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Communication System
Multiplexer Multiplexer
Copper Cable
Communication System Using O.F. Cable
Multiplexer Multiplexer
O.F. Cable
OLTE OLTE
Benefit of optical fibre Cable
Light in Weight
Small Diameter,Excellent Transmission Characteristics
The Enormous Information Capacity
No interference
Long repeater distance
CladdingCore
Principle Operation
All the fibres consists of substructures includes
CORE :which carries most of the light , surrounded by CLADDING: which bends the light and confined in it in to the core
Fiber Cable Structure
Coated Fibers
TYPE OF FIBRES
SINGLE MODE MULTI MODE
Types of cables
Based on installation methods Cable can be Classified as:
Duct Cable
Direct Buried Cable
Aerial Cable
Premise Cable
Type of Optical fibre cable
Duct Cable Loose Tube Cable Uni tube Cable
Type of Optical fibre cable
Duct Cable Loose Tube Cable Uni-tube Cable
v
Peripheral Strength member
Type of Optical fibre cable
Direct Buried Cable Loose Tube Cable Uni-tube Cable
v
Peripheral Strength member
Fiber with mechanical strength member
Steel used as a strength member
Aramid yarn as a strength member
Type of Optical fibre cable
Aerial Cable(ADSS) Loose Tube Cable
All Dielectric self supporting cable(ADSS)
Type of Optical fibre cable
Aerial Cable(OPGW)
Type of Optical fibre cable
Aerial Cable(GWWOP)
Type of Optical fibre cable
Premise Cable
Fibre Optic Cables
Design , Performance
Characteristics,
and
Field Experience
Fibre Optic Cables
Cable Design Considerations
1 Cable can be handled in a straight forward practical manner as of most other communication cables ( e.g Duct cable)
2 The requires mechanical , Optical and environment characteristics for specific use and applications( e. g. Aerial cable )
3 They can be spliced and or connectorised in the field or application with minimum difficulty and time ( e.g. premise cable)
Fibre Optic Cables
Fibre Stresses
1 Tensile Stress
2 Bending Stress
3 Torsional stress
Fibre Stress
Main factors that drive Strength and Protection Main factors that drive Strength and Protection decisions worldwidedecisions worldwide
Minimise Fiber elongation
Eliminate water ingress
Ensure personnel electrical safety
Protect from lightning strike
Minimise cable weight
Protect from rodents/ externals
Minimise hydrogen out gassing
Functional integration
Main factors that drive Strength and Protection Main factors that drive Strength and Protection decisions worldwidedecisions worldwide
Minimise fiber elongation and bending losses
• Cable design and strength members contribute to limit fiber elongation, micro bending and macro bending
• Materials used for strength members should exhibit low thermal expansion and contraction properties
• Metal strength members do not perform well at low temperatures due to larger CTE.
Main factors that drive Strength and Protection Main factors that drive Strength and Protection decisions worldwidedecisions worldwide
Eliminate water ingress
• Specifications and applications moving towards dry cable designs due to
- Ease of manufacture and installation - Flame retardant properties
• However new water blocking materials should ensure - Rapid swelling. Speed of swelling is as important as volume. - Regeneration and long cycle life. - Performance in all types of water environments. - Ease of manufacture. No powdering or flaking.
Main factors that drive Strength and Protection Main factors that drive Strength and Protection decisions worldwidedecisions worldwide
Personnel safety
• Metallic components in cables will require grounding at periodic intervals.
• Insufficient care in grounding has been cause for many equipment failures as well as personnel injuries
• ITU recommendations K and L stipulate various safeguards that need to be taken to ensure personnel safety when using cables with metallic components.
• Most developing countries prefer to minimize metallic components as the surest way of ensuring personnel safety
Main factors that drive Strength and Protection Main factors that drive Strength and Protection decisions worldwidedecisions worldwide
Protect from lightning strike
• Lightning strikes can damage not only aerial, but also underground cables.
• Moist soil, tree roots, minerals in soil etc. can all conduct lightning to u/g cables and cause large scale damage if the cables have metallic components, especially in the core.
• The Bell core study in 1986 and IWCS papers in 1985 and 1990 identified lightning strikes on underground cables as a potential cause of cable failure.
• Eliminating metallic components from the core of the cable has been proven to be the only reliable form of protection.
Main factors that drive Strength and Protection Main factors that drive Strength and Protection decisions worldwidedecisions worldwide
Minimize cable weight
• Cable weight in underground cables is being targeted in order to increase installation speeds and improve productivity.
• In many markets, cable weight has been reduced by substituting heavy components like metallic strength members by lighter elements.
• An actual case of improvement of installation speed due to reduction in cable weight
Main factors that drive Strength and Protection Main factors that drive Strength and Protection decisions worldwidedecisions worldwide
Protect from rodents and other externals
• Cable damage due to rodent or gunshot damage can be prevented in various ways.
• The focus is on devising suitable methods for rodent and ballistic protection that
- does not sacrifice dielectric property - does not increase weight considerably - does not reduce flexibility
Protection to be provided against rodents
Loose Buffered Cable
Main factors that drive Strength and Protection Main factors that drive Strength and Protection decisions worldwidedecisions worldwide
Prevent Hydrogen out gassing
• As hydrogen trapped in cable can corrode fibers, components used in cable must have low hydrogen release levels.
• An ITU study indicates the main hydrogen releasing component in a cable to be metallic strength members.
Main factors that drive Strength and Protection Main factors that drive Strength and Protection decisions worldwidedecisions worldwide
Functional Integration
• This involves combining more functions onto fewer cable components.
• This reduces number of components, cable size, and cost, while improving productivity of manufacturers.
• Many products and technologies are now available which contribute towards functional integration.
Cable Manufacturing Process
Fibre coloring Loose Tubing
Stranding Sheathing
Color Codes for fibers
Cable Manufacturing Process
Fibre coloring
Fibre coloring is required for identification of fibre
Ultra Voilet Coating
Thermal Coating
Cable Design Principles
Fibre Buffering
Loose tubes provides mechanical protection to Fibres
Secondly it generates excess length of fibre which is required to achieve desired cable tensile strength.
Cable Design Principles
1 Fibre Buffering
Tight & semi tight Buffering Loose Tube Buffering
Fibre
Plastic Buffer
Radial Freedom of movement
Buffer Tube
Fill Gel
Cable Design Principles
Loose Buffering
I
S
D
I
S
D2
1 + - 1
S 2S = Fibre Pitch
D = Helix Diameter
I = Fibre Length
= Strain Margin
Theoretically , the fibre in a tube with an inner diameter of 4 mm can achieve an extra length of max 1%( 50 mm fibre bending radius)
Cable Design Principles
Strength member
To serve as core foundation
To enhance the axial properties of cable ( and act as
Anti buckling element)
Protect the Fibre due to low temperature contraction
Required properties
Dielectric, High Modulus , Excellent Temperature stability, Light weight, Low elongation , Dimensional
stability, Hydrolytically stable and corrosion resistance
Cable Design Principles
Cable Core ( stranding)
• To decouple the fibre from the cable structure
• It generates constant Excess fibre length , in the tube
• To improve the bending performance of cable
Cable Design Principles
Peripheral strength member
Aramid
Glass Flex
Other Synthetic fibres
Cable Design Principles
Filling compound
Thixotrophic Gel
Hot melt Gel
Cable Design Principles
Cable sheath
To protect the cable from harmful environmental factors ( Humidity , temperature , chemicals, tensile loads,transversal loads etc)
Typical wall thickness of PE sheath ranges from 1.2 -2.2 mm
Cable Design Principles
Central Tube cable
Sheath
Flex Rein.
Tube
The Glass Flexible reinforcements do not only provide the required tensile performance but also a certain compression resistance.
Cable like this would be suitable for in-house and duct application provided the temperature range is limited
For out door application additional rigid strength member must be included in the sheath to reduce the low temperature induced contraction.
Cable Design Principles
Central Tube cable
1 No Intrinsic fibre excess length
2 Every elongation of the cable would automatically lead to elongation of the fibres
3 However to avoid this , the fibres have to be introduced into the loose tubes with a certain extra length
Cable Design Principles
Central Tube cable
4 The introduction of extra fibre length into a tube generates high tube dimension.(this could result into relatively large permissible minimum cable bending radii)
5 Moreover , the transversal stability of a central buffer tube is reduced with increase in tube diameter
6 Therefore , the central buffer tube constructions are predominantly implemented when fibre counts are low.
Cable Design Principles
Stranded loose Tube cable
1 Excellent Mechanical properties stemming from stranding, such as Flexibility and extra clearance for fibre necessary to protect them from external load
2 Several layers of tubes are possible to reach high fibre count
3 Stranding produces extra excess fibre length
Cable Design Principles
Stranded loose Tube cable
Cable Unloaded Cable Elongated Cable Contracted
Cable Design Principles
Slotted Core (Ribbon) cable
Better Low Temperature performance compared to loose tube cable
Poor tensile performance
Large cable diameter w.r.t Loose tube cable
Mechanical Testing of cable
Tensile Test
Impact Test
Crush Test
Twist Test
flexibility Test
Bend Test
Mechanical Testing of cable
Mechanical Testing of cable
Impact Test
Cable ClampCable Clamp
O.F. Cable
Weight
Mechanical Testing of cable
Impact Test
Cable Clamp Cable Clamp
O.F. Cable
Free fall
Mechanical Testing of cable
Crush Test
Cable ClampCable Clamp
O.F. Cable
Dead Weight
Mechanical Testing of cable
Twist Test
Cable Twisting Mechanism
Fixed Cable Clamp
O.F. Cable
~2 M
Mechanical Testing of cable
Flexibility Test
O.F. Cable15 D Mandrel
Mechanical Testing of cable
Mechanical Testing of cable
Bend Test
Moving Pulley
O.F. Cable
Weight
Mechanical Testing of cable
Bend Test
Moving Pulley
O.F. Cable
Weight
Armored cable
Double Armored Cable
Breakout Cable
Simplex Tight Buffered Cable
Duplex Tight Buffered cable
Cable used for under sea applications
Figure-8 Cable
Hybrid cable(Containing both copper and fiber)
Protection to be provided from fire and smoke
Various Materials Used for Jacket of the Fiber
Outer Jacket Materials used in Fiber manufacturing must chosen accurately depending upon the application
Some of the materials that are commonly used are:
Polyethylene Polyurethane Poly Vinyl Chloride(PVC) Teflon
Questions ?
Splicing Splicing
What is Splicing??
Splicing is a method of joining two properly aligned fibers so that the two fibers are held together and the transmission of light continues
DIFFERENT TECHNIQUES
FOR
JOINING OF FIBER
Splicing/Joining……………Splicing/Joining……………
Why Joining is necessary ?
Types of Joining
Pros and Cons
Why Splicing is necessary ?
Long cable runs
Crowded conduits
Fire-code restrictions
Building or Campus environments
Types of Joining
Temporary Joint
V-Groove Joining
Connectorization
Permanent Joint
Mechanical Splicing
Fusion Splicing
Trade-offs are increased signal loss
Large space requirements
Expensive – increase System cost
Pros and Cons of Splicing
Flexibility for future system reconfiguring
Easy in Testing
Types of Splicing
Mechanical Splicing
A mechanical splice is an optical junction of two or more optical fibers that are aligned and held in place by a self-contained assembly.
Mechanical Splicing can be done using……
A glass alignment tube
V-groove
Spring V-groove
Rotary Mechanical System
A Glass Alignment Tube
V-Groove
Spring V-Groove
Rotary Mechanical System
Index Match Fluid used for Mechanical Splicing
Types of Splicing
Fusion Splicing
A fusion splice is a junction of two (or more) optical fibers that have been melted together. This is accomplished with a machine that performs two basic functions: aligning the fibers and melting them together typically using an electric arc.
Pros and Cons of Fusion Splicing
Low Loss ( < 0.05 dB for SM fiber)
Very Fast & Fully Automated Process
Expensive
Less safer than Mechanical Splicing
Five Steps ahead for Fusion Splicing…………
Fiber End Preparation
Cleave the fiber
Alignment of two (or more) fibers
Fuse the fiber
Protect the fiber
Fiber End Preparation
It mainly concerns with removing bare fiber from OFC and cleaning the fiber.
Required accessories are………
Sheath cutter Jacket stripper Primary coat stripper Alcohol ( > 99 % pure) Lint - free tissue paper Cotton swab
Improper Fiber End Preparation
Cleave the fiber
Good cleaving is key for good splicing
Actually, cleaving is same as cutting a window pane to size, only on a much finer scale; the cleaver first nicks the fiber, and then pulls or flexes it to cause a clean break.
Alignment of two (or more) fibers
Manually
Automated - Micro Manipulators
Misalignment causes bad splicing
Fuse the
fiber
For better Fusion Splicing
set the……….
Current supply to electrodes
Splicing time
Observe & try to maintain……….
Weather Condition
Temperature & Humidity
Some Observations about Fusion Splicing
Protect the fiber
Protect the spliced fiber using protection sleeve
Summary