Fiber U Basics

Lesson 8: Fiber Optic Testing

How are fiber optic cables tested?
Objectives: From this lesson you should learn:
What parameters need to be tested
What instruments are used for fiber optic testing
How to perform basic fiber optic testing
Measurement uncertainty in fiber optic testing
How to troubleshoot problems
Fiber Optic Tests

This lesson, another extensive one, is on fiber optic testing. Testing is the most complex part of fiber optics but one of the most important.

After all fiber optic cables are installed, spliced and terminated, they must be tested. For every fiber optic cable plant, you need to test for continuity and polarity, end-to-end insertion loss and then troubleshoot any problems on every fiber in every cable. If it’s a long outside plant cable with intermediate splices, you will probably want to verify the individual splices with an OTDR test also, since that’s the only way to ensure that each splice is good. If you are the network user, you may also be interested in testing transmitter and receiver power, as power is the measurement that tells you whether the system is operating properly.

Testing involves visual inspection of terminations with a microscope, tracing fibers visually and finding faults, measuring optical power and loss with power meters and light sources and sometimes specialized testing with OTDRs and testers for special issues in long distance links. With this lesson, it's important to learn what needs testing and why, what are the potential errors involved in the tests and where certain tests are appropriate. For example, all installed cable plants require insertion loss testing but some may also need OTDR tests, but OTDR tests are generally not appropriate for short cables and always require a knowledgeable operator to interpret traces - they are not "push button" testers!

Testing gives you data - in this case the loss of the fiber in a cable plant. But does that test data tell you the cable plant loss is good (low enough) or bad (loss is too high)? You need to know that to pass or fail any fiber being tested. The way you estimate the loss of the cable plant is to calculate a "loss budget" for the fibers in a cable plant. Generally the loss budget is done during the design phase of a project and the data used to validate the design for use with communications equipment. But that same data should be used by the installer/tester to compare to test results and make the pass/fail judgement.

The course leads you to read online or printed materials (with an emphasis on the online using the FOA Guide), watch FOA YouTube Videos, complete some activities and take the quizzes. Each lesson plan will be self-contained. Lesson plans open in new pages so the course overview page stays open to lead you to the next lesson or you may use the link at the bottom of the page.

Student Assignment:
Watch the videos, read the references and take the quizzes (Test Your Comprehension)

FOA YouTube Videos:

FOA Lecture 12: Fiber Optic Testing Overview 
FOA Lecture 15: Five Ways To Test Fiber Optic Cable Plants  
FOA Lecture 17: OTDR Testing  
FOA Lecture 26: Loss Budgets 

Optional - Reccommended
FOA Lecture 13: Testing Fiber Visually  
FOA Lecture 14: Testing Optical Power  
FOA Lecture 16: Insertion Loss Testing  
FOA Lecture 18: OTDR Setup  
FOA Lecture 19: OTDR Measurement Uncertainty  
FOA Lecture 20: Other Fiber Optic Tests  
FOA Lecture 21: Visual Fault Locator Demonstration  

Online FOA Reference:

Fiber Optic Testing  
Fiber Optic Test Instruments

5 different Ways To Test Fiber Optic Cables According To International Standards
OTDR testing
FOA Standards, FOA1 to FOA-4
What Loss Should You Expect?, Loss and Power Budgets 

Optional - Reccommended

Visual tracing & fault location
Microscope Inspection of Connectors  
Measuring Optical Power, Units of Measure (dB, dBm) 
Installed Cable Plant Testing (OFSTP-14)  Virtual Hands-On: Insertion loss testing, What Loss Should You Expect?
Patchcord or Single Cable Testing (FOTP-171)

Data Link or Network Testing
OTDR testing  Virtual Hands-On: Using an OTDR

Differences in OTDR and insertion loss measurements

Book Chapter:

Optional - Extra Credit Reading

The fiber optic tester in your pocket 
Reference Cables
Special Applications/Hybrid Cables  
Mismatched Multimode Fiber Losses
Testing cables with different types of connectors.
Loss by Cable Substitution - when other methods will not work
Connector and Splice Loss Testing (FOTP-34)
Testing long haul networks (CD, PMD, Spectral Attenuation)  
FAQs on Fiber Optic Testing  

Optional - Hands-On YouTube Videos
The Fiber Optic Tester In Your Pocket (Using An Old Cell Phone To See Infrared Light)
Insertion Loss Testing 


Test Your Knowledge:

Online Quiz - Testing, Online Quiz - Loss Budgets
Textbook: Take the Quiz at the end of Chapter 8 - Testing and check your answers  

Next: Lesson 9: Fiber Optic Network Design 

Return to Lesson Plan


Table of Contents: The FOA Reference Guide To Fiber Optics

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