FO Cables,Splicing

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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

Duct Cable Loose Tube Cable Uni-tube Cable

Peripheral Strength member

Direct Buried Cable Loose Tube Cable Uni-tube Cable

Peripheral Strength member

Fiber with mechanical strength member

Steel used as a strength member

Aramid yarn as a strength member

Aerial Cable(ADSS) Loose Tube Cable

All Dielectric self supporting cable(ADSS)

Aerial Cable(OPGW)

Aerial Cable(GWWOP)

Premise Cable

Fibre Optic Cables

Design , Performance

Characteristics,

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

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.

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.

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

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.

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

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

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.

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.

1 Fibre Buffering

Tight & semi tight Buffering Loose Tube Buffering

Plastic Buffer

Radial Freedom of movement

Buffer Tube

Fill Gel

Loose Buffering

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)

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 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

Peripheral strength member

Aramid

Glass Flex

Other Synthetic fibres

Filling compound

Thixotrophic Gel

Hot melt Gel

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

Central Tube cable

Sheath

Flex Rein.

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.

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

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.

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

Stranded loose Tube cable

Cable Unloaded Cable Elongated Cable Contracted

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

Impact Test

Cable ClampCable Clamp

O.F. Cable

Weight

Impact Test

Cable Clamp Cable Clamp

O.F. Cable

Free fall

Crush Test

Cable ClampCable Clamp

O.F. Cable

Dead Weight

Twist Test

Cable Twisting Mechanism

Fixed Cable Clamp

O.F. Cable

Flexibility Test

O.F. Cable15 D Mandrel

Bend Test

Moving Pulley

O.F. Cable

Weight

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

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

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

FO Cables,Splicing

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