Fiber Optics Basics

Fiber optic technology is simply the use of light to transmit data. The
general use of fiber optics did not begin until the 1970s. Robert Maurer of
Corning Glass Works developed a fiber with a loss of 20 dB/km,
promoting the commercial use of fiber. Since that time the use of fiber
optics has increased dramatically. Advances in fiber technology, lower
production costs, and installation have all contributed to the wide use of
fiber.
The purpose of this paper is to provide an overview of fiber, its
construction, and functionality.
The heaviest use of fiber is in the telecommunications industry. Telephone
companies initially used fiber to transport high volumes of voice traffic
between central office locations. During the 1980s telephone companies
began to deploy fiber throughout their networks. Fiber technology allows
companies to "future proof" networks. We use the phrase "future proof"
because fiber is theoretically unlimited in bandwidth. Bandwidth is a
measurement of the data carrying capacity of the media (in this case,
fiber). The greater the bandwidth, the more data or information that can
be transmitted. Copper has a bandwidth and a distance limitation,
making it less desirable.
Benefits of fiber include:
„ High bandwidth for voice, video and data applications
„ Optical fiber can carry thousands of times more information than
copper wire. For example, a single-strand fiber strand could carry all
the telephone conversations in the United States at peak hour
„ Fiber is more lightweight than copper. Copper cable equals
approximately 80 lbs./1000 feet while fiber weighs about 9
lbs./1000 feet
„ Low loss. The higher frequency, the greater the signal loss using
copper cabling. With fiber, the signal loss is the same across
frequencies, except at the very highest frequencies
„ Reliability - Fiber is more reliable than copper and has a longer life
span
„ Secure - Fiber does not emit electromagnetic interference and is
difficult to tap
Optical fiber is composed of several elements. The construction of a fiber
optic cable consists of a core, cladding, coating buffer, strength member
and outer jacket. The optic core is the light-carrying element at the center.
The core is usually made up of a combination of silica and germania.
The cladding surrounding the core is made of pure silica. The cladding
has a slightly lower index of refraction than the core. The lower refractive
index causes the light in the core to reflect off the cladding and stay
within the core.
Index of refraction is the ratio of the velocity of light in a vacuum to the
velocity of light in a material. The speed of light in a vacuum is equal to
300,000,000 meters per second.The higher the index of refraction, the
slower the speed of light through the material.
Index of Refraction = Light velocity (vacuum)
Light velocity (material)
For example:
Air = 300,000,000 meters/second
IR = 1
Glass = 200,000,000 meters/second
IR = 1.5
Fiber is either single mode or multimode. Fiber sizes are expressed by
using two numbers: 8/125. The first number refers to the core size in
microns. The second number refers to the core size plus the cladding size
combined