FREE ESSAY ON FIBER OPTICS

FIBER OPTICS

Thesis:
Some of the important features of the fiber optics that we are interested are discussed
below.
Now a days we are using copper wires as they are the most cost effective and reliable
interconnect in parallel machines. However as machines grow more powerful, wire density
becomes critical making fiber possible alternatives because of their small wire size. 
Fiber optics are used mainly to use effectively its high bandwidth. On a single fiber
lots of information/data can be transmitted concurrently and in parallel. Over 1000
high bandwidth (100-200 Mb/s) independant channels or busses can be supported on a single
optical fiber. Furthermore multiple buses can co-exist on a single
fiber. Fiber links allow a number of high speed serial links to replace a large number of
electrical lines. The use of fiber is thus space saving.
The input and output properties of the fiber are very important. They give us an idea
about the nature and working of fiber materials. The fiber cables can transport light
signals from one place to another place just similar to the way the metallic conductors
transport electric signals. The fiber cables guide light around bends and they are able
to carry light for very long distances with very little attenuation. But the transmission
characteristics of the fiber are not complete and completely efficient. The fiber cables
introduce loss of light and smearing of the modulation imposed on the light signals to
represent information. These affects of delay distortion and attenuation limit the
distances that can be spanned without electro-optic repeaters and thus limit the
information rates which can be carried over long distances as well.
Make of fiber optic cables. 
Turns out they can be made of just glass, glass plus polymers, or just polymers (plastic
optical fibers -POF-). The most basic optical fiber consist of:
a) An inner cylinder with high refractive index, called the core. 
b) Middle cylinder with a lower refractive index, called the cladding.
c) An outer protective polymer layer (usually polyurethane or PVC) called the jacket.
For glass optical fibers, the diameter of the core ranges between 10-600 microns, the
cladding thickness is between 125-630 microns, and that of
the jacket varies between 250-1040 microns. For POF all diameters range between 750-2000
microns. As can be seen, one of the main differences
between glass and plastic optical fibers is their diameter. This makes POF easier to
handle.
The material used for currently commercialized fibers (core and cladding) include pure
glass (SiO2), plastic, or a combination of both. The use of
one or the other material will be determined by such factors as quality and economics.
Plastic optical fibers (POF) have the advantage of being made of cheaper materials than
glass and to operate in the visible range of the spectrum.
However, they show a high loss, and for that reason their applications are confined to
short distance transmission. In spite of this, POF is widely
used for medical and industrial instruments, and currently research is carried out about
using POF as a replacement of copper wiring for data
transmission in automobiles.
If you use silica glass for the core, it must be high purity in order to allow the light
to be transmitted along the core with minimal loss.
Some of the advantages associated with the use of fiber optic cables are:
1) Immunity to Electromagnetic Interference
Although fiber optics can solve data communications problems, they are not needed
everywhere. Most computer data goes over ordinary wires. Most data is sent over short
distances at low speed. In ordinary environments, it is not practical to use fiber optics
to
transmit data between personal computers and printers as it's too costly. Electromagnetic
Interference is a common type of noise that originates with one of the basic properties
of electromagnetism. Magnetic field lines generate an electrical current as they cut
across
conductors. The flow of electrons in a conductor generates a magnetic field that changes
with the current flow. Electromagnetic Interference does occur in coaxial cables, since
current does cut across the conductor. Fiber optics are immune to this EMI since
signals are transmitted as light instead of current. Thus, they can carry signals through
places where EMI would block transmission. 
2) Data Security
Magnetic fields and current induction work in two ways. They don't just generate noise in
signal carrying conductors; they also let the information on the conductor to be leaked
out. Fluctuations in the induced magnetic field outside a conductor carry the same
information as the current passing through the conductor. Shielding the wire, as in
coaxial cables can reduce the problem, but sometimes shielding can allow enough signal
leak to allow tapping, which is exactly what we wouldn't want. 
There are no radiated magnetic fields around optical fibers; the electromagnetic fields
are confined within the fiber. That makes it impossible to tap the signal being
transmitted through a fiber without cutting into the fiber. Since fiber optics do not
radiate
electromagnetic energy, emissions cannot be intercepted and physically tapping the fiber
takes great skill to do undetected. Thus, the fiber is the most secure medium available
for carrying sensitive data. 
3) Non Conductive Cables
Metal cables can encounter other signal transmission problems because of subtle
variations in electrical potential. Electronic designers assume that ground is a uniform
potential. That is reasonable if ground is a single metal chassis, and it's not too bad
if
ground is a good conductor that extends through a small building. However, the nominal
ground potential can differ by several volts if cables run between different buildings or
sometimes even different parts of the same building. 
Signal levels in semiconductor circuits are just a few volts, creating a problem known as
ground loop. When the difference in ground potential at two ends of a wire gets
comparable to the signal level, stray currents begin to cause noise. If the differences
grow
large enough, they can even damage components. Electric utilities have the biggest
problems because their switching stations and power plants may have large potential
differences. 
A serious concern with outdoor cables in certain computer networks is that they can be
hit by lightning, causing destruction to wires and other cables that are involved in the
network. Certain computer companies are aware of this problem and trying to solve it
by having protective devices for wire circuits to block current and voltage surges. 
Any conductive cables can carry power surges or ground loops. Fiber optic cables can be
made non-conductive by avoiding metal in their design. These kinds of cables are
economical and standard for many indoor applications. Outdoor versions are more
expensive since they require special strength members, but they can still be valuable in
eliminating ground loops and protecting electronic equipment from surge damage. 
4) Eliminating Spark Hazards
In some cases, transmitting signals electrically can be extremely dangerous. Most
electric potentials create small sparks. The sparks ordinarily pose no danger, but can be
really bad in a chemical plant or oil refinery where the air is contaminated with
potentially explosive vapours. One tiny spark can create a big explosion. potential spark
hazards seriously hinder data and communication in such facilities. Fiber optic cables do
not produce sparks since they do not carry current. 
5) Ease Of Installation
Increasing transmission capacity of wire cables generally makes them thicker and more
rigid. Such thick cables can be difficult to install in existing buildings where they
must go through walls and cable ducts. Fiber cables are easier to install since they are
smaller and more flexible. They can also run along the same routes as electric cables
without picking up excessive noise. 
One way to simplify installation in existing buildings is to run cables through
ventilation ducts. However, fire codes require that such plenum cables be made of costly
fire retardant materials that emit little smoke. The advantage of fiber types is that
they are
smaller and hence require less of the costly fire retardant materials. The small size,
lightweight and flexibility of fiber optic cables also make them easier to be used in
temporary or portable installations. 
6) High Bandwidth Over Long Distances 
Fiber optics have a large capacity to carry high speed signals over longer distances
without repeaters than other types of cables. The information carrying capacity increases
with frequency. This however, doesn't mean that optical fiber has infinit bandwidth, but
it's certainly greater than coaxial cables. Generally, coaxial cables have a bandwidth
parameter of a few MHz/km, where else the fiber optic cable has a bandwidth of 400MHz/km.
(These figures are just approximations and do vary from cable to cable!) This is an
important factor that leads to the choice of fiber for data communications. Fiber can be
added to a wire network so it can reach terminals outside its normal range.
Some fo the problems associated with the use of fiber optic cables:
1) System Reconfiguration
Although fiber optics are renowned for their efficiencies and loads of advantages, there
are a few drawbacks in them and one of them is system reconfiguration. Converting
existing hardware and software for the use of fiber optics does take a lot of time and
money which also reduces the turnover for any profit making firm in the market. Sometimes
it may be more convenient to transmit high speed computer data serially ( one bit after
another ) than sending several bits at a time in parallel over separate wires. This
changeover requires modification in both hardware and software. Minor differences can
cause old programs to crash and make data in old files unreadable. Even though the need
for such modifications can be reduced by designing fiber optic systems with interfaces
that look just like electric ones, it would not make most efficient use of fiber
transmission capacity and would increase costs. 
2) Limitations in Local Area Networks
In Local Area Networks, fiber optics is not used as widely as one would expect. One
reason is the implementation requires great deal of changes in current networks and
systems. This requires a lot of time and effort which the management is not willing to
sacrifice. People are comfortable with what they have and don't want to change. Although
most problems regarding program changing can be solved, the solutions to it will take
much longer than expected. Thus, any new program has to be a big improvement over the
old one to justify a significant change (although the great improvement usually means
that the old program does not work). 
Another fundamental problem in fiber optic LANs is the change in technology. The hardware
and software to make LAN run efficiently add up to an expensive package. If many
terminals in a building must be in constant touch with each other and a variety of
other hardware, such as printers and storage devices, LAN will be cost efficient.
However, if the real need is to keep the terminals in touch with a mainframe computer, it
would be cheaper to run cables between them and the mainframe. If the terminals need to
talk to each other, ordinary telephone lines could very well be used as telephone lines
are much cheaper than fiber optics. 
3) Economic Evaluation
The major practical problem with fiber optics is that it usually costs more than ordinary
wires. All costs elements involved in economic evaluation can be grouped into two main
classes; which are investment costs and operation costs. The investment costs
usually includes expenditures related to acquiring and owning properties and plants, in
this case changing wires to fiber optic cables. All investment costs should be
considered, such as those incurred for equipment and materials (also including storage
and handling costs), engineering costs and miscellaneous costs. Operation costs include
the usage of fiber optics and the wear and tear of it. The higher costs of fiber is often
not by itself. Fiber optic cables are much cheaper than coaxial cables. The main
difference comes when all the other components of fiber optics add up, such as
transmitters, receivers, couplers and connectors. Fiber systems require separate
transmitters and receivers because they cannot directly use the electrical output of
computer devices; that signal must be converted into optical form and then converted back
into electrical form. Fiber optic connectors and couplers are more expensive than any
other electrical components. These costs are the ones that add up and form the major
disadvantage of fiber optics.
Conclusion:
Fiber optic transmission has found a vast array of applications in computer systems. Some
design considerations depend largely on the application. For
certain terminal to terminal application, crucial factors including maximising
transmission speed and distance and minimising fiber and splice loss. By contrast,
connector loss becomes important in local area networks that operate within buildings. In
other systems, it is important to minimise the cost of cable, with the
intention of reducing the cost of terminal equipment. These system considerations make
design and construction of practical fiber optic systems a difficult task.
Guidelines appropriate for one system is usually not suitable for another system. 
There are a number of essential points about fiber optics that have been mentioned
throughout this report. As we move towards a more sophisticated and
modern future, the uses of fiber optics are going to grow in all computer systems as well
as telecommunication networks. Modern information systems handle
ever-increasing data loads which strain the data throughput ability of information
systems. Designers have made significant progress in increasing processor
speeds, however progress in the design of high-speed interconnection networks has lagged
so much so that the most significant bottleneck in today's information
systems is the low speed of communications between integrated chips. These low speed
communications networks consume increasing amounts of power in an
effort to keep up with the faster processors. The slow communications speed is brought on
by the small bandwidth available to existing communications networks
based on the propagation of electrical signals through metallic lines. 
Optical interconnections offer several advantages over metallic interconnections, they
include: higher bandwidth; higher interconnection densities; lower crosstalk; crosstalk
which is independent of data rate; inherent parallelism; immunity from electromagnetic
interference and ground loops; the ability to exploit the third dimension; lower clock
and signal skew; and a higher fan-in/fan-out capability. These advantages mean that
optical interconnections have the potential to exhibit higher data rate communication,
higher densities of interconnections with lower crosstalk, and lower power consumption.
The shortest interconnections however, will remain electrical ones, due in part to the
inverse relationship between electrical interconnection length and power consumption, and
to a length independent minimum latency time inherent to optical interconnections caused
by the time delays required for electrical to optical to electrical conversion.
Agrawal, G.P. (1992). Fiber-optic communication systems. New York: Wiley.
This source provides details pertaining to my research. It provides details regarding the
selection of fiber parameters. It says about the process by which the fiber parameters
are selected. It tells about the impact of the parameters on factors like cost of fiber,
fiber attenuation, ease of cabling, and connection loss. This factors helps in
determining the type of fiber cables we should use.
Bonadedo, N.H. (1995). Fiber Optics theory and practice. New York: McGraw- Hill.
This source provides details about the input-output characteristics of the fiber. It
provides details about attenuation, as it is one of the important features. This feature
helps in determining the loss of light energy when a light pulse propagates down the
fiber.
Buck, J.A. (1992). Fundamentals of optical fibers. New York: Wiley.
This source provides details about the input-output properties of fibers. This
information is helpful in learning how fibers can be used for carrying light over long
distances. The source provides regarding the distances that can be spanned without using
amplifiers.
Cai, M. (2000). Single-mode fiber cables. Optics Letters, 25(19), 1430-2. 
This source provides details about the propagation models of fiber optics. The
information about the propagation of light signals in optical fibers is provided by the
source. We can know about the fields that exist within the fiber.
Chanclou, P. (2001). High return loss at the end face of fiber. Applied Optics, 40(4),
458- 
60.
The details regarding the geometry of the fiber is provided by this source. We study
details about the physical size of the fibers. The details regarding about the core and
cladding region, the materials used for these, and how they varies for multi mode and
single mode fibers. By this we can use suitable fibers basing on the applications.
Clarkson, C. (2000). Fiber shines light on many industries. Laser Focus World, 36(8), 
197-200.
This source provides details about the advantages associated with the use of fiber
optics. It provides details about the data security, immunity to electromagnetic
interference, the ease of installation of fiber cables and the high bandwidth associated
with them.
Damien, B. (2001). Intelligent tools increase recovery. Harts's E&P, 74(1), 45-7.
This source provides details regarding the applications of fiber optics. We learn from
this source about the implementation of fibers in the field of medicine, lasers,
industrial uses and commercial uses. This source helps me in determining which type of
fiber is used in a particular application.
Erdogan, T. (2000). High speed fiber optics. Poptronics 1(11), 13-14.
This source tells about differences between the coaxial cables and fiber optic cables.
This source explains why fiber optic cables are preferred in favor of coaxial cables for
many applications. By this information we can learn how fiber optic cables differ in
performance from ordinary coaxial cables.
Jayo, Yi. (2000). Beam and fiber optics. Optical Physics, 47(11), 1821-7.
This source provides details about the various measurements regarding the fibers. The
various measurements associated with the fiber cables are optical characterization,
quality control measurements, attenuation measurements, bandwidth measurements etc. These
measurements help us to understand the working of the fiber optic cables better.
Karen, B. (2000). Data highway to the stars. IEEE Review, 47(2), 15-18.
This source provides details about the economics associated with the use of fiber optics.
We get know details about the costs associated with installing optical cables and the
cost breakdown.
Larry, P.H. (2000).Blazing Data. Lightning Design & Application, 30(10), 24.
This source provide details regarding the multi mode fibers. We study details about the
features of multi mode fiber cables like their diameter, their construction and how they
differ from single mode fiber cables.
Saleim, M. (2000). Single-mode fiber cables. Optics Letters, 25(19), 1430-2. 
This source provides details regarding the single mode fiber optic cables. Here we study
about the details of single mode fiber cables like their make, the path of light inside
the core etc.
Samuel, R. (1994). Fundamentals of fiber optics. New York: Wiley.
This source provides details about the basics of fiber optic cables. We study about the
basic parts that make up the fiber optics like the transmitters, receivers, fiber cables
design etc. This gives me good knowledge about the fiber optics, which will be important
in my research work.
Tom, N.H. (1995). Fiber Optics theory and practice. New York: McGraw- Hill.
This source gives details about the coaxial cables , their properties their uses etc.
This study helps in determining the types of cables that should for a particular
application. We have a choice to select between the fiber cable and coaxial cable.
Wiseman, C. (2000). Fiber shines light on many industries. Laser Focus World, 36(8), 
197-200.
This source provides details about the details about the implementation of fiber optics
and where they are used.
Bibliography
Agrawal, G.P. (1992). Fiber-optic communication systems. New York: Wiley.
This source provides details pertaining to my research. It provides details regarding the
selection of fiber parameters. It says about the process by which the fiber parameters
are selected. It tells about the impact of the parameters on factors like cost of fiber,
fiber attenuation, ease of cabling, and connection loss. This factors helps in
determining the type of fiber cables we should use.
Bonadedo, N.H. (1995). Fiber Optics theory and practice. New York: McGraw- Hill.
This source provides details about the input-output characteristics of the fiber. It
provides details about attenuation, as it is one of the important features. This feature
helps in determining the loss of light energy when a light pulse propagates down the
fiber.
Buck, J.A. (1992). Fundamentals of optical fibers. New York: Wiley.
This source provides details about the input-output properties of fibers. This
information is helpful in learning how fibers can be used for carrying light over long
distances. The source provides regarding the distances that can be spanned without using
amplifiers.
Cai, M. (2000). Single-mode fiber cables. Optics Letters, 25(19), 1430-2. 
This source provides details about the propagation models of fiber optics. The
information about the propagation of light signals in optical fibers is provided by the
source. We can know about the fields that exist within the fiber.
Chanclou, P. (2001). High return loss at the end face of fiber. Applied Optics, 40(4),
458- 
60.
The details regarding the geometry of the fiber is provided by this source. We study
details about the physical size of the fibers. The details regarding about the core and
cladding region, the materials used for these, and how they varies for multi mode and
single mode fibers. By this we can use suitable fibers basing on the applications.
Clarkson, C. (2000). Fiber shines light on many industries. Laser Focus World, 36(8), 
197-200.
This source provides details about the advantages associated with the use of fiber
optics. It provides details about the data security, immunity to electromagnetic
interference, the ease of installation of fiber cables and the high bandwidth associated
with them.
Damien, B. (2001). Intelligent tools increase recovery. Harts's E&P, 74(1), 45-7.
This source provides details regarding the applications of fiber optics. We learn from
this source about the implementation of fibers in the field of medicine, lasers,
industrial uses and commercial uses. This source helps me in determining which type of
fiber is used in a particular application.
Erdogan, T. (2000). High speed fiber optics. Poptronics 1(11), 13-14.
This source tells about differences between the coaxial cables and fiber optic cables.
This source explains why fiber optic cables are preferred in favor of coaxial cables for
many applications. By this information we can learn how fiber optic cables differ in
performance from ordinary coaxial cables.
Jayo, Yi. (2000). Beam and fiber optics. Optical Physics, 47(11), 1821-7.
This source provides details about the various measurements regarding the fibers. The
various measurements associated with the fiber cables are optical characterization,
quality control measurements, attenuation measurements, bandwidth measurements etc. These
measurements help us to understand the working of the fiber optic cables better.
Karen, B. (2000). Data highway to the stars. IEEE Review, 47(2), 15-18.
This source provides details about the economics associated with the use of fiber optics.
We get know details about the costs associated with installing optical cables and the
cost breakdown.
Larry, P.H. (2000).Blazing Data. Lightning Design & Application, 30(10), 24.
This source provide details regarding the multi mode fibers. We study details about the
features of multi mode fiber cables like their diameter, their construction and how they
differ from single mode fiber cables.
Saleim, M. (2000). Single-mode fiber cables. Optics Letters, 25(19), 1430-2. 
This source provides details regarding the single mode fiber optic cables. Here we study
about the details of single mode fiber cables like their make, the path of light inside
the core etc.
Samuel, R. (1994). Fundamentals of fiber optics. New York: Wiley.
This source provides details about the basics of fiber optic cables. We study about the
basic parts that make up the fiber optics like the transmitters, receivers, fiber cables
design etc. This gives me good knowledge about the fiber optics, which will be important
in my research work.
Tom, N.H. (1995). Fiber Optics theory and practice. New York: McGraw- Hill.
This source gives details about the coaxial cables , their properties their uses etc.
This study helps in determining the types of cables that should for a particular
application. We have a choice to select between the fiber cable and coaxial cable.
Wiseman, C. (2000). Fiber shines light on many industries. Laser Focus World, 36(8), 
197-200.
This source provides details about the details about the implementation of fiber optics
and where they are used.