Fiber Optic Serial Communication

Roy Timpe, P.E.

Course Outline

Fiber optic communication systems have enabled the affordability and ubiquity of the Internet, as well as their earlier application in telephony. These systems are found within buildings, corporate campuses,  undersea cables, and long haul trunk lines between cities.  This four hour online course discusses the most common method used to send data down a fiber. Various factors signal degradation are discussed.  Metrics for signal quality are explained. The student will also be able to identify and avoid some safety issues with the installation and use of these devices.  

This course includes a multiple-choice quiz at the end, which is designed to enhance the understanding of the course materials.

Learning Objective

At the conclusion of this course, the student will:

• Understand how the light used to send serial digital data down a fiber;
• Be able to recognize how low pass filtering, wavelength dispersion, and modal dispersion all effect signal quality;
• Understand the theory of how a sampling oscilloscope functions;
• Understand how to display an EYE diagram on an oscilloscope, and understand the value of the EYE diagram in evaluating the quality of the data;
• Understand how a sampling oscilloscope along with an EYE mask is used to test a laser transmitter;
• Understand the principles of Bit Error Rate Testing using a stressed EYE signal, and how it is a good method to evaluate optical receivers; and
• Be able to use a sampling oscilloscope to measure the signal to noise ratio of an optical signal while properly accounting for the background noise present in the oscilloscope.

Intended Audience

This course is intended for engineers and contractors.

Benefit for Attendee

Attendee of this course will understand how the data is degraded as it propagates down the fiber.  The attendee will also understand how Bit Error Rate testing with stressed EYE signals per I.E.E.E. specifications has assured that system components are interchangeable. The attendee will see how the IEEE 802.3aq standard for 10GBASE-LRM has facilitated the reuse of older installed multi-mode fiber at ten times its intended bit rate.  In addition, the attendee will understand the safety issues associated with these systems.

Course Introduction

Nearly all data sent down optical fibers is NRZ digital data.  Physical phenomenon such as the bandwidth of components, dispersion and attenuation in fiber, as well as noise all work together to degrade the signal.  Older test methodologies did not properly account for all of these real world signal degradations.  This resulted in a situation where components in systems were not always interchangeable.

Testing components with signals that mimicked the real world degradation was needed to assure interchangeability.   Methods of evaluating these signals are introduced.  Measuring each of the signal degradations is introduced.  The concept of Bit Error Rate testing is explained.  Each of these methods are discussed, along with laser safety as it relates to fiber systems.  

Course Content

The course content is contained in the following PDF file:

Fiber Optic Serial Communication

Please click on the above underlined hypertext to view, download or print the document for your study. Because of the large file size, we recommend that you first save the file to your computer by right clicking the mouse and choosing "Save Target As ...", and then open the file in Adobe Acrobat Reader. If you still experience any difficulty in downloading or opening this file, you may need to close some applications or reboot your computer to free up some memory.

Course Summary

Optical transmitters, optical receivers, and the fiber itself comprise the physical layer of these modern communication systems.  Bandwidth of these components, fiber dispersion and attenuation, as well as noise all work together to degrade the signal.   These signal degradations need to be characterized and accounted for to assure a system will function properly when deployed.

Quiz

Once you finish studying the above course content, you need to take a quiz to obtain the PDH credits.

---

DISCLAIMER: The materials contained in the online course are not intended as a representation or warranty on the part of PDH Center or any other person/organization named herein. The materials are for general information only. They are not a substitute for competent professional advice. Application of this information to a specific project should be reviewed by a registered architect and/or professional engineer/surveyor. Anyone making use of the information set forth herein does so at their own risk and assumes any and all resulting liability arising therefrom.

---