Internship Report Pakistan Telecommunbication Company Limited

8/4/2019 Internship Report Pakistan Telecommunbication Company Limited

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INTERNSHIP REPORT

PAKISTAN TELECOMMUNICATION COMPANY LIMITED

(Operation Transmission South, IGE Building Martson Road Karachi)

Submitted by: Hayat Wali

BE-Electronics Iqra University, Defence

View Phase 2 Karachi

Period of internship: July 4, 2011 to August 13, 2011


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Introduction

Pakistan Telecommunication Company Limited is one of the most prestigious

public sector companies of Pakistan, It operates throughout Pakistan. It is

functional in different parts of Karachi.

I was offered internship in Operation Transmission South, IGE Building Marston Road

Karachi. The duration of my internship was one and half months, which I have completed

successes fully. These days were some of the important days of my life, in which I could

achieve a practical knowledge of my theoretical learning. That was an environment fell

equipped with engineering applications

I was supposed to get training in six divisions named as

International transmission and maintenance (ITMC) SMW-3 (South East Asia Middle East West Europe) SMW-4 (South East Asia Middle East West Europe) New cable and network support ( NC & NS) Multimedia and Broad Band (MM & BB) Optical Fiber System (OFS)

These were the six divisions in which I have spent six weeks, with one week at each division.

ITMC

(International transmission and maintenance)

The main task of ITMC is to provide cooperation between local media and

international media. It establishes connectivity between the local haul or back haul

and the forward haul or international media. This connectivity consists of voice

and data. The transmission of voice and data is accomplished by using different

techniques. The signals to be transmitted need to be undergone techniques like


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sampling, quantization, encoding and transmission. To increase the capacity of the

transmission media techniques like multiplexing, modulation are also used.

MODULATION

Original signal superimposed on carrier frequency.Signal transmitted at higher frequency in order to increase efficiency.Carrier frequency changes according to original signal. AM,FM etc

MULTIPLEXING

Different signals are combined together and transmitted along the channel in

order to save the bandwidth. (Many into one)

FOUR TYPES OF MULTIPLEXING ARE:

1.Space Division Multiplexing space is divided.2.Frequency Division Multiplexing frequency is divided.3.Time Division Multiplexing time is divided.4.Code Division Multiplexing space, time and frequency is divided.

PCM (PULSE CODE MODULATION)

PCM is a modulation technique in which analog signals are converted into digital

signals it consists of 3 steps:

Sampling An analog signal is divided into 8000 samples

Quantization each sample is rounded up or down based on the algorithm.

Encoding Finally the sample is encoded.


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PROCESS

1 sample information = 8bit8000 samples processed in 1sec.Therefore 8000sample info = 8*8000 = 64000 bits = 64kb/sec.

30 voice calls are transmitted together.30*8000 = 240000 samples30*64kbps = 1920kbps1frame = 32bits, therefore 32*64 = 2048kb/sec = 2Mb/sec= E1

PLESIOCHRONOUS DIGITAL HIERARCHY

PDH is obsolete in todays world due to drawbacks. Following are thedisadvantages of PDH:

No NMS (Network Management System). No interaction between man andmachine.

No software control.No standard defined internationally.Vendor bounded.(different vendors could not communicate with each

other).

Bit interleaving. (bitwise transmission)No add drop directly.Point to point.

SYNCHRONOUS DIGITAL HIERARCHY(SDH)

SDH is the upgraded version of PDH, fulfilling the drawbacks of PDH.

Characteristics of SDH are:

NMS.Software control.


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Multi vendor.Add drop directly.Byte interleaving.(Byte wise transmission)Point to point and multipoint.International standard.

SMW-3

SWM-3 connects 35 countries to Pakistan by means of optical fiber.STM-64 is 1 i.e. 55 nanometer.IPLC (LEASE CUSTOMER): Uses their own bus a single telephone line

dedicated to themselves.

PFE (Power Feeding Equipment): Power cable travels along the optical fibercable to provide power to regenerators and repeaters in the sea.

DCN (DATA Communications Network): consists of routers which define thewavelength (). Mumbai is connected to fiber pair1 (=4) and Fujairah is

connected to (=6). Router recognizes which cable is of Mumbai and which is

of Fujairah. Cable from DCN connects to SLTE (Submarine Line Terminating

Equipment). Each country has its own SLTE.

ROUTERS TRIBUTRY COMMON TWMA (Trans Wavelength Multiplex

Amplifier)

TWMA(Trans Wavelength Multiplex Amplifier) is used to amplify the signalswhile transmitting

RWDA (Receive Wavelength Differential Amplifier) amplify the signals whilereceiving.

Data rate in tributaries is STM-64.FEC encoder (Forward Error Correction): Encodes the data in tributary to

enable error correction.

Western side is connected by Djibouti at (=4) and (=6).1= STM-64 = 10gbps.De multiplexing occurs while receiving. STM-64 STM-16 STM-4 E1


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STM-4 to STM-64 = Higher Order.E1 to STM-1 = Lower Order.

SMW 4

2 Power Feeding Equipments installed.o 1 for SMW-3.o 1 for SMW-4.

Connects Pakistan to 17 different countries.Process same as SMW-3.Marine cables come and connect to DCN (Data Communication Network).From DCN cables are connected to SLTE.SLTE transfers the cables to ADM.

oSTM-64 gets de multiplexed to STM-16, STM-4, and STM-1.

Then the cables are fed to ODF.o This distributes the connection locally.

We have rectifiers to prevent damage.

SMW-4 connects Pakistan to 17 countries. Few examples are:

East West

Malaysia SA

Singapore UAE India Alexandria

ADM ODF LOWER ORDER MUX

DIRECT CUSTOMER

DCN SLTE ADM ODF


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WDM (Wavelength Division Multiplexing):

Different SDH come and connect to WDM.Based on the frequency WDM allots channels to different signals.Segment grouping of signals (countries are divided into segments) so that

a problem occurs it can be rectified easily.

Last station Marseille(France)Installing new project IMWE(Indian Middle East Western Europe)

Multimedia and Broad Band

.

Broadband

The word broadband is used for the minimum bandwidth which can support the

transmission of multimedia services.

Broadband access

Broadband access is the high speed connection between the end user and internet

through certain kind of network.

Broadband Access Technologies

XDSL

HSDL.High speed digital subscriber

SDSLsymmetric DSL

ADSL.Asymmetric DSL


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VDSLVery high bit rate DSL

EDSL..Ethernet DSL

ISDL..ISDN DSL

UDSL.Ultra high DSL

HFC.Hybrid fiber coaxial

Home PNA..Home phone line

Ethernet

Wireless Broadband

LMDS..local multipoint Distribution

DBSDirect Broad service

Microwave Radio Access

Gprs..General packet Radio service

Optical access network

Plc.Power line cable

SDHsynchronous digital hierarchy

Frame relay.

Theses are some broadband access technologies, which are used to access

internet and other broadband services.

DSL Principles

SHDSL

It is Single pair high bit rate DSL, one pair, symmetric transmission, Variable data

rates


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Generally the variable data rate is 192 Kbps..2.312Kbps

The range is valid up to a range of 5 Km.

VDSL

VDSL is very high data rate DSl, one wire pair, variable Data rates, Valid up to 5 Km.

The data rate is up to 13mbps to 52Mbps.

ADSL

One wire pair, Asymmetric transmission, data rates from 64 Kbps to 1.5 Mbps,

covering a distance of 5 Km.

Optical fiber system (OFS)

Optical fiber system consist a network of optical fibers which are used for the

transmission of optical signals.

Initially all the signals are analog signal which cant be transmitted to long distance

because they undergo transmission impairments and path losses. To minimize

such problems optical fibers have been designed because in which signals arealthough analog but they undergo a very low line problems.

Usually in transmission of signal at a certain distance repeaters are used which

regenerate the signal again; in case of optical fibers these repeaters are installed at

a large distance usually 25 km.

Because of there light weight optical fibers are very easy to install even under

water. Use of Optical fibers has increased the capacity of data transmission

through a media. It is said that the bandwidth of a single optical fiber can be

increased to infinity by using modern multiplexing techniques.

A single optical fiber can support a data of 10 GB. This is used commonly in long

distance transmission.


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STRUCTURE OF OPTICAL FIBER

Optical fiber generally consists of three parts

Core Cladding Jacket

CORE

Core is the inner most section and consists of one or more strands, made up of

glass or plastic, the core has a diameter of 50 micrometer.

CLADDING

A glass or plastic coating having optical properties different from those of the core,and has diameter of 125 micrometer. The interface between core and cladding act

as a reflector to confine light that would otherwise escape the fiber.

JACKET

The jacket is composed of plastic and other materials layered to protect against

moisture, abrasion, crushing and other environmental dangers.

MODES OF TRANSMISSION

The transmission of light signals through an optical fiber is accomplished by using

different transmission modes like Single mode, graded index Multimode, step

index mode.

SINGLE MODE

In single mode, the light rays travel in a straight line. Some Spacing is keptbetween the rays to avoid interference. This mode is used for large distance

communication


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GRADED INDEX MULTIMODE

This mode of transmission is done by varying the index of refraction of the core.

Refractive index is higher at centre whereas it decreases towards the corners.

This transmission mode is used for shorter distances.

STEP INDEX MULTIMODE

Rays at shallow angle are reflected and propagated through along the fiber other

rays are absorbed by the surrounding material. With this mode multi paths exist

due to which signals undergo dispersion and data cant be accurately achieved.

NEW CABLES AND NETWORK SUPPORT

This division of PTCL is associated with the repairing and maintenance of cables

and optical fibers. New cables are put by this division by replacing the existing

worn out cables. This division usually works outside of the terminal. Different

devices are used to repair cable. If somehow a fault occurs in a cable a device

named as megger is used which measures the distance of fault from the terminal.

Megger is also used to check the condition of a cable whether it is propercondition or not.

The device used to repair cable is OTDR or Optical time domain reflect meter.

OPTICAL TIME DOMAIN REFLECTOMETER

It is an optoelectronic device used for estimating the fibers length and overall

attenuation, including splice and mated connectors losses. It may be used to locate

faults, such as breaks and to measure optical return loss. Testing is done for one

end only.


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STEPS INVOLVED IN REPAIRING AN OPTICAL FIBER

An optical fiber is repaired in three steps

Cladding Cleaving Cleaning

Cladding

The first step of repairing an optical fiber is cladding, in which the jacket is

removed. As an optical fiber consists of many pairs so color coding is used to

differentiate between the damaged and sound pairs.

Cleaving

Cleaving is the process of cutting the damaged part. Cleaving is a done by an

instrument which consists of diamond. As the jacket of optical fiber is very strong,

therefore it is necessary to get the job done by some sort of sharp instrument.

Cleaning

Dust particles are removed through an alcoholic gauss. Then splicing machine is

used to join the broken ends.


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CONTENTS

Introduction02

ITMC 02

Modulation02 Types of Multiplexing.02 Synchronous Digital hierarchy.04

SMW-3..05

SMW-4..06

WDM..07Multimedia and Broadband07

Broadband Access Technologies...07 DSL Principles..08

Optical Fiber Systems..09

Structures of optical fiber...10 Modes of transmission..10

New cables and Network Support.11

OTDR..11 Steps of repairing Cable12

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Internship Report Pakistan Telecommunbication Company Limited

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