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By the Number: Testing of Fiber Optic Cable

Part 1

By: Jeff Dominique, Chief Instructor

FNT Consulting & Training


Testing fiber optic cable can be a complex task. First and foremost, one must always start with a test plan, no matter how big or small the test process may seem. When developing your test plan, consider that each and every test shot performed must show a direct correlation to that which was being tested in the field. A clean and understandable test report shows the client that you know what you are doing and that you understand the Standards Documents that govern the test to be performed. A bad or non-correlating test report often means that the client will return it to you to re-do, which could be a costly proposition.

Over the next several months be sure to stay connected with FNT for the Instructor Tip Test Plan Series.

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.

The Subjects to be Tested: Part 1

Within the test plan, it is important to uniquely identify what is to be tested. This becomes increasingly important as the number of overall tests to be performed increases. For example, a multi-strand test of a fiber cable consisting of 12 individual strands to be tested would be far less complex than a cable with 144 strands, simply because of repetitive color codes. In a cable with 12 individual strands, there is just one blue fiber, whereas in a cable with 144 strands, there are 12 blue fibers. Therefore, in a 144 strand fiber cable you have to uniquely identify, which of the 12 blue fibers you’re testing at any given moment and there must be a unique correlation to the final test document representing that fiber.

I have found that because the auto-save/auto-numbering system on many test instruments consists of a 1,2,3, consecutive order generic format, trying to correlate the green fiber in the red tube to the saved test number of 75 can be quite perplexing to the test evaluation engineer, as well as the person performing the test. This can be especially confusing if any re-tests are required in those first 74 tests. For this reason, it is very important for the person performing the test to learn how to set up the job and trace information in the instruments directory in order to keep track of which particular fiber you are testing.

A good way to stay on top of what you are testing, is to first establish exactly what is being tested in the directory and then make directory setting changes between fiber groupings. An example of this would be to make a directory change when you change from one tube (typically every 12 fibers tested) to another and again when you start testing a whole new cable.

The directory change that you would make between fiber optic tubes would be relatively simple, with only a tube color change required, "say blue to orange”. Once you make this change, most test instruments will re-set to the #1 test position. For example Blue 1 through 12, Orange 1 through 12 and so on. Changing from one cable to another would be a bit more complex and may include such directory changes as: cable number, "from end” or "to end” equipment identification and possibly even wavelength changes because the operational wavelength of the link or cable changed.

FNT Instructors Recommend

It is very important for the person performing the test to learn how to set up the job and trace information in the instruments directory in order to keep track of which particular fiber you are testing. FNT suggests to make a directory change for each tube (typically every 12 fibers tested) and again when you start testing a new cable.

Note, changing from one cable to another is more complex and can include directory changes for cable number, "from end” or "to end” equipment identification and even wavelength changes. Implementing this strategy in testing allows for easy identification.

Part 2 will cover the instruments involved in performing the test.

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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