Fiber Optics Essay Research Paper Fiber OpticsFiber

Fiber Optics Essay, Research Paper

Fiber Optics

Fiber Optic Cable Facts

“A relatively new technology with vast potential importance, fiber optics is the

channeled transmission of light through hair-thin glass fibers.”

[ Less expensive than copper cables

[ Raw material is silica sand

[ Less expensive to maintain If damaged, restoration time is faster

(although more users are affected)

[ Backbone to the Information Superhighway

Information (data and voice) is transmitted through the fiber digitally by

the use of high speed LASERs (Light Amplification through the Simulated Emission

of Radiation) or LEDs (Light Emitting Diodes). Each of these methods create a

highly focused beam of light that is cycled on and off at very high speeds.

Computers at the transmitting end convert data or voice into “bits” of

information. The information is then sent through the fiber by the presence, or

lack, of light. Computers on the receiving end convert the light back into data

or voice, so it can be used.

ORIGIN OF FIBER OPTICS

Information (data and voice) is transmitted through the fiber digitally by

the use of high speed LASERs (Light Amplification through the Simulated Emission

of Radiation) or LEDs (Light Emitting Diodes). Each of these methods create a

highly focused beam of light that is cycled on and off at very high speeds.

Computers at the transmitting end convert data or voice into “bits” of

information. The information is then sent through the fiber by the presence, or

lack, of light. So, all of the data is sent light pulses. Computers on the

receiving end convert the light back into data or voice, so it can be used.

All of this seems to be a very “modern” concept, and the technology we use

is. The concept though, was the idea of Alexander Graham Bell in the late 1800’s.

He just didn’t have a dependable light source… some days the sun doesn’t

shine! He thought of the idea that our voices could be transmitted by pulses of

light. The people who thought that audio, video, and other forms of data could

be transmitted by light through cables, were present day scientists. Most of

the things that are possible today, Alexander Grahm Bell could never even have

dreamed of.

Although the possibility of lightwave communications occurred to Alexander

Graham Bell (who invented the telephone), his ideas couldn’t be used until the

LASER or LED had been invented. Most of these advances occurred in the 1970s,

and by 1977 glass-purifying and other fiber-optic manufacturing techniques had

also reached the stage where interoffice lightwave communications were possible.

With further technological development, many intercity routes were in operation

by 1985, and some transoceanic routes had been completed by 1990. Now, in the

mid-90’s, worldwide connections are possible through the Internet.

The light is prevented from escaping the fiber by total internal

reflection, a process that takes place when a light ray travels through a medium

with an Index of Refraction higher than that of the medium surrounding it. Here

the fiber core has a higher refractive index than the material around the core,

and light hitting that material is reflected back into the core, where it

continues to travel down the fiber.

THE PROPAGATION OF LIGHT AND LOSS OF SIGNALS

The glass fibers used in present-day fiber-optic systems are based on

ultrapure fused silica (sand). Fiber made from ordinary glass is so dirty that

impurities reduce signal intensity by a factor of one million in only about 16

ft of fiber. These impurities must be removed before useful long-haul fibers can

be made. But even perfectly pure glass is not completely transparent. It weakens

light in two ways. One, occurring at shorter wavelengths, is a scattering caused

by unavoidable density changes within the fiber. In other words, when the light

changes mediums, the change in density causes interference. The other is a

longer wavelength absorption by atomic vibrations. For silica, the maximum

transparency, occurs in wavelengths in the near infrared, at about 1.5 m

(micrometers).

APPLICATIONS

Fiber-optic technology has been applied in many areas, although its

greatest impact has come in the field of telecommunications, where optical fiber

offers the ability to transmit audio, video, and data information as coded light

pulses. Fiber optics are also used in the field of medicine, all of the wire-

cameras and lights are forms of fiber optic cable. In fact, fiber optics have

quickly become the preferred mode of transmitting communications of all kinds.

Its advantages over older methods of transmitting data are many, and include

greatly increased carrying capacity (due to the very high frequency of light),

lower transmission losses, lower cost of basic materials, much smaller cable

size, and almost complete immunity to any interference. Other applications

include the simple transmission of light for illumination in awkward places,

image guiding for remote viewing, and sensing.

ADVANTAGES OF FIBER OPTIC CABLE

This copper cable contains 3000 individual wires.

It takes two wires to handle one two-way conversation.

That means 1500 calls can be transmitted simultaneously on each cable.

Each fiber optic cable contains twelve fiber wires.

Two fibers will carry the same number of simultaneous conversations as one whole

copper cable.

Therefore, this fiber cables replace six of the larger ones.

And 90,000 calls can be transmitted simultaneously on one fiber optic cable.

LONG DISTANCE

FIBER-OPTIC COMMUNICATIONS SYSTEMS

AT&T’s Northeast Corridor Network, which runs from Virginia to

Massachusetts, uses fiber cables carrying more than 50 fiber pairs. Using a

semiconductor LASER or a light-emitting diode (LED) as the light source, a

transmitter codes the audio or visual input into a series of light pulses,

called bits. These travel along a fiber at a bit-rate of 90 million bits per

second (or 90 thousand kbps). Pulses need boosting, about every 6.2 miles, and

finally reach a receiver, containing a semiconductor photodiode detector (light

sensor), which amplifies, decodes, and regenerates the original audio or visual

information. Silicon integrated circuits control and adjust both transmitter and

receiver operations.

THE FUTURE OF FIBER OPTICS

Light injected into a fiber can adopt any of several zigzag paths, or modes.

When a large number of modes are present they may overlap, for each mode has a

different velocity along the fiber. Mode numbers decrease with decreasing fiber

diameter and with a decreasing difference in refractive index between the fiber

core and the surrounding area. Individual fiber production is quite practical,

and today most high-capacity systems use single fibers. The present pace of

technological advance remains impressive, with the fiber capacity of new systems

doubling every 18 to 24 months. The newest systems operate at more than two

billion bits per second per fiber pair. During the 1990s optical fiber

technology is expected to extend to include both residential telephone and cable

television service.

Currently Bell South is placing fiber cables containing up to 216 fibers,

and manufacturers are starting to build larger ones. Bell South has been

placing fiber cables in the Orlando area since the early 1980s, and currently

has hundreds of miles in service to business and residential customers.

BIBLIOGRAPHY

1. 1995 Grolier Multimedia Encyclopedia, Grolier Electronic Publishing, Inc.

2. 1994 Compton’s Interactive Encyclopedia, Compton’s NewMedia.

3. Fiber Optics abd Lightwave Communications Standard Dictionary, Martin H.

Weik, D.Sc., Van Nostrand Reinhold Company, New York, New York, 1981.

4. Fiber Optics and Laser Handbook, 2nd Edition, Edward L. Stafford, Jr. and

John A. McCann, Tab Books, Inc., Blue Ridge Summit, Pennsylvania, 1988.

5. Fiber Optics and Optoelectronics, Second Edition, Peter K. Cheo, Prentice

Hall, Englewood Cliffs, New Jersey, 1990.