The document is an assignment on optical fiber communication, detailing the history, operation, and uses of optical fibers. Optical fibers are essential for telecommunications and various applications such as lighting, sensors, and medical instruments. The assignment highlights the principles of fiber optics and discusses key developments and figures in the field, such as Charles K. Kao, who contributed to making fiber optics a practical communication medium.

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National University of Modern Languages
Islamabad
Optical Fiber Communication
Assignment# 01
Hassaan Ashraf
Roll # 11050
BEEE 7th
Semester

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Table of Content
History............................................................................................................................................. 4
How its works ................................................................................................................................. 4
Fiber-optic Communication............................................................................................................ 5
Uses of Optical Fiber……………………………………………………………………………...6

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List of Figure
Figure 1: Layers of Optical Fiber.................................................................................................... 5
Figure 2: TOSLINK Plug................................................................................................................ 6
Figure 3: Bundle of Fiber................................................................................................................ 7

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Optical Fiber
An optical fiber is a thin fiber of glass or plastic that can carry light from one end to the other.
The study of optical fibers is called fiber optics, which is part of applied science and engineering.
Optical fibers are mainly used in telecommunications, but they are also used for lighting,
sensors, toys, and special cameras for seeing inside small spaces. It is sometimes used in
medicine to see inside people, like down their throat.
1. History
Guiding light by internal reflection, the principle that makes fiber optics possible, was first
demonstrated by Daniel Colladon and Jacques Babinet in Paris in the early 1840s. John Tyndall
included a demonstration of it in his public lectures in London, 12 years later. Heinrich Lamm
first used the principle for internal medical examinations in the 1930s. Modern optical fibers,
where the glass fiber is coated with a transparent cladding to offer a more suitable refractive
index, appeared later in the decade. Charles K. Kao and George A. Hockham of the British
company Standard Telephones and Cables (STC) were the first to show that the loss of intensity
in optical fibers could be reduced, making fibers a practical communication medium.[2]
They
proposed that the defect in fibers available at the time was caused by impurities that could be
removed. They pointed out the right material to use for such fibers, such as silica glass that has
high purity. This discovery earned Kao the Nobel Prize in Physics in 2009.
2. How it works
An optical fiber is a long, thin strand of clear material. Its shape is usually similar to a cylinder.
In the center, it has a core. Around the core is a layer called the cladding. The core and cladding
are made of different kinds of glass or plastic, so that light travels slower in the core than it does
in the cladding. If the light in the core hits the edge of the cladding at a shallow angle, it bounces
off. Light can travel inside the core and bounce off of the cladding. No light escapes until it
comes to the end of the fiber, unless the fiber is bent sharply or stretched.
If the cladding of the fiber is scratched, it may break. A plastic coating called the buffer covers
the cladding to protect it. Often, the buffered fiber is put inside an even tougher layer, called the
jacket. This makes it easy to use the fiber without breaking it.

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In Figure 1, The layers in one kind of optical fiber.
1: Core 8 µm
2: Cladding 125 µm
3: Buffer 250 µm
4: Jacket 400 µm
Figure 1: Layers of Optical Fiber
3. Fiber-optic Communication
Fiber-optic communication is a method of transmitting information from one place to another by
sending pulses of light through an optical fiber. The light forms an electromagnetic carrier wave
that is modulated to carry information. First developed in the 1970s, fiber-optic communication
systems have revolutionized the telecommunications industry and have played a major role in the
advent of the Information Age. Because of its advantages over electrical transmission, optical
fibers have largely replaced copper wire communications in core networks in the developed
world.
Most optical communication systems have electrical connections. An electric signal controls a
transmitter. The transmitter converts the electric signal to a light signal and sends it through the
fiber to the receiver. The receiver converts the light signal back to an electric signal. In some
systems a series of these links carry the signal far.

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4. Uses of Optical Fiber
The main use of optical fiber is in long-distance communication (telecommunication). Since the
light does not leak out of the fiber much as it travels, the light can go a long distance before the
signal gets too weak. This is used to send telephone and internet signals between cities.
Fiber is sometimes used for shorter links too, such as to carry the sound signals between a
compact disc player and a stereo receiver. The fibers used for these short links are often made of
plastic. TOSLINK is the most common type of optical plug for stereos.
Figure 2: TOSLINK Plug
Optical fibers can be used as sensors. Special fibers are used for this, that change how they pass
light through when there is a change around the fiber. Sensors like this can be used to detect
changes in temperature, pressure, and other things. These sensors are useful because they are
small and do not need any electricity at the place where the sensing happens.
A bundle of fibers can be used to make a device called an endoscope or a fiberscope. This is a
long thin probe that can be put into a small hole, that will send an image of what is inside
through the fiber to a camera. Endoscopes are used by doctors to see inside the human body, and
are sometimes used by engineers to see inside tight spaces in machines.

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Figure 3: Bundle of Fiber
Optical fibers (with special chemicals added) can be used as optical amplifiers. This allows an
optical signal to travel further between endpoints, and without converting, the optical signal to
electrical and back, reducing the overall cost of the components. These optical amplifiers can
also be used to create Lasers. These are called fiber lasers. They can be very powerful, because
the long thin fiber is easy to keep cool, and makes a good quality light beam.

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References
1.Bates, Regis J. 2001. Optical switching and networking handbook. New York: McGraw-Hill.
p. 10.
2.Hecht, Jeff 1999. City of light, the story of fiber optics. New York: Oxford University Press.
p. 114.