TABLE OF CONTENTS Even the simplest fiber optic link is a triumph of innovative design, manufacturing precision, and technical creativity. One of the factors contributing to the high data rates and long transmission distances of fiber optics is knowledge of the principles of light. While the optical fiber is the transmission medium, light is the carrier on which the signals are imposed. Its small wavelengths and high transmission velocity make possible bandwidths that would be unimaginable using other forms of transmission. In order to get the best performance from every part of the fiber optic link, it is important to understand the characteristics of light and the factors within the fiber optic link that affect it.
This chapter describes the basic characteristics of light, especially the type of light used in fiber optic communications. It also discusses the principles and materials that make fiber optic communications possible, along with some of the problems that must be overcome.
Whether it comes from the sun, an electric bulb, or a laser, all light is a form of electromagnetic energy. Electromagnetic energy is emitted by any object that has a temperature above absolute zero ( ?273 C), which means that the atoms in the object are in motion. The electrons orbiting the atoms pick up energy from the motion, and the energy causes them to move to higher orbits, or energy levels. As they drop back to their original energy levels, they release the energy again. The energy takes two forms:...
