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OPTICAL FIBRE CABLEprepared by,
Hasmath Naseera.A
DEFINITION:
An optical fiber cable is a CABLE
containing one or more optical fibers that
are used to carry light.
It is made of glass or plastic and transmits
signals in the form of light.
CHARACTERISTICS
Light travels in a straight line as long
as it is moving through a single
uniform substance.
If a ray of light travelling through one
substance & suddenly enters another
substance, the ray changes direction.
REFRACTION:
If a ray of light travelling through one
substance suddenly enters
another(more or less dense)
substance, its speed changes
abruptly, causing the ray to change
direction.
This change is called Refraction
CRITICAL ANGLE:
A beam of light moving from a more
dense medium to less dense medium.
At some point, the change in the
incident angle results in a refracted
angle of 90 degrees. The incident
angle at this point is known as
CRITICAL ANGLE.
Representation:
REFLECTION:
When the angle of incidence becomes
greater than the critical angle a new
phenomenon occurs called
REFLECTION.
Light no longer passes into the less
dense medium at all.
Angle of incidence = Angle of
reflection
PROPAGATION MODES
MULTIMODE
Multimode is so named because
multiple beams from a light source
move through the core in different
paths.
The beams within the cable depends
on the structure of core.
MULTIMODE STEP INDEX
FIBER
In multimode step index fiber, the
density of the core remains constant
from the centre to the edges.
A beam of light moves through its
constant density in a straight line until
it reaches the interface of the core and
the cladding.
Multimode step index(coned)..
At the interface there is abrupt change
to a lower density that alters the angle
of the beam’s motion.
The term STEP-INDEX refers to
sudden change.
MULTIMODE GRADED-INDEX
FIBER The multimode graded index fiber,
decreases the distortion of signal
through the cable.
The word index refers to the index of
refraction.
DENSITY OF INDEX FIBER
Index of refraction refers to density. A
graded index fiber is one with varying
densities.
Density is highest at the centre of the
core and decreases gradually to its
lowest at the edge
SINGLE MODE:
It uses step index fiber and a highly
focused source of light that limits
beams to a small range of angles.
It is manufactured with with a much
smaller diameter than that of
multimode fibers,and with substantially
lower density(index of refraction).
FIBER SIZES
Optical fibres are defined by the ratio
of diameter of their core to the
diameter of their cladding, both
expressed in terms of micrometers.
TYPE:50/125
CORE:50.0um
CLADDING:125um
MODE:multimode,graded index
FIBER SIZES:
TYPE CORE(um) CLADDING(u
m)
MODE
50/125 50.0 125 Multimode,gr
aded index
62.5/125 62.5 125 Multimode,gr
aded index
100/125 100.0 125 Multimode,gr
aded index
7/125 7.0 125 Single mode
CABLE COMPOSITION
cladding
Core
Optical
fiber
Outer
jacket
CABLE COMPOSITION:
The outer jacket is made of either PVC or teflon.
Inside the jacket are Kevlar strands to strengthen the cable.
Kevlar is a strong material used in fabrication of bulletproof vests.
Below the kevlar is another plastic coating to cushion the fiber.
The fiber is at the centre of the cable, and it consists of cladding and core.
Cable composition:
Operation:
FIBER OPTIC
CONNECTORS
FIBRE OPTIC
CONNECTORS: The subscriber channel(SC) is used
for cable TV.It uses a push/pull locking
system.
The straight-tip (ST) connector is used
for connecting cable to networking
devices.
It uses a bayonet locking s/m and it is
more reliable than SC.
Eg:MT-RJ
Connector:
PERFORMANCE:
Attenuation is flatter than in case of
twisted- pair cable and co-axial cable.
The performance is such that we need
fewer repeaters while using fiber optic
cable.
Performance characteristics:
APPLICATIONS:
Fiber optic cable is backbone of
networks because of its wide
bandwidth and it is cost -
effective.eg:SONET network
Using Wavelength Division
Multiplexing (WDM),we can transfer
data at a rate of 1600Gbps.
Cable TV companies
LAN networks such as 100Base-FX
network &1000Base-X.
ADVANTAGES:
Higher Bandwidth
Less signal attenuation
Immunity to electromagnetic
interference
Resistance to corrosive materials
Light Weight
Greater immunity to tapping
DISADVANTAGES:
Cost
Installation/maintainance
Fragility
Unidirectional light propagation
THANK YOU…
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