Fiber U Self-Study 

Understanding OTDRs (Optical Time Domain Reflectometers)

What You Will Learn In This Basic Self-Study Program:

  • What is an OTDR - optical time domain reflectometer?
  • How is it used in testing optical fiber and cable?
  • What information is in the OTDR trace?
  • How does an OTDR work differently from a light source and power meter or OLTS (optical loss test set)?
  • How do you make measurements of fiber length and attenuation or splice/connector loss and reflectance?
  • How does one set OTDR test parameters correctly?
  • What is the measurement uncertainty of the OTDR test?
  • What are "gainers" and "ghosts"?
  • Practice analyzing traces with an OTDR Simulator

Includes a PC-OTDR Simulator

This self-study course may be used as preparation for the CFOS/T Certification Exam

teting with an OTDR

OTDRs are one of the most powerful tools for fiber optic testing but are also one of the most complicated and, based on the questions we get at FOA, misunderstood and misused. There are two issues, 1) understanding how to use the instrument itself with all the controls needed to operate it and 2) understanding how OTDRs make measurements and how to interpret the results. Manufacturers tend to focus on teaching you how to use the instrument or often tell you the instrument is smarter than you and just use the "autotest" button, instructions that have proven to cause expensive problems. This course is designed to focus on #2 - understanding how the OTDR works and how to interpret the OTDR data.

This course draws on two other Fiber U Courses, Fiber Optic Testing and the Fiber Optic Basic Skills Lab. To complete the lessons, you should use the links to the lesson plans and complete these exercises. You may return to this course to get your Certificate of Completion.

How This Self-Study Program Works:

This Fiber U self-study program has lessons with links to read about OTDRs and an OTDR Simulator to use for practice. Complete the online quizzes to test your comprehension, returning to the study materials to find out why you missed any questions. When you finish all lessons, you should download the OTDR Simulator and practice.

It is assumed that the student has a basic knowledge of fiber optics at least at the basic CFOT or CPCT level. Review of basic fiber optics can be done on the Fiber U website with either the Basic Fiber Optics, Premises Cabling or OSP Fiber Optics self-study courses or by viewing videos on the FOA YouTube channel "thefoainc."

Learning More and Developing Skills

If you are just getting started, you should consider attending an FOA-Approved school where you will be trained in hands-on labs to develop the skills needed to be successful in fiber optics. If you are already a CFOT with field experience, you should consider working toward the FOA CFOS/T specialist certification in fiber optic testing.

Lesson Plan:

Read the materials linked on each lesson plan and use the OTDR Simulator to practice analyzing OTDR traces.

Fiber Optic Testing, Lesson 5: OTDR Testing  Complete the entire lesson and take the quiz.

Reading An OTDR Trace Fiber U MiniCourse

Basic Fiber Optic Skills Lab, Testing 
Complete the exercises under the "OTDR Testing" section, including downloading the OTDR simulator and practicing analyzing traces.

Fiber U Certificate
Get a "Fiber U Certificate of Completion" When You Complete The Course
After you complete the Fiber U online self-study course, you can now take an online exam and, when you pass the exam, get a "Certificate of Completion" for this course. You should complete all lessons including taking the quiz ("Test Your Comprehension") at the end of every lesson. When you think you are prepared, you can take an online exam for a nominal fee ($20) which will give you
a "Certificate of Completion" for this course.

If you are working on FOA certification, print out (PDF) your completed case studies from Lesson 8 and save along with your Fiber U Certificate of Completion for your application for certification.

When you finish all lessons, go here to take the Fiber U Fiber Optic Testing Certificate of Completion Exam  

Please note: receiving this Fiber U Certificate of Completion does not include FOA certification or membership but it does become documentation of your knowledge of fiber optics and should be part of your portfolio of documented knowledge, other training and work experience that can qualify you to apply for FOA direct CFOT certification through the FOA "Work to Cert" program.

More details on getting a Fiber U Certificate of Completion are on the last lesson. Read more about the Fiber U Certificate of Completion program.

For more information on the FOA and its certification programs, go to the FOA page on certification.

For information on the FOA "Work to Cert" direct certification program for those with industry experience, go here.

This information is provided by The Fiber Optic Association, Inc. as a benefit tothose interested in teaching, designing, manufacturing, selling, installing or using fiber optic communications systems or networks. It is intended to be used as aoverview and/or basic guidelines and in no way should be considered to be complete or comprehensive. These guidelines are strictly the opinion of the FOAand the reader is expected to use them as a basis for learning, as a reference and for creating their own documentation, project specifications, etc. Thoseworking with fiber optics in the classroom, laboratory or field should follow all safety rules carefully. The FOA assumes no liability for the use of any ofthis material.


Table of Contents: The FOA Reference Guide To Fiber Optics

(C)2015, The Fiber Optic Association, Inc.