piyush training report

8/3/2019 Piyush Training Report

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TRAINING REPORT

PRESENTED BY

PIYUSH KHANDELWAL

ECE-2

Roll no.: 1461502808

BASED ON TRAINING UNDERTAKEN IN

RELIANCE COMMUNICATION

LIMITED

DURATION

JUNE 3rd to JULY 18th

Department of Electronics and

Communication

MAHARAJA SURAJMAL INSTITUTE OF TECHNOLOGY

NEW DELHI- 110058 ,

2011-2012


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OPTICAL FIBER NETWORK


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ACKNOWLEDGEMENT

Being a part of RelianceCommunications was a pleasure indeed. The bond

and the knowledge shared by the people there was heartening.

I would like to express my sincere gratitude towards Mrs. Prachi Aran of

RelianceCommunications, Delhi who mentored me during the entire

training period. Her profound encouragement, cooperation, guidance and

keen supervision were highly inspiring. I would also like to thank her team

members Mr. Rajesh, Mr. Harsh and Mr. Bhuwan for being enthusiastic

about demonstrating everything about optical fibre. I would also like to

thank the HR Department of the company for their help without which this

training would not have been possible.

Piyush khandelwal

Date: 16th July 11


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INDEX

1) Introduction

2) About RelianceCommunications

a) History

b) Services provided

c) Infrastructure

d) Reliancecommunications, Delhi

3) Optical fiber

a) Functional Basics

i) Total internal reflection

ii) Factors causing attenuation

b) Uses and Advantages

c) Difference between copper and cable and optical fiber

d) Types of fiber

i) Single mode

ii) Multi mode

e) Optical fibre cable(OFC)

f) Cable Installation

i) Digging

ii) Duct laying(coupling)

iii) Duct integrity Test

iv) Cable Jetting

v) Splicing

g) Optical Time Domain Reflectometer(OTDR)


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h) Connectors/attenuators/couplers

4) Synchronous Digital Hierarchy

a) Introduction

b) Synchronization of Digital Signals

c) Basic SDH frame format

d) Principles of SDH

5) WIMAX

a) Definition

b) Uses

c) Wimax concept

d) Wimax Protocols

e) Multiplexing in Wimax


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INTRODUCTION

The World is now a GLOBAL VILLAGE. Communication

Technology has shortened the gap between remotest of places. Every

continent and every country, every company and every home, every man,every woman and every child feels its dire need.

Communication Industry in India and all over the world has

grown exponentially over the past few years. Growing at the pace that it

is, to understand its functionality was my basic objective.

To be able to be a part of a communication company was

very exciting and knowledgeable. On site work gave me a better

understanding of Communication Systems. Classroom acquired

knowledge seemed insufficient and was given more meaning. Thus

suddenly all theories and derivations seemed logical.

The fructifying telecom sector has seen a lot of new players

which has changed the way people communicate. The number of vendors

for telecom equipment and the large number of service providers is huge.

The demand for better, faster and more data carrying technology helps

innovation.

TRAINING:

The laying of fiber optic cable, the connection to each customer,

the link between cities, the network spanning the country, the technology

used for transmission, the equipments handling 1600 Gbps of data,breaking down of the network and testing each fiber is almost all I learnt

during my training.

THE FUTURE:

Evolution is a necessity, thus the telecom sector will always

grow, change and adapt to needs. The equipment and the technology willchange again, to handle more amounts of data. The demands of the


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customer and every individual will increase with time. The telecom

industry will always be on its toes.

1) ABOUT RELIANCECOMMUNICATIONS:

Reliance Communications Ltd. (commonly called RCOM) is anIndian broadband and telecommunications company headquartered inNavi Mumbai, India. RCOM is the world's 16th largest mobile phoneoperator with over 144 million subscribers. Established on 2004, asubsidiary of the Reliance Group. The company has five segments:Wireless segment includes wireless operations of the company;broadband segment includes broadband operations of the company;Global segment include national long distance and international longdistance operations of the company and the wholesale operations of itssubsidiaries; Investment segment includes investment activities of theGroup companies, and Other segment is consists of the customer careactivities and direct-to-home (DTH) activities.

RelianceCommunications is the nodal agency for internationalcommunications from the country and has been the premier provider ofinternational voice and data services. The company operates landingstations, undersea cables, ISP POPs, managed services, leased lines anddata centres across India.

Vision:

Deliver a new world of communications to advance the reach and

leadership of our customers.

Commitment:

Invest in building long-lasting relationships with customers and

partners and lead the industry in responsiveness and flexibility.

Strategy:

Build leading-edge IP-leveraged solutions advanced by our

unmatched global infrastructure and leadership in emerging markets.


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HISTORY:

It ranks among the top 5 telecommunications companies. Retrieved 2010-04-14. in the world

by number of customers in a single country. Reliance Communications limitedclienteleincludes 2,100 Indian and multinational corporations and over 800 global, regional anddomestic carriers. The company has established a pan-India, next-generation, integrated(wireless and wireline), convergent (voice, data and video)digital network that is capable ofsupporting services spanning the entire communications value chain, covering over 24,000towns and 600,000 villages. Reliance Communications owns and operates the next-generation,IP-enabled connectivity infrastructure,comprising over 190,000 kilometers of fiberoptic cable systems in India, USA, Europe, Middle East and the Asia Pacific region.

Main subsidiaries

Reliance Telecommunication Limited (RTL)

In July 2007, the company announced it was buying US-based managed ethernet andapplication delivery services company Yipes Enterprise Limited for a cash amount of 1200crore (the equivalent of US$300 million). The deal was announced of the overseasacquisition, the Reliance group has amalgamated the United States-based Flag Telecom for$210 million (roughly 950 crore). RTL operates in Madhya Pradesh, West Bengal,Himachal Pradesh, Orissa, Bihar, Assam, Kolkata and Northeast, offering GSMservices.

Reliance Globalcom

RGL owns the worlds largest private undersea cable system, spanning 65,000 km seamlesslyintegrated with Reliance Communications. Over 110,000 km of domestic optic fiber providesa robust Global Service Delivery Platform, connecting 40 key business markets in India, theMiddle East, Asia, Europe, and the U.S.

Reliance Internet Data Center (RIDC)

RIDC provides Internet Data center (IDC) services located In Mumbai,Bangalore,Hyderabadand Chennai. Spread across 650,000 sq ft (60,000 m2) of hosting space,it offers IT infrastructure management services to large, medium and small enterprises. It isone of the leading data center service provider in India and provides services like colocationmanaged server hosting, virtual private server and data security. It has launched cloudcomputing services, offering product under its infrastructure as a server (Iaas) and software asa service (Saas) portfolio, which enables enterprises, mainly small and medium, a cost-effective IT infrastructure and application on pay-per-user model.

Reliance Digital TV

Main article: Big Tv

Reliance Big TV launched in August 2008 and thereafter acquired 1 million subscribers

within 90 days of launch ,the fastest ramp-up ever achieved by any DTH operator in the
http://en.wikipedia.org/wiki/Ethernethttp://en.wikipedia.org/wiki/Ethernet


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world. Reliance Big TV offers its 1.7 million customers DVD-quality pictures on over 200channels using MPEG-4 technology.

Acquisition

FLAG Telecom Yipes ethernet service Digicable

SERVICES PROVIDED:

RELIANCECommunications offers the following services to itscustomers can be divided into following categories:

Personal

Broadband Internet Access

Dial-up Internet Access

Wi-Fi

Net Telephony Corporate

International Private Leased Circuits (IPLC)

National Private Leased Circuits (NPLC)

Virtual Private Network (VPN)

Video conferencing

Internet Leased Line

ISDN

Bandwidth on demand

INFRASTRUCTURE:

The state of the art infrastructure of the RCOMnetwork consists of 200,000

sq. km. global network connecting over 200 countries and territories


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having 275 points of presence (PoP). RELIANCE has over 20 terabits of

submarine capacity and over one million square feet of data center space.

The domestic infrastructure of RCOMhas a NLD backbone of35000km covering 300 major cities. It . For MPLS, there are 123 PoPs in

119 cities all over the country.

RELIANCECommunications has 10 data centres in USA andCanada, 12 in Europe and another 12 in Asia including the 7 in India. Theglobal MPLS network of RCOM also has undergone an up gradation and iswell-spread over 4 continents.

As far as the international cables are concerned, RCOM is the only carrierhaving a capacity on 5 out of 5 cables coming to India. It sends its datavia:

FLAG Cable: It connects India to the North European and NorthAfrican countries and is accessed via Mumbai.

SEA-ME-WE 2: It connects India with the Arab and south Europeancountries. It is accessed via Mumbai.

SEA-ME-WE 3: It connects India with the Western Europe, parts ofAfrica, S.E.Asia, China, Japan, Russia and Australia. It is accessed viaMumbai & Cochin.

SAFE/SAT 3: This cable connects India with the South and WestAfrican countries and is accessed via Cochin

SEA-ME-WE 4: It connects India with Sri Lanka, Arab countries and

South Asian countries. It can be accessed via Mumbai and Chennai.

RCOM has its own fiber laid between India and Singapore which has acapacity of 5.12Tbps and is maintained by RELIANCE.

MARKET SCENARIO:

The telecommunications sector is on a boom and is growing

manifold every year. Hence, the no. of players entering the sector is alsoincreasing rapidly and existing players are growing stronger. Hence, there


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is a cut throat competition and to survive in this, one needs to growconstantly.

RCOM with its growth over the past 5 years into various sectorsof services, the quality standards and the customer base, can be called as

Indias first telecom multinational.

International Market:

In the international scenario, RCOM competes with the otherinternational carriers such as AT&T, SingTel etc. As of now, RCOM isamong the top 3 players in the field of wholesale voice transfer. It isundoubtedly, the largest supplier of submarine bandwidth. RCOM is alsoGlobal Tier 1 internet service provider.

Domestic Market:

In India, RELIANCECommunications today faces fiercecompetition from Bharti and Tata,Vodafone. These service providers havea stronger hold on the NLD market and also have a more widespreadnetwork all over India. But in ILD, rcom is still the market leader with over12% market share. In services like IPLC, it has a lions share of 60% in themarket.

RELIANCECOMMUNICATIONS, BANGLA SAHIB ROAD, NEW DELHI:

The office at Bangla Sahib is the regional office of VSNL in Delhi. Itconsists of the following departments:

HR Department

Finance Department

NLD Department

ILD Department

Voice Department

Data Department

Access Department

MAN Department

P&I Department


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OSP Department

2) FIBER OPTIC:

a) FUNCTIONAL BASICS:

The Optical Fiber is basically glass, made out of Silica. The

Optical Fiber is constructed using two concentric layers. The inner layer is

the Core and the outer layer is the Cladding. They have a refractive index

of about 1.5. The core and the cladding have a difference in refractive

index of less than 1%.

Light is guided through the core, and the fiber acts as an optical

waveguide.

Fig: Fiber Optic (Cross-section)

Refractive Index= 1.467-1.468

i. TOTAL INTERNAL REFLECTION:

The Core has higher refractive index than the Cladding. Thedifference creates a denser and a rarer medium. Thus when a ray of light

is passed in the core, it is reflected throughout the length of the fiber

optic.

Refractive index of medium = speed of light in vacuum / speed of

light in medium.

Critical Angle= cos1 (n2/n1)


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The light must enter the fiber optic within the acceptance angle,

which is a function of the refractive index of the core and the cladding.

There is a maximum angle at which the light can enter with respect to the

fiber axis so that it will propagate in the core of the fiber optic cable.

Fiber with large NA allows working and splicing with less

precision.

Fig: Total Internal Reflection happens only when light is within

Acceptance Cone.

Numerical Aperture= sine (max. Angle allowed from acceptance

cone).

Total Internal Reflection is almost lossless. The ray of light

undergoes several reflections and simultaneously diminishes in energy,

and after a certain distance dies off.

ii. FACTORS CAUSING ATTENUATION:

Absorption, Scattering and bending of light are the three

factors which cause attenuation in the transfer of light in

fiber optic.

1. Absorption:

It is caused due to the impurities and imperfections in the

fiber.

Intrinsic Absorption: it is caused due to fiber material and

molecular resonance.


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Extrinsic Absorption: they are present due to OH ions. They

are almost negligible.

2. Scattering:

Collision of light with atom particles causes light to disperse inall directions, also causing some light to escape from the fiber.

It causes 96% of the total attenuation in the fiber.

3. Bending:

Macro Bending: Caused by light escaping the core due to

imperfections at

Core/clad boundary

Macro Bending: Caused due to Bending of the fibre.

Practical Attenuation Figures:

Single Mode Fiber- Loss at 1550nm is 0.2dB/km

Loss at 1310nm is 0.35dB/km.

0.05 dB for a Fusion Splice.

0.1 dB for a Mechanical Splice.

0.2 0.5 dB for a Connector pair.

b) USES AND ADVANTAGES:


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Fiber Optic is used for networking and telecommunication, to

transfer data, voice and video over short and long distances.

Carriers use optical fiber to carry plain old telephone service

across national network and Local Exchange Carriers use it to transfer to

cater directly to home. It is also used for reliable, secure and fast

transmission of data by multinational firms. Its high bandwidth makes it

perfect choice for transmitting broadband signals, such as high-definition

television (HDTV) telecasts. It is used in transportation systems, such with

intelligent traffic lights, automated tollbooths, and changeable message

signs. Another important application for optical fiber is the biomedical

industry. Other applications for optical fiber include space, military,

automotive, and the industrial sector. It is also used by designers to make

home decorative.

ADVANTAGES:

Long distance signal transmission-

The low attenuation found in optical systems allows much

longer intervals of signal transmission than metallic-based systems. This

allows fewer no. of repeaters compared to the copper cable network.

Large bandwidth, light weight, and small diameter-

The fiber optic cables provide a bandwidth which is much

greater than can be supported by the transmitting and receiving devices

installed presently.

Fig: Decorative made of Fiber Optic


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Easy installation and upgrades-

Long lengths make optical cable installation much easier

and less expensive. Optical fiber cables can be installed with the same

equipment that is used to install copper and coaxial cables, with some

modifications due to the small size and limited pull tension and bend

radius of optical cables. The longer cables can be coiled at an

intermediate point and pulled farther into the duct system as necessary.

Non-conductivity-

Another advantage of optical fiber is its dielectric nature.Since optical fiber has no metallic components, it can be installed in areas

with electromagnetic interference (EMI), including radio frequency

interference (RFI). Areas with high EMI include utility lines, power-carrying

lines, and railroad tracks. All-dielectric cables are also ideal for areas of

high lightning-strike incidence.

Security-

Unlike metallic-based systems, the dielectric nature of

optical fiber makes it impossible to remotely detect the signal beingtransmitted within the cable. The signal in a fibre can, however be

"tapped" by bending the fibre and detecting light that then leaks from its

core. The resistance to remote signal interception makes fibre attractive

to governmental bodies, banks, and others with security concerns.

Designed for future applications' needs-

Fiber optics is affordable today, as electronics prices fall

and optical cable pricing remains low. In many cases, fiber solutions are

less costly than copper. As bandwidth demands increase rapidly withtechnological advances, fiber will continue to play a vital role in the long-

term success of telecommunications.

c) DIFFERENCE BETWEEN COPPER CABLE AND FIBER OPTIC.


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The main difference between copper cable and fiber optic

is that copper cable transmits electrical signals while fiber optic transmits

optical signals. Optical signals provide more security. Like electrical

signals can have different voltage, optical signals can have different

frequency and wavelength.

Fig: Copper Cable (Twister Pair)

The copper cable was initially used to transfer data, but

with interference and slow rate of data transmission the fibre optic is

preferred. The cable is twisted to lower the interference. The advantages

of fiber optic over copper cable are given below.

Speed:

Fiber Optic networks operate at high speeds- up into the

gigabits.

Carrying Capacity:

Fiber Optic has no limitations on Bandwidth, thus it has

large carrying capacity. Fiber Optic is thinner thus more fibres can bebundled into a given diameter. Copper Cable has limited bandwidth.

Less Expensive:

Several miles of optical cable can be made cheaper than

equivalent lengths of copper wire. This saves your provider (cable TV,

Internet) and you money.

Distance:


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Signals over Fiber Optic have very little loss thus

fewer no. of repeaters are required over long distances. While copper

cable requires frequent repeaters to refresh the signal

Resistance:

Great resistance to electromagnetic noise such as radio,motors or other nearby cables allows transmission of a pure signal.

Maintenance:

Fiber optic cables costs much less to maintain, and has

no fire hazards since it works on optical signals.

Low power :

Because signals in optical fibers degrade less, lower-

power transmitters can be used instead of the high-voltage electrical

transmitters needed for copper wires. Again, this saves your provider and

you money.

Lightweight :An optical cable weighs less than a comparable copper

wire cable. Fiber-optic cables take up less space in the ground.

d) TYPES OF FIBERS.

The basic difference in the fibers is created due to the

dimensions of the core and the clad. Also a difference is between various

fibers is their Refractive Index.

a. SINGLE MODE FIBER:

It has a core diameter ranging from 5 to 10 m, while

the cladding extends till 125 m and the coating till 250 m. It has a

single refractive index through its length. Its small core avoids any

distortion from overlapping of light pulses. Also since light pulse travels

parallel to the axis there is very little dispersion.

It is used for long distance transmission and works on

LASER diode based fiber optic equipment. It also offers more data rateand transmission bandwidth.


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b. MULTIMODE FIBER:

It has a core diameter ranging from 50 to 100 m, while

the cladding extends from 125 to 140 m and the coating till 250 m. ItsRefractive Index changes with length.

This type of a fiber is created using temperature

difference while manufacturing the fiber. Light waves disperse into

numerous (multiple) paths thus it is known as Multi Mode.

Fig: Multi Mode (Step Index and Graded Index) Fiber and Single Mode (SM)

Fiber.

It is used for short distance transmission and is capable

of working on LED based fiber optic equipments. It offers high capacity (10

100 Mbps) over medium distances (200m to 2km).

Step-index multimode fiber: The Refractive Index decreases sharply

at the core and cladding interface. The diameter of the core is 100 m.

Graded-index multimode fiber: The Refractive index reduces from

the axis of the core to the cladding, but the least is still more than the

refractive index of the cladding. Thus the light travels in a helical path.

Thus there is less difference in speed between the straight and helically

travelling light, thus reducing dispersion.

e) OPTIC FIBER CABLE.


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The Cable containing the Fiber has several layers. These

layers vary for different applications, like in the case of underground and

overhead cables.

The underground cable is an armoured cable. This is to

protect it from rats and other external factors which might bend or break

the fibre. The underground cable also has other fibre type material to

provide strength to the cable.

The overhead cable has fewer fibres and does not

contain the armoured layer, steel. These are easy to install and reduce

time and cost.

The basic structure of a Fiber Optic Cable has following

layers beginning from the centre:

a) Core,

b) Cladding:

These two layers

constitute the basic fiber.

c) Buffer Coating:

This is a gel used for

coating the fiber to

avoid brittleness of the

fiber. This gel also

repels water.

d) Kevlar Strengthening Fibers:

This is used for protection from external environment.

e) Re-enforced Steel:

It is used for providing strength and as protection from

rats and other forceful factors Fig: Construction of Fibre Cable.

which can damage the cable.

f) Cable Jacket:


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This is made out of PVC (Polyvinyl Chloride). This plastic

material is also used for protection from external environment. It also

protects it from catching fire easily.

g) Centre Strength

Material

Fig: Cross-section of

fiber cable.

A cable can contain

fibers varying from 6 to 96.

A cable can have 6, 12, 24, 36, 48, 72 and 96 fibers in it. The cable

contains tubes which inside it contains fibers. The tubes inside the cable

can vary, with a maximum of 8 tubes in a cable. Similarly, the number of

fibers in a tube can vary, with 6 and 12 as minimum and maximum,

respectively. The tubes and fiber are present as multiple of 2.

Each fiber inside the cable can be numbered from 1 to N

(if the Cable contains N number of fibers). This is made possible by the

colour coding of tubes and fibers. Colour coding for both the tubes and the

fibers is as given below

1. Blue,

2. Orange,

3. Green,

4. Brown,

5. Slate (grey),

6. White,

7. Red,

8. Black,

9. Yellow,

10. Violet,

11. Rose (pink),


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12. Aqua (natural).

Let a 48 fiber cable have 6 tubes and each tube have 8

fibers. Thus blue fiber of the blue tube will be the 1st

fiber of the cable, theorange fiber of orange tube will be the 8th fiber of the cable. The white

fiber of the white tube will be the 48th fiber of the cable. This colour coding

is required to map signals in FMS (Fiber Management System) and also for

splicing two cables. The tube is also called Buffer.

Fig: Armoured Cable for burial. The above shown cable has a configuration

of 6x6.

Also available are cables with no tubes, having a

maximum of 48 cables. The coding here is done by winding sets of fibers

with threads. These cables are used exclusively for high data

transmission. These cables sometimes have in them TRUE WAVE fibres.

These fibers are of the purest form and are capable of very high capacity.

In a cable, never will all the fibers be true wave since normal fibers also

provide a very high data. Thus usually a cable of 48 fibers will only have 6

true wave fibers. These are used for ILD (International Long Distance).


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A cable with only 6

fibers is the one with minimum no.

fibers. It is used to connect to end

user as overhead cable, when much

capacity is not required.

Fig: Distribution Cable

f) CABLE INSTALLATION (FIBER LAYING)

1) DIGGING:

Open trench- It should be straight and of the same depth

throughout. The route must be checked for road, soil, bridges

and trees. Bending radius should be more than 20 times the

outer diameter of the duct. Flags, rope with nails or chalk

powder are used to mark the route.

Moiling- Two holes are dug at a distance of 20mts and the

cable is pushed from one to the other. It is a very cheap butunreliable method, since the cable might bend causing

losses.

HDD- It is the most expensive technique and is also known

as trenchless. A JCB machine is put in the hole and is

horizontally driven to the other hole 70-100mts apart. The

machine has a sensor at its head which monitors and avoids

obstructions as far as possible. It is usually used in

metropolitans.

2) DUCT LAYING (COUPLING) :


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Before laying the duct soil and stones must be checked. The

ground must be levelled before laying. Minimum bending

radius of the ground must not be more than 30 gradient.

3) DIT :

This test is used to check the suitability of duct for optical

fiber cable installation through jetting. It is the intermediate

step between duct laying and cable jetting. The test is carried

out to check damages, blockages, leakage, continuity,

spiralling and mud, stone or water in the duct. Four duct

integrity tests are carried out.

Fig: Bending radius not maintained, Damaged Coupler, Spiralling and

Water filled in duct.

a. Air Blowing:

Air is passed through one end and its pressure tested at

the other. If the air flow is normal then the duct in continuous, else in the

case of no air flow, low air pressure or back pressure a fault in the duct

persists. No air flow would hint towards missing coupler or blockage. Back

pressure would mean blockage and Low air pressure would mean a loose

coupler or small blockage or leakage.

b. Shuttle Blowing:

It is used to check if the turning radius has been

maintained and for any kinks or dents. Time for shuttle to come out of the

other end is 1-1.5 min in a 1km long duct.

c. Sponge Blowing:

Sponge is used for the same purpose as shuttle blowing.

d. Air Pressure:


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Air at 5 bars is passed through the duct and the pressure

is checked at the other end. Permissible pressure drop is 0.5 bar, i.e. the

duct is normal. Else a leakage at the coupler or puncture in the duct can

be concluded.

4) CABLE JETTING:

Cable jetting is a technique to install cables in ducts. It is

commonly used to install cables with optical fibers in

underground polyethylene ducts.

Cable jetting is the process of blowing a cable through a

duct while simultaneously pushing the cable into the duct.

Compressed air is injected at the duct inlet and flows throughthe duct and along the cable at high speed. The high speed

air propels the cable due to drag forces and pressure drop.

The friction of the cable against the duct is compensated

locally by the distributed airflow and large forces that would

generate high friction are avoided. Because of the expanding

airflow, the air propelling forces are relatively small at the

cable inlet and large at the air exhaust end of the duct. To

compensate for this, an additional pushing force is applied to

the cable by the jetting equipment. The pushing force, actingmainly near the cable inlet, adds synergistically with the

airflow propelling forces, increasing the maximum jetting

distance considerably. Special lubricants have been developed

for cable jetting to further offset friction.

Fig: First prototype of cable jetting

equipment

5) SPLICING:

Splicing is a technique used to join two fibers, since cablesare available in limited lengths from 1 to 6 km. Splicing can be


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characterized as Fusion Splicing and Mechanical Splicing. Of

all the above mentioned techniques Fusion Splicing is mostly

used, since it offers minimum losses, which is the most

important characteristic.

Fusion Splice: It is a permanent splicing technique with

minimum losses, which are almost negligible, 0.02 dB. The

equipment available for fusion splicing makes it extremely

easy.

Splicing Machine: FITEL S176: The machine makes fusion

splicing extremely easy with its automatic alignment and

fusion mechanism to offer minimum losses.

Fig: Splicing Machine (S176).

STEPS FOR SPLICING:

Fiber Preparation:

The cable is stripped till the

cladding with special tools. First the

cable, strengthening fibre are removed

to obtain the fiber. Then the coating on

the fiber is cleaned using tissue soaked in Isopropyl (alcohol)solution or talcum powder.

Fig: Cleaver (FITEL).

The obtained fiber is then put in a cleaver to cut its end at 90. The

cleaver also helps cut the fiber of a certain length as per the sleeve.

Sleeve is slide into either of the two fibers before stripping.

Set up the machine.


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Load the fiber into the machine making sure the end reaches

the electrodes.

Splice: The splicing machine fuses the fiber with an ElectricArc which produces a temperature of about

2000 C in the range of melting point

of glass.

Check Strength.

Cover Spliced part with sleeve and

heat it for reinforcement.

The process of splicing (including alignment of

fibres) takes approx. 11 seconds.

CAUSES FOR SPLICE LOSS:

1. INTRINSIC FACTORS

Core Diameter Mismatch.

Cladding Diameter Mismatch.

Numerical Aperture Mismatch.

Concentricity

Non-circularity: core might be elliptical.

Refractive Index Mismatch

2. EXTRINSIC FACTORS

End Separation: fiber ends are at a distance.

Angular Misalignment: ends of fiber might not be matching.

Lateral Displacement: axis of core of the two fibers is not aligned.

Fiber Cleaving Angle: end might not be at 90.

Dust.


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g) OTDR (OPTICAL TIME DOMAIN REFLECTOMETER):

Its operation consists of transmitting pulsed Laser

signals in the fiber under test and detecting the scattered and reflections

at different points in the fiber link. This can help detect the signal being

received from the exact position in the fiber, i.e. the distance.

D = c*t / 2N

(D- Distance, c- speed of light, t- time and N is the refractive index)

The equation is divided by two because the total time is that of

transmitting and receiving.

The equipment provides a waveform which on its

vertical axis displays amplitude/loss and on its horizontal axis it has the

distance.

Fig: Graph Obtained from OTDR.

OTDR thus can be used for various factors:

Attenuation Characteristics can be obtained on agraph.

Exact location of broken optical fiber can bedetermined.


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Loss caused by splicing.

Measures Optical Return Loss (ORL) of the connector.

Detect, locate and measure any event at any location

of the fiber link.

OTDR specifies Dynamic Range for distance and loss,

i.e. the maximum distance it can measure the optical

fiber till and the minimum loss that it can differentiate

from noise. This range is determined by the difference

between the backscattered level at starting point and

the noise floor after the far end of the fiber.

h) CONNECTORS/ATTENUATORS/COUPLERS:

Fiber is not endless and need to be joined to equipments at

both the receiving and transmitting ends. They are also used during

subsequent cable cuts.

i.CONNECTORS:

They are used to join the fiber to the equipments at both

the receiving and transmitting end. The benefit of using a connector is

that the end can be removed and joined as needed.

Care must be taken while removing or installing the

connector that they are not exposed to dust. Thus all connectors come

with caps.

Some basic types of connectors are:

FC (Ferrule Connector): it is widely used for

TELECOM and DATACOM. It is made of nickel plated

brass and has a threaded locking system.

Fig: Ferrule Connector.


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SC (Square Connector): It is used for DATACOM and CAPTV. It is

made of moulded plastic and is square in shape. Clips on both sides

allow for easy push in.

Fig: Square Connector.

LC (Lucent Connector): It holds only one fiber

and is half the size of SC. It also is made out of

moulded plastic and has a square front. An RJ

latch allows connecting it to the equipment.

Fig: Lucent Connector.

MU (Miniature Unit) Connector : it is similar to LCbut smaller. Its switch allows easy pull-pull

latching connections. It is well suited for high

density applications.

Fig: Miniature Unit.

E2000 (Euro): It is the latest technology. It has

a moulded plastic structure. Its most important

feature is that it has a cover to protect it from

dust. When removed the cover automaticallycovers the open front.

Fig: E2000.

ii)COUPLERS:

They are used for compatibility between different types of

connectors and equipments. Since equipment end and the fiber end might

be of different types a Coupler is required.

iii.ATTENUATORS:

They are used for attenuating the power of the signal. They

diminish the power of the signal using a smaller sized hole. Attenuators of

different configuration are available i.e. for different losses like 3, 5, 8 dB

etc. These attenuators are available with all kinds of connector


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configurations. Attenuators are used in DWDM applications, Test &

measurement, Optical sensors and Telecommunications applications.

SDH (Synchronous Digital Hierarchy)

SDH (Synchronous Digital Hierarchy) is a standard for telecommunications

transport formulated by the International Telecommunication Union (ITU),

previously called the International Telegraph and Telephone Consultative

Committee (CCITT).

SDH was first introduced into the telecommunications network in 1992

and has been deployed at rapid rates since then. Its deployed at all levels

of the network infrastructure, including the access network and the long-

distance trunk network. Its based on overlaying a synchronous

multiplexed signal onto a light stream transmitted over fibre-optic cable.

SDH is also defined for use on radio relay links, satellite links, and at

electrical interfaces between equipment. The comprehensive SDH

standard is expected to provide the transport infrastructure for worldwide

telecommunications for at least the next two or three decades.


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The increased configuration flexibility and bandwidth availability of SDH

provides significant advantages over the older telecommunications

system.

These advantages include:

A reduction in the amount of equipment and an increase in networkreliability.

The provision of overhead and payload bytes the overhead bytespermitting management of the payload bytes on an individual basisand facilitating centralized fault sectionalisation.

The definition of a synchronous multiplexing format for carryinglower-level digital signals (such as 2 Mbit/s, 34 Mbit/s, 140 Mbit/s)

which greatly simplifies the interface to digital switches, digitalcross-connects, and add-drop multiplexers.

The availability of a set of generic standards, which enable multi-vendor interoperability.

The definition of a flexible architecture capable of accommodatingfuture applications, with a variety of transmission rates.

In brief, SDH defines synchronous transport modules (STMs) for the

fibre-optic based transmission hierarchy.

Synchronisation of Digital Signals

In a set of Synchronous signals, the digital transitions in the signalsoccur at exactly the same rate. There may however be a phase

difference between the transitions of the two signals, and this would

lie within specified limits. These phase differences may be due to

propagation time delays, or low-frequency wander introduced in the

transmission network. In a synchronous network, all the clocks are

traceable to one Stratum 1 Primary Reference Clock (PRC). The

accuracy of the PRC is better than 1 in 10^11 and is derived from

a cesium atomic standard.

If two digital signals are Plesiochronous, their transitions occur atalmost the same rate, with any variation being constrained within

tight limits. These limits are set down in ITU-T recommendation

G.811. For example, if two networks need to interwork, their clocks


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may be derived from two different PRCs. Although these clocks are

extremely accurate, theres a small frequency difference between

one clock and the other. This is known as a plesiochronous

difference.

In the case of Asynchronous signals, the transitions of the signalsdont necessarily occur at the same nominal rate. Asynchronous, inthis case, means that the difference between two clocks is muchgreater than a plesiochronous difference. For example, if two clocksare derived from free-running quartz oscillators, they could bedescribed as asynchronous.

ADVANTAGES OF SDH TECHNIQUE ARE:

i.Transmitting a multiplexed signal can be done from standardized

equipment.

ii. Redirection of channels is done internally using S/W commands.

iii. Compatibility between different vendors is possible.

iv. Better network survivability.

v. Individual channels can be easily added and dropped.

vi. It accommodates both existing and future services. (ATM, B-

ISDN).

vii. Backward compatible, i.e. it supports PDH traffic.

viii.Unlike PDH, its payload is transparent.

ix. It has consistent frame structure throughout the hierarchy.

x. Changing from one level to the other does not require additional

equipments, to provide certain signal to the customer then it can

directly be given.

Basic SDH Signal

The basic format of an SDH signal allows it to carry many different

services in its Virtual Container (VC) because it is bandwidth-flexible. This

capability allows for such things as the transmission of high-speed packet-


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switched services, ATM, contribution video, and distribution video.

However, SDH still permits transport and networking at the 2 Mbit/s, 34

Mbit/s, and 140 Mbit/s levels, accommodating the existing digital

hierarchy signals. In addition, SDH supports the transport of signals based

on the 1.5 Mbit/s hierarchy.

STM-1 FRAME FORMAT:

The number of frames per second is 1 second / 125 s = 8000 Frames per

second.

Therefore the rate transmitted to line is: -

8 bits x 2430 bytes x 8000 per second = 155,520,000 bps or 155 Mbps.

The STM-1 frame structure can be represented by the following

diagram which has 270 columns and 9 rows. Each cell represents one

byte; hence there are 270*9 = 2430 bytes.

There are three main areas of a STM-1 frame:

1. Section Overhead (SOH).

Regenerator Section Overhead (RSOH).

Multiplex Section Overhead (MSOH). Path Overhead (POH).2. Administrative Unit Pointer.

3. Information payload.

STM-1 Frame Structure


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PRINCIPLES OF SDH

1. SDH defines a number of containers, each corresponding to

an existing pleisynchronous rate.

2. Each container has a path overhead added to it. POH

provides network management capability.

3. Container plus POH forms a Virtual Container.

4. All equipment is synchronized to a national clock.

5. Delay associated with the transmission link may vary slightly

with time causing allocation of VC within the STM-1 frame to

move.

6. Variations accommodated by use of a Pointer.

Points to the beginning of VC.

Pointer may be incremented or decremented.

7. When STM-1 payload is full, more network managementcapability is added to from the Section Overhead.


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8. SOH remains with the payload for the fibre section between

synchronous multiplexers.

WIMAX

DEFINITION

WiMAX, meaning Worldwide Interoperability for Microwave

Access, is a telecommunications technology that provides

wireless transmission of data using a variety of transmission

modes, from point-to-multipoint links to portable and fully mobile

internet access. The technology provides up to 3 Mbit/s

broadband speeds without the need for cables. WiMAX is a

wireless digital communications system, also known as IEEE

802.16, that is intended for wireless "metropolitan area

networks". WiMAX can provide broadband wireless access (BWA)

up to 30 miles (50 km) for fixed stations, and 3 - 10 miles (5 - 15

km) for mobile stations. In contrast, the WiFi/802.11 wireless

local area network standard is limited in most cases to only 100 -

300 feet (30 - 100m).

With WiMAX, WiFi-like data rates are easily supported,

but the issue of interference is lessened. WiMAX operates on

both licensed and non-licensed frequencies, providing a regulated

environment and viable economic model for wireless carriers.

WiMAX can be used for wireless networking in

much the same way as the more common WiFi protocol. WiMAX

is a second-generation protocol that allows for more efficient

bandwidth use, interference avoidance, and is intended to allow

higher data rates over longer distances.

The IEEE 802.16 standard defines the technical

features of the communications protocol. The WiMAX Forumoffers a means of testing manufacturer's equipment for

compatibility, as well as an industry group dedicated to fostering

the development and commercialization of the technology.

WiMax.com provides a focal point for consumers,

service providers, manufacturers, analysts, and researchers who

are interested in WiMAX technology, services, and products.

Soon, WiMAX will be a very well recognized term to describe

wireless Internet access throughout the world.


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USES

The bandwidth and range of WiMAX make it suitable for the followingpotential applications:

Connecting Wi-Fi hotspots to the Internet. Providing a wireless alternative to cable and DSL for "last mile" broadband access. Providing data and telecommunications services. Providing a source of Internet connectivity as part of a business continuity plan. That

is, if a business has a fixed and a wireless Internet connection, especially fromunrelated providers, they are unlikely to be affected by the same service outage.

Providing portable connectivity.

WIMAX CONCEPT

Fixed wireless is the base concept for the metropolitan area networking (MAN), given in the802.16 standard. In fixed wireless, a backbone of base stations is connected to a publicnetwork.

Each of these base stations supports many fixed subscriber stations, either public WiFi hotspots or fire walled enterprise networks. These base stations use the media access control(MAC) layer, and allocate uplink and downlink bandwidth to subscribers as per their

individual needs. This is basically on a real-time need basis.

The subscriber stations might also be mounted on rooftops of the users. The MAC layer is acommon interface that makes the networks interoperable. In the future, one can look forwardto 802.11 hotspots, hosted by 802.16 MANs. These would serve as wireless local areanetworks (LANs) and would serve the end users directly too.

WiMax supporters are focusing on the broadband ~Slast mile~T in unwired areas, and onback-haul for WiFi hotspots. WiMax is expected to support mobile wireless technology too,wireless transmissions directly to mobile end users.

WiMax changes the last mile problem for broadband in the same way as WiFi has changedthe last one hundred feet of networking.

WiMAX has a range of up to 31 miles, which can be used to provide both campus-levelnetwork connectivity and a wireless last-mile approach that can bring high-speed networkingand Internet service directly to customers. This is especially useful in those areas that werenot served by cable or DSL or in areas where the local telephone company may need a longtime to deploy broadband service.


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WIMAX PROTOCOL

WiMax has two main topologies ~V namely Point to Point for backhaul and Point to MultiPoint Base station for Subscriber station.

In each of these situations, multiple input multiple output antennas are used. The protocolstructure of IEEE 802.16 ~V Broadband wireless MAN standard is shown below:

The above picture shows four layers ~V Convergence, MAC, Transmission and Physical.These layers map to two of the lowest layers ~V physical and data link layers of the OSI model.

WiMax provides many user applications and interfaces like Ethernet, TDM, ATM, IP, andVLAN.

The IEEE 802.16 standard is versatile enough to accommodate time division multiplexing(TDM) or frequency division duplexing (FDD) deployments and also allows for both full and half-duplex terminals.

802.16 supports three physical layers. The mandatory physical mode is 256-point FFTOFDM (Orthogonal Frequency Division Multiplexing). The other modes are Single carrier(SC) and 2048 OFDMA (Orthogonal Frequency Division Multiplexing Access) modes. Thecorresponding European standard - the ETSI Hiperman standard defines a single PHY modeidentical to the 256 OFDM modes in the 802.16d standard.

The MAC was developed for a point-to-multipoint wireless access environment and canaccommodate protocols like ATM, Ethernet and IP (Internet Protocol). The MAC frame


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structure dynamic uplink and downlink profiles of terminals as per the link conditions. This isto ensure a trade-off of capacity and real-time robustness.

The MAC uses a protocol data unit of variable length, which increases the standardsefficiency. Multiple MAC protocol data unit can be sent as a single physical stream to save

overload. Also, multiple Service data units (SDU) can be sent together to save on MACheader overhead. By fragmenting, you can send large volumes of data (SDUs) across frame

boundaries and can guarantee a QoS (Quality of Service) of competing services. The MACuses a self-correcting bandwidth request scheme to avoid overhead and acknowledgementdelays.

This also allows better QoS handling than the traditional acknowledged schemes. Theterminals have a variety of options to request for bandwidth depending on the QoS and other

parameters. The signal requirement can be polled or a request can be piggybacked.

MULTIPLEXING IN WIMAX

OFDM

Support for OFDM (orthogonal frequency division multiplexing), which cancontinue to beimplemented in various ways by different operators (the precise variant ofOFDM can oftenbe their key differentiator).OFDM is well established and is incorporated in some new generationcarrier services aswell as being fundamental to digital TV. It transmits multiple signalssimultaneously acrossone cable or wireless transmission path, within separate frequencies, withthe orthogonal

element spacing these frequencies to avoid interference. It is alsosupported in the 802.11aWLAN standard.802.16a has three PHY options: an OFDM with 256 sub-carriers the onlyoption supportedin Europe by the ETSI, whose rival HiperMAN standard is likely to besubsumed intoWiMAX; OFDMA, with 2048 sub-carriers; and a single carrier option forvendors that thinkthey can beat multipath problems in this mode. OFDM will almost certainlybecomedominant in all wireless technologies including cellular and its industrybody, the OFDM Forum, is a founder member of WiMAX Forum.


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