Fiber Optic Cable Lecture

8/9/2019 Fiber Optic Cable Lecture

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)ince any light ray incident on the boundary above the critical angle will be reflected internally,

many different rays will be bouncing around at different angles. *ach ray is said to have a

different mode, so a fiber having this property is called a +!"+/* F"B*0 %++F&.

"f the fibers diameter is reduced to a few wavelengths of light, the fiber acts like a wave guide

and the light can only propagate in a straight line, without bouncing, yielding a )"23*

+/* F"B*0 %)+F&.

FIBER OPTIC CABLE

Fiber optic cables are similar to coa$, e$cept without the braid.

At the center is the glass core through which the light propagates. "n multimode fibers, the core

is typically 4 microns in diameter, about the thickness of a human hair. "n single-mode fibers,

the core is 5 to 1 microns.

!he core is surrounded by a glass cladding with a lower inde$ of refraction than the core, to

keep all the light in the core.

2e$t comes a thin plastic 6acket to protect the cladding. Fibers are typically grouped in bundles,

protected by an outer sheath.

!he light-guiding parts of an optical fiber are called the coreand the cladding. !he core is

usually very pure glass with a high inde$ of refraction. 7hen a cladding layer of glass or plastic

with a low inde$ of refraction surrounds the core glass, light can be trapped in the fiber core.

!his process is called total internal reflection

o !he following summari8es the features of fiber-optic cables:

9 Speed and throughput+ore than 1 3B;)

9 Average cost per node*$pensive

9 Media and connector sie)mall

9 Ma!i"u" cab#e #ength+ore than 1 km for single mode( up to < km for multimode


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T$pes o% %iber optic

"t is classified into two types depending on the way the light is transmitted:

multi-mode fiber %++F&

single-mode fiber %)+F&

M&LTI'MO(E FIBER

)ince any light ray incident on the boundary above the critical angle will be reflected

internally, many different rays will be bouncing around at different angles. *ach ray is

said to have a different mode, so a fiber having this property is called a +!"+/*

F"B*0 %++F&.

+ultimode fiber cable allows multiple modes of light to propagate through the fiber.

/iameter=s range is between 4 to 1 microns.

!he ma$imum cable length is < >m. ess e$pensive.

!here are two types of ++F are: Mu#ti"ode Step'Inde! Fiberand Mu#ti"ode

)raded'Inde! Fiber.

M&LTIMO(E STEP'I*(E+ FIBER

!he reflective walls of the fiber move the light pulses to the receiver

M&LTIMO(E )RA(E('I*(E+ FIBER

Acts to refract the light toward the center of the fiber by variations in the density


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SI*)LE'MO(E FIBER

"f the fibers diameter is reduced to a few wavelengths of light, the fiber acts like a wave

guide and the light can only propagate in a straight line, without bouncing, called a

)"23* +/* F"B*0 %)+F&.

)ingle-mode fiber cable allows only one mode of light.

/iameter=s range is between 5.? to 1 microns.

+a$imum cable length is more than 1 km

"t is capable of higher bandwidth and greater distances than multimode fiber.

+uch more e$pensivethen ++F.

)ince there is only one light the problem associated with the multimode fiber does not

e$ist and by this it can give a higher transmission rate and also it can be used for longerdistance.

&SE,

Because of greater bandwidth %


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2ot susceptible to electrical interference %lightning& or crosstalk.

3reater repeater distance than coa$.

(isadvantages,

/ifficult to terminate, reuires fiber hubs etc.

CO**ECTORS &SE( FOR FIBER OPTIC CABLES

!wo types of connectors are widely used for fiber communication are:

SC -Stic. n C#ic./

) type connectors feature a push-pull connects and disconnect method. !o make a

connection, the connector is simply pushed into the receptacle %device holding the light&.

!o disconnect, the connector is simply pulled out.


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SC

ST -Stic. n Turn/

)! fiber-optic connector is fully inserted into the receptacle and is then twisted in a

clockwise direction to lock it into place.

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Fiber Optic Cable Lecture