Sir Syed Ptcl Report

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INTERNSHIP REPORT

PAKISTAN TELECOMMUNICATION COMPANY

LIMITED(PTCL)(Operation Transmission South, IGE Building Marston Road Karachi)

Submitted by:

BS-Electronics Sir Syed University Of Engineering AndTechnology(SSUET), Karachi.

SHEIKH MUHAMMAD OVAIS S/O SHEIKH ZAIN-UL-ABEDINNIC NO. ( 42201-7361339-5 )

MUHAMMAD ADIL ALI S/O

NIC NO. ( )

SYED TALHA ALI S/ONIC NO. ( 41304-8062807-5 )

ASHAR ALI BABAR S/ONIC NO. ( 42101-1231041-7 )

ALL STUDENTS BELONG TO SSUET BATCH 2010 BS-ELECTRONICS

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Period of internship: June 27, 2011 to August06, 2011

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 BuildingMarston 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

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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 weekat each division.

ITMC

(International transmission and maintenance)

The main task of ITMC is to provide cooperation between loca

media and international media. It establishes connectivity between

the local haul or back haul and the forward haul or internationa

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 sampling, quantization, encoding and transmissionTo increase the capacity of the transmission media techniques like

multiplexing, modulation are also used.

MODULATION

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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 = 8bit

8000 samples processed in 1sec.

Therefore 8000sample info = 8*8000 = 64000 bits =64kb/sec.

30 voice calls are transmitted together.

30*8000 = 240000 samples

30*64kbps = 1920kbps

1frame = 32bits, therefore 32*64 = 2048kb/sec =2Mb/sec= E1

PRESYNCHRONOUS DIGITAL HIERARCHY

PDH is obsolete in todays world due to drawbacks.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

the disadvantages of PDH:

No NMS (Network Management System). No interactionbetween man and machine.

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.

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SYNCHRONOUS DIGITAL HIERARCHY(SDH)

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

PDH. Characteristics of SDH are:

NMS.

Software control.

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 fiber cable to provide power to regenerators

and repeaters in the sea.

DCN (DATA Communications Network): consists of routers

which define the wavelength (). 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.

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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 signals while transmitting

RWDA (Receive Wavelength Differential Amplifier)

amplify the signals while receiving.

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).

.= STM-64 = 10gbps1

De multiplexing occurs while receiving. STM-64 STM-16

STM-4 E1

STM-4 to STM-64 = Higher Order.

E1 to STM-1 = Lower Order.7

ADM ODF LOWER ORDER

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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.

o STM-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

WDM (Wavelength Division Multiplexing):

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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

(MM&BB)

.

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

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SDSLsymmetric DSL

ADSL.Asymmetric DSL

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.

These are some broadband access technologies, which are used to

access internet and other broadband services.

DSL Principles

SHDSL

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It is Single pair high bit rate DSL, one pair, symmetric

transmission, Variable data rates

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 Kbpsto 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 transmittedto long distance because they undergo transmission impairments

and path losses. To minimize such problems optical fibers have

been designed because in which signals are although 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 opticalfibers these repeaters are installed at a large distance usually 25

km.

Because of there light weight optical fibers are very easy to instal

even under water. Use of Optical fibers has increased the capacity

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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.

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 toprotect against moisture, abrasion, crushing and other

environmental dangers.

MODES OF TRANSMISSION

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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 kept between the rays to avoid interference. This mode

is used for large distance communication

GRADED INDEX MULTIMODE

This mode of transmission is done by varying the index o

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 materialWith 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

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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

proper condition 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.

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.

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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.

SDH AND SONET REVIEW

Synchronous optical networking (SONET) and synchronous digitalhierarchy (SDH) are standardized multiplexingprotocols thattransfer multiple digitalbit streams over opticalfiberusing lasers or light-emitting diodes(LEDs). Lower data ratescan also be transferred via an electrical interface. The method wasdeveloped to replace the Presynchronous Digital Hierarchy(PDH)system for transporting larger amounts oftelephonecallsand data traffic over the same fiber without synchronization

problems. SONET generic criteria are detailed inTelcordiaTechnologiesGeneric Requirements document GR-253-CORE. Generic criteria applicable to SONET and other transmissionsystems (e.g., asynchronous fiber optic systems or digital radiosystems) are found in Telcordia GR-499-CORE.

SONET and SDH, which are essentially the same, were originallydesigned to transport circuit mode communications(e.g., DS1, DS3) from a variety of different sources, but they were

primarily designed to support real-time, uncompressed, circuit-switched voice encoded in PCMformat. The primary difficulty indoing this prior to SONET/SDH was that the synchronizationsources of these various circuits were different. This meant thateach circuit was actually operating at a slightly different rate andwith different phase. SONET/SDH allowed for the simultaneous

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transport of many different circuits of differing origin within asingle framing protocol. SONET/SDH is not itself a communicationsprotocolper se, but a transport protocol.

DIFFERENCE OF SDH FROM PDH

Synchronous networking differs from Plesiochronous Digital

Hierarchy(PDH) in that the exact rates that are used to transportthe data on SONET/SDH are tightly synchronizedacross the entirenetwork, using atomic clocks. This synchronization systemallowsentire inter-country networks to operate synchronously, greatlyreducing the amount of buffering required between elements inthe network.

Both SONET and SDH can be used to encapsulateearlier digitaltransmission standards, such as the PDH standard, or they can be

used to directly support either Asynchronous Transfer Mode (ATM)or so-called packet over SONET/SDH(POS) networking. As such, itis inaccurate to think of SDH or SONET as communicationsprotocols in and of themselves; they are generic, all-purposetransport containers for moving both voice and data. The basicformat of a SONET/SDH signal allows it to carry many differentservices in its virtual container (VC), because it is bandwidth-flexible.

THE BASIC UNIT OF TRANSMISSION

The basic unit of framing in SDH is a STM-1 (SynchronousTransport Module, level 1), which operates at 155.52 megabits persecond(Mbit/s). SONET refers to this basic unit as an STS-3c(Synchronous Transport Signal 3, concatenated) or OC-3c,depending on whether the signal is carried electrically (STS) or

optically (OC), but its high-level functionality, frame size, and bit-rate are the same as STM-1.

SONET offers an additional basic unit of transmission, the STS-1(Synchronous Transport Signal 1) or OC-1, operating at 51.84Mbit/sexactly one third of an STM-1/STS-3c/OC-3c carrier. Thisspeed is dictated by the bandwidth requirements for PCM-encoded

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telephonic voice signals: at this rate, an STS-1/OC-1 circuit cancarry the bandwidth equivalent of a standard DS-3 channel, whichcan carry 672 64-kbit/s voice channels. In SONET, the STS-3c/OC-3c signal is composed of three multiplexed STS-1 signals; the STS-3C/OC-3c may be carried on an OC-3 signal. Some manufacturersalso support the SDH equivalent of the STS-1/OC-1, known as STM-

0.

Framing

In packet-oriented data transmission, such as Ethernet, a packetframe usually consists of a header and a payload. The header istransmitted first, followed by the payload (and possibly a trailer,such as a CRC). In synchronous optical networking, this is modifiedslightly. The header is termed the overhead, and instead of being

transmitted before the payload, is interleaved with it duringtransmission. Part of the overhead is transmitted, then part of thepayload, then the next part of the overhead, then the next part ofthe payload, until the entire frame has been transmitted.

SDH frame

An STM-1 frame. The first nine columns contain the overhead andthe pointers. For the sake of simplicity, the frame is shown as arectangular structure of 270 columns and nine rows but theprotocol does not transmit the bytes in this order.

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For the sake of simplicity, theframe is shown as a rectangular structure of 270 columns and ninerows. The first three rows and nine columns contain regeneratorsection overhead (RSOH) and the last five rows and nine columnscontain multiplex section overhead (MSOH). The fourth row fromthe top contains pointers.

The STM-1 (Synchronous Transport Module, level 1) frame is thebasic transmission format for SDHthe first level of thesynchronous digital hierarchy. The STM-1 frame is transmitted inexactly 125 s, therefore, there are 8,000 frames per second on a155.52 Mbit/s OC-3 fiber-optic circuit.[nb 1] The STM-1 frame consists

of overhead and pointers plus information payload. The first ninecolumns of each frame make up the Section Overhead andAdministrative Unit Pointers, and the last 261 columns make upthe Information Payload. The pointers (H1, H2, H3 bytes) identifyadministrative units (AU) within the information payload. Thus, anOC-3 circuit can carry 150.336 Mbit/s of payload, after accountingfor the overhead.

Carried within the information payload, which has its own frame

structure of nine rows and 261 columns, are administrative unitsidentified by pointers. Also within the administrative unit are oneor more virtual containers (VCs). VCs contain path overhead andVC payload. The first column is for path overhead; it is followed bythe payload container, which can itself carry other containers.Administrative units can have any phase alignment within the STMframe, and this alignment is indicated by the pointer in row four.

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The section overhead (SOH) of a STM-1 signal is divided into twoparts: the regenerator section overhead(RSOH) and the multiplexsection overhead(MSOH). The overheads contain information fromthe transmission system itself, which is used for a wide range ofmanagement functions, such as monitoring transmission quality,detecting failures, managing alarms, data communication

channels, service channels, etc.

The STM frame is continuous and is transmitted in a serial fashion:byte-by-byte, row-by-row.

Transport overhead

The transport overhead is used for signaling and measuringtransmissionerror rates, and is composed as follows:

Section overhead

Called RSOH (regenerator section overhead) in SDHterminology: 27 octets containing information about the framestructure required by the terminal equipment.

Line overhead

Called MSOH (multiplex section overhead) in SDH: 45 octetscontaining information about error correction and AutomaticProtection Switching messages (e.g., alarms and maintenancemessages) as may be required within the network.

AU PointerPoints to the location of the J1 byte in the payload (the firstbyte in the virtual container).

Path virtual envelope

Data transmitted from end to end is referred to aspathdata. It is composed of two components:

Payload overhead (POH)

Nine octets used for end-to-end signaling and errormeasurement.

Payload

User data (774 bytes for STM-0/STS-1, or 2,340 octets forSTM-1/STS-3c)

CONTENTS

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Introduction

02

ITMC

02

Modulation02

Types

Multiplexing

.02

Synchronous Digita

hierarchy.04

SMW-

3

..05

SMW-

4..06

WDM

..07

Multimedia and

Broadband

07 Broadband Access

Technologies.

..07

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DSL

Principles

..08

Optical Fiber

Systems..

09

Structures of optica

fiber.

..10

Modes of

transmission

..10

New cables and Network

Support.11

OTDR

..11

Steps of repairingCable

12

SDH and SONET REVIEW

.13

Difference of SDH from PDH14

Basic unit of transmission14

Framing ..

.

15

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SDH

frame..

15 - 17

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