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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
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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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