Print this page Fiber Optics I - Theory
Lee Layton, P.E.
Course Outline
Volume I is divided into three chapters. Chapter one covers the theory of light transmission including wave motion and the transmission of energy.
Chapter two covers the transmission of light along optical fibers and discusses the structure of an optical fiber. Two methods are used to describe how light is transmitted along the optical fiber. The first method, ray theory, uses the concepts of light reflection and refraction. The second method, mode theory, treats light as electromagnetic waves. The basic optical properties of the materials used to make optical fibers and how these properties affect how light is transmitted through the fiber is discussed.
Chapter three describes the classification of optical fibers. Optical fibers are classified into two types. The first type is single mode fibers. The second type is multimode fibers. As each name implies, optical fibers are classified by the number of modes that propagate along the fiber.
At the end of the course is a summary of the key terms presented.
This course includes a multiple-choice quiz at the end, which is designed to enhance the understanding of the course materials.
Learning Objective
Upon completing course, you should be able to do the following:
- Describe fiber optics;
- List the parts of a fiber optic data link;
- Understand the function of each fiber optic data link part;
- Describe the trade-offs in fiber properties and component selection in the design of fiber optic systems;
- List the advantages and the disadvantages of fiber optic systems compared to electrical communications systems;
- Discuss the electromagnetic theory of light;
- Describe the properties of light reflection, refraction, diffusion, and absorption. Explain how optical fibers transmit light;
- Identify the basic optical fiber material properties;
- Describe the ray and mode theories of light propagation along an optical fiber;
- State the difference between multimode and single mode optical fibers;
- Explain how optical fibers attenuate and distort light signals; and
- Understand the processes of light attenuation and dispersion.
Intended Audience
This course is intended for electrical engineers and others who want to learn more about fiber optic cables.
Benefit to Attendees
Fiber optic cables are becoming the backbone for all ground-based communications in the world. This course will give you a thorough understanding of data is transmitted using light and how fiber optic cables are designed, built, and used.
Course Introduction
Electrical systems include telephone, radio, cable television (CATV), radar, and satellite links. In the past 30 years, researchers have developed a new technology that offers greater data rates over longer distances at costs lower than copper wire systems. This technology is fiber optics.
Fiber optics uses light to send information (data). Fiber optics is the branch of optical technology concerned with the transmission of radiant power (light energy) through fibers.
A fiber optic data link sends input data through fiber optic components and provides this data as output information. It has the following three basic functions:
- To convert an electrical input signal to an optical signal
- To send the optical signal over an optical fiber
- To convert the optical signal back to an electrical signal
A fiber optic data link consists of three parts - transmitter, optical fiber, and receiver.
A fiber optic data link needs a transmitter that can effectively convert an electrical input signal to an optical signal and launch the data-containing light down the optical fiber. A fiber optic data link also needs a receiver that can effectively transform this optical signal back into its original form. This means that the electrical signal provided as data output should exactly match the electrical signal provided as data input.
The transmitter converts the input signal to an optical signal suitable for transmission. The transmitter consists of two parts, an interface circuit and a source drive circuit. The transmitter's drive circuit converts the electrical signals to an optical signal.
The optical source launches the optical signal into the fiber. The optical signal will become progressively weakened and distorted because of scattering, absorption, and dispersion mechanisms in the fiber waveguides.
The receiver converts the optical signal exiting the fiber back into an electrical signal. The receiver consists of two parts, the optical detector and the signal-conditioning circuits. An optical detector detects the optical signal. The signal-conditioning circuit conditions the detector output so that the receiver output matches the original input to the transmitter. Noise effects and limitations of the signal-conditioning circuits cause the distortion of the receiver's electrical output signal.
Much of this information is covered in subsequent courses. In this course, Volume I, we will look at the properties of light, how light is transmitted through optical fibers, and the types of optical fibers.
Course Content
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Course Summary
Fiber optics is the branch of optical technology concerned with the transmission of radiant power (light energy) through fibers. A fiber optic data link has three basic functions: to convert an electrical input signal to an optical signal, to send the optical signal over an optical fiber, and to convert the optical signal back to an electrical signal. It consists of three parts: transmitter, optical fiber, and receiver. The transmitter consists of two parts, an interface circuit and a source drive circuit. The transmitter converts the electrical input signal to an optical signal by varying the current flow through the light source. The receiver consists of two parts, the optical detector and signal conditioning circuits. The receiver converts the optical signal exiting the fiber back into the original form of the electrical input signal.
In this course, we have introduced fiber optic data transmission and looked at the theory behind fiber optic data transmission. Subsequent courses will cover the design, manufacturing, testing, and other components of a fiber optic system.
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.
