9.Optical Fiber Cables

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Optical Fiber Cables


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Introduction Fiber optic cable is available in many physical

variations.

Regardless of the final outer constructionhowever, all fiber optic cable contains one ormore optical fibers.

These fibers are protected by an internalconstruction that is unique to fiber optic cable.

The two most common protection schemes inuse today are to enclose the tiny fiber in a loosefitting tube or to coat the fiber with a tightfitting buffer coating.


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Fiber Optic Cable Buffering Generally strength member will be present at

the center of the cable which absorbs stressduring the installation.

In some cases aramid yarn is used to handleexternal tension

Some times there

cannot bestrengthmembers and thecable rely onouter structure to

handle stress.


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Fiber Optic Color Codes


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Loose Buffered cable


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Loose Tube cable Cable containing loose buffer-tube fiber is

generally very tolerant of axial forces of the

type encountered when pulling throughconduits or where constant mechanical stress ispresent such as cables employed for aerial use.

Since the fiber is not under any significant

strain, loose buffer-tube cables exhibit lowoptical attenuation losses.

The cable core, typically uses aramid yarn, asthe primary tensile strength member.


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Loose Tube cable


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Loose Tube cable


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Armored Loose Tube cable

Single Jacket Armoredcable

Dual Jacket Armoredcable

Armored Single TubeCable
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Loose Tube cable The loose tube design provides stable

and highly reliable transmission

parameters for a variety of applications. The design also permits significant

improvements in the density of fiberscontained in a given cable diameter

while allowing flexibility to suit manysystem designs.

These cables are suitable foroutdoor,aerial, and direct buried installationsetc.,


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Features Different fiber types available within a

cable (hybrid construction). Lowest losses at long distances, for use

in outdoor, aerial, and direct buriedapplications.

Wide range of fiber counts (up to 216). Available with single mode and

multimode fiber types. All dielectric or steel central member.


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Features Loose Tube Cable is also available with

armored construction for added

protection. Loose tube cables have lower signal

attenuation due to micro bending.

They provide excellent isolation fromexternal forces.

Under continuous mechanical stress,loose buffer cable exhibit better

transmission characteristics.


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Tight-buffered cable

In the tight buffer construction, a thickcoating of a plastic-type material is applied

directly to the outside of the fiber itself. This results in a smaller overall diameter of

the entire cable and one that is moreresistant to crushing or overall impact-type

forces. Because the fiber is not free to "float"

however, tensile strength is not as great.


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Tight buffer cable is normally lighter in weightand more flexible than loose-tube cable and is

usually employed for less severe applicationssuch as within a building or to interconnectindividual pieces of equipment.


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As can be seen from the diagram, in all cases thefiber/buffer tube is first enclosed in a layer ofsynthetic yarn such as Kevlar for strength.

Tight buffertube cablesare more

suitable forindoorapplications.


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Fiber Optic Cable

An outer jacket of PVC (Polyvinyl chloride) orsimilar material is then extruded over everythingto protect the inside of the cable from the rigors of

the operating environment. In multi-fiber cables, an additional strengthmember is also often added.

While most fiber optic cables aremanufactured of totally non-conductive

materials, there are some cable thatemploy steel tape-wound outer jackets forrodent resistance (direct burial types) ormetallic strength members such as steelwire for aerial (telephone pole) use.
http://www.go4fiber.com/image/category/3/121/290/GYTA33-2w.jpghttp://www.go4fiber.com/image/category/3/121/290/GYTA33-2w.jpg


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Cable Types

Distribution Cable

It is a compact

building cable,packages individual900m bufferedfiber reducing size

and cost whencompared tobreakout cable.


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Cables Types

Indoor/Outdoor TightBuffer:

These cables areflexible, easy to handleand simple to install.

Since they do not usegel, the connectors canbe terminated directlyonto the fiber without

difficult


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Cables Types

Indoor/Outdoor Breakout Cable: Indoor/outdoor rated breakout style cables are easy

to install and simple to terminate. Breakout cables are designed

with alldielectric construction to

insure EMI immunity

Aerial Cable/Self-Supporting:

Aerial cable provides ease of

installation and reduces time

and cost.


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Cables Types

Distributed and Breakout cables areconsidered as two types oftight buffer

cables.

Distribution cables feature a large number offibers in a compact cable and mainly used in

vertical cable runs with in buildings. Distribution cables are lighter than loose

tube cables, provides more flexibility but lessisolation from outside stress.


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Cables Types

Because of its

sensitivity fromexternal forces, itsuffers fromattenuation due to

micro bending thanother cables.


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Cables Types

Breakout cable containtight buffered fibers

individually enforcedwith aramid yarn.

They are the largest andheaviest of fiber cables

and are mainly used forhorizontal runs and alsofor cross connects.


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Cables Types

The term breakout means at any location along thecable one could breakout several fibers and route otherfibers to elsewhere.

These cables aremainly used forLAN, videosystems, industrialcontrol processetc.,


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Cables Types

Hybrid Cable:

Cables that contain both optical fibers and twistedpairs (copper coax) are known as hybrid cables.

Hybrid cables areused in fiber tohome applications,LAN and televisionsystems also.


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Cables Types

One type of Tightbuffered cable that is

finding its use in officesis under carpet styleand by using this thereis no need to cut fiber

in to walls. This kind of cables is

convenient forconnectivity to

desktops.


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Cables Types ABF

ABF (Air Blown Fiber)

ABF is a tight cable

with no of smalldiameter tubes whichare initially installed.

At junction boxes smallpush to fit connectorsconnect tubes togetherto complete fiber route.


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Cables Types

ABF (Air Blown Fiber)

High pressure air is

then used to blow fiberon it through thetubes.

Installation is quickand efficient and also itis easy to makechanges in the

network.


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Cables Types

Armored Cable: Armored cable can be used for rodent

protection in direct burial if required. This cable is non-gel filled and can also be used

in aerial applications. The armor can be removed leaving the inner

cable suitable for any indoor/outdoor use


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Fiber Types

The International Telecommunication Union(ITU-T), which is a global standardizationbody for telecommunication systems and

vendors, has standardized various fibertypes.

These include

the 50/125-m graded index fiber (G.651), Non-dispersion-shifted fiber (G.652), dispersion-shifted fiber (G.653), 1550-nm loss-minimized fiber (G.654), and

NZDSF (G.655).


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Fiber Types

the 50/125-m graded index fiber(G.651)

MMF, gradded index, 1300/850 nm, 0.8dbloss

Non-dispersion-shifted fiber (G.652)

SMF, dispersion-shifted fiber (G.653),

1550-nm loss-minimized fiber (G.654),and NZDSF (G.655).


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Fiber Types

The outer jacket used for cable must bechosen carefully with respect to the

application. Cables that are used for outdoor Ariel

applications are exposed to elements andmust be able to with stand heat, cold,

moisture, pollution, fungus attacks, ultraviolet rays.

Polyethylene is a thermo plastic with goodchemical and moisture resistant and is used

in Ariel and direct burial applications.


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Fiber Types

Polyurethane, Poly Vinyl Chloride, Teflon etc.,are other types of materials which can be usedas fiber outer jackets.

There are number of fiber cables designed touse for specific cables. For example in Arielapplications, fiber cables are used on high

voltage poles or towers. Metallic components with in a cable accumulate

dangerous electric charges due to inductionproviding a safety hazard to service personnel.


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Fiber Types

In addition, metallic components couldattract lightning strikes which could

damage the cable. All Dielectric Self Supporting Cable (ADSS)

finds extensive use on high voltagetransmission towers.

It is made up of purely dielectric materialswith increased strength members to allowcables to cross long spans.


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Fiber Types

ADSS will handle thethermal changes with

out excessive expansionand contraction.

For Ariel applications,

where proximity to highvoltage is not a problemthere are specificcables.


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Fiber Types

Here a cable is shownwhich is bonded to a

metal messenger along itsentire length.

This kind of cables does

not handle thermalexpansion well because ofdifferent coefficients ofexpansion of glass and

metal component.


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Many organizations require specialcable designs to meet their uniquerequirements.

One type of special cable is Opticalpower ground wire (OPGW).

This type of cable is used in top ofhigh voltage towers to channellightning away from phase conductors.

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9.Optical Fiber Cables

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