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

2.The Nexans Certified System Warranty

3.Field Test Procedures

3.1.Background

3.1.1.Acceptable link loss calculation

3.1.2.Loss Parameters and limits

3.2.Field-testing equipment for Nexans Certified System installations

3.3.Loss testing methodologies

3.3.1.Multimode fibre link

3.3.2.Singlemode fibre link

3.4.The material you need

3.5.Test tool configuration

3.6.Testing

3.6.1.Single fibre measurement

3.6.2.Dual fibre measurement

3.7.OF Warranty Application

3.7.1.Warranty certification procedure

3.7.2.OF Warranty Application form

4.Troubleshooting

5.ANNEXES

5.1.A1 - Normative references

5.2.A2 - Fibre Optic Loss Measurement

5.2.1.Definitions

5.2.2.Fibre Optic cabling compliance testing requirements

5.2.3.Loss Parameters and limits

5.2.4.Acceptable link loss calculation

5.2.5.Other requirements and limitations

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

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)

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

Optical Fibre type / Loss/km / Loss
850 nm / 1310 nm / 1550 nm / Connector / Splice
(in dB) / (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

3.2.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

The specific fibre test adaptors to be used are:

Table 03 – Fibre test adaptors

Brand name / Balanced cable tester / Multimode / Singlemode / 1 test for both λ
OM1 & OM2 / OM3
Fluke / DSP serie / FTA410S/420S / FTA440S / FTA430S / Yes
Microtest / OMNIScanner / OMNIFIBER MM / ----- / OMNIFIBER SM / Yes
Agilent / WireScope 350 / SmartProbe N2597A-030 / ----- / SmartProbe N2597A-040 / No
Ideal / Lantek 6 and 7 / FiberKit+MM / ----- / FiberKit+ALL / 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

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

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)

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

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.

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

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:

  • Loss1 =P11 - P21
  • 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)

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

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.

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

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

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.