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By the Number: Testing of Fiber Optic Cable

Part 4

By: Jeff Dominique, Chief Instructor

FNT Consulting & Training


Fiber Optic Test Plan Outline to be discussed:

  • Part 1: The subject(s) to be tested.
  • Part 2: The instruments involved in performing the test.
  • Part 3: How the instruments are to be configured for the test.
  • Part 4: Identification of test reference method(s) and reference jumpers or launch cords needed to perform the referencing step.
  • Part 5: Validation and gathering proof of instrument(s) calibration.
  • Part 6: Identification and documentation of "to end(s)” and "from end(s)”.
  • Part 7: Identification of wavelength(s) used to perform the test.
  • Part 8: Identification of job specification test requirement i.e. single direction test or bi-directional test.
  • Part 9: Gathering of information regarding test location, client information.

Identification of test reference method(s) and reference jumpers or launch cords needed to perform the referencing step: Part 4

So why is it important to choose the correct test reference method?

Standards, specifically EIA/TIA 526 identifies three different test reference methods for basic optical loss testing with a power meter and light source, Method A.1, A.2 and A.3. These three methods were created in order to provide a consistent test set-up for either Permanent Link or Channel testing.

Permanent Link testing refers to testing the main portion of the permanently installed network and not necessarily the end to end link which would typically include a patch cable on each end. Channel testing would include a completed end to end link test.

Permanent Link tests are common for brand new installations because more often than not, the user’s end patch cable is not added into the scheme until after computers and end connection devices are installed. This usually occurs long after the network installer has left the job. Channel testing is used more often on older networks for trouble shooting or preventive maintenance testing, which is designed to include both end patch cables.

A.1 is considered the One Jumper Cable Method and is ideally suited for the performance of Channel testing. This test includes, all of the Permanent Link portion of the network as well as the server end patch cable. In this type of test, the main server end of the Permanent Link is often fitted with a certified patch cable which is considered part of the permanent portion of the network. The A.1 One Jumper Method, after a zero reference has been established, provides the test technician with a power meter connected to a certified jumper on one end with a plug type configuration. The opposite end (or) source is disconnected from the One Jumper Patch Cable, setting up a socket configuration. Hence, the A.1 Test Reference Method offers one plug end and one socket end for tying into the network.

The A.2 Two Jumper Cable Method is probably the most popular of all the methods because it can be configured with both ends being socket (with the addition of another coupler) or with both ends being plug configured by eliminating the center coupler after the zero function has been accomplished. This allows the A.2 Reference Method to perform either Channel or Permanent Link Testing. In addition, when bi-directional testing is specified, no special reconfiguration steps are required.

Reference Method A.3 was developed by Standards to accommodate dissimilar end connections. The best way that I can tell you to implement this Method is to obtain three quality certified conversion patch cables with various end connections. Let’s say that your network has LC connector styles on one end and SC connectors on the other. If your source and meter have SC port configurations, what you will need to use the A.3 Test Reference Method is two SC to LC patch cables and one SC to SC patch cable. Plug the SC ends of one of the SC to LC patch cables into your source and plug the SC to SC patch cable into your power meter. Add-in two couplers to the circuit, one SC/SC and the other LC/LC then add the third jumper (the extra SC to LC) into the equation. After Zero Function has been complete, remove the center jumper to create two ends of different connector configurations (one LC and the other SC). Leave the couplers on for Channel Testing or remove the two couples for Permanent Link Testing.

In regard to testing with the OTDR, the only way that the test technician can legitimately reference and set up an acceptance test is to perform a bi-directional test, then average the two trace loss values or to install a certified launch cable on the front end as well as a certified launch cable on the far end. When using the two launch cable method, it is not necessary to perform a bi-directional test.

FNT Instructors Recommend

Standards identify three different test reference methods for basic optical loss testing, A.1, A.2, and A.3.

These methods were created to provide a consistent test set-up for Permanent Link or Channel testing. A.1 is the One Jumper Cable Method, ideally suited for the performance of Channel testing.

A.1 Test Reference Method offers one plug end and one socket end for tying into the network. The A.2 Two Jumper Cable Method is the most popular of all methods because it can be configured with both ends being socket or with both ends being plug configured by eliminating the center coupler after the zero function has been accomplished.

This allows the A.2 Reference Method to perform either Channel or Permanent Link Testing. Reference Method A.3 was developed by Standards to accommodate dissimilar end connections.

OTDR testing requires a test technician to set up an acceptance test is to perform a bi-directional test, and then average the two trace loss values or install a certified launch cable.

 

Part 5: Validation and gathering proof of instrument(s) calibration.

Sources: FNT Fiber Network Training and Consulting Services, Certified Test Technician Course June 2013, ANSI EIA/TIA 568 C, ANSI EIA/TIA 526-7, ANSI EIA/TIA 526-14, ANSI EIA/TIA 606A, ANSI EIA/TIA TSB140 IEEE 1682-2011, IEEE 1428-2004

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