RGM TTC
BSNL
A Presentation on
OPTIC FIBRE CABLE
BY
Rajiv Gandhi Memorial
Telecom Training Centre
(ISO 9001:2000 Certified)
Chennai-600027 Email – [email protected]
G. Shankar, Faculty, RGM TTC
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BSNL OPTIC FIBRE CABLE
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Objectives• What is OFC?
• OFC Advantages
• OFC Types & Applications
• Specifications
• Future Trends
•OFC Installation
• Pulling Method with Nylon rope
• Blowing Method
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Limitations of copper network
•Copper is costlier and scarce material.
•Fault prone.
•Maintenance difficult
•Vulnerable for EMI.
•Installation time consuming.
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Limitations of copper based network
•Expansions make congestions in MDF •B/W LIMITED.•Loop Resistance restricts the length of operation.
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BSNL What is OFC ?Fibre Optic cable functions as a
“LIGHT GUIDE”, guiding the light
introduced at one end of the cable
through to the other end.
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BSNL Advantages of Optic Fibre• More Bandwidth - Thousands of Channels
• Low Loss - 0.5db per km
• Less number of Repeaters
• Electro Magnetic Immunity
• Small size & Light Weight - Easy to handle
• Greater Safety - No Electric Hazards
• Higher Security
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BSNL OFC Applications•Telecommunication Network
•Junction Network & Long Distance Network
•Submarine cable
•High EMI areas
•Explosive environment
•Computer links & Local Area Network
•Cable television
•Medical Field , Automobile Field
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Construction of Fibre•Centre Core – Glass – More RI 8-10 micrometer
Light is transmitted through the core
•Cladding – Glass – Less RI 125 micro meter
--Outside optical layer that traps the light into the core by Total Internal Reflection and guides the light along the core
•Primary Coating – Protection & Identification of Fibre
OFC Construction
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TIR is achieved since Core and Cladding having different Refractive Indices.
Core RI – 1.48
Cladding RI – 1.47
Principle of Working
Total Internal reflection
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•Centre Strengthening Member – GRP, FRP
•Loose Tube Buffers – 2.4 mm Dia
• Fibres are placed inside the Buffers along with
Jelly to prevent moisture entry.
•Primary Strength Member – Aramid Yarn -Kevlar
•Inner Sheath – Black
•Outer Nylon Sheath - Orange
Construction of Cable
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Construction of CableConstruction of Cable
Centre Strengthening Centre Strengthening Member – GRP, FRPMember – GRP, FRP
Loose Tube Buffers – 2.4 Loose Tube Buffers – 2.4 mm Dia, Fibres are mm Dia, Fibres are placed inside along with placed inside along with jelly.jelly.
Primary Strength Primary Strength Member – Aramid YarnMember – Aramid Yarn
Inner Sheath – BlackInner Sheath – Black
Outer Nylon Sheath - Outer Nylon Sheath - OrangeOrange
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BSNLLoose Tube Buffers•The Fibres are loosely drawn inside the Buffer Tubes to take care of Temp. Variations
•The OFC which is used outside is known as Loose Tube Buffers
•The Correction Factor is 0.985
•985 metres of OFC will contain 1000 metres Fibre inside
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Construction Of Cable
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These are tight Buffered cable
•Has only one fibre per cable
•Connector ended
•Used in the indoor applications
•Connecting equipment to outside OFC cable
•Connecting meters to the equipment
micrometer
Pig Tail Cable
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BSNLParameters of Cabling•Tensile Strength ( Pull)
•Crushing Resistance
•Protection from Excess Bending
•Abrasion Protection
•Anti-Twist
•Chemical protection
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Specification Of OFCFibre - Core - 8-10 Microns (Single Mode)
50 - 100Microns (Multimode)
Cladding - 125 Microns (overall Dia)
Attenuation - better than 0.5 db /KM
Primary Coating 250 Microns UV cured Acrylate
Secondary Coating –2.4 mm nylon PE Jelly filled tube
Central Strength Member – Fibre Reinforced Plastic (FRP)
Moisture Barrier- non metallic polythylene sheet free from pinholes and other defects
Polythene sheath Polythene free from pin holes
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Nylon Outer Sheath (0.7mm thickness)- Protective sheath against termite & partially against rodent
Strength to withstand a load - 3X9.8 W Newtons, where W is weight of O/F cable per KM in Kg
MAX Strain allowed in fibre - 0.25%
MAX attenuation variation - Permissible + 0.02 dB from normal 20 degree centigrade to 60 degree centigrade
Flexibility – Maximum bending radius allowed 24d, d is the diameter of OF cable
Cable drum lengths - 2 KM +10%
Cable ends - one end fitted with grip
Other end sealed with cap
Specification Of OFC
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Propagation of Light inside the Fibre
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OFC types
•Single Mode Fibre
•Multi Mode Fibre
•Plastic Optic Fibre
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•A much smaller core Diameter
•The Core dia is 8 to 10 Micrometer
•Cladding Dia is 125 Micrometer
•Very large bandwidth
•Light can go for very long distances
Single Mode Fibre
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Has a large Core Diameter Core Diameter - 50, 62.5, 100 Micro meter
Cladding dia - 125 Micro meter
Light waves are dispersed into number of paths
Multiple path of light cause signal distortion
Suitable for shorter length like LAN
Multimode
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Graded Index Fibre
Multi Mode Fibre
Step Index Fibre
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BSNL Plastic Optic Fibre
•Large Core - 1 MM Dia
•Multimode Fibre
•Used in Automobile Industry instead of Copper
•MOST (Media Orientated System of transport )
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OFC Sizes
•6 Fibre
•12 Fibre
•24 Fibre
•48 Fibre
•96 Fibre
Standard drum length is 2000M +10% 0r 4000 m
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1.1Pulling Method
•HDPE pipe laying ( High density Poly ethylene )
•OFC Pulling
2.Blowing Method
• PLB – Permanently lubricated Pipe laying
• Laying the OFC through blowing method
OFC LAYING
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•Depth – 165CM
•Top Width – 45CM
•Bottom Width –30CM
•After laying HDPE pipes, the depth should be 150CM from the top
barrel of the pipe.
Specification of Trench
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•Standard length of the pipe – 5 M
•Diameter of the pipe - 50mm, 75mm, 110mm
•The work is taken up in sections of 200M and pipes are buried .
•Between two sections a gap of 2M is left known as intermediate manhole
HDPE Pipe Laying
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Stores required for 200M pipe laying
HDPE pipes 50mm - 40 Numbers
Couplers - 39 Numbers
End Caps - 2 Numbers
4mm Nylon Rope - one coil of 205 to 210M
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•10 Sections of 200M each HDPE pipes are buried
•Open all the 9 intermediate Manholes
•Before laying the cable, ensure no blockage
•Bring the cable drum to the center at 1000M
•Center laying method is adopted
OFC pulling method
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BSNL At Road Crossings•RCC pipes should be used
•The RCC pipe should extend 3M on either side from the edge of the road.
•The HDPE Duct will be pulled inside the RCC pipe
•The road cutting work will be done during night times with proper warning boards.
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BSNL At Culverts / Bridges•Galvanised iron pipes are used on the wheel guard / footpath
•Gradual sloping to be given on either side of the bridge by reducing the depth of the trench to achieve the zero depth at bridges.
•For depths less than one meter, GI pipe should be provided and cement concreted.
•Inside GI pipes , HDPE Ducts are pulled
•The GI pipes should be cement concreted
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BSNLAt Railway Crossing
•Permission should be applied well in advance
•Cast Iron pipes are used below the tracks
•With in this CI pipe, HDPE should be drawn
•Angle of crossing should be 90 degrees
•The work is carried out by railway authorities
•Thrust boring method is used
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BSNLHandling of Cable Drum
•Drum should never be given any shock by dropping
•Drum should not be rotated on flanges
•Cable should not be bent while uncoiling
•The radius of curvature should not be less than 60CM
•Cable should not be twisted
•Use cable grip along with anti twist device while pulling the cable
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OFC Pulling in the
HDPE Duct for 2KM
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BSNL CABLE LAYING – OFC
1. Survey of Cable Route (Route PLG & SELECTION)
2. Testing of OFC in drums before laying
3. Permission from Highways, Municipality & Rly Authorities
4. Procurement of HDPE pipes 50mm, 75 mm, 110 mm
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CABLE LAYING – OFC – contd.
5. Procuring RCC Pipes, GI Pipes, CI Pipes
6. Procuring Nylon rope 4mm, 12mm
7. Procuring HDPE Couplings, End Caps
8. Taking Cable trench – 1.65m depth (earth digging)
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BSNL Pipe LayingHDPE pipes laid with couplings inserting 4mm Nylon rope inside the pipe.
9.Distance between the Intermediate Man Holes – 200m
40 Nos. of HDPE Pipe – 5m each
39 number of coupling + 2 End Cap
Split RCC Pipes if required (in city limits)
10.Closing of Cable trench
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BSNL11.Placing Route Indicators
12.Placing Joint Indicators
13.OFC Cable Pulling or Drawing
OFC Cable is pulled in the already buried HDPE pipe. First open all Intermediate Man Holes. After cable is pulled the portion of exposed OFC is covered with Split Pipe of Higher dia at the Intermediate Man Hole.
14.Route Index Diagram to be prepared.
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OFC Installation into PLB Ducts
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BSNL BLOWING METHODBLOWING METHOD
• Blowing is the process of pushing the cable through pre – prepared, pressurized, integral OFC ducts with the help of heavy air blowing pressure at 10 bar plus.
• The main driving force in the technology is blowing of air at high penetrating pressure.
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BSNL Advantages Of PLB Ducts
•Pipes are permanently lubricated
•Lubricants are built into Polymer base
•Mechanical protection to OFC
•Empty Ducts can be placed for future use.
•Eliminates Redigging
•Saving in Reinstatment charges
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BSNLADVANTAGESADVANTAGES
• Protection to OFC cable against destructing tensile forces.
• Work execution at a great speed with minimum risk to OFC.
• Replacement of existing faulty cable or Replacement within no time at a later stage.
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PLB-HDPE Ducts•Standard length - 200M, 1000M
•Diameter - 32/26mm, 40/33mm, 50/42mm
•Couplers will be placed for jointing two lengths
•Nylon rope approximately 4mm dia is placed inside the ducts.
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BSNL Duct Laying•Place the jack along the side of the trench
•Duct should be uncoiled from the bottom
•Drive the reel slowly to avoid over spinning
•Avoid twist and kinks
•When multiple ducts are placed in a single trench,
Duct spacer to be used so that the pipes do not cross each other.
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PREREQUISITEPREREQUISITE
• Duct integrity
• Duct uniformity
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BSNL OFC Installation into Ducts
Cable Blowing
•Cable jet blowing machine with compressor is used
•Air is blown into the Duct at high pressure & distributed along the entire cable through Duct
•The cable should be pushed from the blowing end to achieve more blowable length.
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CABLE JET MACHINECABLE JET MACHINE
• Make: SWITZERLAND
• Cable jet machine comes with appropriate spacers.
• These spacers range from 11 mm to 18.5 mm to suit different makes of OFC.
• The spacer suitable for sterlite 2001 make is 11 to12.5, 14-15.5 and 15-18.5.
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PROCEDUREPROCEDURE
• Complete duct integrity test for the entire modem section.
• Prepare stringent drum planning for entire route with ear marked below Points(B1, B2…..etc…,)
• Transport the ear marked drums to the specified below points and uncoil the drums into figure “8” formation.
•
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Prepare the cable end suitable for blowing by adding a spacer heading bullet.
Place cable jet machine inside the blow pit and fix the top cover of the jet machine.
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PROCEDURE CONTD…PROCEDURE CONTD…
• Insert sponge into the duct and fix the top cover of the jet machine.
• Fix the air – blowing hose pipe to the cable jet machine.
• Start the compressor and blow air at 10 – bar pressure.
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Confirm the receipt of sponge at the other end of the duct.
Remove the top cover of the cable jet machine, insert the spear headed
Cable end into the duct and restore the top cover
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PROCEDURE CONTD…PROCEDURE CONTD…
• Remove the jet machine and carefully normal the loop by lowering the duct.
• Tighten the coupler
• Continue the same for other modem section.
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PRECAUTIONSPRECAUTIONS
• Provisioning for extra cable length for bends and shrinkage of duct during drum planning.
• Care to be taken while lowering the duct at the end of blowing operation.
• Personnel must be beware of high operating air pressures
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Factors Influencing
Blowable length•Inside diameter of the duct
•Outside Diameter of the cable
•Weight of the cable
•Number of slopes
•cable stiffness
•Straightness of the route
•Ambient temperature
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BSNL Blowing ChamberChambers are placed at a distance of one KM
Size of the blowing chamber is 3M X 1MX 1.5M(LXWXD )
These are temporary chambers and refilled after accomplishing blowing operation
Average blowable length is 700M to 2000M depending upon the factors
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Submarine Cable LayingSubmarine Cable Laying
Cable Laying
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BSNL Submarine Cable Submarine Cable RepairingRepairing
Cable Repairing
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THANK YOU
