Nexans Cabling Solutions
Field Testing Procedures
of Optical Fibre Cabling
Nexans Cabling Solutions
Alsembergsesteenweg 2, b3
1501 Buizingen - Belgium
Edition July 05, 2002
Revision 1.2
Table of Contents
1.
INTRODUCTION ................................................................................................. 3
2.
THE NEXANS CERTIFIED SYSTEM WARRANTY ............................................ 3
3.
FIELD TEST PROCEDURES .............................................................................. 4
3.1.
Background ......................................................................................................................................... 4
3.1.1.
Acceptable link loss calculation ......................................................................................................... 4
3.1.2.
Loss Parameters and limits................................................................................................................. 5
3.2.
Field-testing equipment for Nexans Certified System installations ........................ 5
3.3.
Loss testing methodologies .......................................................................................................... 7
3.3.1.
Multimode fibre link ............................................................................................................................ 7
3.3.2.
Singlemode fibre link ........................................................................................................................... 7
3.4.
The material you need .................................................................................................................... 7
3.5.
Test tool configuration ................................................................................................................... 8
3.6.
Testing.................................................................................................................................................... 8
3.6.1.
Single fibre measurement.................................................................................................................... 9
3.6.2.
Dual fibre measurement .....................................................................................................................11
3.7.
OF Warranty Application............................................................................................................13
3.7.1.
Warranty certification procedure ....................................................................................................13
3.7.2.
OF Warranty Application form .......................................................................................................13
4.
TROUBLESHOOTING .......................................................................................15
5.
ANNEXES ..........................................................................................................16
5.1.
A1 - Normative references ..........................................................................................................16
5.2.
A2 - Fibre Optic Loss Measurement .....................................................................................17
5.2.1.
Definitions ..............................................................................................................................................17
5.2.2.
Fibre Optic cabling compliance testing requirements ................................................................17
5.2.3.
Loss Parameters and limits................................................................................................................18
5.2.4.
Acceptable link loss calculation ........................................................................................................19
5.2.5.
Other requirements and limitations ................................................................................................20
OF testing procedure
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Field Testing Procedures
of Optical Fibre Cabling
1. Introduction
This document specifies the procedure for field-testing the transmission performance of
Nexans installed optical fibres links in premises. The procedure complies with the ISO/IEC
14763-3 standard.
The ISO/IEC 14763 standard specifies the implementation and operation of customer
premises cabling.
The part 3 of this ISO document (14763-3) details test procedures for optical fibre cabling
designed in accordance with ISO/IEC 11801 and installed according to the recommendations
of ISO/IEC 14763-2 (Planning and installation of customer premises cabling).
The optical link test configuration as defined further in this document shall be used to verify the
performance of permanently installed OF cabling.
All 100 % of the installed OF links have to be tested and must pass the acceptance criteria in
order to apply for the Nexans performance warranty certificate.
Make sure that the operator doing the tests has been properly trained and that the field-test
equipment and cords work properly.
The tester has to be normalised in accordance with the manufacturer’s guidelines.
Test limits and required results are specified further in this document.
2. The Nexans Certified System Warranty
For a complete overview of the Nexans Cabling Solutions Warranty for the different systems
and products, please refer to the respective warranty modules
OF testing procedure
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3. Field Test Procedures
3.1.
Background
Fibre-optic Tests applied to links and exclude equipment and work area cord.
OF Attenuation testing is used to verify the initial performance of the installed link.
The attenuation of the link is measured using the insertion loss method. This method uses an
optical source and an optical power meter to compare the difference between two optical
power levels:
 First measuring how much light is put into the link at the near end (P1)
 Then measuring how much light exits at the far end of the link (P2)
These absolute optical power levels are measured in dBm. 0 dBm is equivalent to 1 mW of
power. The attenuation values (in dB) are determined by subtraction of the two absolute power
levels (in dBm).
Attenuation or Loss (dB) = P1 (dBm) – P2 (dBm)
If the measured attenuation of the links has a lower value than the acceptable link attenuation
calculated, the subsystem is OK and can be certified. If not, additional actions to rectify the
problem will have to be taken.
3.1.1.
Acceptable link loss calculation
The measured value of attenuation of a FO link should not exceed the sum of allowable
attenuation of each component of the link.
These components are
 The fibre-optic cable
 The termination OF connectors
 The splices (if any)
The specifications within the ISO 11801 standard are representative of the following formulas
Link loss (dB) = Cable loss + Connectors loss + Splices loss
Cable loss (dB) = Cable length (km) x Loss coefficient (dB/km)*
Connector loss (dB) = number of connector pairs x connector loss (dB)*
Splice loss = number of splices x splice loss (dB)*
 *: from Table 1 – Attenuation criteria
The Cable length shall be optically measured or calculated using cable sheath length
markings. (Refer also to Annex 2)
OF testing procedure
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3.1.2.
Loss Parameters and limits
The attenuation of one link at specified wavelength shall not exceed the sum of the specified
attenuation values for all the components of that link.
Table 01 - Attenuation criteria
Loss/km
Optical Fibre type 850 nm 1310 nm 1550 nm
(in dB)
Multimode 62,5 µm
3,5
1,5
NA
Multimode 50 µm
3,5
1,5
NA
Singlemode
NA
1,0
1,0
3.2.
Loss
Connector Splice
(in dB)
0,75
0,3
0,75
0,3
0,75
0,3
Field-testing equipment for Nexans Certified System installations
A stabilized light source and an optical power meter (Also known as Loss Test Set) are used
to measure the attenuation of each terminated fibre link.
Factory-terminated OF test cords shall be used to ensure accurate results.
Test equipment shall be capable of measuring relative or absolute optical power in accordance
with IEC 61280-4-1 for multimode fibres and IEC 61280-4-2 for singlemode fibres.
Single fibre measurement test set can be used but Nexans Cabling Solutions recommends the
use of enhanced measurement test set designed for testing of FO cabling subsystem in
premise LAN.
Pre-programmed OF field Certification tools
Instrument manufacturers have introduced fibre test adapters to be attached to their standard
balanced cabling test equipments.
These cable testers comply with the standard specifications and provide features to ease and
speed up the testing and the certification process:
 Test two fibres and two wavelengths at one time
 Measure optical loss, fibre length and propagation delay
 Save OF measurement results
 Utilize specific software to manage results and generate electronic reports
 Calculate the loss budget and report the “Pass/Fail” margin against
the ISO standard (and Gigabit Ethernet standard for some adapters)
 Test certify and document fibre and copper with one tester
OF testing procedure
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The specific fibre test adaptors to be used are:
Table 03 – Fibre test adaptors
Brand name
Fluke
Microtest
Agilent
Ideal
Balanced cable
tester
Multimode
OM1 & OM2
OM3
DSP serie
FTA410S/420S
OMNIScanner OMNIFIBER MM
SmartProbe
WireScope 350
N2597A-030
Lantek 6 and 7
FiberKit+MM
FTA440S
-------------
Singlemode
1 test for
both λ
FTA430S
OMNIFIBER SM
SmartProbe
N2597A-040
Yes
Yes
FiberKit+ALL
No
No
1 test for both λ (wavelengths): Fluke and Microtest OF test adaptors are able to test the
attenuation for both wavelengths (850nm + 1310nm for MM – 1310nm + 1550nm for SM).
Other adaptors (Agilent and Ideal) can only test one wavelength in each direction.
In other words, it is necessary to swap the fibres during the testing process to have both fibres
measured at both wavelengths.
The use of dual wavelengths test adaptors is quicker and safer. Furthermore, the swap of the
fires could become a problem when testing SFF terminated fibres: no swap possible at least
for some of them (MT-RJ).
Maintenance of the field instruments involves ensuring the adapters and connectors are
maintained in good condition. Follow the manufacturer’s guidelines to keep the rechargeable
batteries in good condition. Always store the instrument and equipment in a case.
Software upgrades are relatively easy and often contain instrument performance
improvements. Software upgrades are usually obtained directly by downloading new
executable files into a computer and transferring the files to the field instruments. It is a good
idea to check the manufacturer’s web site on a frequent basis to ensure the field tester has the
latest software and is up-to-date with the revisions to standards limits.
Optical Time Domain Reflectometer (OTDR)
OTDR shall not be used to measure cable plant loss.
 No official standard regarding OTDR testing has been developed for general or LAN
use
 Furthermore, the use of an OTDR in short LAN lengths is expensive and performance
is usually slow. The limited distance resolution of the OTDR makes it very hard to use
in a LAN or building environment.
 OTDR Loss measurements have to be carefully interpreted by a trained technician and
are not as accurate as direct measurement of the attenuation.
Therefore, OTDR can only be used for length measurement and for fault location.
Nexans Cabling Solutions will not accept loss measurement performed with an OTDR.
Warranty application
If the loss test set doesn’t provide test results storage features, the measurements must
be transmitted to Nexans Cabling Solutions (NCS) using the NCS OF data form.
More information can be found in the chapter 3.7: OF Warranty Application
OF testing procedure
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3.3.
Loss testing methodologies
3.3.1. Multimode fibre link
The test procedure described bellow is based on the use of the “one-jumper method” specified
by Method 2 of IEC 61280-4-1. This procedure is used for testing links for which the connector
loss is a significant portion of the total link attenuation. This is the case for LAN premises links.
This method is only valid for links terminated with single-fibre connectors such as SC and ST
connectors. SC is the preferred connector specified in the ISO11801 standard. However, SFF
connectors can also be used.
Small Form Factor (SFF) connectors
Adapted test solutions to be used to certify links terminated with SFF connectors will be
issued.
In particular, specific methodologies will be issued to match the unique characteristics of the
SFF connectors: MT-RJ (dual-fibre connector and pinned + unpinned), LC, VF45 and
OptiJack.
3.3.2. Singlemode fibre link
The test procedure to be applied is the same and is based on the use of the “one-jumper
method” specified by Method 1a of IEC 61280-4-2. This procedure is used for testing links for
which the connector loss is a significant portion of the total link attenuation. This is the case for
LAN premises links.
This method is only valid for links terminated with single-fibre connectors such as SC and ST
connectors. SC is the preferred connector specified in the ISO11801 standard. However, SFF
connectors can also be used.
Small Form Factor (SFF) connectors
Adapted test solutions to be used to certify links terminated with SFF connectors will be
issued.
3.4.
The material you need
To test fibre optic links, you will need the following items:
 Dual wavelength fibre-optic source and power meter
Wavelengths: 850 & 1310 nm for MM fibres / 1310 & 1550 nm for SM fibres.
 Launch and Receive reference single fibre cords
Connectors (ST, SC, FC, MT-RJ…) and fibre types (MM 50µ, MM 62.5µ, SM)
compatible with the OF subsystem to be tested.
These cords shall be factory terminated and maintained in perfect shape.
 Mating adapters for connectors (Coupling)
Not necessary for most of the procedures but it could be useful to check the quality
of the reference cords or to analyse a failed link.
 Lint free cleaning wipes and pure isopropyl alcohol.
Airborne dirt (transported by the air) use to be as big as the core of a SM fibre and
big enough to cause high loss in MM fibre. Always clean connectors before testing.
 A fibre scope
This tool will be useful to inspect the connectors and for trouble-shooting
 NCS OF Warranty Application Data form
if the loss test set doesn’t provide test results storage features
OF testing procedure
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3.5.
Test tool configuration
Check the loss test set to be sure it is fully functional, the battery is charged, and all the
necessary equipment or adapters are available.
Inspect the connectors of the reference cords for polish and cleanliness. Nexans Cabling
Solutions recommend the use of a fibre scope to perform this inspection.
Calibration and set-up
Calibration and set-up procedures vary per field tester.
Check with the field tester documentation for the correct procedure.
When using Pre-programmed OF field-testing certification tools, the required settings also
include the following items: test standard, fibre type, adapter type, adapter and splice
numbers, index of refraction…
3.6.
Testing
To measure the loss of an OF link, we have to compare the difference between two optical
power levels:
 First measuring how much light is put into the link at the near end (P1)
 Then measuring how much light exits at the far end of the link (P2)
The attenuation value (in dB) is determined by subtraction of the two absolute power levels (in
dBm).
Attenuation or Loss (dB) = P1 (dBm) – P2 (dBm)
OF testing procedure
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3.6.1. Single fibre measurement
This procedure has to be used when testing with basic optical source and power meter.
Using a basic loss test set, fibres have to be tested one at a time.
If the loss test set doesn’t provide test results storage features, the measurements must
be transmitted to Nexans Cabling Solutions (NCS) using the NCS OF data form.
Step 1: Reference – P1 measurement
Fig.1 - Reference power mea surement
Source
Not to be
disrupted once
reference is set
Reference
launching cord
P1 mea sure
for both wavelengths
(in dBm)
Power
Meter
Disconnecting
cord end
 Clean all fibre connections
Dirt is harmful to connectors and causes loss which affect measurements.
Always cover the connectors with a dust cap when not in use.
 Power Meter: Select the dBm range
 Source: Select the wavelength ()
 850 nm and 1310 nm for multimode loss test set
 1310 nm and 1550 nm for singlemode loss test set
 For both wavelengths, measure the power at the power meter
 Record these values: P11 & P12
These are your two reference power levels for all loss measurements
Significant notes
 Once the reference is set, do not disconnect the launching cord from the source.
If the connection between the source output and the cord is disrupted, the
reference is lost because the P1 value will most probably be different when you will
reconnect the cord to the source. If you disconnect it, it is mandatory to repeat the
step 1 to have a new reference before continuing the test of the links.
 To ensure the stability of the reference, we recommend installing the source at the
Building Distributor side (OF backbone testing) to avoid any move of the source to
a different location.
 We also recommend periodically re-establishing the reference, at least if you have
to move the source or if situations indicate a need to do it.
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 All optical power measurements shall be recorded to one significant digit after the
decimal place (For example: -23.6 dBm)
 The power meter connection, the link connector and the launching cord free-end
connector shall match together. If not, it will be impossible to stick to this procedure.
Step 2: Test – P2 measurement
Fig.2 - Test power mea surement
Link under test
Source
Launching
cord
Receiving
cord
Adapter
Adapter
P2 mea sure
for both wa velengths
(in dBm)
Link loss = (P1 - P2)
Fibre + 2 connectors
+ splices (If a ny)






Power
Meter
Move the power meter to the far end of the link
Attach the receiving cord to the power meter
Connect the free ends of the cords to the terminations of the link on both sides
For both wavelengths, measure the power at the power meter
Record these values: P21 & P22
Repeat the step 2 for all the fibres of the link
Step 3: Test results evaluation
 Loss measurement calculation:
o Loss1 = P11 - P21
o Loss2 = P12 - P22
 Compare these results with the acceptable losses calculated in advance
(refer to §3.1.1 and Annex A2)
 Measured loss values shall be lower or equal to the calculated ones
 Record the measurements values in the OF data form
(Refer to §3.7: OF Warranty Application)
OF testing procedure
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3.6.2. Dual fibre measurement
This procedure has to be used when testing with
 A dual optical loss test set
 OF LAN certification tools
Using a dual-fibre loss test set, fibres are tested two at a time.
If the loss test set doesn’t provide test results storage features, the measurements must
be transmitted to Nexans Cabling Solutions (NCS) using the NCS OF data form and the
evaluation of the results must be done according to the procedure described in the former
chapter (3.6.1).
Step 1: Reference – P1 measurement
Fig.3 - Dua l reference power mea surement
Not to be disrupted
once reference is set
Test
Tool
2 reference
launching cords
IN
OUT
OUT
IN
Disconnecting
cord ends
Remote
Unit
P1: mea sure of the fibre pa ir
for both wa velengths (in dBm)
 Clean all fibre connections
Always cover the connectors with a dust cap when not in use
 Setting up for fibre tests
Configure your test tool according to the users manual
 Select the remote unit configuration for fibre pair measurement
 Set the reference power levels
The tester will record P11 & P12 for both fibres
These are your two reference power levels for all loss measurements
Significant notes
 Once the reference is set, do not disconnect the launching cords from the output
ends (sources) of the testers.
If the connection between the testers outputs and the cords is disrupted, the
reference is lost because the P1 values will most probably be different when you
will reconnect the cords to the sources. If you disconnect it, it is mandatory to
repeat the step 1 to have new references before continuing the test of the links.
OF testing procedure
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 Testing links terminated with Small Form Factor connectors (SFF) require the
method to be adapted. Please refer to the specific method described in a separated
document.
 All optical power measurements shall be recorded to one significant digit after the
decimal place (For example: -23.6 dBm)
 The tester connections, the link connectors and the launching cords free-end
connectors shall match together. If not, it will be impossible to stick to this
procedure.
Step 2: Test – P2 measurement
Fig.4 - Fibre pa ir test power mea surement
Lauching cords
Not to be
disrupted once
reference is set
OF pair Link under test
Test
Tool
Receiving
Launching
IN
Cords
OUT
Cords
IN
OUT
Launching
Adapters
Link loss = (P1 - P2)
Fibre + 2 connectors
+ splices (If a ny)
Receiving
Adapters
Remote
Unit
P2 mea sure
of the fibre pa ir
for both wa velengths
(in dBm)





Move the remote unit to the far end of the link
Attach the receiving cords to the test tool and the remote unit
Connect the free ends of the cords to the terminations of the link on both sides
Perform the test – Run the autotest
When using single wavelength test heads, you have to swap the fibre during the
autotest procedure. The swap shall be done on the patch panel side. Do not
disconnect the launching cords from the output ends (sources) of the testers.
 Check the result:
Pass: go to next step
Fail: go to the troubleshooting chapter
 Save the results of the test
 Repeat the step 2 for all the fibre pairs of the link
Step 3: Test results evaluation
 Check the result: Pass/Fail and headroom
Pass: proceed to the measurement of the next dual OF link
Fail: troubleshooting
OF testing procedure
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3.7.
OF Warranty Application
3.7.1. Warranty certification procedure
The procedure to be applied is similar to the one you must use to apply for a copper warranty
certification.
Only the new Warranty Application Form can be used to apply for a warranty and it will only be
accepted in electronic format. This Warranty Application Form is similar to the previous
warranty application form and the checklist that had to be used.
The test results have to be saved and sent in electronic format. A hard copy may be added.
Test results shall be exported from the certification tool in .fcm format from FLUKE, .mdb
format from WIRESCOPE or .dat format from MICROTEST.
.csv format is only accepted if the used tester tool (WAVETEK, …) does not support .fcm,
.mdb or .dat formats.
3.7.2. OF Warranty Application form
If the loss test set doesn’t provide test results storage features, the measurements must
be transmitted to Nexans Cabling Solutions (NCS) using the NCS OF Warranty
Application data form.
OF Warranty Application data form explanation
The data form includes 3 sheets:
 Data collection: legend, procedure summary and 11 data fields to be completed.
 Test report 1: measurement at the first wavelength (850nm for MM and 1310 for
SM)
 Test report 2: measurement at the second wavelength (1310nm for MM and 1550
for SM)
The file is foreseen to report the test of one complete OF link: 2 to 24 fibres.
One report file has to be created and saved for every OF cable whatever the fibre quantity.
The cells are coloured to highlight the ones that have to be filled up:
 Light turquoise cells: explanation / description
 Light Green cells: will be automatically filled up – do not type in these cells
 Tan cells: the value has to be chosen from the list: when the cell is
selected, click on the arrow to see the list of values
 White cells: to be filled up
On the first sheet (Data collection), there are 10 fields to be filled up: Tan and white cells.
All these cells shall be filled up because these values are used to automatically fill up the TAN
cells from the second and third sheet.
On the two last sheets (Test reports 1 & 2), only white cells have to be filled up with the
measured power values: reference value (P1) + far end measurement.
The reference value is the same for all measurements performed on the same link (One value
for each test report sheet: the reference value is different for each wavelength).
OF testing procedure
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If you set the reference measurement (P1) to zero in your tester, enter ‘0’ in the reference
power measurement cell from sheet 2 and 3. When using the zero reference feature, your tool
already perform the P1-P2 calculation. That’s why the reference power has to be set to 0.
Power measurement expressed in dBm used to be negative (O dBm = 1 mW / Led output
power used to be around –20 dBm).
To ensure that the automatic calculation provide correct values, always type the figures
with their minus sign.
The calculation of the acceptable link loss is automatically done according to the fields filled up
on the Data collection sheet.
The margin and the Pass/Fail fields are also automatically calculated once the measured
values have been typed in the corresponding cells. Fails are highlighted in red.
When printing, if you select the 3 sheets beforehand (Click on the first one and shift + click on
the third one), it will be numbered from 1/3 to 3/3.
Not to be filled cells are locked to prevent accidental erasing of the formulas.
The Excel file itself is also protected: Read only. To save your files, select File – Save as and
change the file name.
OF testing procedure
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4. Troubleshooting
A test failure is a measurement failure and could be caused by the cabling, the field
instrument, poor installation practices, or a combination of these. Depending upon the test that
failed, several diagnostic alternatives may be available. Before attempting any changes to the
cabling, always ensure that the field tester is providing accurate results and the correct test
configuration has been set up.
 The presence of dust, dirt and other contaminants at the interfaces to the cabling
under test may produce misleading results and in some cases damage the cabling
under test and/or the cabling interface adapter. The mating connector end faces of
cabling interface adaptors and the cabling under test shall be cleaned in
accordance with the connecting hardware manufacturers instructions prior to
mating.
 Always clean the fibre end faces before making the connections. Use lint-free
swabs or wipes moistened with pure isopropyl alcohol or pre-moistened wipes
approved for use in fibre connectors.
 If no power is measured at the source, the optical source or the patch cords could
be defective.
 If the power loss is more than expected
o Fibres could be connected to the wrong port of the unit
o Fibres could be swapped at one end of the link
o One Patch cord could be broken
o There could be one or more dirty connections in the link
o Setting up of the parameters in the tester could be wrong
o Patch cord(s) and fibre from the link could have a different core size
 If the measure of the length of cable is too long or too short, the index of refraction
could have been set up correctly.
DO NOT look into an active optical fibre (especially with a microscope) as harmful radiation
that can cause eye damage may be present.
OF testing procedure
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5. ANNEXES
5.1.
A1 - Normative references
This testing procedure comply with the following International Standards:
ISO/IEC 11801 - latest draft of the 2nd edition: Generic cabling for customer premises
ISO/IEC 14763-3: Implementation and operation of customer premises cabling –
Part 3: Testing of optical fibre cabling
IEC 61280-4-1: Part 4-1: Test procedures for fibre optic cable plant and links –Multimode fibre
optic cable plant attenuation measurement
IEC 61280-4-2: Part 4-2: Test procedures for fibre optic cable plant and links - Single mode
fibre optic cable plant attenuation measurement
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5.2.
A2 - Fibre Optic Loss Measurement
5.2.1.
Definitions
A Link is the transmission circuit between any two telecommunications active devices not
including the patch cords.
Horizontal link extends from a patch panel located in the cabinet (Floor Distributor) to the
telecommunications outlet (TO) at the user side. The link excludes equipment and work
area cords, and cross-connections, but does includes the optional consolidation point.
Intra-building primary backbone link extends from a patch panel (PP) located in the cabinet
of the Building Distributor (BD) to a PP located in the Floor Distributor (FD). This link forms
the main circuit between the BD and one FD. The BD is the head end of the intra-building
backbone.
Secondary backbone link forms a circuit between two FDs or a second (backup) circuit
between the BD and the FD.
Inter-building backbone link forms a circuit between the Campus Distributor (CD) and one
Building Distributor. The CD is the head end of the inter-building backbone.
A Channel represents the complete end-to-end path between any two pieces of telecom
active equipment. The channel includes the link components, the work area cord, the
equipment cord, and the cross-connect.
Horizontal channel forms the end-to-end path between the user equipment (PC, phone,
video equipment, printer…) and the active equipment at the cabinet side (switch, hub,
PABX, video equipment).
Backbone (vertical) channel forms the end-to-end path between any two pieces of active
equipment located in both distributors rooms (FDs, BDs, CD).
The Link and Channel definitions can be applied to both copper and optical fibre
circuits.
5.2.2.
Fibre Optic cabling compliance testing requirements
After installation, links must be tested for compliance with the normative requirements in order
to validate the installed cabling.
To characterize a fibre optic (FO) circuit, we need to know its limits. One of the most important
limitations for the performance of an optical fibre is the attenuation or loss.
According to the applicable standards (Refer to §3.2), the end-to-end optical attenuation has to
be tested for all installed FO links as a means of validating the FO cabling subsystem.
End-to-end attenuation
Measure of the optical power loss between cable termination points (Link measurement)
Acceptable attenuation values are different for each link. The value is dependent upon the link
length, the wavelength, and the number of connectors and splices.
This value has to be calculated in accordance to the specifications within ISO/IEC 11801.
OF testing procedure
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To pass the test, the measured attenuation of a FO link should always be lower than the
acceptable link loss value calculated for this link.
Link performance
If all the links pass the test, the FO subsystem will be validated but the warranted performance
can vary according to the characteristics defined during the design phase.
Channel performance
Applications requiring a high bandwidth (example: Gigabit network applications) will only be
warranted if the following elements have been chosen according to the specific needs of the
customer:
A: Optical fibre type: OM1, OM2, OM3, OS1
Core diameter 50µ or 62.5µ for OM types only
B: Channel class: OF-300, OF-500 or OF-2000
For more information, please refer to clause 8, clause 9.4 and annex F from the second edition
of the ISO 11801 standard.
As the present procedure is related to field-testing we only focus on the OF measurement that
will lead to the validation of the FO subsystem link performance.
5.2.3.
Loss Parameters and limits
The link attenuation or link loss shall be tested.
The attenuation of one link at specified wavelength shall not exceed the sum of the specified
attenuation values for all the components of that link.
Table 01 - Attenuation criteria
Loss/km
Optical Fibre type
850 nm
1310 nm
Loss
1550 nm
(in dB)
Connector
Splice
(in dB)
Multimode 62,5 µm
3,5
1,5
NA
0,75
0,3
Multimode 50 µm
3,5
1,5
NA
0,75
0,3
Singlemode
NA
1,0
1,0
0,75
0,3
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5.2.4.
Acceptable link loss calculation
The measured value of attenuation of a FO link should not exceed the sum of allowable
attenuation of each component of the link.
These components are
 The fibre-optic cable
 The termination OF connectors
 The splices (if any)
The specifications within the ISO 11801 standard are representative of the following formulas
Link loss (dB) = Cable loss + Connectors loss + Splices loss
Cable loss (dB) = Cable length (km) x Loss coefficient (dB/km)*
Connector loss (dB) = number of connector pairs x connector loss (dB)*
Splice loss = number of splices x splice loss (dB)*
 *: from Table 1 – Attenuation criteria
Examples
a) Link loss for 84 meters of 62.5/125µ OF terminated on field installable ST connectors
Cable loss at 850nm:
Connector loss:
Splice loss:
Acceptable Link Loss
0,084 km X 3,5 dB/km
2 X 0,75 dB
0 x 0.3 dB
= 0.3 dB
= 1,5 dB
= 0,0 dB
= 1,8 dB
b) Link loss for 350 meters of 50/125µ OF terminated on SC pigtails
Cable loss at 1310nm:
Connector loss:
Splice loss:
Acceptable Link Loss
0,350 km X 1,5 dB/km
2 X 0,75 dB
2 x 0.3 dB
= 0.5 dB
= 1,5 dB
= 0,6 dB
= 2, 6 dB
The Cable length shall be optically measured or calculated using cable sheath length
markings.
The length measurement can be performed with an Optical Time Domain Reflectometer
(OTDR). The refractive index of the fibre to be tested has to be set to the right value. This
parameter is used by the OTDR to calculate the length of the cable. It is so important to
introduce the right value to retrieve the right length measurement from the OTDR tool.
OF testing procedure
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The refractive index of a fibre is a characteristic that may vary from one OF manufacturer to
another. Here are the values to be used with the Nexans fibres.
Table 02 – Index of refraction
Index of refraction
Optical Fibre type
850 nm
1310 nm
1550 nm
Multimode 62,5 µm
1,4989
1,4935
NA
Multimode 50 µm
1,4850
1,4840
NA
NA
1,4710
1,4719
Singlemode
5.2.5.
Other requirements and limitations
Horizontal link



Link length: a multimode horizontal optical fibre cabling subsystem is limited to 90
meter length
Horizontal link shall be tested at 850 nm and 1310 nm in one direction
Test method 2 of IEC 61280-4-1 shall be used (Refer to the testing procedure
chapter)
Multimode backbone link



Link length: may vary upon Optical fibre type (OM1, OM2, OM3) and Channel class:
OF-300, OF-500 or OF-2000
Multimode backbone link shall be tested at 850 nm and 1310 nm in one direction
Test method 2 of IEC 61280-4-1 shall be used (Refer to the testing procedure
chapter)
Singlemode backbone link



Singlemode backbone link shall be tested at 1310 nm and 1550 nm in one direction
Test method A1 of IEC 61280-4-2 shall be used (Refer to the testing procedure
chapter)
All singlemode links shall be certified with test tools using laser light sources at 1310
nm and 1550 nm
OF channel topology
The models described in the ISO 11801 standard (clauses 7.2 & 7.3 – fig. 11 & 12) are
applicable to horizontal and backbone cabling using copper AND fibre.
That is why the same 90m-length limitation is applicable for both media.
However the delivery of fibres to the TO (FTTD) will generally not require transmission
equipment at the Floor Distributor. The standard allow the creation of a combined
backbone/horizontal channel (Fig.13 – clause 8.4 from ISO 11801).
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OF testing procedure
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