Industrial training provides students with a significant chance to actively participate in the telecommunications industry and get practical knowledge that is essential for their career advancement even before they graduate. The primary aim of industrial training is to impart pupils with a comprehensive comprehension of their particular domain and to confer certification for subsequent utilization. This program cultivates attributes such as careful adherence to industry regulations, unshakeable reliability, a deep sense of accountability, and successful collaboration with colleagues. This curriculum provides graduates with the necessary practical skills to effectively supervise network equipment that complies with industry standards, handle different types of connections, and operate cards within the telecommunications infrastructure. Throughout this session, we got the opportunity to examine the extensive network architecture of BTCL and get knowledge about the wide array of services provided by the company. Furthermore, we analyzed the complexities of losses that arise inside BTCL's operations and the corresponding tariffs. We have developed expertise in comprehending the protocols and procedures essential for the functioning of a telecommunications network. Through this extensive training, we have gained a deep understanding of the fundamental elements, equipment, and procedures that form the foundation of BTCL's telecommunications infrastructure. This course has enhanced our practical understanding and broadened our view of the telecoms industry in Bangladesh.

1. INTERNATIONAL ISLAMIC UNIVERSITY CHITTAGONG
BACHELOR OF SCIENCE IN ELECTRONIC AND
TELECOMMUNICATION ENGINEERING
Industrial Training Book
Course name: Industrial Training
Course Code: ETE-4804
Submitted by:
Md Inzamul Hoque
ID: T-191066
Submitted to:
Engr. Mohammad Jashim Uddin
Associate Professor
Department of ETE
IIUC, Chittagong
December, 2023
Course name: Industrial Training
Course Code: ETE-4804
Submitted by:
Md Inzamul Hoque
ID: T-191066

2. ii
Weekly Work Plan
Day Date Session Details
1 15-10-23 Company Introduction and introducing on
BTCL.
2 16-10-23 Switching & MDF room visit.
3 17-10-23 Introducing on Router, GPON, and ADSL.
4 19-10-23 Introducing on TNT Line Server.
5 22-10-23 Field Visit-1 (Cabinet, Drop wire, Subscriber).
6 25-10-23 Concept and ideas of ONU, Long distance, Short
Distance.
7 26-10-23 Field Visit-2 and Ending Ceremony.

3. i
Acknowledgement
I express my gratitude to the Almighty Allah (SWT) for His direction and inspiration,
which enabled me to successfully finish this training report. I extend my compliments
and prayers to the esteemed Prophet Mohammad (PBUH).
My sincere gratitude is extended to Engr. Mohammad Jashim Uddin, who is an
Associate Professor in the ETE Department and a well-respected member of the
Industrial Training Committee. His unwavering dedication and diligent efforts played
a pivotal role in coordinating the Industrial Training short course at BTCL. His
guidance was crucial in optimizing the assessment procedure for our graduation. I
express sincere gratitude for the chance to participate in industrial training at BTCL,
which was facilitated by the effective organization overseen by Md Mostafa Amir
Faisal, Assistant Professor and Proctor of the ETE Department at IIUC.
I would like to extend my genuine gratitude to the BTCL authority, comprising the
General Manager, the Support team, and all the assisting workers. Their endurance and
steadfast backing throughout my participation in this vocational training program were
crucial for the accomplished fulfillment of my duties. I couldn't have done this without
their assistance; their guidance and support were invaluable.
To sum up, I want to thank my parents and friends for their unwavering encouragement
and support, which contributed to the joy and motivation that characterized my training
experience. Their consistent dedication served as a constant source of motivation and
greatly contributed to the seamless and triumphant conclusion of my industrial training.
Md. Inzamul Hoque
T191066

4. ii
Declaration by the Candidate
I hereby verify that the "Industrial Training Report" I submitted to the Electronics and
Telecommunication Engineering department at IIUC meets certain requirements for the
B.Sc. degree in ETE from the ETE department, as it is based on my documented
experiences during industrial training. Furthermore, I certify that none of the
information contained in this report has ever been submitted before or will ever be
presented in whole or in part for the awarding of any other degree at this university or
any other domestic or foreign establishment.
Name: Md. Inzamul Hoque
ID: T191066
Section: B
Semester: 8th
Department of Electronic &
Telecommunication
Engineering, IIUC
Industrial Training Committee:
Convener
Engr. Mohammad Jashim
Udddin
Associate Professor, Department
of Electronic and
Telecommunications Engineering,
IIUC

5. iii
Table of Contents
Weekly Work Plan...................................................................................................................... ii
Acknowledgement......................................................................................................................i
Declaration by the Candidate .................................................................................................... ii
Table of Contents......................................................................................................................... iii
List of Figures............................................................................................................................ vi
List of Acronyms....................................................................................................................... vii
Abstract......................................................................................................................................1
Chapter 1....................................................................................................................................2
Introduction ...............................................................................................................................2
1.2 Introduction: ....................................................................................................................2
1.2 Background of the report: ...............................................................................................2
1.3 Over View of the Company:.............................................................................................3
1.4 objective of the training report: ......................................................................................3
Chapter 2....................................................................................................................................4
Introduction to BTCL..................................................................................................................4
2.1 What is BTCL?...................................................................................................................4
2.2 History of BTCL:................................................................................................................4
2.3 Services of BTCL: ..............................................................................................................5
2.4 Mission of the BTCL: ........................................................................................................6
2.5 Vision of the BTCL: ...........................................................................................................7
Chapter 3....................................................................................................................................8
Services that BTCL Offers...........................................................................................................8
3.1 Service Provided By BTCL:................................................................................................8
3.2 Conventional fixed-line telecommunication services:.....................................................9
3.3 High-speed internet connectivity options: ......................................................................9
3.4 GPON:...............................................................................................................................9
3.5 Leased Line Internet (LLI):..............................................................................................10
3.5.1 EFM (Ethernet Over the First Mile):........................................................................10
3.5.2 Full Fibre (Ethernet Access Direct and Fibre Ethernet):..........................................10
3.5.3 EoFTTC (Ethernet over FTTC): .................................................................................11
3.6 International Internet gateway (IIG):.............................................................................11
3.7 Interconnection Exchange (ICX):....................................................................................11
3.8 Internet Service Provider (ISP):......................................................................................11
3.9 CO-Location Facilities:....................................................................................................12
3.10 Domain Registration: ...................................................................................................12

6. iv
3.11 Asymmetric digital subscriber line (ADSL):..................................................................12
Chapter 4..................................................................................................................................14
BTCL construction features......................................................................................................14
4.1 BTCL comprises various departments:...........................................................................14
4.2 Electricity Supply Division:.............................................................................................14
4.3 Server Department: .......................................................................................................15
4.4 Coding Division & Switching Division:............................................................................15
4.5 Data Transmission Division:...........................................................................................16
4.6 Maintenance and Problem-solving Unit:.......................................................................16
Chapter 5..................................................................................................................................17
Hardware utilized by BTCL.......................................................................................................17
5.1SFP:..................................................................................................................................17
5.2 Passcot: ..........................................................................................................................18
5.3 DSL MODEM:..................................................................................................................18
5.4 optical power meter: .....................................................................................................19
5.5 LC-LC Cable:....................................................................................................................20
5.6 Ethernet Media Converter:............................................................................................21
5.7 ONU:...............................................................................................................................21
5.8 Cards That BTCL Uses:....................................................................................................22
Chapter 6..................................................................................................................................24
Wire Used By BTCL...................................................................................................................24
6.1Copper Cable:..................................................................................................................24
6.1.1CAT5:........................................................................................................................24
6.1.2 CAT6:.......................................................................................................................24
6.2 Optical Fiber:..................................................................................................................24
6.2.1 FTTP.........................................................................................................................25
6.2.2 FTTC.........................................................................................................................25
6.2.3 FTTB.........................................................................................................................26
6.3 Submarine Cable:...........................................................................................................27
6.4 Underground Cable:.......................................................................................................28
6.5 Splitter:...........................................................................................................................28
Chapter 7..................................................................................................................................30
Functionalities of BTCL.............................................................................................................30
7.1 Diagram of a Power System Blog:..................................................................................30
7.2 OLD Phone Exchange: ....................................................................................................31

7. v
7.3 GPON (New Phone Exchange): ......................................................................................32
7.4 Modulation Technique:..................................................................................................34
7.4.1 PCM:........................................................................................................................34
7.4.2 QPSK:.......................................................................................................................35
7.5 Subscriber Signaling:......................................................................................................35
7.6 Subscriber Looping:........................................................................................................36
7.8 Switching Method:.........................................................................................................36
1. Circuit Switching: .........................................................................................................36
2. Packet Switching: .........................................................................................................37
3. VoIP (Voice over Internet Protocol) Switching: ...........................................................38
Chapter 8..................................................................................................................................40
BTCL's losses ............................................................................................................................40
8.1 Fiber loss:.......................................................................................................................40
8.2 Loss of connection: ........................................................................................................40
8.3 Loss due to splicing: .......................................................................................................40
8.4 Splitter Loss:...................................................................................................................40
Chapter 9..................................................................................................................................41
Conclusion................................................................................................................................41
9.1 Conclusion:.....................................................................................................................41
9.2 My Experience: ..............................................................................................................41
Reference:................................................................................................................................43
Photo Gallery ...........................................................................................................................45
Plagiarism Report.....................................................................................................................46

8. vi
List of Figures
Fig 3.1 Services of BTCL..............................................................................................................8
Fig 4.1 AC & DC System............................................................................................................14
Fig 4.2 Server Section...............................................................................................................15
Fig 4.3 OLT................................................................................................................................15
Fig 4.4 switching Rack & Subscriber Card ................................................................................16
Fig 4.5 Transmission Division...................................................................................................16
Fig5.1 SFP.................................................................................................................................17
Fig 5.2 passcot..........................................................................................................................18
Fig 5.3 DSL MODEM .................................................................................................................19
Fig5.4 optical power meter......................................................................................................20
Fig5.5 LC-LC Cable....................................................................................................................21
Fig5.6 Ethernet Media Converter ............................................................................................21
Fig5.7 ONU...............................................................................................................................22
Fig 6.1 Cat 5 & Cat 6 Cable.......................................................................................................24
Fig6.2 FTTP Cable.....................................................................................................................25
Fig6.3 FTTC...............................................................................................................................26
Fig6.4 FTTB...............................................................................................................................27
Fig6.5 submarine cable............................................................................................................27
Fig 6.6 Underground Cable Intersection..................................................................................28
Fig6.7 Splitter...........................................................................................................................29
Fig7.1 Power System................................................................................................................30
Fig7.2 OLD Phone Exchange.....................................................................................................31
Fig7.2 GPON.............................................................................................................................32
Fig 7.1 sampled Signal..............................................................................................................34
Fig7.2: quantization .................................................................................................................34
Fig 7.3 QPSK Signal...................................................................................................................35
Fig7.4 circuit switching.............................................................................................................37
Fig7.5 packet Switching............................................................................................................38
Fig7.6 VOIP...............................................................................................................................39

9. vii
List of Acronyms
Acronyms
AC: alternating current.............................................................................................................14
ADC: Analogue to Digital Converter ......................................................................................15
ADSL: Asymmetric Digital Subscriber Line,..........................................................................12
ADSL: Asymmetrical Digital Subscriber Line..........................................................................8
ANS: Access Network Switch .................................................................................................31
BTCL: Bangladesh Telecommunications Company Limited....................................................3
BTRC: Bangladesh Telecommunication Regulatory Commission............................................5
BTTB: Bangladesh Telegraph & Telephone Board...................................................................4
DC: Direct current....................................................................................................................14
DNS: Domain name system.......................................................................................................8
DP: Distribution Points............................................................................................................32
DSLAM: Digital subscriber line access multiplexer ...............................................................12
EFM: Ethernet Over the First Mile..........................................................................................10
EoFTTC: Ethernet over Fiber to the Cabinet...........................................................................11
ETE: Electronic and Telecommunication Enginnering .............................................................2
FTTB: Fiber-to-the-Building ...................................................................................................26
FTTC: Fibre to the Cabinet......................................................................................................11
FTTP: Fiber-to-the-Premises ...................................................................................................25
GBIC: Gigabit Interface Converter..........................................................................................17
GPON: Gigabit Passive Optical Network..................................................................................8
IASP: Internet Access Service Provider ....................................................................................8
ICX: Interconnection Exchange...............................................................................................11
IIG: International Internet Gateway.........................................................................................11
IIUC: International Islamic University Chittagong ................................................................... ii
IP:Internet Protocol..................................................................................................................37
IPLC: International private leased circuit ..................................................................................8
ISP: Internet Service Providers..................................................................................................9
LLI: Leased Line Internet ..........................................................................................................10
LTE: Long-Term Evolution.......................................................................................................6
MDF:Main Distribution Frame................................................................................................32
MNO: Mobile |Network Operator............................................................................................31
NGN: Next-Generation Network...............................................................................................6
ODF: Optical Distribution Frame ............................................................................................33
OLLI: Dedicated Leased Line Internet ......................................................................................8
OLT: Optical Line Terminal......................................................................................................9
ONT: Optical Network Terminal.............................................................................................33
ONU: Optical Network Unit......................................................................................................9
OPM: optical power meter.......................................................................................................19
PBUH: Peace be upon him......................................................................................................... ii
PCM: Pulsed Code Modulation ...............................................................................................15
PSK: Phase Shift Keying .........................................................................................................35
PSTN: public switched telephone network................................................................................4

10. viii
QPSK: Quadrature Phase Shift Keying ...................................................................................35
SFP: Small form-factor pluggable ...........................................................................................17
TCP: Transmission Control Protocol.......................................................................................37
TDMA: Time Division Multiple Access ...................................................................................9
VoIP: Voice over Internet Protocol ...........................................................................................9
.

11. 1
Abstract
Industrial training provides students with a significant chance to actively participate in the
telecommunications industry and get practical knowledge that is essential for their career
advancement even before they graduate. The primary aim of industrial training is to impart
pupils with a comprehensive comprehension of their particular domain and to confer
certification for subsequent utilization. This program cultivates attributes such as careful
adherence to industry regulations, unshakeable reliability, a deep sense of accountability, and
successful collaboration with colleagues. This curriculum provides graduates with the
necessary practical skills to effectively supervise network equipment that complies with
industry standards, handle different types of connections, and operate cards within the
telecommunications infrastructure. Throughout this session, we got the opportunity to
examine the extensive network architecture of BTCL and get knowledge about the wide array
of services provided by the company. Furthermore, we analyzed the complexities of losses
that arise inside BTCL's operations and the corresponding tariffs. We have developed
expertise in comprehending the protocols and procedures essential for the functioning of a
telecommunications network. Through this extensive training, we have gained a deep
understanding of the fundamental elements, equipment, and procedures that form the
foundation of BTCL's telecommunications infrastructure. This course has enhanced our
practical understanding and broadened our view of the telecoms industry in Bangladesh.
Keyword: Telecommunications, IT Devices, Network, ISP, OLTIP/MAC, OTDR, Fiber Optic
Broadband, Data Communication, Network Security.

12. 2
Chapter 1
Introduction
1.2 Introduction:
Industrial training is a crucial element of professional education, particularly in
engineering programs. Throughout these training sessions, students are afforded the
chance to visit enterprises, acquiring direct exposure to the internal operations of these
organizations. These industrial excursions aim to raise students' awareness of the actual
difficulties that firms face in the professional realm. Instead of merely acquiring
theoretical knowledge about these problems, students undergo a concrete firsthand
experience of them. Industrial trips are crucial for improving students' comprehension
of diverse management ideas. When students observe these concepts being used in real-
life situations, their understanding greatly intensifies. It is not solely about acquiring
knowledge on management principles from reading; rather, it is about witnessing their
application in a real-world corporate setting.
1.2 Background of the report:
Industrial training is a mandatory component of the final year curriculum in the ETE
department at IIUC. It offers students a valuable opportunity to get practical experience
and improve their employability skills. The training is conducted at a government-
owned enterprise situated in the city of Chattogram. The primary objective of this
program is to offer students hands-on experience in a professional work environment
and enhance their proficiency. The training program is subject to rigorous examination
and adjustments to consistently improve its efficacy in equipping students with the
essential skills and information required for their future employment. This guarantees
that academic learning is tightly synchronized with the practical requirements of the
industry.
The primary goal of this industrial training program is to bridge the gap between
theoretical knowledge obtained via university education and the practical skills required
in the professional field. The program also seeks to foster core values such as integrity,
proficiency, and self-confidence in students, with a focus on ethical conduct and strong
work ethics. Furthermore, it familiarizes students with pertinent safety regulations in
the industry and fosters cooperation and beneficial relationships between students and
experts.
In the current labor market, where graduate unemployment is a significant problem,
there is an increasing interest in exploring opportunities for self-employment. Industrial
training is a highly valuable approach that equips students with the necessary abilities
to tackle real-world challenges and prepares them for post-graduation. Companies
endorse this approach to ensure that their students are sufficiently prepared for the job
market, regardless of their chosen academic field. This report fulfills the practical
requirement of the final year undergraduate degree program in the ETE department.
The portfolio demonstrates the knowledge and skills gained during the training, as well
as the intern's expertise in technical areas, writing capabilities, and ability to adapt.

13. 3
1.3 Over View of the Company:
The Bangladesh Telecommunications Company Limited (BTCL) is a notable state-
owned telecommunications organization in Bangladesh. BTCL is the dominant
telecommunications service provider in the country and holds a substantial position in
the telecommunications industry. The company provides an extensive array of services,
encompassing landline telephony, broadband internet, and data-related products.BTCL
plays a vital role in delivering telecommunications infrastructure and services in both
urban and rural regions of Bangladesh. The organization is dedicated to enhancing the
nation's connectivity and reducing the digital divide by providing dependable and easily
accessible telecommunications services to a diverse population.
BTCL, historically recognized for its supply of fixed-line telecommunications services,
has diversified its portfolio to encompass broadband internet and data solutions, in
response to the evolving needs of its clientele. The company is committed to expanding
its network, improving service quality, and adapting to the dynamic
telecommunications landscape in Bangladesh. BTCL, as a government-owned
enterprise, plays a pivotal role in the overall progress and modernization of the
telecommunications sector in the nation.
1.4 objective of the training report:
The primary goal of this study is as follows:
 To comprehend BTCL's prospective strategies and goals for its future expansion
and advancement.
 To examine the sophisticated technologies and methodologies utilized by
BTCL.
 The objective is to evaluate the impact of BTCL's operations on the telecoms
landscape in its area.
 The purpose is to examine the legal and regulatory aspects of BTCL's activities
and ensure its compliance with the established laws.
 To investigate BTCL's initiatives in mitigating the digital divide among the
local community
 The objective is to assess the manner in which BTCL engages with its clients
and fulfills their needs, as well as the resulting consequences of these
interactions.
 In order to understand the eco-friendly initiatives undertaken by BTCL to
reduce its environmental impact
 The objective is to examine BTCL's collaborations with international
telecommunications organizations in order to enhance worldwide connectivity.

14. 4
Chapter 2
Introduction to BTCL
2.1 What is BTCL?
BTCL, short for Bangladesh Telecommunications Company Limited, is the leading
telecommunications provider in Bangladesh. The origins of this can be attributed to the
establishment of the Bangladesh Telegraph & Telephone Board (BTTB) following the
country's hard-won independence in 1971. BTCL, boasting a staff of 12,636 employees,
is at the forefront of delivering vital communication services to the country.
BTCL provides a wide range of services that include land-line telephone services
specifically designed for urban regions in Bangladesh. This encompasses domestic
long-distance calling and international connectivity, guaranteeing that individuals
remain linked on a local and global scale. Moreover, the corporation has a robust
presence in the internet service industry, playing a significant role in enhancing the
digital connectivity of the country.
Significantly, BTCL's supremacy underwent a revolutionary period in 2004 when the
Bangladesh Government granted PSTN licenses to private businesses. Nevertheless,
these new entrants were initially barred from offering services in the highly desirable
Dhaka market, which constitutes a significant share of the country's
telecommunications industry. The era of BTCL's monopoly started to decline in 2007
as other operators gradually acquired licenses, signifying a notable change in the
telecommunications industry.
2.2 History of BTCL:
The history of BTCL, or the Bangladesh Telecommunications Company Limited,
encompasses a period of more than one hundred years and is characterized by notable
changes. The inception of the Telegraph branch within the Posts and Telegraph
Department in British India occurred in 1853. The Telegraph Act of 1885 established
regulations for this initial communication service, paving the way for subsequent
advancements.
In 1962, the Pakistan Telegraph and Telephone Department was established in East
Pakistan, which laid the foundation for advanced telecommunications in the area. In
1971, after achieving independence, the Bangladesh Telegraph and Telephone
Department was established. The department underwent a transformation and became
a corporate organization called the 'Telegraph and Telephone Board' after the Telegraph
and Telephone Board Ordinance was passed in 1975.
In 1853, the establishment of the Posts and Telegraph Department in British India
provided the groundwork for the legacy of BTCL by building the structure for early
communications services.
In 1885, the Telegraph Act was passed to regulate the growing telegraph services by
establishing important standards and norms.
In 1933, the Wireless Act of 1933 was introduced, which was a significant milestone
in the advancement of wireless communication in the area.
In 1962, the creation of the Pakistan Telegraph and Telephone Department in the area
that was known as East Pakistan was a major development in the telecommunications
industry of the region. The objective of this restructure was to enhance and broaden
communication services through modernization.

15. 5
In 1971, after the hard-won independence of Bangladesh, the establishment of the
Bangladesh Telegraph and Telephone Department marked the beginning of a new era
in telecommunications. It was positioned inside the Ministry of Posts and
Telecommunications.
In 1975, the Bangladesh Telegraph and Telephone Department underwent a change and
was restructured into a corporate organization called the 'Telegraph and Telephone
Board.' The changeover was made easier by the enactment of the Telegraph and
Telephone Board Ordinance in 1975.
In 1979, a significant event occurred when the Telegraph and Telephone Board
underwent further restructuring with the implementation of the Bangladesh Telegraph
and Telephone Board (BTTB) Ordinance. This legislation conferred upon BTTB the
power to issue licenses for Telecom and Wireless services, so broadening its sphere of
operation.
In 1998, the Telecommunication Policy-1998 was implemented, which outlined a plan
for the future progress of telecommunications in Bangladesh, directing the industry
towards significant advancements.
In 2001, the Telecommunication Act of 2001 was implemented, leading to the
formation of the Bangladesh Telecommunication Regulatory Commission (BTRC).
The former Frequency and Wireless Board, which was a division of the Ministry of
Posts and Telecommunications, was replaced by this organization.
In 2008, a significant change took place when the Bangladesh Telegraph and Telephone
Board (BTTB) was converted into the Bangladesh Telecommunications Company
Limited (BTCL) on July 1st, 2008. The telecommunications landscape saw a notable
transformation as the Bangladesh Government assumed complete ownership of BTCL,
with subsequent intentions to establish public ownership of shares.
In 2009, the telecommunications sector saw further development with the
implementation of the Bangladesh Telegraph and Telephone Board (Amendment) Act,
2009. This act played a crucial role in establishing the regulatory framework and
governing the operations of the sector.
2.3 Services of BTCL:
BTCL bears a substantial obligation to provide critical telecommunications services
throughout the nation. At present, BTCL caters to almost 1 million telephone
subscribers, encompassing both Upazila (Thana) and growing centers. A significant
number of these consumers also have the ability to utilize dial-up internet services.
BTCL possesses the most extensive telecommunications infrastructure in the nation,
encompassing copper cables, microwave linkages, satellite connections, and optical
fiber networks.
BTCL stands out for its competitive phone and internet rates, which make its services
more cost-effective compared to other telecom carriers. In addition, they offer ADSL
broadband internet, which currently has a capacity of 33,000 connections. Moreover,
BTCL holds the top position as the primary provider of fixed telephone services in
Bangladesh. Their range of services encompasses landline telephony, dial-up internet,
ADSL internet, high-capacity local and international leased lines, VPN (Virtual Private
Network), MPLS (Multiprotocol Label Switching), country domain registration, co-
location services, and additional offerings.

16. 6
BTCL intends to provide Next-Generation Network (NGN) soft switch-based services
and triple play services, encompassing phone, video, and data transmission, supplied
through fiber optic cables directly to residential premises. In addition, they are
contemplating entering the market for LTE wireless services. BTCL is a versatile
participant in the telecommunications sector, offering voice services, international and
national gateways, internet services, network infrastructure, and domain registration.
This positions them as a major telecommunications provider in Bangladesh.
2.4 Mission of the BTCL:
BTCL's objective is to become a prominent and inventive telecommunications provider
in Bangladesh, committed to fulfilling the communication and connection requirements
of the country. Their mission can be succinctly defined as:
Universal Connectivity: BTCL is dedicated to expanding dependable communication
and internet connectivity to every part of Bangladesh, including distant and underserved
regions, guaranteeing that every individual, business, and organization has access to
vital telecoms services.
Quality and Reliability: The objective of the company is to offer telecommunications
services that are of superior quality and reliability. This includes providing fixed-line
telephone connections and broadband internet, with a specific emphasis on delivering
clear and consistent communication to consumers.
BTCL is committed to adopting technical breakthroughs and fostering innovation in
the telecoms industry. Their objective is to remain at the forefront of the market by
implementing innovative solutions and services, such as NGN soft switch-based
services and triple play over fiber, in order to fulfill the changing needs of customers.
Accessibility and affordability are fundamental aspects of their purpose, aiming to
ensure that telecommunications services are within reach and reasonably priced for a
wide range of individuals. BTCL strives to provide cost-effective pricing without
compromising on the quality of service.
Business Support: BTCL aims to enhance the expansion and productivity of enterprises
and organizations through the provision of high-capacity leased lines, network
management solutions, and co-location services. Their objective is to play a crucial role
in facilitating Bangladesh's economic and technological advancement.
BTCL's primary objective is to establish international connectivity by acting as a
gateway, linking Bangladesh to the worldwide telecommunications network. This
guarantees a smooth flow of international communication and data interchange for the
nation.
Comprehensive Range of Services: BTCL's objective is to offer an extensive array of
services, encompassing voice and data communication, internet connectivity, and
domain registration, in order to cater to the varied requirements of their customer base.
Prepared for the future: BTCL is strategically positioning itself to adapt and expand in
response to the changing telecoms landscape, with plans to offer LTE wireless services
and use constant technological advancements.

17. 7
2.5 Vision of the BTCL:
BTCL aims to expand into an innovative and flexible organization that continues to
have a leading position in Bangladesh's telecommunications industry. This vision
highlights the company's commitment to keeping up with the swiftly changing technical
environment and maintaining its position as a leader in the industry.
The fundamental elements of this vision include:
Agile Evolution: BTCL is dedicated to adapting and modifying itself in response to the
constantly changing telecoms landscape. This dedication demonstrates a concentration
on adaptability, originality, and promptness in addressing developing technology and
changing client needs.
The Company is determined to maintain its dominant position in the telecoms industry.
This indicates a resolute dedication to providing exceptional services and maintaining
a competitive edge in terms of infrastructure, technology, and client contentment.
Improved Telecommunication Infrastructure: A crucial element of this strategy entails
the extension and enhancement of the telecommunication infrastructure. This involves
the creation of strong networks, advanced communication technologies, and wider
coverage to effectively address the communication and connection needs of the
country.
Technological Advancement: BTCL aims to adapt and utilize cutting-edge technology
and solutions in order to provide the highest quality services to its consumers. This
could involve allocating funds towards the development of advanced networks and
digital communication technologies.
Customer-Centric Strategy: In order to sustain its position of leadership, it is imperative
to prioritize customer happiness. The company's vision certainly includes a dedication
to providing outstanding customer service, cost efficiency, and reliability.
BTCL, as a prominent telecommunications company, aims to contribute to the socio-
economic development of Bangladesh by enabling widespread access to
communication and information for all sectors of the people.

18. 8
Chapter 3
Services that BTCL Offers
3.1 Service Provided By BTCL:
 Traditional landline telephone services.
 High-speed internet connectivity alternatives.
 Gateway products include the Global Connectivity Gateway, Network
Interconnection Hub, and International Online Connection Gateway.
 Online services include Domain Name Registration, Website Hosting, and
DNS Management.
 Company offers many solutions for transmitting data, including options such
as data transfer bandwidth, telecom tower facilities, shared facility space, and
international private leased circuit (IPLC) local loop.
 The conventional public telephone network.
 The technology being referred to is Advanced Gigabit Passive Optical
Network (GPON).
 Service offers a Dedicated Leased Line Internet (OLLI)...
 ADSL, short for Asymmetrical Digital Subscriber Line,
 An Internet Access Service Provider (IASP).
Fig 3.1 Services of BTCL

19. 9
3.2 Conventional fixed-line telecommunication services:
Using copper lines to physically transfer your speech to the other party, a landline is a
type of analog telephone service that allows voice communication.
The progress in technology has resulted in the development of diverse forms of landline
telephone services. These choices include Voice over Internet Protocol (VoIP), which
operates over an internet connection, and wireless landline service, which establishes
connections by linking to nearby cell towers. While traditional landlines were known
for their reliability, they could not match the variety and speed of wireless phones.
Consequently, BTCL has gradually reduced its provision of landline services in recent
years.
This transition is motivated by the need to conform to the changing communication
environment and fulfill the requirements of a progressively mobile and internet-
connected society.
3.3 High-speed internet connectivity options:
BTCL's high-speed internet service enables internet connectivity via a conventional
telephone line. Users can fast and conveniently access the internet by connecting their
computer's modem to the phone jack through the landline line and setting it to dial a
specific number provided by the online service providers (ISP). This service provides a
smooth connection between traditional telecommunication infrastructure and the digital
world, allowing consumers to efficiently access the internet.
3.4 GPON:
GPONs, an integral component of BTCL's infrastructure, are advanced optical cable
networks designed primarily for efficient data transfer. Currently, GPONs have
emerged as the prevailing standard in Passive Optical Networks. Remarkably, they
provide an exceptional user-to-fiber ratio of 1:64 or 1:128 on a solitary optical strand,
showcasing their efficacy in accommodating a substantial number of users. GPONs, in
contrast to conventional copper-wire networks, demonstrate a notable 95%
enhancement in energy efficiency, aligning with the global movement towards more
environmentally-friendly technologies. Moreover, their innate ability to readily adapt
in size and be cost-effective makes them particularly appealing in densely populated
areas that are covered by BTCL. This is a result of employing splitters, which enable
the network to accommodate an increasing number of users as it expands. The Optical
Line Terminal (OLT) is an essential element of GPON technology, with the
responsibility of supervising the network's operations. GPONs employ a Time Division
Multiple Access (TDMA) mechanism to assign bandwidth to specific Optical Network
Units (ONUs). The maximum downstream rate that an Optical Network Unit (ONU)
may reach is 2.488 Gbits/s. Nevertheless, the upstream rate may vary due to its
distribution among multiple ONUs. The Optical Network Units (ONUs) establish
connection with the Optical Line Terminal (OLT), which utilizes sophisticated
algorithms to precisely assess the distances and time delays of subscribers. This
guarantees the efficient and reliable transport of data.
BTCL's network infrastructure incorporates GPON technology, showcasing the
organization's commitment to cutting-edge telecommunications solutions. This design
integrates the core principles of sustainability, efficiency, and adaptability, with a
specific focus on addressing the evolving needs of densely populated regions, while
maintaining a strong commitment to environmental consciousness. BTCL employs
GPON technology to offer its customers uninterrupted and cost-effective connectivity.

20. 10
This network optimally optimizes bandwidth resources, leading to uninterrupted and
rapid data transfer in both directions. The technology showcased here exemplifies
BTCL's dedication to providing superior services, underscoring the organization's
pivotal role in delivering cutting-edge telecommunications solutions to its users.
3.5 Leased Line Internet (LLI):
BTCL provides a reliable communication network, demonstrated by a leased line that
effortlessly connects two or more locations. A leased line is a contractual agreement
between a service provider and a consumer that guarantees the uninterrupted and
dependable transmission of data between these two sites. On a monthly basis, service
providers charge a predetermined fee for this data connection. These dedicated leased
lines utilize optical fiber cables, guaranteeing high-speed connectivity and ample
bandwidth, making them well-suited for a variety of purposes:
 Facilitating internet access.
 Enabling or assisting with telephone conversations.
 Enabling staff to operate remotely using their personal laptops.
 Setting up networks between workstations and computers in different settings.
BTCL provides a Leased Line Internet (LLI) service that offers a two-way
telecommunications line, enabling smooth connectivity between various sites. The
rental cost differs among suppliers and is often invoiced on a monthly basis. A wide
range of organizations depend on strong and reliable internet connectivity, improved
speed, and sufficient capacity to optimize their operations and specialized applications.
Certain firms rely significantly on telecommuting and remote staff to access office
software and transfer crucial data. Leased lines provide flexible alternatives that are
carefully organized to satisfy specific connectivity requirements within BTCL's
extensive range of services, guaranteeing a dynamic and dependable network solution.
BTCL provides a variety of leased line choices, each designed to meet specific
connectivity requirements:
3.5.1 EFM (Ethernet Over the First Mile):
EFM, also known as Ethernet broadband, creates a network that sends data to
businesses utilizing traditional copper lines, thereby replacing the connection with a
fully fiber Ethernet link. EFM utilizes the utilization of paired copper cables to
guarantee continuous communication. The redundancy system ensures continuous
functioning by smoothly transitioning to another pair in the event of a failure. EFM
serves as a substitute for businesses that do not have access to nearby fiber cabinets,
while its speed is comparatively lower than that of optical fibers.
3.5.2 Full Fibre (Ethernet Access Direct and Fibre Ethernet):
Full-fiber connectivity, also known as Ethernet Access Direct or Fibre Ethernet, is
renowned for its outstanding performance, high speed, and wide bandwidth. It has
earned the nickname "big daddy" in the realm of internet access. This option enables
the establishment of a direct and fast Ethernet connection by utilizing optical fiber
cables. This service establishes a direct and exclusive connection between a company's
physical location and the Internet Service Provider (ISP), providing a guaranteed and
uninterrupted connection with speeds of up to 1Gbps. Despite its high cost, this product
represents the epitome of dependability and swiftness.

21. 11
3.5.3 EoFTTC (Ethernet over FTTC):
EoFTTC, which stands for Ethernet over Fiber to the Cabinet, is a cost-effective
alternative to Ethernet in the First Mile.It utilizes both copper and dedicated fiber wires.
Businesses frequently opt for Ethernet over Fiber to the Cabinet (EoFTTC) as a means
of connecting to nearby fiber-based cabinets. Nevertheless, the speed of the connection
may vary depending on the proximity of the business to the local cabinet. Certain
providers offer symmetrical connections, which can sometimes result in faster
download speeds in comparison to upload speeds.
BTCL offers a range of leased line alternatives that are designed to meet various
corporate needs, providing a reliable and customized connectivity solution.
3.6 International Internet gateway (IIG):
IIGs are purpose-built to function as a conduit for the management and processing of
global internet data flow, encompassing both inbound and outbound traffic. The
primary function of this gateway is to create a connection with the existing undersea
cable, serving as its main link. Additionally, it is equipped with a Satellite Earth
Station/VSAT as a secondary backup. The backup will be employed until an alternative
submarine cable becomes available. All Internet Service Providers (ISPs) will employ
the International Internet Gateway System (IIGS) to establish connections with the
global internet. The IIG Licensee is responsible for procuring both submarine cable
bandwidth and backup satellite bandwidth. Data and voice transfers can both be made
using this infrastructure.
3.7 Interconnection Exchange (ICX):
The operations of ICXs are connected to those of IGWs and the Access Network
Service (ANS). All international voice calls, including VoIP calls, must, in accordance
with the IDLTS Policy, be routed to and initiated from within Bangladesh via
Interconnection Exchanges (ICX) and international Gateways (KW). ICX will make it
easier to manage the voice call services that are provided by domestic inter-operators.
This will result in an improvement in the overall quality of voice services, as well as a
more equitable distribution of traffic among all operators. Additionally, ICX will
provide easier access to the national telecom network for telecom operators. In addition
to this, it makes it easier to preserve call data, which provides authorities with assistance
in the identification, surveillance, and tracking of potential criminals. Through the
implementation of International Mobile Equipment Identity (IMEI) registration, ICX
can contribute to the decrease of thefts involving mobile phones. Number portability is
made possible by ICX, which makes it possible to move mobile network services
without having to alter one's cell number. This makes switching mobile networks much
more convenient.
3.8 Internet Service Provider (ISP):
ISP stands for "Internet Service Provider," and it refers to a company that offers Internet
connectivity to consumers in a variety of settings, including homes and businesses.
Internet service is provided by BICL, which is an example of an ISP. BTCL is well-
known for the provision of extremely quick Internet access, and illustrious
organizations like RUET make use of these services. In addition to providing customers
with Internet access, Internet service providers frequently also provide supplementary
services, such as website hosting and domain name registration. For instance, BTCL is
an Internet Service Provider (ISP) that welcomes and encourages connections from
other ISPs to its network. After then, these secondary Internet service providers offer

22. 12
Internet access to both individuals and enterprises. Nevertheless, it is essential to bring
to your attention the fact that BTCL will on occasion provide a direct Internet
connection to both corporate entities and individual users.
3.9 CO-Location Facilities:
A co-location facility is a type of data center that allows businesses to rent out space
for the purpose of storing their servers and other types of computing equipment. Co-
location services are one of the many things that BTCL has to offer, and the company
also rents transmission towers on a monthly basis so that microwaves and other waves
can be sent. The facility provides the infrastructure, which may include the building,
cooling, power, bandwidth, and physical security, in a co-location agreement;
nevertheless, the user is responsible for supplying their own servers and storage
devices. In most cases, the space within the facility is rented out on the basis of a per-
rack, per-cabinet, or per-cage basis, or on a per-room basis. A number of companies
that provide co-location services have extended the scope of their product lines to
include managed services. These services contribute to the achievement of the business
goals of the companies' customers. Co-location can be beneficial for some businesses,
but it is crucial to evaluate the potential drawbacks, such as increased travel expenses
as a result of the location picked and the possibility of being trapped by long-term
contracts that make it more difficult to renegotiate rates when prices drop.
3.10 Domain Registration:
BTCL offers exclusive domain registration services for .bd domains, a provision that is
not provided by other ISPs. An organization that manages domain name registration
and associates IP addresses with domain names to facilitate access to websites through
alphanumeric aliases is known as a domain name registrar. BTCL provides domain
registration services specifically for .bd domains.
3.11 Asymmetric digital subscriber line (ADSL):
ADSL, short for Asymmetric Digital Subscriber Line, is a method employed to transmit
internet services via copper cable connections. It provides faster connectivity speeds
than traditional dial-up internet when compared to standard telephone lines. ADSL has
been instrumental in enabling fast broadband internet, shaping the era of Web 2.0 and
beyond. It operates by exploiting the existing copper telephone lines, which have long
been used for voice communication, to transmit digital data at high speeds. This enables
activities such as sending emails and streaming YouTube movies.
To establish a functional ADSL connection, various technologies work together in a
coordinated manner.Users require an ADSL modem that is linked to a nearby telephone
exchange using standard copper telephone wires. At the exchange, the copper wires and
other connections from the local area are connected to a digital subscriber line access
multiplexer (DSLAM). The user's ADSL modem establishes connection with the
DSLAM by employing discrete frequencies to distinguish digital data from potential
voice conversations delivered over the same telephone line. At the exchange, these
signals are segregated and routed to various networking technologies further up in the
hierarchy, ultimately establishing a connection between the user and the target server
or telephone. It is imperative to recognize that ADSL is limited by a maximum speed
constraint of around 50 Mbps, which is dictated by the bandwidth capacity of the copper
lines.However, there are many factors that can affect the speed of an ADSL connection,
and a large number of these factors are outside the control of the end user.

23. 13
Exchanges have the responsibility of overseeing and controlling telephone connections
in the ADSL system. The primary stock exchange in Bangladesh is located in Sher-E-
Bangla Nagar, Dhaka. Each exchange is intricately linked with underground copper
wire wires. At the start, a call is connected to the Dhaka exchange, which then directs
it to the desired destination, such as the Chittagong exchange. ADSL employs the
Quadrature Phase Shift Keying (QPSK) modulation technique. Before the introduction
of optical fiber, ADSL was a widely recognized and commonly used technology.
Digital Subscriber Line Access Multiplexer (DSLAM):
Internet Service Providers (ISPs) are the organizations that make use of a piece of
hardware known as a Digital Subscriber Line Access Multiplexer (or just DSLAM for
short). These devices are typically installed in telephone exchanges or distribution
points, and their primary function is to facilitate the connection of a large number of
Digital Subscriber Line (DSL) customers to the internet or a high-speed digital
communication channel. DSLAM accomplishes this by utilizing a device known as a
multiplexer. This device combines a number of signals into a single signal, which
enables all of the signals to share the same communication channel.
The provision of extremely quick internet connectivity to customers is the primary goal
served by technologies such as DSLAM. This is accomplished by routing all of the
incoming requests from DSL subscribers into a single multiplexer in the data center.
When connecting to the internet, the multiplexer makes use of its own high-speed
capabilities that it has built into it. It makes the user's surfing sessions more enjoyable
by providing responses from the websites that they have visited. Multiplexing is used
to combine voice and data traffic into a single unified "signal" that is transmitted by
DSLAM hardware. This is accomplished by collecting data from a large number of
modem ports. Depending on the architecture and configuration of the DSLAM, it may
be able to consolidate DSL lines through the use of a variety of network protocols.
These protocols may include Asynchronous Transfer Mode (ATM), frame relay, or
Internet Protocol (IP). PTM-TC is an abbreviation for the Packet Transfer Mode -
Transmission Convergence protocol stack, which is used by some DSLAMs.
In order to prevent metal corrosion, BTCL applies a negative voltage to the cards, which
is typically in the range of -48 volts. This precaution not only ensures the well-being of
individuals but also reduces the probability that rust will cause difficulties in the future.

24. 14
Chapter 4
BTCL construction features
4.1 BTCL comprises various departments:
 Maintenance
 Networking
 Official
 Customer Service.
Within this framework, we will collectively discuss the maintenance and networking
departments. These departments consist of several specialized divisions dedicated to
networking and maintenance.
1. Division responsible for providing electricity supply.
2. Department in charge of servers.
3. Divisions responsible for coding and switching.
4. Division responsible for data transmission.
5. Unit dedicated to maintenance and problem-solving.
4.2 Electricity Supply Division:
The power division within BTCL is crucial for ensuring the smooth operation of
networking and maintenance equipment. It consists of two independent power
allocation systems: one for alternating current (AC) and another for direct current (DC).
The AC system supplies a consistent 220-volt AC voltage, while the DC system
accommodates the power needs of the equipment, whether it is AC or DC.
It is essential to be aware that all of the components that make up this division function
at a negative voltage level, more especially one that is around -48 volts. The device is
shielded from any potential harm that could be brought on by sudden spikes in voltage
thanks to the protection provided by the negative voltage. This innovative technology
significantly improves the equipment's reliability and lifespan, so assuring that BTCL's
network and maintenance operations will continue to get uninterrupted assistance.
Fig 4.1 AC & DC System

25. 15
4.3 Server Department:
The BTCL Server Department's primary responsibility is to monitor and control the
allocation of necessary bandwidth in order to maintain connectivity to the internet.
Because of its capability of data transmission at high rates, optical fiber is the preferred
choice for the cable alternative. This section contains ports that are both inbound and
outgoing to the region. The outgoing port is responsible for distributing bandwidth to
customers, while the incoming port makes it possible to establish a direct connection
with the underwater cable. Internet service can be provided over either copper-based
connections or optical fiber lines, the differences between which will be discussed in
further depth in the following paragraphs.
Fig 4.2 Server Section
4.4 Coding Division & Switching Division:
Coding Division: The management of tasks relating to signaling and voice processing
falls under this section's purview. The method known as Pulsed Code Modulation
(PCM) is implemented within the system, and it also serves the purpose of an Analogue
to Digital Converter (ADC).Converting analog voice signals that have low frequencies
into their digital equivalents is one of the steps involved in this process. Additionally, a
Pulse Code Demodulator is utilized in this part of the process in order to convert digital
signals back into analog voice signals.
Fig 4.3 OLT.
Switching Division: This division is the most important site in terms of where digital
switching really takes place. Microprocessors are utilized in every step of the switching
activity pre-reconfiguration process. It is essential to highlight the fact that there are
multiple transactions, each of which serves a unique purpose. All incoming and
outgoing trunks as well as subscriber lines, which are all made up of two-wire lines, are
interconnected with one another in this part. There are various slots available for
subscribers to use, specifically fifty slots, and each slot has the capacity to hold four
cards. This enables a maximum of two hundred simultaneous calls to be made. The

26. 16
Switching division's primary component is linked to the Transmission section, while
the division's secondary component is connected to the Coding section.
Fig 4.4 switching Rack & Subscriber Card
4.5 Data Transmission Division:
The Transmission Division at BTCL plays a vital role in establishing a direct
connection between subscriber and trunk lines, which are ultimately connected to the
Switching Section.The primary objective of this department is to establish connectivity
with the broader external network.
Fig 4.5 Transmission Division
4.6 Maintenance and Problem-solving Unit:
The Maintenance and Troubleshooting Section in BTCL plays a crucial role in
overseeing, detecting faults, and repairing the whole system. Maintenance personnel
diligently oversee the system to swiftly detect and resolve any problems. When users
encounter connectivity interruptions, they notify the office department, which then
begins the troubleshooting operations. Specific priority criteria are set for various client
segments. When an issue occurs in a subscriber line, the dedicated server card is
temporarily taken out, repaired, and then put back in. The control room is furnished
with an assortment of computers to efficiently handle a range of subscriber-related
matters.

27. 17
Chapter 5
Hardware utilized by BTCL
5.1SFP:
The SFP, or small form-factor pluggable, often known as mini-GBIC (gigabit interface
converter), is a highly popular transceiver due to its numerous advantages. The device's
small size enables it to be used in limited networking environments, making it easier to
establish fast connection between switches and essential network elements. The broad
acceptance of SFP connections can be attributed to their adaptability, as they are
compatible with both copper and fiber optics. This makes networks that are unable to
leverage SFP connections a rare exception. Moreover, the ability to hot-swap SFP
modules makes it highly suitable for expanding or altering current networks without
requiring a total replacement of the cable infrastructure. BTCL places great significance
on this matter, as the minimum coverage area for SFP in Bangladesh is 10 kilometers.
Furthermore, it is designed to effortlessly interact with other modem networks.
When considering copper-based connections, SFP modules are primarily associated
with 1000BASE-T and 1000BASE-TX modules for gigabit Ethernet networking. SFP
modules are highly efficient for enabling communication between switches in confined
areas, with a maximum distance of 100 meters.
There is a wide array of solutions accessible within the domain of fiber optics. SFP
modules are specifically engineered to accommodate both single-mode and multi-mode
fiber, enabling the use of both simplex and duplex topologies. Their wavelength
selections span from 850 nm to 1550 nm, including a broad spectrum. As a result,
BTCL's operations in Chittagong benefit greatly from the networking capabilities that
cover distances ranging from approximately 10 kilometers to over 100 kilometers.
Fig5.1 SFP

28. 18
5.2 Passcot:
The telephone cabinet houses yellow passcot wires, mostly used as optical connections
that originate from the switch. These optical linkages consist of optical fibers, although
they are commonly referred to as "passcots" for convenience during phone
conversations. The passcots are equipped with blue connectors that establish
connections with SFP (small form-factor pluggable) devices.
Fig 5.2 passcot
5.3 DSL MODEM:
A DSL modem facilitates the establishment of a link between a computer or router and
a phone line. This service offers DSL broadband Internet connectivity. Through the use
of an Ethernet connector, a USB port, or a PCI slot in a computer, this modem connects
to a computer or router.
However, the more common DSL router is a separate device that performs both routing
and DSL modem tasks. It allows for the connection of several computers thanks to its
built-in wireless access point or multiple Ethernet connections. DSL routers, also
known as residential gateways, are commonly used to manage and share DSL Internet
connections in smaller office and home networks. While there are various varieties of
DSL modems, ADSL modems are what BTCL in Chittagong employs. An Asymmetric
Digital Subscriber Line (ADSL) modem, often known as a DSL modem, is a type of
DSL modem technology that enables faster data transmission over copper telephone
lines than a regular voice band modem. ADSL is unique in that it prioritizes data flow
from the service provider to the customer's premises over the other way around, which
is the norm for most Internet connections. Providers sometimes market ADSL as an
Internet access service whose primary function is to download content from the Internet
rather than to host content for external users.
These days, full-duplex mode is the norm for ADSL communication. Frequency-
division-duplex (FDD), echo-cancellation-duplex (ECD), and time-division-duplex
(TDD) are the three most prevalent ways for accomplishing this on a twisted pair line.
For its ADSL service, BTCL has opted for FDD. Upstream and downstream bands are
the two frequency ranges used in frequency division duplexing (FDD).The downstream
band is responsible for communication from the telephone central office to the end user,

29. 19
whereas the upstream band permits communication from the end user to the central
office.
ADSL modems employ discrete multitoned modulation (DMT), which is a type of
frequency division multiplexing, to create a connection with the DSLAM (Digital
Subscriber Line Access Multiplexer). The modem utilizes frequencies beyond 8 kHz to
minimize interference with traditional telephone service. The frequency range spanning
from 8 kHz to about 1 MHz is divided into 247 separate channels, each with a
bandwidth of 4 kHz. Every channel is assigned a unique carrier signal for the purpose
of transmitting information. This technology operates with high efficiency by
simultaneously functioning as 247 distinct modems. The incoming digital data bits are
divided and transmitted concurrently across many channels, with each channel
employing an error-correcting code to rectify minor errors in the bits that may arise due
to noise during reception. The majority of these channels operate in a unidirectional
manner, transferring data from the DSLAM to the modem for downloading purposes.
However, a small number of the lower frequency channels provide bidirectional
communication.
Fig 5.3 DSL MODEM
5.4 optical power meter:
An optical power meter (OPM) is a device used to measure the optical signal strength,
typically in fiber optic networks. A regulated sensor, amplification for taking
measurements, and a screen are the standard components. The sensor's photodiode was
chosen because it is most suited to the working range of wavelengths and power levels.
Information about the optical power and the selected wavelength is shown on the
screen. The meters can be purchased as independent tabletop models, portable tools, or
as part of a testing package that also includes an optical light source and a visual fault
locator. They are crucial in determining how effective and secure optical networks are.
Optical power meters provide a well-defined measurement range, typically extending
from around -70 dBm to -50 dBm. However, specific specialized variants have the
ability to handle power levels that are either higher or lower. The accuracy of these
meters often lies within a 1% range, making them suitable for various practical uses. In

30. 20
order to accurately calculate the maximum power for pulse measurements, it is essential
to possess information regarding the duty cycle of the signal. However, it is essential
to ensure that the instantaneous peak power does not exceed the specified maximum
limit of the meter, as this could result in inaccurate data. Optical power meters with
high pulse rates has the capability to deliver many readings per second, making them
suitable for various applications. Moreover, laser power meter devices commonly rely
on thermal detection principles and are employed to assess laser power in various
settings.
Optical Power Meters play a vital role in the field of optical communication and fiber
optic technologies. They offer precise measurement of optical signal strength, hence
improving the efficiency of optical network operations and maintenance. Whether
utilized autonomously or as constituents of a comprehensive testing toolkit, these
meters are indispensable for ensuring the quality and reliability of optical systems.
Fig5.4 optical power meter
5.5 LC-LC Cable:
The LC-LC patch cord is now a crucial component in high-density cabling network
setups. Manufacturers have developed LC-LC patched cables with distinct attributes to
cater to the special requirements of data centers and enhance network efficiency, hence
broadening the scope of LC-LC fiber patch connections. The abbreviation LC, derived
from lucent connection, sometimes referred to as the "little connector," is one of the
smallest fiber optic connectors currently available. It has almost half the dimensions of
the commonly used Square Connector (SC). LC connectors utilize latch locking
mechanisms and are commonly employed in high-density patch panels, offering
flexibility for future expansion. LC connectors are preferred for single-mode fiber optic
cables because they have the ability to transmit larger amounts of data across long
distances. In the industry, LC fiber patch cables are the most commonly utilized type of
fiber optic cable, featuring two LC fiber connectors terminated at both ends.
When compared to standard fiber optic cables, LC fiber cables excel in density and
deliver consistent performance across a wide range of uses. These ubiquitous LC fiber
patch cables come in single-mode (OS1/OS2) and multimode
(OM1/OM2/OM3/OM4/OM5) varieties, as well as duplex and simplex fiber cable
configurations.

31. 21
.
Fig5.5 LC-LC Cable
5.6 Ethernet Media Converter:
In Bangladesh Telecommunications Company Limited (BTCL) and other
communication networks, the Ethernet media converter is a crucial component. These
devices are extremely helpful in facilitating the transfer of data between different parts
of a network that make use of different physical media, such as copper and fiber optic
cables. Ethernet media converters are used throughout BTCL's network to facilitate
reliable data transmission between antiquated copper-based systems and cutting-edge
fiber optic networks. BTCL can improve the reliability and speed of data transfer over
its network with the use of this technology. When upgrading or expanding an existing
network, it is essential to incorporate different media types to ensure compatibility and
performance, which is where Ethernet media converters shine.
These devices are flexible, allowing BTCL to meet the evolving demands of its
customers and the telecommunications sector as a whole. Ethernet media converters
provide a low-cost way to upgrade a network's capabilities by allowing for the seamless
integration of new technologies and higher data speeds. Ethernet media converters
allow BTCL to improve its network's reach, meet rising bandwidth needs, and ensure
the consistent delivery of high-quality telecommunications services.
Fig5.6 Ethernet Media Converter
5.7 ONU:
Optical Network Units (ONUs) are an integral part of BTCL's (Bangladesh
Telecommunications Company Limited) network. The ONU, designed specifically for
fiber-optic networks, is a crucial component that connects individual consumers or
subscribers to the larger telecommunications network. The Optical Network Unit

32. 22
(ONU) is the customer-premises terminal equipment in the BTCL architecture; it
interfaces with the provider-provided optical fiber network.
High-speed internet access, VoIP, and IPTV are just a few of the many
telecommunications services made possible by ONUs in BTCL. In order for the
customer's electronics, such computers, phones, and TVs, to function, these devices
convert the optical impulses sent from the central office into electrical signals. Data and
communication services may now be sent quickly and easily via the fiber-optic network
thanks to this conversion process.
Users are ensured access to consistent and high-quality telecommunications services
thanks to the deployment of ONUs in BTCL. Last-mile connectivity from the optical
backbone network to the homes and offices of end customers is made possible with the
help of these devices. Optical Network Units (ONUs) allow BTCL to supply its
customers with a wide range of cutting-edge telecommunications services while also
guaranteeing high-quality connections.
Fig5.7 ONU
5.8 Cards That BTCL Uses:
PTWVM: The PTWVM card was designed for use only with voice transmissions. It
has 64 dedicated phone lines for making and receiving calls. The supply of dependable
and superior voice services is largely dependent on this card, as it is commonly used
for voice communication.
ACWV: The ACWV card has the capability to transport both speech and data signals.
It has a crucial function in delivering ADSL (Asymmetrical Digital Subscriber Line)
connections and internet services. ACWV cards provide consumers with simultaneous
access to high-speed internet and voice services, making them a versatile and integral
component of a telecommunications network.
PRWGS: The PRWGS Card, often known as a power card, is a crucial element in the
network infrastructure. The main purpose of this device is to receive electrical energy
and distribute it to the power supply system of BTCL (Bangladesh Telecommunications
Company Limited). The card guarantees a consistent and dependable provision of
electricity, which is essential for the continuous functioning of telecommunications
equipment.

33. 23
SCXN: SCXN cards are utilized in pairs for each port, with one card specifically
assigned for read activities and the other for write operations. They play a crucial role
in the network's data transmission and reception operation. If a problem or failure
occurs in one SCXN card, the other card can be used as a backup to ensure reliable data
flow. SCXN cards are essential for maintaining uninterrupted data connectivity
throughout the network.

34. 24
Chapter 6
Wire Used By BTCL
6.1Copper Cable:
BTCL provides Public Switched Telephone Network (PSTN) services using mostly
CAT5 and CAT6 copper wires. Customers in need of increased bandwidth can opt for
CAT5 cables, whereas those who require fast Ethernet connections might use CAT6
cables. The choice between CAT5 and CAT6 is contingent upon the customer's
proximity to BTCL. CAT5 is utilized for extended distances, whilst CAT6 is selected
for shorter connections.
6.1.1CAT5:
CAT5 is now the standard for both data networks and telephones. Four pairs of 24-
gauge copper wires terminate in a standard RJ-45 socket. For transmissions of up to
328 feet (100 meters), copper twisted pair cabling is recommended. Only two of the
four copper wire lines are in service at any given time. Both solid and stranded CAT5
cables are commercially available. Ethernet connections beyond hundreds of meters in
length typically use solid cables, which are common in commercial environments like
offices. Connections over shorter distances benefit more from the flexibility of stranded
CAT5 cables..
6.1.2 CAT6:
Networks are increasingly switching to CAT6 cabling as the new standard. Twisted pair
wiring has evolved still again into Category 6 cabling. It uses the same configuration
as CAT5 with four pairs of copper wires that join at an RJ-45 socket. Whereas CAT5
only made use of two pairs of copper wires, CAT6 makes use of all four pairs.
Fig 6.1 Cat 5 & Cat 6 Cable
6.2 Optical Fiber:
Optical fiber is the primary element of BTCL's telecommunications network, serving a
vital function in transporting data at rapid rates and enabling the delivery of various
communication services. BTCL employs meticulously engineered optical fibers,
typically composed of glass or plastic, to deliver consumers with remarkably high-
speed internet connectivity, uninterrupted video streaming, and a wide array of data-
intensive services. BTCL employs optical fibers to carry data through the use of light
pulses, hence meeting the increasing demand for rapid connectivity and data retrieval.
Furthermore, the significant long-distance networking capabilities of optical fiber have
fundamentally transformed BTCL's operations by enabling the business to expand its
coverage to the most remote and inaccessible locations in Bangladesh. BTCL is able to
extend its reliable communication services nationwide because to the remarkable ability
of optical fiber to transmit data over great distances without compromising signal
quality. The technology's ability to endure electromagnetic interference and reduce
signal degradation enhances the dependability of the network, making it a superior

35. 25
choice, especially in regions prone to environmental factors and other forms of
interference. Furthermore, the ample bandwidth capacity, ability to scale, and long-
lasting nature of optical fiber ensure that BTCL can not only meet current
telecommunications needs but also adjust to future customer demands, solidifying its
position as a leading telecommunications provider in Bangladesh.
6.2.1 FTTP
The backbone of BTCL's network architecture is made up of FTTP (Fiber-to-the-
Premises) cables, which provide dependable, fast internet and phone services. These
cables are composed of slender glass or plastic fibers specifically engineered for
transmitting data by light pulses. They provide high-speed data transfer, which is well-
suited for bandwidth-intensive activities such as streaming HD videos and playing
games online. This meets the increasing need for services that require large amounts of
data. Fiber-to-the-premises (FTTP) cables preserve the integrity of data signals across
extended distances, guaranteeing dependable and uniform service quality. Furthermore,
the capacity of BTCL to scale and its architecture that is prepared for the future enable
the company to adjust to changing client requirements. This positions BTCL to offer
advanced telecommunications services directly to residential and commercial
establishments.
Fig6.2 FTTP Cable
6.2.2 FTTC
FTTC, also known as Fiber-to-the-Curb, is a network technology used by BTCL to
connect the central exchange or cabinet with clients' properties. FTTC cables are
comprised of a hybrid of optical fiber and conventional copper wires.Fiber-optic cables
extend to a distribution point or curb, located in close proximity to clients' residences
or commercial establishments, where the ultimate connection to individual premises is
established via copper wires.
By adopting this hybrid strategy, BTCL is able to offer clients high-speed internet and
telecommunications services, but at a somewhat slower rate compared to FTTP (Fiber-
to-the-Premises). FTTC provides higher capacity compared to conventional DSL
(Digital Subscriber Line) connections, leading to enhanced data speeds and dependable
access. It offers an economical method for extending high-speed broadband services to
a wider range of customers, particularly in regions where installing complete fiber
connections may be difficult or excessively costly.

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Fig6.3 FTTC
6.2.3 FTTB
BTCL uses a network technology called Fiber-to-the-Building (FTTB) to connect
apartment buildings, office buildings, and other large buildings with fiber optic cables.
To reach the building's communications room, or MDF (Main Distribution Frame), a
fiber-optic cable is laid out in this layout.
Typically, the connection to individual apartments or offices is established via
conventional copper or Ethernet wiring. Fiber-to-the-building (FTTB) presents notable
benefits compared to conventional DSL or cable internet services, since it can deliver
faster data speeds and more dependable connections. It is particularly advantageous for
places with high population density and huge structures, where the installation of fiber
optics to each individual unit may present logistical difficulties or be prohibitively
expensive.
FTTB technology allows BTCL to provide fast internet and telecommunications
services to several clients in one building, satisfying the need for modern connectivity
in residential and commercial settings with multiple units. It provides a streamlined
method to enhance and update the infrastructure of a building in order to facilitate
sophisticated telecommunications services, without requiring massive installation of
fiber optic cables across the entire building.

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Fig6.4 FTTB
6.3 Submarine Cable:
BTCL's global telecommunications infrastructure is mainly dependent on underwater
cables. The positioning of these specialized undersea cables on the seabed is essential,
as they facilitate the establishment of a connection between Bangladesh and the global
telecommunications network. BTCL's customers depend on the company to fulfill a
vital function in facilitating international communication, sharing data, and building
worldwide connectivity.
These cables provide an exceptional ability to transmit data, enabling BTCL to meet
the growing demand for high-speed internet access, international telephony, and data
services. Submarine cables play a crucial role in enabling international trade and
seamless global communication.
Furthermore, submarine cables are widely recognized for their robust construction and
capacity to endure challenging oceanic environments. BTCL's dependability guarantees
a consistent and steady global connectivity, minimizing the likelihood of any
disruptions and offering uninterrupted communication services to its clients. BTCL has
successfully extended its network internationally by building these undersea
connections. The integration of Bangladesh into the global telecommunications system
has enabled seamless international communication for individuals and enterprises, free
from any disruptions.
Fig6.5 submarine cable

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6.4 Underground Cable:
BTCL primarily utilizes subterranean cables for the provision of long-distance
communication services. Using underground cables to connect the system's multiple
nodes has advantages and disadvantages. Subterranean cables offer numerous benefits,
such as enhanced visual appeal, reduced interference with neighboring equipment,
decreased occurrence of faults, and diminished voltage fluctuations. Conversely, they
involve greater costs for manufacturing and installation and are frequently employed
when it is impractical or unsafe to use overhead lines. Consequently, they have
discovered valuable uses in metropolitan areas as well as submerged situations such as
submarine cables. To maintain the secure and dependable functioning of a conductor in
an underground cable, many layers of insulation and protection are commonly
employed.
Based on their voltage ratings, falling into the following categories:
1.Low-tension cables, with a maximum voltage capacity of 1000V.
2.High-tension cables, with a specified voltage limit.
3.Super-tension cables, capable of handling up to 33kV.
4. Ultra-high-tension wires made for 66kV voltages.
5. Cables with extra high voltage are designed for uses that need energies higher than
132kV..
Fig 6.6 Underground Cable Intersection
6.5 Splitter:
In order to ensure a consistent supply of electricity and prevent power outages, BTCL
employs splitters. A "cable splitter" is necessary to connect two coaxial cables
simultaneously from the same wall socket or another cable source. When there is a
scarcity of cable wall jacks but a requirement to connect multiple TVs, modems, or
other devices, these splitters serve as a prevalent and practical option. It is crucial to
bear in mind that employing several splitters on a solitary cable connection can diminish
the signal quality emanating from the outlet.
Although the term "cable" most commonly refers to coaxial cable, numerous other
kinds of wires and cables are used in television and computer systems. In cable TV and
cable internet installations, coaxial cable is used to carry data from an outlet to a TV,
receiver, or modem. This is done in both types of installations. The male end has

39. 29
dimensions that are nearly average in both width and height, and it has a single
cylindrical prong to distinguish it from the female end. In its most basic form, a cable
splitter is a piece of equipment that, when attached to a single wall outlet, makes it
possible for many cables to be connected to one outlet. These splitters are most
commonly used to connect multiple televisions to a single socket.
Fig6.7 Splitter

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Chapter 7
Functionalities of BTCL
BTCL is a company that primarily provides services pertaining to telecommunications
and the internet. Telecommunication allows for the establishment of communication at
a distance. The switching and coding, as well as the transmission, are the two primary
elements that make up the telephone system. Transmission in BTCL can be performed
through the use of optical fiber or coaxial cable. In a simple transmission system, there
are only three components: the sender, the receiver, and the medium. In the following
section, we will discuss these.
7.1 Diagram of a Power System Blog:
Fig7.1 Power System
Ac Supply(220~230V):The AC supply is an external power system that delivers
voltage ranging from 220 to 230 volts at a frequency of 50Hz. The AC supply functions
as the main power source for the BTCL infrastructure.
Generator: BTCL integrates a generator into its power system to provide continuous
power supply. The generator has the ability to provide electricity in case of an
interruption in the AC power supply or any other disturbances in the power system. It
serves as a dependable backup resource, ensuring the continuous operation of the
network.
Rectifier: A rectifier is used to connect the generator output and the AC supply. The
rectifier is tasked with converting the incoming alternating current (AC) power into
direct current (DC) power. The utilization of this direct current (DC) electricity is
crucial for multiple functions within the system.
Battery Equipment: A portion of the DC supply from the rectifier is allocated for the
purpose of recharging backup batteries. These batteries function as an auxiliary power

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reserve and are essential for preserving network operation during prolonged power
failures.
-48 Volt Dc Supply: The rectifier supplies a separate -48 volt DC power source to
ensure stability for the essential equipment in the BTCL infrastructure. The reliable
power supply guarantees optimal efficiency of the network components.
Ground Connection: The positive terminal of the power system is firmly linked to the
ground (GND) to provide safety and electrical stability.
7.2 OLD Phone Exchange:
Fig7.2 OLD Phone Exchange
MNO (Mobile Network Operator): The block diagram commences with the linkage
to diverse Mobile Network Operators (MNOs) including Robi, Grameenphone, Airtel,
Telitalk, and others. These Mobile Network Operators (MNOs) offer external
connectivity to the BTCL phone exchange system.
ICX: The Internal Voice Exchange (ICX) is the subsequent element depicted in the
diagram. The ICX functions as an internal switching system that primarily manages
voice communications within the BTCL network. It enables the efficient routing and
exchange of voice communications.
ANS (Access Network Switch): The Access Network Switch (ANS) is shown in the
diagram after the ICX. This component serves as the primary interface, linking the
internal voice exchange to external networks, such as Mobile Network Operators
(MNOs). It functions as the intermediary for voice traffic to enter or exit the BTCL
network.
Exchange: The Exchange, often known as a switch, is a fundamental component in the
block diagram. Within the BTCL network, it has a crucial function in directing,

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exchanging, and overseeing the transmission of voice calls and data.This is the location
where call connections are initiated, controlled, and concluded.
MDF: The connections emanating from the Exchange are linked to the horizontal side
of the Main Distribution Frame (MDF). The MDF functions as a central hub for
interconnecting many distribution cables originating from the Exchange. It has a crucial
function in coordinating and disseminating these relationships.
Cabinet: The vertical side of the MDF is connected to many strategically positioned
cabinets throughout the BTCL network base. Every cabinet is specifically built to
contain the necessary equipment for local distribution and is configured to support four
DP (Distribution Point) connections. This design adheres to BTCL's power distribution
regulations, guaranteeing optimal power administration across the network.
DP: Distribution Points (DPs) serve as the final destination for the connections
originating from the cabinets. Distribution points (DPs) function as the final link in
connecting to end-users or subscribers. The purpose of these points is to strategically
direct connections to particular clients, guaranteeing the provision of telephone
services.
7.3 GPON (New Phone Exchange):
Fig7.2 GPON
OLT: The GPON diagram begins with the OLT, which is an abbreviation for Optical
Line Terminal. The Optical Line Terminal (OLT) is a pivotal component in a Gigabit
Passive Optical Network (GPON) that functions as the primary point of interface
between the optical fibers and the customer premises. It controls the flow of data sent
to the recipients.

43. 33
Switch: A switch is connected above the OLT. This switch is essential for network
administration and routing in the GPON architecture. It enables the efficient transport
of data and the management of traffic.
Router: The connection from the switch is extended to a router. The router functions
as a crucial element in the management and routing of network traffic. It provides three
separate connections:
 A single connection is responsible for routing international internet traffic
through the IIG (International Internet Gateway), which plays a crucial role in
managing such traffic.
 Another link is specifically aimed towards the IMS (IP Multimedia Subsystem),
which is utilized for voice communication services.
 The third connection is associated with the BRAS (Broadband Remote Access
Server), which serves as the main platform for administering and delivering
broadband data services.
ODF: The Optical Distribution Frame (ODF) is the component where the optical fibers
are connected to the Optical Line Terminal (OLT). The Optical dissemination Frame
(ODF) functions as an intermediary location for the dissemination of optical signals
inside the Gigabit Passive Optical Network (GPON).
The optical signals from the ODF are dispersed using a splitter with a ratio of 1:8. This
implies that a single incoming optical signal is divided into eight distinct optical signals.
Each of these optical signals is routed to a designated destination.
Cabinets: The splitter's optical signals are subsequently directed to cabinets,
strategically positioned throughout the GPON network. These cabinets function as
localized distribution hubs, akin to what was previously discussed.
DP: A Distribution Point (DP), with a 1:4 ratio, is where the connections from the
cabinets are directed. The DPs uphold a 1:4 proportion, signifying that a single
incoming optical signal is separated into four distinct connections. These data
processors play a vital role in directing connections to specific subscribers or end-users.
ONT/ONU: The ONT/ONU (Optical Network Terminal/Optical Network Unit) acts as
the customer premises equipment that connects subscribers to the GPON network. It
receives the optical signals before they reach the end-users.
End-User: Ultimately, the optical connections originating from the Distribution Points
(DPs) are directed towards the end-users, guaranteeing the provision of high-speed
broadband services to the subscribers inside the GPON network.

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7.4 Modulation Technique:
7.4.1 PCM:
In digital signal processing, analog signals are digitally represented using Pulse Code
Modulation (PCM) with two-step sampling and quantization. Here's how the procedure
works:
Sampling: PCM commences with the sampling procedure, wherein an analog signal is
measured at consistent intervals. In the context of two-step sampling, two samples are
acquired during each signal cycle. Consequently, the analog signal is sampled twice per
cycle, thereby enhancing the accuracy in capturing its fluctuations. Increasing the
number of samples per cycle allows for a more precise capture of small details.
Fig 7.1 sampled Signal
Quantization: The process of converting the sampled values into a discrete set of
values. Quantization entails the allocation of a precise digital value to every sample.
Two-step quantization involves the process of quantizing each sample twice, resulting
in an increased level of precision. The quantization method commonly employs a
predetermined number of quantization levels (sometimes denoted by a defined number
of bits) to encode the analog signal. Increased quantization levels result in enhanced
precision when representing the original analog signal.
Fig7.2: quantization
A PCM machine contains a total of 32 ports, 30 of which are intended for subscribers,
1 of which is used for signaling, and the remaining port is utilized for voice
communication. This configuration is used by BTCL. When the maximum number of
simultaneous calls is exceeded, which is currently set at 32, call dropouts may occur.
In order to find a solution to this issue, a module distribution system is developed. This
system consists of connecting a single wire to a module, which is subsequently
connected to a number of subscribers.