categories can be made, using the approaches of this standard, but the source conditions for the other categories have not been defined.

Prüfverfahren für Lichtwellenleiter-Kommunikationsuntersysteme - Teil 4-1: Lichtwellenleiter-Kabelanlagen - Mehrmoden-Dämpfungsmessungen (IEC 61280-4-1:2009)

Procédures d'essai des sous-systèmes de télécommunication à fibres optiques - Partie 4-1: Installation câblée - Mesure de l'affaiblissement en multimodal (CEI 61280-4-1:2009)

La CEI 61280-4-1:2009 s'applique à la mesure de l'affaiblissement d'une installation de câblage en fibre optique utilisant des fibres multimodes, généralement sur des longueurs allant jusqu'à 2 000 m. Cette installation de câblage peut inclure des fibres multimodes, des connecteurs, des raccords et des épissures. Dans la présente norme, les types de fibres abordées comportent les fibres multimodes de catégorie A1a (50/125 µm) et A1b (62,5/125 µm) spécifiées dans la CEI 60793-2-10. Les mesures d'affaiblissement des autres catégories multimodales peuvent être effectuées en utilisant les approches de la présente norme, mais les conditions de source des autres catégories n'ont pas été définies. Les principales modifications portant sur cette précédente édition sont:
- Une méthode de mesure supplémentaire basée sur la réflectométrie optique dans le domaine temporel (OTDR) est rapportée, avec des indications sur les meilleures pratiques d'utilisation de l'OTDR et d'interprétation des tracés de l'OTDR.
- L'exigence concernant les sources utilisées pour mesurer les fibres multimodes passe d'une exigence basée sur le taux de puissance couplée (CPR) et l'exigence relative au mandrin à une exigence basée sur des mesures en champ proche à la sortie du cordon d'essai d'amorce.
- La mise en valeur de l'importance et la fourniture de directives sur de bonnes pratiques de mesure incluant le nettoyage et l'examen des faces d'extrémité des connecteurs.

Postopki preskušanja optičnega komunikacijskega podsistema - 4-1. del: Vgrajene žične oblike - Meritev slabljenja večpredstavnosti (IEC 61280-4-1:2009)

Ta del IEC 61280-4 velja za meritve slabljenja vgrajenih žic iz optičnih vlaken z uporabo večpredstavnostnih optičnih vlaken, praviloma z dolžinami do 2.000 m. Te žice lahko vključujejo večpredstavnostna optična vlakna, konektorje, adapterje in spoje. Specifikacije za tovrstne žice vsebujejo standardi za zasnovo žic, kot so ISO/IEC 11801, ISO/IEC 24702 in ISO/IEC 24764. ISO/IEC 14763-3, ki podpira standarde za zasnovo, se sklicuje na preskusne metode tega standarda. V tem standardu vrste obravnavanih optičnih vlaken vključujejo večpredstavnostna optična vlakna kategorije A1a (50/125 μm) in A1b (62,5/125 μm), kot je določeno v IEC 60793-2-10. Z uporabo pristopov tega standarda se lahko opravijo meritve slabljenja drugih večpredstavnostnih kategorij, vendar izvorni pogoji za druge kategorije niso opredeljeni.

General Information

• Status: Withdrawn
• Publication Date: 20-Jan-2010
• Withdrawal Date: 15-Aug-2022
• ICS: 33.180.01 - Fibre optic systems in general
• Technical Committee: MOC - Mobile Communications
• Current Stage: 9900 - Withdrawal (Adopted Project)
• Start Date: 29-Jul-2022
• Due Date: 21-Aug-2022
• Completion Date: 16-Aug-2022
• Ref Project: EN 61280-4-1:2009 - Fibre optic communication subsystem test procedures - Part 4-1: Installed cable plant - Multimode attenuation measurement

Relations

• Replaced By: SIST EN IEC 61280-4-1:2019 - Fibre-optic communication subsystem test procedures - Part 4-1: Installed cable plant - Multimode attenuation measurement (IEC 61280-4-1:2019)
• Effective Date: 06-Aug-2019
• Replaces: SIST EN 61280-4-1:2005 - Fibre-optic communication subsystem test procedures -- Part 4-1: Cable plant and links - Multimode fibre-optic cable plant attenuation measurement
• Effective Date: 13-May-2010
• Replaces: SIST EN 61280-4-1:2005 - Fibre-optic communication subsystem test procedures -- Part 4-1: Cable plant and links - Multimode fibre-optic cable plant attenuation measurement
• Effective Date: 28-Jan-2023
• Replaces: SIST EN 61280-4-1:2005 - Fibre-optic communication subsystem test procedures -- Part 4-1: Cable plant and links - Multimode fibre-optic cable plant attenuation measurement
• Effective Date: 07-Jun-2022

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN 61280-4-1:2010
01-februar-2010
3RVWRSNLSUHVNXãDQMDRSWLþQHJDNRPXQLNDFLMVNHJDSRGVLVWHPDGHO9JUDMHQH
åLþQHREOLNH0HULWHYVODEOMHQMDYHþSUHGVWDYQRVWL,(&
Fibre optic communication subsystem test procedures - Part 4-1: Installed cable plant -
Multimode attenuation measurement (IEC 61280-4-1:2009)
Prüfverfahren für Lichtwellenleiter-Kommunikationsuntersysteme - Teil 4-1:
Lichtwellenleiter-Kabelanlagen - Mehrmoden-Dämpfungsmessungen (IEC 61280-4-
1:2009)
Procédures d'essai des sous-systèmes de télécommunication à fibres optiques - Partie 4
-1: Installation câblée - Mesure de l'affaiblissement en multimodal (CEI 61280-4-1:2009)
Ta slovenski standard je istoveten z: EN 61280-4-1:2009
ICS:
33.180.01 6LVWHPL]RSWLþQLPLYODNQLQD Fibre optic systems in
VSORãQR general
SIST EN 61280-4-1:2010 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------

SIST EN 61280-4-1:2010

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SIST EN 61280-4-1:2010

EUROPEAN STANDARD
EN 61280-4-1

NORME EUROPÉENNE
December 2009
EUROPÄISCHE NORM

ICS 33.180.01 Supersedes EN 61280-4-1:2004


English version


Fibre optic communication subsystem test procedures -
Part 4-1: Installed cable plant -
Multimode attenuation measurement
(IEC 61280-4-1:2009)


Procédures d'essai des sous-systèmes  Prüfverfahren für Lichtwellenleiter-
de télécommunication à fibres optiques - Kommunikationsuntersysteme -
Partie 4-1: Installation câblée - Teil 4-1: Lichtwellenleiter-Kabelanlagen -
Mesure de l'affaiblissement en multimodal Mehrmoden-Dämpfungsmessungen
(CEI 61280-4-1:2009) (IEC 61280-4-1:2009)




This European Standard was approved by CENELEC on 2009-10-01. CENELEC members are bound to comply
with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard
the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and notified
to the Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Cyprus, the
Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Central Secretariat: Avenue Marnix 17, B - 1000 Brussels


© 2009 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 61280-4-1:2009 E

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SIST EN 61280-4-1:2010
EN 61280-4-1:2009 - 2 -
Foreword
The text of document 86C/879/FDIS, future edition 2 of IEC 61280-4-1, prepared by SC 86C, Fibre optic
systems and active devices, of IEC TC 86, Fibre optics, was submitted to the IEC-CENELEC parallel vote
and was approved by CENELEC as EN 61280-4-1 on 2009-10-01.
This European Standard supersedes EN 61280-4-1:2004.
The main changes with respect to EN 61280-4-1:2004 are listed below:
– an additional measurement method based on optical time domain reflectometry (OTDR) is
documented, with guidance on best practice in using the OTDR and interpreting OTDR traces;
– the requirement for the sources used to measure multimode fibres is changed from one based on
coupled power ratio (CPR) and mandrel requirement to one based on measurements of the near field
at the output of the launching test cord;
– highlighting the importance of, and giving guidance on, good measurement practices including
cleaning and inspection of connector end faces.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2010-07-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2012-10-01
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 61280-4-1:2009 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standards indicated:
IEC 60793-1-40 NOTE  Harmonized as EN 60793-1-40:2003 (modified).
IEC 60793-2 NOTE  Harmonized as EN 60793-2:2008 (not modified).
IEC 60793-2-10 NOTE  Harmonized as EN 60793-2-10:2007 (not modified).
IEC 60793-2-50 NOTE  Harmonized as EN 60793-2-50:2008 (not modified).
IEC 61300-3-6 NOTE  Harmonized as EN 61300-3-6:2009 (not modified).
__________

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SIST EN 61280-4-1:2010
- 3 - EN 61280-4-1:2009
Annex ZA
(normative)

Normative references to international publications
with their corresponding European publications

The following referenced documents are indispensable for the application 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.

NOTE  When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD
applies.

Publication Year Title EN/HD Year

1) 2)
IEC 60825-2 - Safety of laser products - EN 60825-2 2004
Part 2: Safety of optical fibre communication
systems (OFCS)


3) 3)
IEC 61280-1-3 - Fibre optic communication subsystem test EN 61280-1-3 -
procedures -
Part 1-3: General communication
subsystems - Central wavelength and
spectral width measurement


1) 4)
IEC 61280-1-4 - Fibre optic communication subsystem test EN 61280-1-4 200X
procedures -
Part 1-4: General communication
subsystems - Light source encircled flux
measurement method


1)
IEC/PAS 61300-3-35 - Fibre optic interconnecting devices and - -
passive components - Basic test and
measurement procedures -
Part 3-35: Examinations and measurements -
Fibre optic cylindrical connector endface
visual inspection


1) 2)
IEC 61315 - Calibration of fibre-optic power meters EN 61315 2006


1)
IEC 61745 - End-face image analysis procedure for the - -
calibration of optical fibre geometry test sets


1) 2)
IEC 61746 - Calibration of optical time-domain EN 61746 2005
reflectometers (OTDR)




1)
Undated reference.
2)
Valid edition at date of issue.
3)
At draft stage.
4)
To be ratified.

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SIST EN 61280-4-1:2010

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SIST EN 61280-4-1:2010
IEC 61280-4-1
®
Edition 2.0 2009-06
INTERNATIONAL
STANDARD


Fibre-optic communication subsystem test procedures –
Part 4-1: Installed cable plant – Multimode attenuation measurement


INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
XB
ICS 33.180.01 ISBN 2-8318-1045-4
® Registered trademark of the International Electrotechnical Commission

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SIST EN 61280-4-1:2010
– 2 – 61280-4-1 © IEC:2009(E)
CONTENTS
FOREWORD.5
1 Scope.7
2 Normative references .7
3 Terms, definitions, graphical symbols and acronyms .8
3.1 Terms and definitions .8
3.2 Graphical symbols.9
3.3 Acronyms .11
4 Measurement methods .11
4.1 General .11
4.2 Cabling configurations and applicable test methods .12
4.3 Overview of uncertainties .12
4.3.1 General .12
4.3.2 Test cords .13
4.3.3 Launch conditions at the connection to the cabling under test .13
4.3.4 Optical source .13
4.3.5 Output power reference .13
4.3.6 Received power reference .14
5 Apparatus.14
5.1 General .14
5.2 Light source .14
5.2.1 Stability .14
5.2.2 Spectral characteristics .14
5.2.3 Launch cord .14
5.3 Receive or tail cord .15
5.4 Substitution/dummy cord .15
5.5 Power meter – LSPM methods only .15
5.6 OTDR apparatus .15
5.7 Connector end-face cleaning and inspection equipment .16
5.8 Adapters .16
6 Procedures.16
6.1 General .16
6.2 Common procedures .17
6.2.1 Care of the test cords .17
6.2.2 Make reference measurements (LSPM methods only) .17
6.2.3 Inspect and clean the ends of the fibres in the cabling.17
6.2.4 Make the measurements.17
6.2.5 Make the calculations .17
6.3 Calibration.17
6.4 Safety .17
7 Calculations .17
8 Documentation .18
8.1 Information for each test.18
8.2 Information to be available .18
Annex A (normative) One-cord reference method.19
Annex B (normative) Three-cord reference method .21

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SIST EN 61280-4-1:2010
61280-4-1 © IEC:2009(E) – 3 –
Annex C (normative) Two-cord reference method .23
Annex D (normative) Optical time domain reflectometer.26
Annex E (normative) Requirements for the source characteristics for multimode
measurement.32
Annex F (informative) Measurement uncertainty examples.35
Annex G (informative) OTDR configuration information .44
Annex H (informative) Test cord insertion loss verification .53
Bibliography.61

Figure 1a – Socket and plug assembly.10
Figure 1b – Connector set (plug, adapter, plug) .10
Figure 1c – Light source .10
Figure 1d – Power meter.10
Figure 1 – Connector symbols .10
Figure 2 – Symbol for cabling under test.10
Figure 3 – OTDR schematic .16
Figure A.1 − Reference measurement.20
Figure A.2 − Test measurement .20
Figure B.1 − Reference measurement.22
Figure B.2 − Test measurement .22
Figure C.1 − Reference measurement.24
Figure C.2 − Test measurement.24
Figure C.3 – Test measurement for plug-socket style connectors.24
Figure D.1 − Test measurement for Method D.27
Figure D.2 − Location of the cabling under test ports .28
Figure D.3 − Graphic construction of F and F .29
1 2
Figure D.4 − Graphic construction of F , F , F and F .30
1 11 12 2
Figure E.1 – Encircled flux template example.33
Figure F.1 – Initial power measurement .37
Figure F.2 – Verification of reference grade connection .38
Figure F.3 – Two offset splices .38
Figure F.4 – Five offset splices .38
Figure F.5 – EF centred .40
Figure F.6 – EF underfilling.40
Figure F.7 – EF overfilling.41
Figure F.8 – L1 loss with mandrel .41
Figure F.9 – L1 loss with mandrel and mode conditioner.42
Figure F.10 – L2 loss (adjusted) with mandrel.42
Figure F.11 – L2 loss (adjusted) with mandrel and mode conditioning.42
Figure F.12 – L3 loss (adjusted) with mandrel.43
Figure F.13 – L3 loss (adjusted) with mandrel and mode conditioning.43
Figure G.1 − Splice and macro bend attenuation measurement.47
Figure G.2 − Attenuation measurement with high reflection connectors.48

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SIST EN 61280-4-1:2010
– 4 – 61280-4-1 © IEC:2009(E)
Figure G.3 − Attenuation measurement of a short length cabling.49
Figure G.4 − OTDR trace with ghost .50
Figure G.5 − Cursors positioning.51
Figure H.1 − Obtaining reference power level P .54
0
Figure H.2 − Obtaining power level P .55
1
Figure H.3 − Obtaining reference power level P .56
0
Figure H.4 − Obtaining power level P .56
1
Figure H.5 − Obtaining reference power level P .57
0
Figure H.6 − Obtaining power level .57
Figure H.7 − Obtaining reference power level P .58
0
Figure H.8 − Obtaining power level P .58
1
Figure H.9 − Obtaining power level P .58
5
Figure H.10 − Obtaining reference power level P .59
0
Figure H.11 − Obtaining power level P .59
1

Table 1 – Cabling configurations.12
Table 2 – Test methods and configurations.12
Table 3 – Spectral requirements .14
Table E.1 – Threshold tolerance .33
Table E.2 – EF requirements for 50 μm core fibre cabling at 850 nm .34
Table E.3 – EF requirements for 50 μm core fibre cabling at 1 300 nm .34
Table E.4 – EF requirements for 62,5 μm core fibre cabling at 850 nm .34
Table E.5 – EF requirements for 62,5 μm core fibre cabling at 1 300 nm.34
Table F.1 – Expected loss for examples (note 1).35
Table G.1 – Default effective group index of refraction values.46

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SIST EN 61280-4-1:2010
61280-4-1 © IEC:2009(E) – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

FIBRE-OPTIC COMMUNICATION SUBSYSTEM
TEST PROCEDURES –

Part 4-1: Installed cable plant –
Multimode attenuation measurement


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 provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
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) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61280-4-1 has been prepared by subcommittee 86C: Fibre optic
systems and active devices, of IEC technical committee 86: Fibre optics.
This second edition cancels and replaces the first edition, published in 2003, and constitutes
a technical revision.
The main changes with respect to the previous edition are listed below:
– An additional measurement method based on optical time domain reflectometry
(OTDR) is documented, with guidance on best practice in using the OTDR and
interpreting OTDR traces.
– The requirement for the sources used to measure multimode fibres is changed from
one based on coupled power ratio (CPR) and mandrel requirement to one based on
measurements of the near field at the output of the launching test cord.

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SIST EN 61280-4-1:2010
– 6 – 61280-4-1 © IEC:2009(E)
– Highlighting the importance of, and giving guidance on, good measurement practices
including cleaning and inspection of connector end faces.
The text of this standard is based on the following documents:
FDIS Report on voting
86C/879/FDIS 86C/892/RVD

Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all the parts in the IEC 61280 series, under the general title Fibre-optic
communication subsystem test procedure, can be found on the IEC website.
For the Part 4, the new subtitle will be Installed cable plant. Subtitles of existing standards in
this series will be updated at the time of the next edition.
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site 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.
A bilingual version of this publication may be issued at a later date.

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SIST EN 61280-4-1:2010
61280-4-1 © IEC:2009(E) – 7 –
FIBRE-OPTIC COMMUNICATION SUBSYSTEM
TEST PROCEDURES –

Part 4-1: Installed cable plant –
Multimode attenuation measurement



1 Scope
This part of IEC 61280-4 is applicable to the measurement of attenuation of installed fibre-
optic cabling using multimode fibre, typically in lengths of up to 2 000 m. This cabling can
include multimode fibres, connectors, adapters and splices.
Cabling design standards such as ISO/IEC 11801, ISO/IEC 24702 and ISO/IEC 24764 contain
specifications for this type of cabling. ISO/IEC 14763-3, which supports these design
standards, makes reference to the test methods of this standard.
In this standard, the fibre types that are addressed include category A1a (50/125 μm) and A1b
(62,5/125 μm) multimode fibres, as specified in IEC 60793-2-10. The attenuation
measurements of the other multimode categories can be made, using the approaches of this
standard, but the source conditions for the other categories have not been defined.
2 Normative references
The following referenced documents are indispensable for the application 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 60825-2, Safety of laser products – Part 2: Safety of optical fibre communication systems
(OFCS)
IEC 61280-1-3, Fibre optic communication subsystem basic test procedures – Part 1-3: Test
procedures for general communication subsystems – Central wavelength and spectral width
measurement
IEC 61280-1-4, Fibre optic communication subsystem test procedures – Part 1-4: General
1
communication subsystems – Light source encircled flux measurement method
IEC 61300-3-35, Fibre optic interconnecting devices and passive components − Basic test
and measurement procedures − Part 3-35: Examinations and measurements − Fibre optic
cylindrical connector endface visual inspection
IEC 61315, Calibration of fibre-optic power meters
IEC 61745, End-face image analysis procedure for the calibration of optical fibre geometry
test sets
IEC 61746, Calibration of optical time-domain reflectometers (OTDRs)
—————————
1
 A new edition is in preparation.

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SIST EN 61280-4-1:2010
– 8 – 61280-4-1 © IEC:2009(E)
3 Terms, definitions, graphical symbols and acronyms
For the purposes of this document, the following terms, definitions, graphical symbols and
acronyms apply.
3.1 Terms and definitions
3.1.1
attenuation
reduction of optical power induced by transmission through a medium such as cabling, given
as L (dB)
L = 10 log (P /P )
10 in out
where P and P are the power, typically measured in mW, into and out of the cabling
in out
3.1.2
light source power meter
LSPM
test system consisting of a light source (LS), power meter (PM) and associated test cords
used to measure the attenuation of installed cable plant
3.1.
...