Business Communication

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Executive Summary
The world has entered a new era of communication technology. We are facing challenges of the
twenty-first century. Technologies are improving day by day. Optical fiber technology is the most
advanced technology in communication system. Fiber optic communication is being currently used in
telephone, submarine cable and special security and alarm systems, electronic instrumentation
systems, medical systems, satellite ground stations, industrial automation and process controls.
Communication engineers have always dreamt of higher information bandwidth with low attenuation
and cost. Moreover, fiber is not affected by electromagnetic interference, power surges or lightning.
For these reasons communication engineers have chosen Optical fiber for network purposes as
transmission medium. Moreover, for high speed and longer distances, local area networks (LANs) are
based on Fiber optics. So, it was decided to study the Optical fiber communication system. Some other
reasons are given below:
- Exploit the enormous bandwidth of an optical fiber
To utilize the available optical bandwidth (THz) by different users
- Increase the transmission capacity:
Due to limitations imposed by dispersion and nonlinear effects transmission rate per channel < 10
Gb/s
- Resource sharing:
To share the same optical fiber channel and equipment by a number of users
- Reduce the overall transmission cost per channel

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Chapter-One: Introduction
1.1 Introduction
In Bangladesh, application of Optical fiber as communication links has already been
started. The introduction of optical fiber communication system into the public network has
stimulated investigation and application of the transmission techniques by public utility
organizations, which provide their own communication facilities over moderately long distances.
SONET (Synchronous Optical Network) or SDH(Synchronous Digital Hierarchy) as it's known in
Europe, is a set of standards for interfacing Operating Telephone Company(OTC) optical networks.
They are a set of global standards for interfacing equipment from different vendors (One of the few
where telephony is concerned).
SONET is the protocol for North America and Japan while SDH is the definition for Europe. The
differences between SONET and SDH are slight.
1.2 Background of the study
MBA project report is an attempt to provide business students an orientation to a real life business
situation in which we can observe and evaluate the use and applicability of the theoretical concepts.
As per norm, this report is the requirement of the fulfillment of the MBA program. This report “Third
Generation Fiber Optic Communication Systems” is the outcome of 4 weeks works on
Communication Sector. During this period, my job has related to this department. My honorable
supervisor is Dr. Muhammad Shariat Ullah , Assistant Professor of Dhaka International University.
The authorized this report to me to acquire the practical knowledge.
With some 1,200 million telephone connections in use today and the number of Internet users growing
rapidly, network providers must deal effectively with increased telephone traffic. In response, several
methods and technologies have been developed within the last 50 years to address these market needs
as economically as possible. Then communications engineers introduced frequency division multiplex
(FDM) systems that modulated each individual telephone channel with a different carrier frequency.
The signals could then be shifted into different frequency ranges to transmit several telephone
connections over a single cable.
The advent of semiconductor circuits and a continuing demand for telephone capacity in the 1960s
resulted in the development of the pulse code modulation (PCM) transmission method.
With PCM (using a single line multiple times through digital time-domain multiplexing), the analog
telephone signal is first sampled at a 3.1 kHz bandwidth, quantized and encoded and then transmitted
at a 64 kbps rate. Collecting 30 such coded channels together into a frame along with the necessary
signaling information can achieve a 2048 kbps transmission rate.

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1.3 Objectives of the study
The specific objective of this report includes
� All basic concepts, which are necessary to interact with SDH experts or to understand fully the
technical documentation of SDH systems;
� Basics of optical transmission systems (WDM, OTDM);
� Advantages and drawbacks of PDH and SDH systems;
� Operation principles of PDH and SDH with emphasis on practical aspects;
� the SDH frame structure, pointer justification mechanism, overhead and multiplexing schemes;
� Functions and system-level description of SDH equipment (regenerators, terminal and add-drop
multiplexers, digital cross-connects);
� Several examples of network applications of SDH equipment;
� SDH networks architectures;
� Traffic protection and restoration in SDH networks;
� Techniques for broadband data transport over SDH (ATM, IP, VCAT, LCAS, GFP, GbE);
� Other aspects relevant to the design and operation of SDH transmission networks, such as SDH
network synchronization, management and testing (in laboratory and on field).
1.4 Scope of the study
There are so many communication systems in Bangladesh. MetroNet Bangladesh Ltd is one of them.
It is a Fiber optic communication systems compare than others. There are only three Communication
systems engineers works. There are above 450 labors and 40 staff works here. Though the
organization is not so big and all related department situated in one building so that I can easily
identify the person who had hold the relevant information needed to my study and collected data from
engineer and other staffs ( Labors and officers) and management team of various department.
The development of optical fiber transmission and large-scale integrated circuits made more complex
standards possible. There are demands for improved and increasingly sophisticated services that
required large bandwidth better performance monitoring facilities and greater network flexibility.
1.5 Methodology
01. Primary source: The primary information collected various Third Generation Fiber Optic
Communication Systems report.
- Different Lecture sheet of Prof. Dr. S. P. Majumder
02. Secondary Source :
 Organizational report
 Web site Information.
 Different files of the company

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1.4.1 Comparison between Conventional Communication Systems and Optical Fiber
Communication Systems:
The block diagram of general communication system and optical fiber communication system
is shown in fig. bellow:
Figure 3.1 (a) Conventional communication system.
Figure 3.1 (b) Optical fiber communication system.
In a conventional communication system, the information source provides an electrical signal to a
transmitter which converts the signal into a suitable form for propagation over the transmission
medium. The transmission medium may consist of a· pair of wires, a coaxial cable or a radio link
through free space down which the signal is transmitted to the receiver, where it is transformed into
the being passed to the destination. In this communication system, the information is attenuated in the
transmission medium.
For optical fiber communication system the information source provides an electrical signal
to a transmitter comprising an electrical stage which drives an optical source to give modulation of
light wave currier. The optical source which provided the electrical conversion may be either a
semiconductor laser or LED. The transmission medium consists of an optical detector which drives a
further electrical stage and hence provides demodulation for detection of the optical signal or the
optical electrical conversion. In this communication system attenuation is negligibly small.
1.4.2 Advantage of optical fiber communication
Several advantages come with taking the fiber optics route.
• High Bandwidth ~ 1014 Hz
• Low signal attenuation < 0.2 dB/km
• Low signal distortion
• Low power requirement
• Low material usage
• Small space requirement
• Low cost
In addition to the advantages of having extra information bandwidth using like as the carrier
signal, the optical fiber communication system have several other advantages over the conventional
systems.
Information
Source
Transmitter X-mission
Medium
Receiver
(Demodulation)
Destination
Information
Source
Electrical
Transmitter
Optical Source Optical Fiber
Cable
DestinationElectrical
Receiver
Optical
detector

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1.4.3 Disadvantage of optical fiber communication
Highly skilled staff would be required for maintenance
a) Only point to point working is possible on optical fiber
b) Precise and costly instruments would be required
c) Costly if under utilized
d) Accept unipolar codes only
e) Jointing of fiber and splicing is also time consuming.
1.6 Limitations
1. There exist no worldwide standard except for regional digital signals and frame structures.
2. Therefore it no flexible network topology.
3. Has low utilization of digital equipment and,
4. Provides no optimal routing.
5. Multiplexing structure based on point to point transmission.

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Chapter-Two: SDH Background
2.1 Historical Perspective
2.1.1 First Generation Systems
• Deployed in 1977
• Used multimode fiber near 850 nm wavelength
• Suffer from severe limitations:
• attenuation (2dB/km)
• chromatic dispersion
• multimode dispersion
• bit rate 45 Mbps
 repeater spacing 10 km
2.1.2 Second Generation Systems
 introduced in the 1980’s
 avoid chromatic dispersion by operation at 1300 nm
 it has low attenuation of 1 dB/km
 use multimode fiber
o suffer from modal dispersion
o bit rate 45 Mb/s
o repeater spacing 30 km
2.1.3 Third Generation Systems
• deployed in the mid- 1990’s
• operating at 1300 nm wavelength
• use single-mode fiber
• avoid modal dispersion
• bit rate 1 Gb/s
• repeater spacing 40 km
• suffer from transmission losses
• attenuation (< 1 dB/km)

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2.1.4 Fourth Generation Systems
• introduced in 1995
• operate at 1500 nm wavelength
• low attenuation (< 0.3 dB/km)
• repeater spacing 100 km
• bit rate 10 Gb/s
• use single-mode fiber
Still suffer from chromatic dispersion
2.1.5 Fifth Generation Systems
• utilize dispersion shifted and flattened fibers
• use optical amplifiers and WDM systems
• dispersion managed fibers
• attenuation < 0.2 dB/km
• repeater spacing 1000km
• bit rate 10 – 50 Gb/s
• optical solution system
• balance between dispersion and non-linearity

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Chapter-Three: SDH Functions
3.1 Definition of SDH
Communications networks gradually converted to digital technology after PCM was introduced in the
1960s. A multiplex hierarchy known as plesiosynchronous digital hierarchy (PDH) evolved to cope
with the demand for ever-higher bit rates. The bit rates start with the basic multiplex rate of 2 Mbps
with further stages of 8, 34, and 140 Mbps. In North America and Japan, however, the primary rate is
1.5 Mbps with additional stages of 6 and 44 Mbps, as shown in Figure 1 on page 5. This fundamental
Developmental difference made gateway setup between the networks both difficult and expensive.
In response to the demand for increased bandwidth, reliability, and high-quality service, SDH
developed steadily during the 1980s, eliminating many inherent disadvantages in PDH. In turn,
network providers began to benefit from the many technological and economic advantages this new
technology introduced as discussed in this section.
3.1.1 High transmission rates
Transmission rates of up to 10 G can be achieved in modern SDH systems making it the most
suitable technology for backbones, the superhighways in today’s telecommunications
networks.
3.1.2 Simplified add and drop function
Compared to the older PDH system, low-bit-rate channels can be easily extracted from and
inserted into the high-speed bit streams in SDH, eliminating the need for costly demultiplexing
and re-multiplexing the plesiosynchronous structure.
3.1.3 High availability and capacity matching
SDH enables network providers to react quickly and easily to their customers’ requirements,
such as switching leased lines in just minutes. Network providers can use standardized network
elements (NE) that they can control and monitor from a central location with a
telecommunications management network (TMN) system.
3.1.4 Reliability
Modern SDH networks include various automatic backup-circuit and repair mechanisms that
management can monitor to cope with system faults so that link or NE failures do not lead to
an entire network failure.
3.1.5 Future-proof platform for new services
SDH is the ideal platform for a wide range of services including POTS, ISDN, mobile radio,
and data communications, such as LAN and WAN. It can also handle more recent services
such as video on demand and digital video broadcasting via ATM.
This tutorial course provides a thorough overview on several topics that are usually not presented in a
single book neither in any competing course on SDH. In particular, we shall learn:
technical documentation of SDH systems;
SDH with emphasis on practical aspects;

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-level description of SDH equipment (regenerators, terminal and add-
drop multiplexers, digital cross-connects);
cts relevant to the design and operation of SDH transmission networks, such as SDH
network synchronization, management and testing (in laboratory and on field).

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Chapter-Four: Network analysis
Network Generic Applications
4.1 Evolutionary Pressures
The need to reduce network operating costs and increase revenues were the drivers behind the
introduction of SDH. The former can be achieved by improving the operations management
of networks and introducing more reliable equipment. SDH scores high on both. Increase in
revenues can come from meeting the growing demand for improved services, including
broadband, and an improved response, such as greater flexibility and reliability of networks.
For broadband services typically based on ATM, a number of techniques exist for high-
quality routing over PDH networks. The characteristics of SDH, however, make it much more
suitable for this application, because it offers better transmission quality, enormous routing
flexibility, and support for facilities such as path self-healing.
SDH and ATM provide different but essentially compatible features, both of which are
required in the network.
4.2 Operations
Managing capacity in the network involves such operations as the following:
a. Protection, for circuit recovery in milliseconds
b. Restoration, for circuit recovery in seconds or minutes
c. Provisioning, for the allocation of capacity to preferred routes
d. Consolidation, or the funneling of traffic from unfilled bearers onto fewer bearers in order
to reduce waste of traffic capacity
e. Grooming or the sorting of different traffic types from mixed payloads into separate
destinations for each type of traffic.
4.3 Bit Rates
4.2.1 Bit Rates:
Optical Level Electrical Level Line Rate (Mbps) SDH Equivalent
OC-1 STS-1 51.84 ---
OC-3 STS-3 155.520 STM-1
OC-9 STS-9 466.56 STM-3
OC-12 STS-12 622.080 STM-4
OC-18 STS-18 933.120 STM-6
OC-24 STS-24 1244.160 STM-8
OC-36 STS-36 1866.240 STM-13
OC-48 STS-48 2488.320 STM-16
OC-96 STS-96 4976.640 STM-32
OC-192 STS-192 9953.280 STM-64

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4.2.2 International organization defined standardized bit rates:
4.4 SDH Features and Management
4.4.1 Traffic Interfaces
SDH defines traffic interfaces that are independent of vendors. At 155 Mbps they are defined
for both optical and copper interfaces and at higher rates for optical ones only. These higher
rates are defined as integer multiples of 155.52 Mbps in an n x 4 sequence, giving for
example, 622,08 Mbps(622Mbps) and 2488.32Mbps(2.5Gbps). To support network growth
and the demand for broadband services, multiplexing to even higher rates such as 10 Gbps
continues in the same way, with upper limits set by technology rather than by lack of
standards as was the case with PDH.
4.4.2 SDH Layers
In the multiplexing process, payloads are layered into lower-order and higher-order virtual
containers, each including a range of overhead functions for management and error
monitoring. Transmission is then supported by the attachment of further layers of overheads.
This layering of functions in SDH, both for traffic and management, suits the layered concept
of a service-based network better than the transmission-oriented PDH standards.
4.4.3 Management Functions
To support a range of operations, SDH includes a management layer whose communications
are transported within dedicated data communications channel (DCC) time slots inside the
interface rate. These have a standard profile for the structure of network-management
messages, irrespective of vendor or operator. However, there has been no agreement on the
definition of the message sets to be carried, so there is no interworking of management
channels between equipment vendors at the SDH interface.

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4.4.4 Standard Frame Representation
Everywhere in the world, the standard SDH frame
Representation is a: MATRIX with 9 rows
4.5 SDH Frame Structure
4.5.1 Outline
The frame has a repetitive structure with a period of 125 microseconds-the same as for pulse
code modulation (PCM)-and consists of nine equal-length segments. At the gross transport
rate of 155.52 Mbps for the base synchronous transport module (STM-01), there is a burst of
nine overhead bytes at the start of each segment, as shown at the top figure 5. This figure also
depicts how the SDH frame at STM -1 is conventionally represented, with the segments
displayed as from nine rows and 270 columns. Each byte is equivalent to 64 kbps, so eac
column of nine bytes is equivalent to 570 kbps.

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4.5.2 SDH Frame structure
All SDH frames have the same structure:
4.4.2.1 Transport Overhead: SOH

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• Transport Overhead: AU 4 pointer

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In order to illustrate the pointer working:
We have exactly the same phenomenon in SDH :
4.6 SDH Multiplexing
SDH is a new way of multiplexing slow signals onto a faster signal. It has mechanisms for dealing
with tributaries that are not running at the same clock rate.

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Translation of the previous picture in SDH language:
4.6.1 The SDH Multiplexing map
4.7 Equipment:
4.7.1 Optical cross-connect
Optical cross-connects are known in the united states as digital cross-connect switches
(DCCs) and as DXCs elsewhere. They are classified as DCSp/q or DXC p/q, where p is the
traffic component that is switched within that port bit rate.
Some cross-connect designs allow all traffic interfaces to be in PDH form for compatibility
with existing equipment. In particulars, these designs might allow the p hierarchcal level in a
DXC p/q cross-connect to be at either 34 or 140 Mbps in PDH format, as an alternative to 155
Mbps, so that network flexibility becomes available where SDH infrastructure does not yet
exist. In these cross-connects, a port at 34 or 140 Mbps can include an embedded PDH
multiplex equipment for internal conversion to and from 2 mbps, which provides a trans-
multiplexer function between PDH and SDH area of the network.

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4.7.2 Virtual Containers
At each level, subdivisions of capacity can float individually between the payload areas of
adjacent frames. This individuation allows for clock differences and wandering as payloads
traverse the network and are interchanged and multiplexed with others. In this way, the
inevitable imperfections of network synchronization can be accommodated. Each subdivision
can be readily located by its own pointer that is embedded in the overheads. The pointer is
used to find the floating part of the AU or TU, which is called a virtual container (VC). The
AU pointer located a higher-order VC, and the TU pointer located a lower-order VC. For
example, an AU-3 contains a VC-3 plus a pointer, and a TU-2 contains a VC-2 plus a pointer.
4.8 Cable lay-out method
At the time of making trench lay-out it should be taken in mind the position of bridge and bend
road. The splicing point should be given considering this point. The two sides of the bridge there
should be placed handhold and splicing point .The distance between two handhold and splicing
point should be declarer in meter in the drawing. The line will be marking by line and straight.
The position of underground cable and railway office their lay-out plans.
4.8.1 Cable Installation
The optical Fiber cable has been made by blowing machine at the time of blowing A man should
be kept the front handhold. 25m cable should be kept in the handhold and 30m cable should be
kept where the splicing point. For beginning the next blowing, the blowing machine should be
placed next the handhold function will be method.
Reading of the cable should be recorded at the closure terminal; at splicing loss more then o.3
will be taken. At the time of splicing the joint point will have to heating by giving heat will
smove. The fiber will have to arrange fairly in cloggier tray. If the fiber number is 12 then they
have separate by 6 in each arrangement. If this work functions for 48 fibers will have to finish.
The trench will have to kept between two closure and heaved to kept fairly by closure rubber
band. The point of closure has to close by heating. They indicate the direction of cable by
arranging circle order in the handhold ammoniating striker have to given and at last the open
path of the handhold will have to close by the handhold key.
4.8.2 List of the Instruments
1. Blowing machine
2. Optical fiber cable
3. Splicing machine
4. OTDR
5. Power Meter
6. Laser Gun
7. Closure
8. Smove
9. SDH MUX/DMUX

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Network Coverage MAP in CAD
1. Over all MAP
2. Distribution MAP in CAD
3. Back Bone MAP in CAD
Over all MAP
Distribution MAP in CAD

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Back Bone MAP in CAD
Optical-fiber-joint-enclosure
 Chassis Media Converter For Monitoring
POP end
Client End

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POP End Status:
Client Status

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Monitoring Server:
Final Checking in Field:
When the lying of the cable is complete next important point is to check weather there is any loop.
This is done by passing laser beam from one tower to another. If there are us any leakage or loss or any
other technical problem is easily detected by this method.
01. SplicingMachine 02. SplicingMachine andtray

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03. Optical FiberRack 04. O. T. D. R.
4.9 Network Topology:
The flexibility of SDH can be used to best advantage by introducing a new network topology.
Traditional networks make use of mesh and hub( i.e., start) arrangements, but SDH, with the help of
DXCs and hub multiplexers, allows these to be used in a much more comprehensive way. SDH also
enables these arrangement to be combined with rings and chains of ADMs to improve flexibility and
reliability across the core and access of a network.

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4.9.1 Network Block Diagram
4.9.2 NOC Block Diagram:
4.9.3POP End DistributionBlock Diagram:

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Chapter –Five: Conclusion and recommendation
5.1 Conclusion
The main disadvantage of fiber optic cables is their cost. Expensive to install and more fragile
than their metal counterparts, fiber optic cables are difficult to split as well. This makes them
more difficult to work with and install onsite, some optical fibers are subjected to "fiber fuse", an
occurrence caused when too much light reaches an imperfection in the line that destroys
connectivity. "Fiber fuse" can be minimized with defection circuitry at a transmitter. Some fiber
optic cables also can't carry electrical power to operate terminal devices, buit this feature is
becoming passes with the wider availability of mobile phones, wireless PDAs, and other remote
devices.
- Access to the fiber-optic submarine cable network will have an evolutionary impact on the
development of information and communication Technology (ICT) sector in Bangladesh. The
most important and remarkable impacts are :
- Almost free access to the global ICT resources and server network in the advanced countries at
a gigabit transmission rate;
-- Radical development in economy, human resources development, education, health and
medical services and business;
- Fast internet access through mobile network which will provide mobile internet facilities;
- Support to mobile banking, e-shopping, e-commerce, e-education, e-health and telemedicine
etc...
- Support to telecommunication infra-structure for e-governance.
Although we get some disadvantages Optical communication, Such as:
1. The flexibility of the base fibers.
2. Some problems involved with joining low T-couplers.
3. Some doubt in relation to the long-term reliability of optical fiber in the presence of
moisture.
4. The small size of the fibers & cables which creates some difficulties with splicing &
forming connector.
5. An independent electrical power feed is required for any repeaters, etc.
But the technology has developed. So both continuing developments and experience with optical
fiber system are generally reducing these problems.

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5.2 Recommendation
- To provide infrastructure for the submarine cables, optical fiber should be established in phases
throughout the country.
- Additional people should be employed and they should be well trained on optical
communication system, its maintenance and repairing.
- Sophisticated repair equipments need to be imported. Workshops should be improvised To
exploit the full bandwidth of FON capacity.
We are now at the peak of the century of technology and communication. We should think about
the easiest and noiseless communication technology. In this purpose, the optical fiber
communication system has made a tremendous change in the field of data communication
system, although it is not familiar in our country, but it is hopeful that optical fiber is being
introduced gradually. An optical fiber is allowing us with its Terabyte standard speed in data
communication, So we have no other choice like fiber optics comparing with coaxial cable. Our
neighboring country, India has made a great development in the field of communication
technology by introducing fiber optics backbone network recently. We should also be able to
develop our communication system to a world standard by familiarizing Optical fiber in our
country. We may change the status by improving fiber optic technology.

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Bibliography
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Prothom alo, (In Bangla) Friday, May 21, 2004.
II. Choudhury, J.R. "A Presentation on Prospects of Information and Communication
Technology (ICT) of Bangladesh" in DSCSC, July 25, 2005.
III. Mujibur Rahman Md, The Role of BTTB to facilitate the growth of ICTs in Bangladesh,
TELETECH, May 2004, P 56.
IV. Barta Correspondent, 100 Mbps Data Transfer in Dhaka, Monthly Computer Barta, July
2004, p 31.
V. A Souvenir published by Bangladesh Computer Council on 28 July2005, P-26.
VI. Jahangir Alam, Submarine Cable and Bangladesh, Monthly Computer Tomorrow, April
2004, p 34.