In this Assignment I discuss about Optical fiber, Evolution of optical fiber: from the beginning to present and beyond, Types of optical fibers used in commercial applications, Losses in optical fiber link, Submarine cable system worldwide, SONET, Fiber optic network backbone in Bangladesh, Applications of optical fiber in 4G technologies and beyond
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Optical Fiber Communication & Bangladesh
1. Department of Electrical & Electronic Engineering
Assignment on
Optical Fiber Communication & Bangladesh
Course Code: EEE-4117
Course Title: Optical Fiber Communication
Presented by
Md. Atiqur Rahman
Department of Electrical & Electronic Engineering
Leading University
2. 2
Contents
Optical Fiber ................................................................................................................................ 3
Evolution of optical fiber .............................................................................................................. 3
The Nineteenth Century ........................................................................................................... 3
The Twentieth Century ............................................................................................................. 5
The Twenty-first Century and Beyond ....................................................................................... 7
Types of optical fibers used in commercial applications ................................................................ 8
Losses in optical fiber link............................................................................................................. 9
Modal and chromatic dispersion............................................................................................... 9
Modal Dispersion.................................................................................................................. 9
Chromatic Dispersion .......................................................................................................... 10
Total Dispersion.................................................................................................................. 10
Splice ..................................................................................................................................... 10
Connector .............................................................................................................................. 11
Fiber Attenuation ................................................................................................................... 11
Bending Loss....................................................................................................................... 12
Absorption ......................................................................................................................... 13
Scattering ........................................................................................................................... 13
Submarine cable system worldwide ........................................................................................... 14
First Commercial Cables ......................................................................................................... 15
Transatlantic Telegraph Cable................................................................................................. 15
Cable to India, Singapore, Far East and Australia ..................................................................... 15
Submarine Cable across the Pacific ......................................................................................... 15
Submarine cable in Bangladesh .............................................................................................. 15
Synchronous Optical Network (SONET) ....................................................................................... 16
Fiber optic network backbone in Bangladesh .............................................................................. 17
Applications of optical fiber in 4G technologies and beyond ........................................................ 18
Reference .................................................................................................................................. 20
3. 3
Optical Fiber
Optical fiber is a glass/plastic filament or wire which carries light.
It is a cylindrical waveguide that operate at optical frequency.
It confines electromagnetic energy in the form of light.
It can be used to transfer information (in light form) from one point to another.
Wavelength: 1.7μm – 0.8μm
Frequency: 176 THz to 375 THZ
Evolution of optical fiber
In the assignment I divided the evolution of optical fiber in three era
The Nineteenth Century
The Twentieth Century
The Twenty-first Century and Beyond
The Nineteenth Century
The earliest attempts to communicate via light undoubtedly go back thousands of years. Early
long distance communication techniques, such as "smoke signals". Larger scale version of this
optical communication technique was the "optical telegraph" deployed in France and elsewhere
in the late 18th century.
Jean-Daniel Colladon, a 38-year-old Swiss professor at University of Geneva, demonstrated
light guiding or TIR for the first time in 1841. He wanted to show the fluid flow through various
holes of a tank and the breaking up of water jets. However, in the lecture
hall the audience could not see the flowing water. He solved the problem
by collecting and piping sunlight through a tube to the lecture table. The
light was focused through the water tank and was made to incident on the
edge of the jet at a glancing angle. TIR trapped the light in the liquid
forcing it to follow the curved path until the water jet broke up. Instead of
traveling in a straight line, the light followed the curvature of the water
flow. Colladon later on wrote: "I managed to illuminate the interior of a
Jean-Daniel Colladon
stream in a dark Space. I have discovered that this strange arrangement offers
in results one of the most beautiful, and most curious experiments that one can perform in a course on
Optics." (Comptes Rendes, 15, 800-802 Oct. 24, 1842).
Colladon sent a paper to his friend Francois Arago who headed the French Academy of
Sciences and edited its journal Comptes Renedes. Arago recalled that
Jacques Babinet, a French specialist in Optics had made similar
demonstrations in Paris. He focused candle light on to the bottom of a
glass bottle as he poured a thin stream of water from the top. TIR guided
the light along the jet. Arago asked Babinet to write down his work, but
Babinet did not think that the work is very important. Yet he made a
comment that "the idea also works very well with a glass shaft curved in
whatever manner and I had indicated that (it could be used) to illuminate
Jacques Babinet
the inside of the mouth (Comptes Rendes 15, Oct. 24, 1842). After sending his letter to Arago,
Babinet never returned to guiding of light before he died in 1872.
4. 4
In 1870, John Tyndall, using a jet of water that flowed from one container to
another and a beam of light, demonstrated that light used internal reflection
to follow a specific path. As water poured out through the spout of the first
container, Tyndall directed a beam of sunlight at the path of the water. The
light, as seen by the audience, followed a zigzag path inside the curved path
of the water. This simple experiment, illustrated in, marked the first research
into the guided transmission of light.
Typical Early TIR (Tota l Internal Reflection) Demons tration
John Tyndal l
William Wheeling, in 1880, patented a method of light transfer called “piping light.” Wheeling
believed that by using mirrored pipes branching off from a single source of illumination, i.e. a
bright electric arc, he could send the light to many different rooms in the same way that water,
through plumbing, is carried throughout buildings today. Due to the ineffectiveness of
Wheeling’s idea and to the concurrent introduction of Edison’s highly successful incandesce nt
light bulb, the concept of piping light never took off.
That same year, Alexander Graham Bell developed an optical voice transmission system he
called the photophone. The photophone used free-space light to carry the
human voice 200 meters. Specially placed mirrors reflected sunlight onto a
diaphragm attached within the mouthpiece of the photophone. At the other
end, mounted within a parabolic reflector, was a light-sensitive selenium
resistor. This resistor was connected to a battery that was, in turn, wired to
a telephone receiver. As one spoke into the photophone, the illuminated
diaphragm vibrated, casting various intensities of light onto the selenium
resistor. The changing intensity of light altered the current that passed
Alexander Graham Bell
through the telephone receiver which then converted the light back into speech. Bell believed
this invention was superior to the telephone because it did not need wires to connect the
transmitter and receiver. Today, free-space optical links find extensive use in metropolita n
applications.
5. 5
The Twentieth Century
Fiber optic technology experienced a phenomenal rate of progress in the second half of the
twentieth century. Early success came during the 1950’s with the development of the
fiberscope. This image-transmitting device, which used the first practical all-glass fiber, was
concurrently devised by Brian O’Brien at the American Optical Company and Narinder
Kapany (who first coined the term “fiber optics” in 1956) and colleagues at the Imperial
College of Science and Technology in London. Early all-glass fibers experienced excessive
optical loss, the loss of the light signal as it traveled through the fiber, limiting transmis s ion
distances.
Optical Fiber with Cladding
This motivated scientists to develop glass fibers that included a separate glass coating. The
innermost region of the fiber, or core, was used to transmit the light, while the glass coating,
or cladding, prevented the light from leaking out of the core by reflecting the light within the
boundaries of the core. This concept is explained by Snell’s Law which states that the angle at
which light is reflected is dependent on the refractive indices of the two materials - in this case,
the core and the cladding. The lower refractive index of the cladding (with respect to the core)
causes the light to be angled back into the core as illustrated.
The fiberscope quickly found application inspecting welds inside reactor vessels and
combustion chambers of jet aircraft engines as well as in the medical field. Fiberscope
technology has evolved over the years to make laparoscopic surgery one of the great medical
advances of the twentieth century.
The development of laser technology was the next important step in the establishment of the
industry of fiber optics. Only the laser diode (LD) or its lower-power cousin, the light-emit t ing
diode (LED), had the potential to generate large amounts of light in a spot tiny enough to be
useful for fiber optics. In 1957, Gordon Gould popularized the idea of using lasers when, as a
graduate student at Columbia University, he described the laser as an intense light source.
Shortly after, Charles Townes and Arthur Schawlow at Bell Laboratories supported the laser
in scientific circles. Lasers went through several generations including the development of the
ruby laser and the helium-neon laser in 1960. Semiconductor lasers were first realized in 1962;
these lasers are the type most widely used in fiber optics today.
Because of their higher modulation frequency capability, the importance of lasers as a means
of carrying information did not go unnoticed by communications engineers. Light has an
information-carrying capacity 10,000 times that of the highest radio frequencies being used.
However, the laser is unsuited for open-air transmission because it is adversely affected by
environmental conditions such as rain, snow, hail, and smog. Faced with the challenge of
6. 6
finding a transmission medium other than air, Charles Kao and Charles Hockham, working at
the Standard Telecommunication Laboratory in England in 1966, published a landmark paper
proposing that optical fiber might be a suitable transmission medium if its attenuation could be
kept under 20 decibels per kilometer (dB/km). At the time of this proposal, optical fibers
exhibited losses of 1,000 dB/ km or more. Even at a loss of only 20 dB/km, 99% of the light
would still be lost over only 3,300 feet. In other words, only 1/100th of the optical power that
was transmitted reached the receiver. Intuitively, researchers postulated that the current, higher
optical losses were the result of impurities in the glass and not the glass itself. An optical loss
of 20 dB/km was within the capability of the electronics and optoelectronic components of the
day.
Intrigued by Kao and Hockham’s proposal, glass researchers began to work on the problem of
purifying glass. In 1970, Drs. Robert Maurer, Donald Keck, and Peter Schultz of Corning
succeeded in developing a glass fiber that exhibited attenuation at less than 20 dB/km, the
threshold for making fiber optics a viable technology. It was the purest glass ever made.
The early work on fiber optic light source and detector was slow and often had to borrow
technology developed for other reasons. For example, the first fiber optic light sources were
derived from visible indicator LED's. As demand grew, light sources were developed for fiber
optics that offered higher switching speed, more appropriate wavelengths, and higher output
power. For more information on light emitters see Laser Diodes and LED's.
Fiber optics developed over the years in a series of generations that can be closely tied to
wavelength. Figure 6 shows three curves. The top, dashed, curve corresponds to early 1980’s
fiber, the middle, dotted, curve corresponds to late 1980’s fiber, and the bottom, solid, curve
corresponds to modern optical fiber. The earliest fiber optic systems were developed at an
operating wavelength of about 850 nm. This wavelength corresponds to the so-called “first
window” in a silica-based optical fiber. This window refers to a wavelength region that offers
low optical loss. It sits between several large absorption peaks caused primarily by moisture in
the fiber and Rayleigh scattering.
Four Wavelength Regions of Optical Fiber
The 850 nm region was initially attractive because the technology for light emitters at this
wavelength had already been perfected in visible indicator and infrared (IR) LED's. Low-cost
silicon detectors could also be used at the 850 nm wavelength. As the technology progressed,
the first window became less attractive because of its relatively high 3 dB/km loss limit.
7. 7
Most companies jumped to the “second window” at 1310 nm with lower attenuation of about
0.5 dB/km. In late 1977, Nippon Telegraph and Telephone (NTT) developed the “third
window” at 1550 nm. It offered the theoretical minimum optical loss for silica-based fibers,
about 0.2 dB/km.
Today, 850 nm, 1310 nm, and 1550 nm systems are all manufactured and deployed along with
very low-end, short distance, systems using visible wavelengths near 660 nm. Each wavelength
has its advantage. Longer wavelengths offer higher performance, but always come with higher
cost. The shortest link lengths can be handled with wavelengths of 660 nm or 850 nm. The
longest link lengths require 1550 nm wavelength systems. A “fourth window,” near 1625 nm,
is being developed. While it is not lower loss than the 1550 nm window, the loss is comparable.
The Twenty-first Century and Beyond
Today, DWDM technology continues to develop. As the demand for data bandwidth increases,
driven by the phenomenal growth of the Internet, the move to optical networking is the focus
of new technologies. At this writing, over 800 million people have Internet access and use it
regularly. That's over 12% of the entire world's population of 6.4 billion people. The world
wide web already hosts over 350 million domain names, 8 billion web pages (that's only the
visible, indexed, Internet, the invisible Internet is estimated to be up to 100 times larger), and
according to estimates people upload more than 3.5 million new web pages every day. The
Internet dominates traditional voice communication.
Projected Internet Traffic Increases
The important factor in these developments is the increase in fiber transmission capacity, which
has grown by a factor of 200 in the last decade. Figure 8 illustrates this trend.
The Growth of Optical Fiber Transmission Capacity
8. 8
Types of optical fibers used in commercial applications
CATV (cable television) services are supplied via a fiber optic network to an optical node,
which converts and distributes the electrical signal to subscribers via a coaxial cable
connection. CATV applications utilizes both single mode and multimode signals within
different areas of the network. Single Mode fiber is used to distribute signal from the central
office to optical nodes, where it can be converted to multimode.
Data transmission fiber optics, simply put, is the sending and receiving of data from point-to-point
via a network. It ranges from very simple cables connecting servers or storage arrays
inside a network or telecommunications system, to large multi-fiber distribution cables
supporting intra-building connectivity and beyond.
INTERNET: Bandwidths of up to 10Gbps, Streaming Movies in HD (High Defination),
Effortless video conferencing with no lagging, gaming and so on.
The Independent Telecommunication Providers segment is an area of the industry that provides
service(s) in rural areas, typically supporting residential and small to medium businesses. The
services offered in these areas can range from basic telephone to triple play depending on the
provider, subscriber location, and service availability. Expanded service can include televis ion
broadcast (high definition in some cases), VoIP (voice over internet protocol) phone service,
and security over a single broadband connection. However, more and more of these various
services are becoming available in rural locations nationwide.
The most significant and prevalent applications of fiber optics in medicine are in the imaging
and illumination components of endoscopes. Flexible and rigid multi-fibers composed of step-index
fibers and graded-index imaging rods are extensively used for visualization of internal
organs and tissue which are accessible through natural openings or transcutaneous. The design
of distinct endoscopes is described with a detailed review of their use in various medical
specialties. Low-loss optical fibers are employed to transmit laser energy for surgery and
photocoagulation. Multicolor laser light is transmitted through a single thin optical fiber to
provide adequate illumination for viewing and color photography. Past attempts to develop
plastic imaging multi- fibers and their future potential viewing and color photography. Past
attempts to develop plastic imaging multi- fibers and their future potential are discussed. Other
uses of fiber optics in medicine include remote spectrophotometry, pressure and position
sensing, or scintillation counting. These and other applications, such as intravascular pressure
transducers and in vivo ox-meters, are described.
9. 9
Losses in optical fiber link
Light traveling in an optical fiber loses power over distance. The loss of power depends on the
wavelength of the light and on the propagating material. For silica glass, the shorter
wavelengths are attenuated the most. The lowest loss occurs at the 1550-nm wavelength, which
is commonly used for long-distance transmissions.
Transmission of light by fiber optics is not 100% efficient. There are several reasons for this
including absorption by the core and cladding (caused by the presence of impurities) and the
leaking of light from of the cladding. When light reflects off the cladding /core interface it
actually travels for a short distance within the cladding before being reflected back. This leads
to attenuation (signal reduction) by up to 2db/Km for a multi-mode fiber. For example, with
this level of attenuation, if light travelled over 10kM of cable only 10% of the signal would
arrive at the following end.
The loss of power in light in an optical fiber is measured in decibels (dB). Fiber optic cable
specifications express cable loss as attenuation per 1-km length as dB/km. This value is
multiplied by the total length of the optical fiber in kilometers to determine the fiber's total loss
in dB.
Optical fiber link loss is caused by a number of factors
Higher-order mode losses
Modal and chromatic dispersion
Connector
Splice
Fiber attenuation
Modal and chromatic dispersion
Modal Dispersion
Modal Dispersion is the distortion in fiber or waveguide. Signal is spread due to differe nt
propagation velocity of optical signal in different mode.
Intermodal dispersion (also called modal dispersion) is the phenomenon that the group velocity
of light propagating in a multimode fiber (or other waveguide) depends not only on the optical
frequency (chromatic dispersion) but also on the propagation mode involved.
Intermodal dispersion results from different propagation characteristics of higher-order
transverse modes in waveguides, such as multimode fibers. This effect can severely limit the
possible data rate of a system for optical fiber communications based on multimode fibers.
Intermodal di spers ion
10. 10
Intermodal dispersion (also called modal dispersion) is the phenomenon that the group velocity
of light propagating in a multimode fiber (or other waveguide) depends not only on the optical
frequency (chromatic dispersion) but also on the propagation mode involved.
Chromatic Dispersion
Chromatic dispersion (or material dispersion) is produced when different frequencies of light
propagate in fiber with different velocities. Chromatic dispersion is larger for the wider source
bandwidth. Thus it is largest for LEDs and smallest for LASERs. LED BW is about 5% of λ0,
Laser BW about 0.1 % or below of λ0.
In addition to chromatic dispersion, there exists also waveguide dispersion that is significa nt
for single mode fibers in longer wavelengths. Chromatic and waveguide dispersion are denoted
as Intra- modal dispersion and their effects cancel each other at a certain wavelength. Total
dispersion is determined as the geometric sum of intra-modal and inter-modal (or mode)
dispersion with the net pulse spreading.
Chromatic and waveguide di spers ion cancel each other at certa in wavelength
Total Dispersion
Total dispersion is determined as the geometric sum of intra-modal and inter-modal (or
mode) dispersion with the net pulse spreading:
2 2 2
tot intermod intramod
Splice
Splice loss occurs at all splice locations. Mechanical splices usually have the highest loss,
commonly ranging from 0.2 to over 1.0 dB, depending on the type of splice. Fusion splices
have lower losses, usually less than 0.1 dB. A loss of 0.05 dB or less is usually achieved with
good equipment and an experienced splicing crew. High loss can be attributed to a number of
factors, including:
o Poor cleave
o Misalignment of fiber cores
o An air gap
11. 11
o Contamination
o Index-of-refraction mismatch
o Core diameter mismatch to name just a few.
Connector
Losses at fiber optic connectors commonly range from 0.25 to over 1.5 dB and depend greatly
on the type of connector used. Other factors that contribute to the connection loss include:
o Dirt or contaminants on the connector (very common)
o Improper connector installation
o A damaged connector face
o Poor scribe (cleave)
o Mismatched fiber cores
o Misaligned fiber cores
o Index-of-refraction mismatch
Fiber Attenuation
Attenuation means loss of light energy as the light pulse travels from one end of the cable to
the other. It is also called as signal loss or fiber loss. It also decides the number of repeaters
required between transmitter and receiver. Attenuation is directly proportional to the length of
the cable.
Attenuation is defined as the ratio of optical output power to the input power in the fiber of
length L.
α= 10log10 Pi/Po [dB/km]
Where, Pi= Input Power
Po= Output Power, α is attenuation constant
Fiber Attenuation
12. 12
The various losses in the cable are due to
Bending
Absorption
Scattering
Bending Loss
Bend loss occurs at fiber cable bends that are tighter than the cable's minimum bend radius.
Bending loss can also occur on a smaller scale from such factors as:
o Sharp curves of the fiber core
o Displacements of a few millimeters or less, caused by buffer or jacket imperfections
o Poor installation practice
This light power loss, called micro-bending, can add up to a significant amount over a long
distance. The loss which exists when an optical fiber undergoes bending is called bending
losses.
There are two types of bending:
Macroscopic bending
Bending in which complete fiber undergoes bends which causes certain modes not to be
reflected and therefore causes loss to the cladding.
Macros copic bending
Microscopic Bending
Either the core or cladding undergoes slight bends at its surface. It causes light to be reflected
at angles when there is no further reflection.
Micros copic Bending
13. 13
Absorption
In the telecom region of the spectrum, caused primarily by excitation of chemical bond
vibrations. Overtone and combination bands predominate near 1550 nm. Low-energy tail of
electronic absorptions dominate in visible region. Electronic absorptions by color centers cause
loss for some metal impurities.
There are two types of absorption:
o Intrinsic Absorption
o Extrinsic Absorption
Intrinsic Absorption
Caused by the interaction with one or more components of the glass
Occurs when photon interacts with an electron in the valence band & excites it to a
higher energy level near the UV region.
Extrinsic Absorption
Also called impurity absorption.
Results from the presence of transition metal ions like iron, chromium, cobalt, copper
& from OH ions i.e. from water.
Scattering
It occurs due to microscopic variations in the material density, compositional fluctuations,
structural in homogeneities and manufacturing defects.
Scattering are two types
o Linear Scattering
Rayleigh Scattering losses
Mie Scattering Losses
Waveguide Scattering Losses
o Non-linear Scattering
Stimulated Brillouin Scattering(SBS)
Stimulated Raman Scattering(SRS)
Rayleigh scattering Losses
These losses are due to microscopic variation in the material of the fiber.
Unequal distribution of molecular densities or atomic densities leads to Rayleigh
scattering losses
Glass is made up of several acids like SiO2, P2O5, etc. compositions, fluctuations can
occur because of these several oxides which rise to Rayleigh scattering losses.
Mie Scattering Losses
These losses results from the compositional fluctuations & structural in homo generics &
defects created during fiber fabrications, causes the light to scatter outside the fiber.
Waveguide Scattering Losses
It is a result of variation in the core diameter, imperfections of the core cladding interface,
change in RI of either core or cladding.
14. 14
SBS Scattering:
Stimulated Brillouin Scattering (SBS) may be regarded as the modulation of light
through thermal molecular vibrations within the fiber.
Pb = 4.4x10-3d2λ2α dB v watts
Where, λ= operating wavelength (μm)
d= fiber core diameter (μm)
v = source bandwidth in (GHz)
SRS Scattering
Stimulated Raman Scattering is similar to SBS except that high frequency optical
phonon rather than acoustic phonon is generated in scattering processes.
Pb = 5.9x10-2 d2λα dB watts
Submarine cable system worldwide
A massive network of fiber optic cables lies deep under the seas across the Earth. The cables
allow us to quickly send our emails and videos, and connect our browsers and phone calls to
sites in far-away lands. This network isn’t new. Submarine data cables date back to 1850, when
the first international telegraph cable (with a capacity of 10 words per minute) spanned the
channel between England and France. As early as 1901, telegraph cables crisscrossed the
oceans and connected all the continents except for Antarctica.
Submarine Cable is the cable designed to be placed underwater. Such cables must be specially
protected against moisture. At shallow depths on continental shelves, submarine cables
commonly are plowed in and armored to protect them against ship anchors, trawler nets, and
sharks, which are attracted to the electromagnetic fields and like to gnaw on the cables and
repeaters. Submarine Cable was first inaugurated in 1956 containing 4000 voice circuits,
termed as TAT-1. Later TAT-8 version, containing 3500 voice circuits was come out in 1983.
TAT stands for Trans-Atlantic Telephone.
Subsequent cable generations included upgrades to telephone cables and data communicat ions
cables. Analog coaxial cables of steel-wrapped copper were widespread under the oceans
beginning in the 1950s. The bandwidth of analog cable increased quickly in the 1960s and 70s,
but the highest capacity systems required electrically powered repeaters to boost the signal
every 6 to 9 kilometers, making them very expensive to install across oceans.
Starting in 1988, a massive 10-year build-out replaced the vast majority of these copper
network cables with long-haul fiber optic cables. Today virtually all of the undersea long-haul
communication cables are optical, as are land-based ones. Submarine data cables handle more
than 95 percent of IP voice and data traffic between countries and continents, and 100 percent
of international Internet traffic. Users in the United States, Europe and other well-conne cted
regions often take for granted the ease of global communications.
The underwater cable network is a critical component to global commerce, and it’s growing.
Spurring this growth is ever-increasing IP traffic, demand for higher bandwidth at reduced
deployment cost and the need for additional routes and redundant cable systems that ensure
resiliency. According to a comprehensive market research report by Global Industry Analysts,
15. 15
cumulative global installation of submarine optical fiber cable is projected to reach two million
kilometers by 2018, up from just over a million kilometers in 2009.
First Commercial Cables
In August 1850, John Watkins Brett's Anglo-French Telegraph Company laid the first line
across the English Channel. It was simply a copper wire coated with gutta-percha, without any
other protection. The experiment served to keep alive the concession, and the next year, on
November 13, 1851, a protected core, or true cable, was laid from a government hulk, the
Blazer, which was towed across the Channel. The next year, Great Britain and Ireland were
linked together. In 1852, a cable laid by the Submarine Telegraph Company linked London to
Paris for the first time. In May, 1853, England was joined to the Netherlands by a cable across
the North Sea, from Oxford Ness to The Hague. It was laid by the Monarch, a paddle steamer
which had been fitted for the work.
Transatlantic Telegraph Cable
The first attempt at laying a transatlantic telegraph cable was promoted by Cyrus West Field,
who persuaded British industrialists to fund and lay one in 1858. Subsequent attempts in 1865
and 1866 with the world's largest steamship, the SS Great Eastern, used a more advanced
technology and produced the first successful transatlantic cable. The Great Eastern later went
on to lay the first cable reaching to India from Aden, Yemen, in 1870.
Cable to India, Singapore, Far East and Australia
An 1863 cable to Bombay provided a crucial link to Saudi Arabia. In 1870 Bombay was linked
to London via submarine cable in a combined operation by four cable companies, at the behest
of the British Government. In 1872 these four companies were combined to form the mammot h
global spanning Eastern Telegraph Company, owned by John Pender. A spin-off from Eastern
In 1872, Australia was linked by cable to Bombay via Singapore and China and in 1876 the
cable linked the British Empire from London to New Zealand
Submarine Cable across the Pacific
This was completed in 1902–03, linking the US mainland to Hawaii in 1902 and Guam to the
Philippines in 1903. Canada, Australia, New Zealand and Fiji were also linked in 1902.Decades
later, the North Pacific Cable system was the first regenerative (repeater) system to completely
cross the Pacific from the US mainland to Japan. The US portion of NPC was manufactured in
Portland, Oregon, from 1989–1991 at STC Submarine Systems, and later Alcatel Submarine
Networks. The system was laid by Cable & Wireless Marine on the CS Cable Venture in 1991.
Submarine cable in Bangladesh
Bangladesh Submarine Cable Company (BSCCL) is a fiber optic submarine cable tele-communications
company based in Bangladesh. Emerging in July 2008 from former BTTB
(Bangladesh Telegraph & Telephone Board)’s submarine cable project, BSCCL presently
handles Bangladesh’s lone submarine cable as a member of the SEA-ME-WE4 international
submarine cable consortium that runs a total length of 20,000 km through 17 landing points in
Singapore, Malaysia, Thailand, Bangladesh, India, Sri Lanka, Pakistan, United Arab Emirates,
Saudi Arabia, Egypt, Tunisia, Italy, Algeria and France.
16. 16
Synchronous Optical Network (SONET)
High-speed (up to 2.5 Gbps) synchronous network specification developed by Bellcore and
designed to run on optical fiber. STS-1 is the basic building block of SONET. Approved as an
international standard in 1988. On a larger scale, the telecommunications industry uses the
SONET standard for optical transport of TDM data. SONET, used in North America, is related
standards that specify interface parameters, rates, framing formats, multiplexing methods, and
management for synchronous TDM over fiber.
SONET is the American National Standards Institute standard for synchronous data
transmission on optical media. The international equivalent of SONET is synchronous digita l
hierarchy (SDH). Together, they ensure standards so that digital networks can interconnect
internationally and that existing conventional transmission systems can take advantage of
optical media through tributary attachments.
SONET provides standards for a number of line rates up to the maximum line rate of 9.953
gigabits per second (Gbps). Actual line rates approaching 20 gigabits per second are possible.
SONET is considered to be the foundation for the physical layer of the broadband ISDN
(BISDN).
Asynchronous transfer mode runs as a layer on top of SONET as well as on top of other
technologies. SONET defines a base rate of 51.84 Mbps and a set of multiples of the base rate
known as "Optical Carrier levels (OCx)."
SONET
The figure displays an example of statistical TDM. SONET takes n bit streams, multiplexes
them, and optically modulates the signal, sending it out using a light emitting device over
fiber with a bit rate equal to (incoming bit rate) x n. Thus traffic arriving at the SONET
multiplexer from four places at 2.5 Gb/s goes out as a single stream at 4 x 2.5 Gb/s, or 10
Gb/s. This principle is illustrated in the figure, which shows an increase in the bit rate by a
factor of four in time slot T.
17. 17
Fiber optic network backbone in Bangladesh
Establishment of fiber optic links in Bangladesh began in 1986, along with the installation of
new digital switches. Starting with the optical fiber link between Dhaka’s Maghbazar and
Gulshan telephone exchanges, all intra-city inter- exchange connections are now established
through short distance fiber-optic links. The intercity portions between the major cities started
with the completion of the STM-16 fiber link between Dhaka to Chittagong in 2001. Bogra to
Joypurhat to Ragpur and Dinajpur in the north west of Bangladesh is already connected by
STM-4 optical link while Dhaka to Bogra optical fiber link via the Jamuna Bridge is currently
under construction. In addition, there is a plan to connect Dhaka to Sylhet and Dhaka to Khulna
on the optical fiber network.
Bangladesh’s Grameenphone has opened a new fiber optic cable link through the 4.8 kilometer
long Jamuna Multipurpose Bridge becoming the first mobile phone operator in the country to
do so. The fiber optic cable links Elenga in Tangail and Nolka in Sirajganj and covers a length
of about 40 kilometers through the Jamuna Bridge. This link completes the Grameenphone
fiber optic transmission backbone between the East and West zones of the country. The fiber -
optic transmission backbone will ensure a more secure network providing high quality voice
and data services in the Northern and Southern districts.
In the last three years BTTB built about 1375 Km optical fiber network in the country under
two projects. The most modern SDH technology was adopted in all these optical fiber links.
Dhaka – Comilla – Feni – Chittagong backbone optical link and Feni – Choumuhini –
Noakhali, Choumuhini – Lakshmipur, Comilla – B. Baria spur optical links were impleme nted
under Dhaka – Chittagong high capacity optical fiber project. The total length of optical cable
laid under this project is about 450 Km. 18 core optical cables were used in backbone link
whereas spur links were built with 12 core O.F cables. The transmission capacity of the
backbone is 2.5 GB/s (STM-16). Transmission capacity of Feni – Choumihini spur link is 622
MB/s (STM-4) whereas the transmission capacity of Choumuhini – Noakhali, Choumuhini -
Lakshmipur and Comilla – B. Baria spur links is 155 MB/s (STM-1). Some short haul optical
links like Tongi – Gazipur and B.Baria Microwave Station – B.Baria Exchange of STM-1
capacity were also built under this project. The SDH transmission equipment used in this
network are from Alcatel CIT. Under the project entitled “Installation and Expansion of Digita l
Telephone Exchanges in various District Head Quarters of Bangladesh” which is commonly
known as 216 KL project, about 925 Km 12 core optical fiber cable network was built. The
SDH transmission equipment used in this network are also from Alcatel CIT. The backbone
optical link built under this project is Bogra – Palashbari – Rangpur – Saidpur – Dinajpur –
Thakurgaon – Panchagarh. Bogra – Palashbari – Rangpur portion of this backbone is of STM-
4 capacity and rest is of STM-1 capacity. Now the present requirement of E1 claims that the
Rangpur – Saidpur – Dinajpur section of the link should be upgraded to STM-4. Some spur
links also were built in different areas of the country under 216 KL project.
18. 18
Map of the exi s ting fi ber-optic network in Bangladesh
Applications of optical fiber in 4G technologies and beyond
In a world of fast changing technology, there is a rising requirement for people to communic ate
and get connected with each other and have appropriate and timely access to informa t ion
regardless of the location of the each individuals or the information. The increasing demands
and requirements for wireless communication systems ubiquity have led to the need for a better
understanding of fundamental issues in communication theory and electromagnetic and their
implications for the design of highly-capable wireless systems. In continuous development of
mobile environments, the major service providers in the wireless market kept on monitor ing
the growths of 4th generation (4G) mobile technology. 2G and 3G are well-established as the
mainstream mobile technology around the world. 3G is stumbling to obtain market share for a
different reasons and 4G is achieving some confidence.
In 2010, the total mobile subscriber base in North America, Europe and Asia Pacific, is
expected to grow up to 2500 million and penetration will be over 50%. This kind of demand
growth will require the support of higher capacity networks.
Given the technology at large, 4G mobile technology as an example, will give people a more
convenience and ease in lifestyle. With the “anytime, anywhere, anything,” capability, 4G
wireless technology will benefit every individual regardless of time and place. Considering
global standpoint, this technology stands to be the way to communicate and connect all the
time with more ubiquitous means. Therefore, given the ubiquitous networking, e-commerce
(or even m-commerce), unified messaging, and peer-to-peer networking, expansion to the
mobile and wireless surroundings must reach its maximum possibilities.
The trail going to 4G mobile technology embraces lots of significant trends. Major mobile
players have been investing to 2G and the succeeding technology. 4G mobile technologies are
perceived to provide fast and high data rate or bandwidth, and offer packetized data
communications. Since 4G is still in the cloud of the sensible standards creation, ITU and IEEE
19. 19
form several task forces to work on the possible completion for the 4G mobile standards as
well.
Users’ experiences of latest booming Internet forces industry to investigate means to provide
high data rate regardless of mobility. 4G is being discussed as a solution to the inquiry and its
vision and requirements are being standardized in various standardization bodies. 4G service
vision is given from this research. There still have large room for the purpose of service
application vision: 3G is being delayed in its commercialization and about a decade of change
is left for 4G. However, we believe this paper will promote discussion of 4G services by
presenting our vision of 4G services.
In recent years the evolution of mobile communication proceeded mainly under the influe nce
of the 3GPP initiative (3rd Generation Partnership Project). 3GPP is a consortium, or
collaboration, of standardization bodies in mobile communications. An important movement
is the standardization of advanced mobile communication systems, in particular of the new
technologies long term evolution (LTE) and LTE advanced (LTE-A). LTE technologies set
new standards in mobile communication concerning band- width. In future, users of one radio
cell will share more than 100 Mbit/s of bandwidth. Moreover, on the country- side, where
neither appropriate DSL-based technology nor fiber-to-the-home technology is available, LTE
offers new possibilities to provide flexible broadband solutions. For instance, in August 2010,
Deutsche Telekom turned on the first LTE node in Kyritz, which is located in a rural area
approximately 100 km north east of Berlin. To take advantage of next generation mobile
networks, an adjustment and optimization of basic transport layers is inevitable. It will be
necessary to analyze, which influence LTE and LTE-A take on traffic in access networks and
on aggregation is- sues. The recent developments in telecommunication networks show the
growing tendency that important network elements are concentrated at few locations. The
number of sites with active hardware in access networks is reduced from tens of thousands to
a few hundreds, by utilizing the optical transmission technology in combination with the
increasing growth of the optical fiber network.