Technical Note 002 - Optical fibre testing of Permanent Links and Links with LSPM To the requirements of ISO/IEC 14763-3:2012 Enhanced Three-Test-Cord Reference Method - ISO


Text in red italics underlined is derived from the new ISO/IEC 14763-3: 2014 standard

Text in blue italics is derived from the AS/NZS ISO/IEC 14763-3: 2012 and also applies to 2014 standard

1.        Applicability

The following applies to permanent link and link cabling installations in Australia and New Zealand seeking performance conformance of optical fibre permanent links and links to ISO/IEC 11801 using ISO/IEC 14763-3 Ed2: 2014 light source and power meter (LSPM) testing methods.    ISO/IEC 14763-3: 2014 will be the basis for the next revision of AS/NZS ISO/IEC 14763.3: 2012.

It is expected that there will be some modification to ISO/IEC 14763-3: 2014 to make it more applicable to the Australian and New Zealand cabling industry when AS/NZS ISO/IEC 14763.3 is revised.  Items significantly different from the 2012 standard are shown here in red text underlined. [Underlined in case of black & white printing.]

2.       Background

Clause E.1 of ISO/IEC 14763-3 1 states; The enhanced three-test-cord reference method can be used for measuring the attenuation of channels as well as for measuring the attenuation of permanent links.

Clause E.1 also states; The one-test-cord method of reference setting can be used only for measuring the attenuation of permanent links and links.

Either One-Test-Cord Reference Method or Enhanced Three-Test-Cord Reference Method (See TN-002) may be used to test a Permanent Link and Link.  Both reference methods include the contribution of the end connectors and both meet ISO/IEC 14763.3.

3.       Link definition

Permanent Link is horizontal cabling between floor distributor and telecommunications outlet.  Link is any other cabling usually comprising a single fixed cable with connectors at each end. 

Hereinafter the word ‘Link’ is used to collectively describe both a permanent link and a link.

4.       Bi-directional Testing

Clause 9.1.1.4 of ISO/IEC 14763.3 1 states;

For a link comprising a single fixed cable and terminating connectors, uni-directional testing may be performed.  Where the link is of a complex construction (e.g. two links joined by a fibre CP) or where there is a risk that components within the cabling under test cause differences in attenuation depending on the direction of transmission (e.g. damage/stress on components during installation or maintenance, or fixed fibres when joined have differences in performance or index of refraction) then

bi-directional measurements shall be carried out.

It is expected that the new AS/NZS version of 14763-3 standard will continue to state that;

For Australia and New Zealand testing of links and channels with light source and power meter shall be bi-directional and at least at two appropriate wavelengths.

For bi-directional testing using LSPM, the worst of the two measured results shall be considered as the overall measured result.  (ISO/IEC 14763-3 Ed2: 2014, Clause 9.1.1.5)

5.       Test Cords

The three-test-cord reference method uses the following test cords 2;

·      LTC         Launch Test Cord             (2 – 10 m with reference connector at link interface end)

·      STC         Substitution Test Cord   (2 – 10 m with reference connector at link interface end)

·      TTC         Tail Test Cord                     (2 – 10 m with reference connector at link interface end)

All multimode and singlemode test cords for simplex and duplex testing shall be inspected and tested for proper functioning. 3

The LTC for multimode and singlemode shall meet the launch modal distribution 4 at the output of the launch test cord.  For multimode, this is also known as meeting Encircled Flux requirements.  The singlemode launch condition requires that launch cords contain a minimum of two single air-coiled turns or mandrel wraps of 35 mm to 50 mm in diameter.  However this is usually provided within the test instrument and it is then not necessary to include an external wrap on the launch test cord.5

The LTC, STC and TTC for multimode and singlemode must have a connector and end face that will mate with the link connectors.  All connectors should be inspected and cleaned as necessary before reference setting and before each and every individual test.

6.       Enhanced Three-Test-Cord Reference Method for Optical Fibre Links

6.1.    Allow the light source to warm up following the tester manufacturer’s recommendations.  This could take up to 15 minutes.

6.2.    Connect the LTC to the light source at one end and to the power meter at the other end.  Ensure EF compliance of the LTC for multimode and modal distribution for singlemode.

6.3.    Set the reference to 0.0 dB or record the reference power in dBm or watts.

6.4.    Connect the STC and TTC using reference adaptors between the LTC and power meter.  

6.5.    Measure and record the attenuation or power of the three test cords.

This step enhances the accuracy and reduces the uncertainty of the final test result.  Hence the name Enhanced Three-Test-Cord Reference Method

The max attenuation of the two pairs of reference-to-reference connector sets not exceed,

·           MMF 0.20 dB  

·           SMF   0.40 dB. 

Note:  If the attenuation is more than the allowable value, clean all end faces, inspect then reconnect and re-test.  Re-set the reference if necessary.  Use alternate test cords if necessary.

6.6.    Remove the STC and reference adaptors; connect the LTC and TTC to the cleaned link under test. 

Do not remove test cords from the testers; otherwise re-set the reference as per Item 6.2.


6.7.    Measure and record the attenuation of the link, which includes the two end connections.

6.8.    During testing reference power measurements shall be repeated periodically 6 i.e. the launch, substitution and tail test cords be connected together on occasions to ensure the value is still below the maximum allowed in Item 6.5.

 

7.       Treatment of Link Test Results

Clause 9.1.1.8 of ISO/IEC 14763.3 Ed2:2014 contains the following formulae;

Using the One- or Three-Test-Cord Reference Method, the PASS limit for link attenuation is;

MMF Limit  =  (2 x 0.5 dB) + Σ (cable attenuation) + Σ (embedded connector attenuation)

SMF Limit  =  (2 x 0.75 dB) + Σ (cable attenuation) + Σ (embedded connector attenuation)

These formulae are from Corrigenda 1 to ISO/IEC 14763-3 Ed2 dated 17.03.2015.

 

Table 6  Allowable Attenuation Values

 

 

Component and Wavelength

ISO/IEC 14763-3 Ed2: 2014

Attenuation (Loss) Maximum

Mated Ref to Ref Connection

at   850 & 1300 nm

at 1310 & 1550 nm

 

              MMF  0.10  dB

                SMF  0.20  dB

Mated Ref to Non-Ref Connection

at   850 & 1300 nm

at 1310 & 1550 nm

 

Non-Ref to Non-Ref at all wavelengths

 

                MMF  0.50  dB           (new value)

                  SMF  0.75  dB           (new value)

 

  MMF & SMF  0.75  dB

Splice                        at    850 & 1300 nm

at  1310 & 1550 nm

 

                          0.30  dB

MMF    All multimode fibres

at   850 nm

at 1300 nm

 

3.50  dB/km

1.50  dB/km

SMF at 1310 & 1550 nm                   OS1

OS2

1.0   dB/km

0.4   dB/km

 

Ref = Reference Connector             Non-Ref = Non-reference (embedded) Connector

 

8.       Apparent Gains

 

It is expected that the following will continue to be contained in AS/NZS ISO/IEC 14763.3 Ed2.

Apparent gains shall not exceed the measurement uncertainty.   (Appn ZZ2 Cl 5.3.5)

·      Measurement uncertainty using the enhanced three-test-cord reference method for;

MMF is ≤0.09 dB and SMF is ≤0.11 dB. 7

·      Measurement uncertainty using the one-test-cord reference method for;

MMF is ≤0.09 dB and SMF is ≤0.11 dB. 7

 

9.       Mated Connections in Close Proximity

 

It is expected that the following will continue to be contained in AS/NZS ISO/IEC 14763.3 Ed2.

 

Mated connections in close proximity shall be considered as two mated connector interfaces when determining optical attenuation budget.8 

Applies to MPO Cassettes, Stub connectors, Pigtails.

 

10.   Measurement Uncertainty

The measurement uncertainty for MMF is the same for both the one-test-cord reference and the enhanced three-test-cord reference methods.

The measurement uncertainty for SMF is the same for both the one-test-cord reference and the enhanced three-test-cord reference methods.

 

References

 

1  ISO/IEC 14763.3 Ed2: 2014

2  ISO/IEC 14763.3 Ed2: 2014  Clause 6.3.3.1

3  ISO/IEC 14763.3 Ed2: 2014  Clause D.1

4  ISO/IEC 14763.3 Ed2: 2014  Clause 6.4

5  ISO/IEC 14763.3 Ed2: 2014  Clause 6.5

6  ISO/IEC 14763.3 Ed2: 2014  Clause D.2

7  AS/NZS CT001-02 Calculation V5.8

8  AS/NZS ISO/IEC 14763.3:2012 Appn ZZ2 Cl 9.1.1.3

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