By: Juan C. Zapata
Introduction to Management Information Systems
Professor: John Khayata
Embry Riddle University
September 20, 2011
TABLE OF CONTENTS:
II. HISTORY OF FIBER OPTICS
III. HOW FIBER OPTICS WORK
IV. ADVANTAGES OF OPTICAL FIBERS
V. DIGITAL ENCODING
VI. TRANS-OCEANIC CABLES
The fiber-optic communication theory has been around us for years. In the last decades, this theory has changed the world of communications making possible to send messages over great distances in matter of fractions of a second by using the technology of transmitting digital signals over a simple optical fiber. These fiber-optic transmissions use pulses of laser-generated light and offer significant advantages in terms of reduced size and installations, greater communication capacity, much faster transmission speeds and freedom from electrical interface.
HISTORY OF FIBER-OPTICS
Guiding light through a transparent medium was first demonstrated in the early 1850s by John Tyndell an Irish scientist and mathematician. In his experiment he demonstrated that light was guided along a stream of water flowing down from a container and this light would follow the bend of the water stream down to the catching container. This demonstration proved that light did not need to travel in straight line (see figure 1). But, it was not until 1880 after his telephone invention in 1876 that Alexander Graham Bell invented what was known as the Photophone (fig 2). Using the same principle of Tyndell’s experiment—light reflection and refraction, in 1880 Graham Bell was able to use this device to transmit a sound through a beam of light. Graham Bell and his assistant used a sensitive selenium crystal and a mirror that would vibrate in response to a sound. On June 3, 1880 Alexander Graham Bell sent the first wireless telephone communication over a beam of light. Bell described his invention as:
We have found that the simplest form of apparatus for producing the effect (transmitter/modulator) consists of a plane of mirror of flexible material against the back of which the speaker’s voice is directed. Under the action of the voice the mirror becomes alternately convex and concave and thus alternately scatters and condenses the light. Graham Bell’s invention is the origin of today’s laser and fiber-optics communication and information systems although; it would take years for the development of reliable information carrying channels.
HOW FIBER-OPTICS WORK
Fiber-optics work using the principles of light reflection and refraction. The optical fiber is a small glass cylinder with a core made out of extremely pure optical glass and a cladding—mirror-like walls. As the light enters the optical fiber it changes its direction due to a phenomenon known as Refractive Index. Refractive Index is defined as the change of angle and speed of a wave when it passes from one medium of propagation to another. Once the light has changed its angle of travel and its speed, it starts bouncing off, of the cladding material. The speed that the signal can travel along the core in the optical fiber can be around 200,000 meters per second (125,000 miles). This means that a phone call from New York City to Sidney, Australia (12,000 kilometers) will have a delay of about 60 milliseconds; of course there would be additional delays due to communication equipment and the process of encoding and decoding the digital signals into voice. Generally the materials used to make the glass optical fibers is silica. Silica offers special properties that make the material very desirable from fiber-optic use. For example,...