Post on 05-Apr-2018
8/2/2019 421 Fiber Optics Based Computer
1/21
CONTENTS
PAGE NO.
1. Introduction . 1
2. First a bit history .. 2
3. What is optical fiber .. 3
4. How fiber works ...... 4
5. Types of optical fiber .. 6
5.1 Multimode Fiber . 6
5.1.1 Multimode Step-index Fiber .... 6
5.2 Single-mode Fiber . 7
5.3 Difference between single-mode and multi-mode 7
5.4 Light propagation . 8
6. Optical computing .. 9
7. Optical fiber connectors .. 10
7.1 Connector cleaning .. 10
8. Advantages and Disadvantages of optical fiber . 12
8.1 advantages 12
8.2 disadvantages 14
9. Applications 15
9.1 Optical fiber communication 15
9.2 A fiber-optic Christmas tree . 16
10. Conclusion . 18
11. References ..19
8/2/2019 421 Fiber Optics Based Computer
2/21
1.INTRODUCTIONIn recent years it has become apparent that fiber-optics are steadily replacing copper wire
as an appropriate means of communication signal transmission. They span the long distancesbetween local phone systems as well as providing the backbone for many network systems. Other
system users include cable television services, university campuses, office buildings, industrial
plants, and electric utility companies.
A fiber-optic system is similar to the copper wire system that fiber-optics is replacing. The
difference is that fiber-optics use light pulses to transmit information down fiber lines instead of
using electronic pulses to transmit information down copper lines. Looking at the components in a
fiber-optic chain will give a better understanding of how the system works in conjunction with
wire based systems.
1
8/2/2019 421 Fiber Optics Based Computer
3/21
2. FIRST A BIT HISTORY
In 1870, John Tyndall demonstrated that light follows the curve of a stream of water
pouring from a container, it was this simple principle that led to the study and development of
applications for this phenomenon. John Logie Baird patented a method of transmitting light in a
glass rod for use in an early colour TV, but the optical losses inherent in the materials at the time
made it impractical to use. In the 1950's more research and development into the transmission of
visible images through optical fibres led to some success in the medical world, as they began using
them in remote illumination and viewing instruments. In 1966 Charles Kao and George Hockham
proposed the transmission of information over glass fibre, and they also realised that to make it a
practical proposition, much lower losses in the cables were essential. This was the driving force
behind the developments to improve the optical losses in fibre manufacturing, and today optical
losses are significantly lower than the original target set out by Charles Kao and George Hockha
2
3. WHAT IS OPTICAL FIBER?
8/2/2019 421 Fiber Optics Based Computer
4/21
A technology that uses glass (or plastic) threads (fibers) to transmit data. A fiber optic
cable consists of a bundle of glass threads, each of which is capable of transmitting messages
modulated onto light waves. An optical fiber (orfibre) is a glass or plastic fiber designed to guide
light along its length. Fiber optics is the overlap of applied science and engineering concernedwith such optical fibers. Optical fibers are widely used in fiber-optic communication, which
permits transmission over longer distances and at higher data rates than other forms of wired and
wireless communications. Fibers are used instead of metal wires because signals propagate along
them with less loss, and they are immune to electromagnetic interference. Optical fibers are also
used to form sensors, and in a variety of other applications.
In fibers with large core diameter, the confinement is based on total internal reflection. In
smaller core diameter fibers, (widely used for most communication links longer than 200 meters)
the fiber acts as a waveguide. There are many different designs of optical fibers, including graded-
index optical fibers, step-index optical fibers which are characteristics of an optical fiber and
different types of optical fiber as singlemode fibers (SMF) in which there are three kinds of fibers,
non-dispersion shifted fibres (NDSF), nonzero dispersion-shifted fibers (NZDSF) and dispersion-
shifted fibers (DSF), multimode fibers (MMF), birefringentpolarization-maintaining fibers (PMF)
and more recentlyphotonic crystal fibers (PCF), with the design and the wavelength of the light
propagating in the fiber dictating whether or not it will be multi-mode optical fiberorsingle-mode
optical fiber. Because of the mechanical properties of the more common glass optical fibers,
special methods of splicing fibers and of connecting them to other equipment are needed.
Manufacture of optical fibers is based on partially melting a chemically doped preform and pullingthe flowing material on a draw tower. Fibers are built into different kinds of cables depending on
how they will be used.
3
4. HOW FIBER WORKS
http://www.webopedia.com/TERM/f/data.htmlhttp://www.webopedia.com/TERM/f/fiber_optics.htmlhttp://www.webopedia.com/TERM/f/fiber_optics.htmlhttp://www.webopedia.com/TERM/f/modulate.htmlhttp://en.wikipedia.org/wiki/Lighthttp://en.wikipedia.org/wiki/Applied_sciencehttp://en.wikipedia.org/wiki/Engineeringhttp://en.wikipedia.org/wiki/Fiber-optic_communicationhttp://en.wikipedia.org/wiki/Electromagnetic_interferencehttp://en.wikipedia.org/wiki/Sensorhttp://en.wikipedia.org/wiki/Total_internal_reflectionhttp://en.wikipedia.org/wiki/Meterhttp://en.wikipedia.org/wiki/Waveguidehttp://en.wikipedia.org/wiki/Graded-index_fiberhttp://en.wikipedia.org/wiki/Graded-index_fiberhttp://en.wikipedia.org/wiki/Step-index_profilehttp://en.wikipedia.org/wiki/Singlemode_fiberhttp://en.wikipedia.org/wiki/Nonzero_dispersion-shifted_fiberhttp://en.wikipedia.org/wiki/Dispersion-shifted_fiberhttp://en.wikipedia.org/wiki/Dispersion-shifted_fiberhttp://en.wikipedia.org/wiki/Multimode_fiberhttp://en.wikipedia.org/wiki/Polarization-maintaining_optical_fiberhttp://en.wikipedia.org/wiki/Photonic_crystal_fibershttp://en.wikipedia.org/wiki/Multi-mode_optical_fiberhttp://en.wikipedia.org/wiki/Single-mode_optical_fiberhttp://en.wikipedia.org/wiki/Single-mode_optical_fiberhttp://en.wikipedia.org/wiki/Cablehttp://www.webopedia.com/TERM/f/data.htmlhttp://www.webopedia.com/TERM/f/fiber_optics.htmlhttp://www.webopedia.com/TERM/f/fiber_optics.htmlhttp://www.webopedia.com/TERM/f/modulate.htmlhttp://en.wikipedia.org/wiki/Lighthttp://en.wikipedia.org/wiki/Applied_sciencehttp://en.wikipedia.org/wiki/Engineeringhttp://en.wikipedia.org/wiki/Fiber-optic_communicationhttp://en.wikipedia.org/wiki/Electromagnetic_interferencehttp://en.wikipedia.org/wiki/Sensorhttp://en.wikipedia.org/wiki/Total_internal_reflectionhttp://en.wikipedia.org/wiki/Meterhttp://en.wikipedia.org/wiki/Waveguidehttp://en.wikipedia.org/wiki/Graded-index_fiberhttp://en.wikipedia.org/wiki/Graded-index_fiberhttp://en.wikipedia.org/wiki/Step-index_profilehttp://en.wikipedia.org/wiki/Singlemode_fiberhttp://en.wikipedia.org/wiki/Nonzero_dispersion-shifted_fiberhttp://en.wikipedia.org/wiki/Dispersion-shifted_fiberhttp://en.wikipedia.org/wiki/Dispersion-shifted_fiberhttp://en.wikipedia.org/wiki/Multimode_fiberhttp://en.wikipedia.org/wiki/Polarization-maintaining_optical_fiberhttp://en.wikipedia.org/wiki/Photonic_crystal_fibershttp://en.wikipedia.org/wiki/Multi-mode_optical_fiberhttp://en.wikipedia.org/wiki/Single-mode_optical_fiberhttp://en.wikipedia.org/wiki/Single-mode_optical_fiberhttp://en.wikipedia.org/wiki/Cable8/2/2019 421 Fiber Optics Based Computer
5/21
Fiber optic technology is based on the use of light energy to transmit data. Basically, the
encoded data is converted from electrical signals to optical light pulses and then transmitted
through the medium to its destination, where it is then converted back. From this, we can see that
there are basically three mainelements in any fiber optic data link: a transmitter, an optical cable(the transmission medium), and a receiver. The transmitter handles the conversion from electrical
to light energy, the optical cable carries the light waves, and the receiver handles the conversion
from light pulses back to the original electrical format.
After translating the electrical signals, the transmitter uses either a light emitting diode
(LED) or an injection laser diode (ILD) to generate the light pulses. Using a lens, this light energy
is then sent down the fiber optic cable. The principle that makes this possible is referred to as total
internal reflection. According to John Huber in an article in R&D Magazine, this principle of totalinternal reflection states that when the angle of incidence exceeds a critical value, light cannot get
out of the glass; instead, the light bounces back in (Huber 115). This happens when two materials
with different refractive indices cause the angle of incidence to be too large for refraction
(bending) of light to take place. Since the light cannot be bent and exit the material, this means that
100 percent is reflected back. Thus, when a fiber optic cable, which consists of a glass or plastic
core surrounded by a cladding with a lower refractive index, receives a light ray, the light ray is
confined and travels down the core to the receiving end. Simply put, the difference in the materials
used for the core and the cladding make an extremely reflective surface at the point where they
interface, which makes the principle of total internal reflection possible. This is the fundamental
concept behind all fiber optic transmissions.
In addition to the core and the cladding, a fiber optic cable also has an outer jacket that
protects it from abrasion and other forces. Most high end cabling will also have a protective buffer
and strength material between the cladding and the outer jacket. These outer layers are added to
help protect the fragile core and cladding from damage. There are two common types of cabling
used for most fiber optic applications: single-mode and multi-mode. Single-mode fiber is generally
used for long distance communications. It has a narrower core diameter, generally 8-10 microns,
with a 125-micron cladding. Single-mode optical fiber only allows one mode of light to traveldown its core. On the other hand, multi-mode fiber generally has a 62.5-micron core diameter with
a 125-micron cladding.
4
In order to receive the signal and then convert it back to its original format, a fiber optic
receiver uses a phototransistor to convert the light energy into an electrical current. This current is
8/2/2019 421 Fiber Optics Based Computer
6/21
then sent into an amplifier in order to boost the electrical signal back to its original level, and then
a digitizer circuit is used to convert the signal into the appropriate digital voltage levels to be used
by the external logic. At this point, the electronic signal is ready to be received by the
communications device, whether it is a switch, router, computer, etc.
5
5. TYPES OF OPTICAL FIBER
8/2/2019 421 Fiber Optics Based Computer
7/21
Understanding the characteristics of different fiber types aides in understanding the
applications for which they are used. Operating a fiber optic system properly relies on knowing
what type of fiber is being used and why. There are two basic types of fiber: multimode fiber and
single-mode fiber. Multimode fiber is best designed for short transmission distances, and is suited
for use in LAN systems and video surveillance. Single-mode fiber is best designed for longer
transmission distances, making it suitable for long-distance telephony and multichannel television
broadcast systems.
5.1. Multimode Fiber
Multimode fiber, the first to be manufactured and commercialized, simply refers to the fact that
numerous modes or light rays are carried simultaneously through the waveguide. Modes result from the
fact that light will only propagate in the fiber core at discrete angles within the cone of acceptance. This
fiber type has a much larger core diameter, compared to single-mode fiber, allowing for the larger number
of modes, and multimode fiber is easier to couple than single-mode optical fiber. Multimode fiber may be
categorized as step-index or graded-index fiber .
5.1.1. Multimode Step-index Fiber
The principle of total internal reflection applies to multimode step-index fiber. Because the
coresindex of refraction is higher than the claddings index of refraction, the light that enters at
less than the critical angle is guided along the fiber.
Three different lightwaves travel down the fiber. One mode travels straight down the center
of the core. A second mode travels at a steep angle and bounces back and forth by total internal
reflection. The third mode exceeds the critical angle and refracts into the cladding. Intuitively, it
can be seen that the second mode travels a longer distance than the first mode, causing the two
modes to arrive at separate times.
This disparity between arrival times of the different light rays is known as dispersion, and
the result is a muddied signal at the receiving end. For a more detailed discussion of dispersion, see"Dispersion in Fiber Optic Systems;" however, it is important to note that high dispersion is an
unavoidable characteristic of multimode step-index fiber. . 6
5.2. Single-mode Fiber
http://n_window%28%27http//www.fiber-optics.info/glossary-l.htm#LAN')http://n_window%28%27http//www.fiber-optics.info/glossary-m.htm#Mode');http://n_window%28%27http//www.fiber-optics.info/glossary-wxyz.htm#Waveguide')http://n_window%28%27http//www.fiber-optics.info/glossary-g.htm#Graded-Index_Fiber')http://n_window%28%27http//www.fiber-optics.info/glossary-g.htm#Graded-Index_Fiber')http://n_window%28%27http//www.fiber-optics.info/glossary-ijk.htm#Index_of_Refraction')http://n_window%28%27http//www.fiber-optics.info/glossary-ijk.htm#Index_of_Refraction')http://n_window%28%27http//www.fiber-optics.info/glossary-c.htm#Critical%20Angle');http://n_window%28%27http//www.fiber-optics.info/articles/dispersion.htm');http://n_window%28%27http//www.fiber-optics.info/glossary-l.htm#LAN')http://n_window%28%27http//www.fiber-optics.info/glossary-m.htm#Mode');http://n_window%28%27http//www.fiber-optics.info/glossary-wxyz.htm#Waveguide')http://n_window%28%27http//www.fiber-optics.info/glossary-g.htm#Graded-Index_Fiber')http://n_window%28%27http//www.fiber-optics.info/glossary-ijk.htm#Index_of_Refraction')http://n_window%28%27http//www.fiber-optics.info/glossary-c.htm#Critical%20Angle');http://n_window%28%27http//www.fiber-optics.info/articles/dispersion.htm');8/2/2019 421 Fiber Optics Based Computer
8/21
Single-mode fiber allows for a higher capacity to transmit information because it can retain
the fidelity of each light pulse over longer distances, and it exhibits no dispersion caused by
multiple modes. Single-mode fiber also enjoys lower fiberattenuationthan multimode fiber. Thus,
more information can be transmitted per unit of time. Like multimode fiber, early single-modefiber was generally characterized as step-index fiber meaning the refractive index of the fiber core
is a step above that of the cladding rather than graduated as it is in graded-index fiber. Modern
single-mode fibers have evolved into more complex designs such as matched clad, depressed clad
and other exotic structures.
Single-mode fiber has disadvantages. The smaller core diameter makes coupling light into
the core more difficult. The tolerances for single-mode connectorsand splices are also much more
demanding.
5.3. What's the difference between single-mode and multi-mode?
With copper cables larger size means less resistance and therefore more current, but with
fibre the opposite is true. To explain this we first need to understand how the light propagates
within the fibre core.
Figure 5.3 7
http://n_window%28%27http//www.fiber-optics.info/glossary-a.htm#Attenuation')http://n_window%28%27http//www.fiber-optics.info/glossary-a.htm#Attenuation')http://n_window%28%27http//www.fiber-optics.info/glossary-c.htm#Connector')http://n_window%28%27http//www.fiber-optics.info/glossary-c.htm#Connector')http://n_window%28%27http//www.fiber-optics.info/glossary-s.htm#Splice')http://n_window%28%27http//www.fiber-optics.info/glossary-a.htm#Attenuation')http://n_window%28%27http//www.fiber-optics.info/glossary-c.htm#Connector')http://n_window%28%27http//www.fiber-optics.info/glossary-s.htm#Splice')8/2/2019 421 Fiber Optics Based Computer
9/21
5.4. LIGHT PROPAGATION
Light travels along a fiber cable by a process called 'Total Internal Reflection' (TIR), this is
made possible by using two types of glass which have different refractive indexes. The inner core
has a high refractive index and the outer cladding has a low index. This is the same principle as thereflection you see when you look into a pond. The water in the pond has a higher refractive index
than the air, and if you look at it from a shallow angle you will see a reflection of the surrounding
area, however, if you look straight down at the water you can see the bottom of the pond. At some
specific angle between these two view points the light stops reflecting off the surface of the water
and passes through the air/water interface allowing you to see the bottom of the pond. In multi-
mode fibres, as the name suggests, there are multiple modes of propagation for the rays of light.
These range from low order modes which take the most direct route straight down the middle, to
high order modes which take the longest route as they bounce from one side to the other all the
way down the fibr
This has the effect of scattering the signal because the rays from one pulse of light, arrive at
the far end at different times, this is known as Intermodal Dispersion (sometimes referred to as
Differential Mode Delay, DMD). To ease the problem, graded index fibres were developed. Unlike
the examples above which have a definite barrier between core and cladding, these have a high
refractive index at the centre which gradually reduces to a low refractive index at the
circumference. This slows down the lower order modes allowing the rays to arrive at the far end
closer together, thereby reducing intermodal dispersion and improving the shape of the signal.
8
6. OPTICAL COMPUTING
8/2/2019 421 Fiber Optics Based Computer
10/21
An optical computer is a computer that uses light instead of electricity (i.e. photons rather
than electrons) to manipulate, store and transmit data. Photons have fundamentally different
physical properties than electrons, and researchers have attempted to make use of these properties
to produce computers with performance and/or capabilities greater than those of electroniccomputers. Optical computer technology is still in the early stages: functional optical computers
have been built in the laboratory, but none have progressed past the prototype stage.
Most research projects focus on replacing current computer components with optical
equivalents, resulting in an optical digital computer system processing binary data. This approach
appears to offer the best short-term prospects for commercial optical computing, since optical
components could be integrated into traditional computers to produce an optical/electronic hybrid.
Other research projects take a non-traditional approach, attempting to develop entirely newmethods of computing that are not physically possible with electronics.
An optical computer is a device that uses visible light or infrared beams, rather than electric
current, to perform digital computations.Optical computers promise speeds, which will be
thousands, even millions of times faster than those of today's most efficient supercomputers.The
optical computer could revolutionize computing in much the same way that the semiconductor chip
revolutionized electronics 30 years ago.An electric current flows at only about 10 percent of the
speed of light.
9
7. OPTICAL FIBER CONNECTORS
http://en.wikipedia.org/wiki/Photonshttp://en.wikipedia.org/wiki/Electronshttp://en.wikipedia.org/wiki/Photonshttp://en.wikipedia.org/wiki/Electrons8/2/2019 421 Fiber Optics Based Computer
11/21
Fiber optic connectors have traditionally been the biggest concern in using fiber optic
systems. While connectors were once unwieldy and difficult to use, connector manufacturers have
standardized and simplified connectors greatly. This increasing user-friendliness has contributed to
the increase in the use of fiber optic systems; it has also taken the emphasis off the proper care and
handling of optical connectors.
Fiber-to-fiber interconnection can consist of a splice, a permanent connection, or a
connector, which differs from the splice in its ability to be disconnected and reconnected. Fiber
optic connector types are as various as the applications for which they were developed. Different
connector types have different characteristics, different advantages and disadvantages, and
different performance parameters.
7.1. connector cleaning
Another important thing to remember in handling fiber optic connectors is that the fiber
end face and ferrule must be absolutely clean before it is inserted into a transmitter or receiver.
Dust, lint, oil (from touching the fiber end face), or other foreign particles obscure the end face,
compromising the integrity of the optical signal being sent over the fiber. From the optical signals
point-of-view, dirty connections are like dirty windows. Less light gets through a dirty window
than a clean one.
It is hard to conceive of the size of a fiber optic connector core. Single-mode fibers have
cores that are only 8-9 m in diameter. As a point of reference, a typical human hair is 50-75 m
in diameter, approximately 6-9 times larger! Dust particles can be 20 m or larger in diameter.
Dust particles smaller than 1 m can be suspended almost indefinitely in the air. A 1 m dust
particle landing on the core of a single-mode fiber can cause up to 1 dB of loss. Larger dust
particles (9 m or larger) can completely obscure the core of a single-mode fiber. Fiber optic
connectors need to be cleaned every time they are mated and unmated; it is essential that fiber
optics users develop the necessary discipline to always clean the connectors before they are mated.
10
Connector damage can occur if foreign particles are caught in the end face area of mated
connectors.Connector cleaning is simply completed by wiping the connector ferrule and end face
with some isopropyl alcohol and a lint free tissue. Another option for connector cleaning is the
http://n_window%28%27http//www.fiber-optics.info/glossary-c.htm#connector')http://n_window%28%27http//www.fiber-optics.info/glossary-s.htm#Splice')http://n_window%28%27http//www.fiber-optics.info/glossary-s.htm#Single-mode%20(SM)%20Fiber');http://n_window%28%27http//www.fiber-optics.info/glossary-c.htm#connector')http://n_window%28%27http//www.fiber-optics.info/glossary-s.htm#Splice')http://n_window%28%27http//www.fiber-optics.info/glossary-s.htm#Single-mode%20(SM)%20Fiber');8/2/2019 421 Fiber Optics Based Computer
12/21
cassette type cleaners which use a dry tape system where the tape is advanced every time the
cassette is opened ensuring the clean section of tape is used each time.
11
ABSTRACT
With the growth of computing technology the need of high performance Computers (HPC)
have significantly increased.The use of light for the transmission of information is far from a new
idea. Fiber optics is a relatively new technology that uses rays of light to send information over
hair-thin fibers at blinding speeds. These fibers are used as an alternative to conventional copper
wire in a variety ofapplications such as those associated with security, telecommunications,
instrumentation and control, broadcast or audio/visual systems.
8/2/2019 421 Fiber Optics Based Computer
13/21
Optical computing technology is, in general, developing in two directions. One approach is
to build computers that have the same architecture as present day computers but using optics that is
Electro optical hybrids. Another approach is to generate a completely new kind of computer, which
can perform all functional operations in optical mode.
8/2/2019 421 Fiber Optics Based Computer
14/21
8. ADVANTAGES AND DISADVANTAGES OF
FIBER OPTIC SYSTEMS
8.1. ADVANTAGES
Because of the Low loss, high bandwidth properties of fiber cable they can
be used over greater distances than copper cables, in data networks this can be as
much as 2km without the use of repeaters. Their light weight and small size also
make them ideal for applications where running copper cables would be
impractical, and by using multiplexors one fibre could replace hundreds of copper
cables. This is pretty impressive for a tiny glass filament, but the real benefits in the
data industry are its immunity to Electro Magnetic Interference (EMI), and the fact
that glass is not an electrical conductor. Because fibre is non-conductive, it can be
used where electrical isolation is needed, for instance between buildings where
copper cables would require cross bonding to eliminate differences in earth
potentials. Fibres also pose no threat in dangerous environments such as chemical
plants where a spark could trigger an explosion. Last but not least is the security
aspect, it is very, very difficult to tap into a fibre cable to read the data signals.
fiber optic systems have many attractive features that are superior to
electrical systems. These include improved system performance, immunity to
electrical noise, signal security, and improved safety and electrical isolation.
Fiber optic transmission systems - a fiber optic transmitter and receiver,
connected by fiber optic cable - offer a wide range of benefits not offered by
traditional copper wire or coaxial cable. These include:
The ability to carry much more information and deliver it with greater
fidelity than either copper wire or coaxial cable.
Fiber optic cable can support much higher data rates, and at greater
distances, than coaxial cable, making it ideal for transmission of serial digital data.
12
The fiber is totally immune to virtually all kinds of interference,
including lightning, and will not conduct electricity. It can therefore come in direct
8/2/2019 421 Fiber Optics Based Computer
15/21
contact with high voltage electrical equipment and power lines. It will also not
create ground loops of any kind.
As the basic fiber is made of glass, it will not corrode and is unaffected by
most chemicals. It can be buried directly in most kinds of soil or exposed to most
corrosive atmospheres in chemical plants without significant concern.
Since the only carrier in the fiber is light, there is no possibility of a spark
from a broken fiber. Even in the most explosive of atmospheres, there is no fire
hazard, and no danger of electrical shock to personnel repairing broken fibers.
Fiber optic cables are virtually unaffected by outdoor atmospheric
conditions, allowing them to be lashed directly to telephone poles or existing
electrical cables without concern for extraneous signal pickup.
A fiber optic cable, even one that contains many fibers, is usually much
smaller and lighter in weight than a wire or coaxial cable with similar information
carrying capacity. It is easier to handle and install, and uses less duct space. (It can
frequently be installed without ducts.)
Fiber optic cable is ideal for secure communications systems because it is
very difficult to tap but very easy to monitor. In addition, there is absolutely no
electrical radiation from a fiber.
Fiber optics is a particularly popular technology for local-area networks. In
addition, telephone companies are steadily replacing traditional telephone lines with
fiber optic cables. In the future, almost all communications will employ fiberoptics.
13
8.2. DISADVANTAGES
http://www.webopedia.com/TERM/f/local_area_network_LAN.htmlhttp://www.webopedia.com/TERM/f/local_area_network_LAN.html8/2/2019 421 Fiber Optics Based Computer
16/21
Because of the relative newness of the technology, fiber optic components
are expensive. Fiber optic transmitters and receivers are still relatively expensive
compared to electrical interfaces. The lack of standardization in the industry has
also limited the acceptance of fiber optics. Many industries are more comfortablewith the use of electrical systems and are reluctant to switch to fiber optics.
However, industry researchers are eliminating these disadvantages.
Standards committees are addressing fiber optic part and test
standardization.
The cost to install fiber optic systems is falling because of an increase in
the use of fiber optic technology. Published articles, conferences, and lectures on
fiber optics have begun to educate managers and technicians. As the technology
matures, the use of fiber optics will increase because of its many advantages overelectrical systems.
14
9. APPLICATION IN DIFFERENT FIELDS:
8/2/2019 421 Fiber Optics Based Computer
17/21
9.1. Optical fiber communication
Optical fiber can be used as a medium for telecommunication and
networking because it is flexible and can be bundled as cables. It is especiallyadvantageous for long-distance communications, because light propagates through
the fiber with little attenuation compared to electrical cables. This allows long
distances to be spanned with few repeaters. Additionally, the light signals
propagating in the fiber can be modulated at rates as high as 40 Gb/s and each fiber
can carry many independent channels, each by a different wavelength of light
(wavelength-division-multiplex WDM). In total, a single fiber-optic cable can carry
data at rates as high as 14.4 Pb/s (circa 14 million Gb/s). Over short distances, such
as networking within a building, fiber saves space in cable ducts because a single
fiber can carry much more data than a single electrical cable. Fiber is also immune
to electrical interference, which prevents cross-talk between signals in differentcables and pickup of environmental noise. Also, wiretapping is more difficult
compared to electrical connections, and there are concentric dual core fibers that
are said to be tap-proof. Because they are non-electrical, fiber cables can bridge
very high electrical potential differences and can be used in environments where
explosive fumes are present, without danger of ignition.
Although fibers can be made out of transparent plastic, glass, or a
combination of the two, the fibers used in long-distance telecommunicationsapplications are always glass, because of the lower optical attenuation. Both multi-
mode and single-mode fibers are used in communications, with multi-mode fiber
used mostly for short distances (up to 500 m), and single-mode fiber used for
longer distance links. Because of the tighter tolerances required to couple light into
and between single-mode fibers (core diameter about 10 micrometers), single-mode
transmitters, receivers, amplifiers and other components are generally more
expensive than multi-mode components.
Optical fibers can be used as sensors to measure strain, temperature,
pressure and other parameters. The small size and the fact that no electrical power
is needed at the remote location gives the fiber optic sensor advantages to
conventional electrical sensor in certain applications. 15
http://en.wikipedia.org/wiki/Computer_networkhttp://en.wikipedia.org/wiki/Optical_communications_repeaterhttp://en.wikipedia.org/wiki/Gigabithttp://en.wikipedia.org/wiki/Petabithttp://en.wikipedia.org/wiki/Gigabithttp://en.wikipedia.org/wiki/Plastic_optical_fiberhttp://en.wikipedia.org/wiki/All-silica_fiberhttp://en.wikipedia.org/wiki/Plastic-clad_silica_fiberhttp://en.wikipedia.org/wiki/Attenuationhttp://en.wikipedia.org/wiki/Computer_networkhttp://en.wikipedia.org/wiki/Optical_communications_repeaterhttp://en.wikipedia.org/wiki/Gigabithttp://en.wikipedia.org/wiki/Petabithttp://en.wikipedia.org/wiki/Gigabithttp://en.wikipedia.org/wiki/Plastic_optical_fiberhttp://en.wikipedia.org/wiki/All-silica_fiberhttp://en.wikipedia.org/wiki/Plastic-clad_silica_fiberhttp://en.wikipedia.org/wiki/Attenuation8/2/2019 421 Fiber Optics Based Computer
18/21
Optical fibers are used as hydrophones for seismic or SONAR
applications. Hydrophone systems with more than 100 sensors per fiber cable have
been developed. Hydrophone sensor systems are used by the oil industry as well as
a few countries' navies. Both bottom mounted hydrophone arrays and towed
streamer systems are in use. The German company Sennheiser developed a
microphone working with a laserand optical fibers.
Optical fiber sensors for temperature and pressure have been developed
for downhole measurement in oil wells. The fiber optic sensor is well suited for this
environment as it is functioning at temperatures too high for semiconductor sensors
(Distributed Temperature Sensing).
Another use of the optical fiber as a sensor is the optical gyroscope which
is in use in the Boeing 767 and in some car models (for navigation purposes) and
the use in Hydrogen microsensors.
Fiber-optic sensors have been developed to measure co-located
temperature and strain simultaneously with very high accuracy. This is particularly
useful to acquire information from small complex structures.
9.2. A fiber-optic christmas tree
Optical fiber is also used in imaging optics. A coherent bundle of fibers is
used, sometimes along with lenses, for a long, thin imaging device called an
endoscope, which is used to view objects through a small hole. Medical endoscopes
are used for minimally invasive exploratory or surgical procedures (endoscopy).
Industrial endoscopes are used for inspecting anything hard to reach, such as jet
engine interiors.
16
An optical fiber doped with certain rare-earth elements such as erbium can
be used as the gain medium of a laser or optical amplifier. Rare-earth doped optical
http://en.wikipedia.org/wiki/Hydrophonehttp://en.wikipedia.org/wiki/Sonarhttp://en.wikipedia.org/wiki/Sennheiserhttp://en.wikipedia.org/wiki/Laser_microphonehttp://en.wikipedia.org/wiki/Laserhttp://en.wikipedia.org/wiki/Distributed_Temperature_Sensinghttp://en.wikipedia.org/wiki/Fibre_optic_gyroscopehttp://en.wikipedia.org/wiki/Boeing_767http://en.wikipedia.org/wiki/Hydrogen_microsensorhttp://en.wikipedia.org/wiki/Hydrophonehttp://en.wikipedia.org/wiki/Sonarhttp://en.wikipedia.org/wiki/Sennheiserhttp://en.wikipedia.org/wiki/Laser_microphonehttp://en.wikipedia.org/wiki/Laserhttp://en.wikipedia.org/wiki/Distributed_Temperature_Sensinghttp://en.wikipedia.org/wiki/Fibre_optic_gyroscopehttp://en.wikipedia.org/wiki/Boeing_767http://en.wikipedia.org/wiki/Hydrogen_microsensor8/2/2019 421 Fiber Optics Based Computer
19/21
fibers can be used to provide signal amplification by splicing a short section of
doped fiber into a regular (undoped) optical fiber line. The doped fiber is optically
pumped with a second laser wavelength that is coupled into the line in addition to
the signal wave.
Both wavelengths of light are transmitted through the doped fiber, which
transfers energy from the second pump wavelength to the signal wave. The process
that causes the amplification is stimulated emission.
Optical fibers doped with a wavelength shifter are used to collect
scintillation light in physics experiments.
Optical fiber can be used to supply a low level of power (around one watt)
to electronics situated in a difficult electrical environment. Examples of this are
electronics in high-powered antenna elements and measurement devices used in
high voltage transmission equipment.
17
8/2/2019 421 Fiber Optics Based Computer
20/21
10. CONCLUSION
The applications of the fiber optics field are still emerging and developing so rapidly that, it
is impossible to keep track each and every innovations and inventions. All the above compilationsgives idea about the tremendous potential associated with this field.The future is not so distant
when scientists and researchers will come up with more and more futuristic products and
applications using optical fibers.
18
8/2/2019 421 Fiber Optics Based Computer
21/21
11. References[1] T Okoshi and K Kikuchi, Coherent optical fiber communication (Kluwer Academic, Boston,
1988)
[2] A Hasegawa, Optical solitons in fibers (Springer Verlag, New York, 1989)
[3] S E Millar and I P Kaminow, eds, Optical fiber telecommunications - II(Academic, New
York 1988)
[4] G P Agrawal,Nonlinear fiber optics (Academic, New York, 1989)
[5] C Yeh,Handbook of fiber optics (Academic, New York, 1990)
[6] G P Agrawal,Fiber optic communication systems (John Wiley, Singapore, 1993)
[7] N S Bergano and C R Davidson, Wavelength division multiplexing in long-haul transmissionsystems,J. Lightwave Tech. 14, 1299 (1996)
[8] E Desurvire,Erbium doped fiber amplifiers (John Wiley, New York, 1994)
[9] R J Hoss and EA Lacy,Fiber optics 2nd edition (Prentice Hall, New Jersey, 1993)
[10] M Nakazawa, Soliton transmission in telecommunication networks,IEEE. Communication
magazine, March 24 (1994)
19