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

Text in Blue Italics is derived from the standards

1. Applicability

The following applies only to telecommunication cabling installations in Australia and New Zealand seeking performance conformance of optical fibre permanent links and links to AS/NZS 3080 using ISO/IEC 14763-3 Ed2 2014 light source and power meter (LSPM) testing methods.

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.

This Technical Note explains the enhanced three-test-cord reference method for testing optical fibre permanent links and links using the LSPM test method in ISO/IEC 14763-3 Ed2 2014.

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

Appn ZZ2 Cl 9.1.1.2 of AS/NZS ISO/IEC 14763.3:2012 states;
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.

5. Test Cords

The three-test-cord reference method uses the following test cords (2);
       LTC Launch Test Cord (1 - 5 m with reference connector at link interface end)
       STC Substitution Test Cord (1 - 5 m with reference connector at link interface end)
       TTC Tail Test Cord (1 - 5 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, except if tester source already meets this condition.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.


The max attenuation of the two reference-to-reference connector sets must be less than;
    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 refrence if necessary. Use Alternate cords if necesssay.

6.6. Remove the STC and reference adaptors; connect the LTC and TTC to the 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, it is strongly recommended that 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 AS/NZS ISO/IEC 14763.3: 2012 states;
The calculated limit of testing the link is;
MMF:  Limit = (0.4 dB) + Σ (cable attenuation) + Σ (embedded connector attenuation)
SMF:   Limit = (0.6 dB) + Σ (cable attenuation) + Σ (embedded connector attenuation)


These formulae will be updated to be in line with corrigenda to ISO/IEC 14763-3 Ed2 when adopted by AS/NZS.

Table 6  Allowable Attenuation Values

Component and Wavelength

AS/NZS ISO/IEC 14763-3:2012
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 0.30 dB
SMF 0.50 dB

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

1.00 dB/km
0.40 dB/km

8. Apparent Gains

AS/NZS ISO/IEC 14763.3: 2012 states;
Apparent gains shall not exceed the measurement uncertainty.   (Appn ZZ2 Cl 5.3.5)
 Measurement uncertainty using the 3-test-cord reference method for;
MMF is ≤2 dB, and SMF is ≤0.4 dB 
  (Appn ZZ2  Cl 10.2.2)
Measurement uncertainty using the 1-test-cord reference method for;
MMF and SMF is 0.0 dB 
  (Appn ZZ2  Cl 10.2.2)

9. Mated Connections in Close Proximity

AS/NZS ISO/IEC 14763.3: 2012, Appn ZZ2 Cl 9.1.1.3 states;
Mated connections in close proximity shall be considered as two mated connector interfaces when determining optical attenuation budget. 
Applies to MPO Cassettes, Stub connectors, Pigtails.

10. Measurement Uncertainty

Annex E.1 of ISO/IEC 14763.3 states;
The expected uncertainty 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 3.2
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

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