Transcript what are optical fibers

Optical Fiber
& OF Cables
THE PRESENTATION
What this presentation is about?
This presentation is about giving a broad idea about the
concepts of Optical Fiber and OF Cables, (OPGW, Lashed
cables, ADSS, Under Ground & Duct Cables ) without
going into the deep technicalities. So that as and when
OF is being discussed the person who has attended this
presentation is able to understand and follow the
discussion.
Brief Flow of the Presentation.
1. What are Optical Fibers?
2. Advantages / Disadvantages of OF….
3. Various Types of OF Cables. Their
Construction , Specifications etc…
4. Some Test Equipments & Instruments
used in OF Communications.
WHAT ARE OPTICAL FIBERS ?
Optical Fibers are thins long (km) strands of ultra pure glass
(silica) or plastic that can to transmit light from one end to
another without much attenuation or loss.
The glass used to make Optical Fibers is so pure that if the
Pacific Ocean was filled with this glass then we would be
able to see the ocean bottom form the surface….!!!!
This is to be believed as repeater distances on long haul
routes for optical fibers vary from 50 to 150 km.
Q.) And how deep is the Pacifica ocean?
Ans) At the deepest point called the Marina Trench, The
pacific ocean is all of just 13km deep…..!!!!!
Working of Optical fibers?
The light source (LAZER) at
the transmitting (Tx) end is
modulated by the electrical
signal and this modulated
light energy is fed into the
Optical Fiber.
At the receiving end (Rx)
this light energy is made
incident on photo-sensors
which convert this light
signal back to electrical
signal.
ADVANTAGES OF OPTICAL FIBERS
1.
VERY HIGH INFORMATION CARRING CAPACITY.
2.
LESS ATTENUATION (order of 0.2 db/km)
3.
SMALL IN DIAMETER AND SIZE & LIGHT WEIGHT
4.
LOW COST AS COMPARED TO COPPER (as glass
is made from sand..the raw material used to make
OF is free….)
5.
GREATER SAFETY AND IMMUNE TO EMI & RFI,
MOISTURE & COROSSION
6.
FLEXIBLE AND EASY TO INSTALL IN TIGHT
CONDUICTS
7.
ZERO RESALE VALUE (so theft is less)
8.
IS DILECTRIC IN NATURE SO CAN BE LAID IN
ELECTICALLY SENSITIVE SURROUNDINGS
9.
DIFFICULT TO TAP FIBERS, SO SECURE
10. NO CROSS TALK AND DISTURBANCES
DISADVANTAGES OF OPTICAL FIBERS…
1. The terminating equipment is still costly as compared to copper
equipment.
2. Of is delicate so has to be handled carefully.
3. Last mile is still not totally fiberised due to costly subscriber premises
equipment.
4. Communication is not totally in optical domain, so repeated electric –
optical – electrical conversion is needed.
5. Optical amplifiers, splitters, MUX-DEMUX are still in development stages.
6. Tapping is not possible. Specialized equipment is needed to tap a fiber.
7. Optical fiber splicing is a specialized technique and needs expertly
trained manpower.
8. The splicing and testing equipments are very expensive as compared to
copper equipments.
Composition of optical fibre





Silica based glass or plastic filaments are spun
and packed into bundles of several hundreds or
thousands. Bundles may be put together as rods
or ribbons and sheets.
These bundles are flexible and can be twisted
and contorted to conduct light and images around
corners
The thin glass center of the fibre where the light
travels is called the “core”.
The outer optical material surrounding the core
that reflects the light back into the core is called
the “cladding”.
In order to protect the optical surface from
moisture and damage, it is coated with a layer of
buffer coating.
Cross section of a bundle
Figure 7.14 Fiber construction
7.9
Operation of the fibre optic system

Light is ejected into the glass core
at the correct angle and
transmitted; it will reflect back
repeatedly with internal
reflections, even when the rod is
curved. Light cannot escape from
a fibre optics cable. A bundle of
rods of fibres is capable of taking
an image projected at one end of
the bundle and reproducing it at
the other end.
Reflected path of light in the glass rod
Two main types of cables
Step Index Fibre

This cable has a specific index of refraction for
the core and the cladding. It causes deformations
due to the various paths lengths of the light
ray. This is called modal distortion. It is the
cheapest type of cabling. Within the cladding and
the core, the refractive index is constant.
Graded Index Fibre

In graded index fibre, rays of light follow
sinusoidal paths. Although the paths are different
lengths, they all reach the end of the fibre at the
same time. Multimode dispersion is eliminated
and pulse spreading is reduced. Graded Index
fibre can hold the same amount of energy as
multimode fibre. The disadvantage is that this
takes place at only one wavelength.
APPLICATIONS OF OPTICAL FIBERS…
1. LONG DISTANCE COMMUNICATION BACKBONES
2. INTER-EXCHANGE JUNCTIONS
3. VIDEO TRANSMISSION
4. BROADBAND SERVICES
5. COMPUTER DATA COMMUNICATION (LAN, WAN etc..)
6. HIGHT EMI AREAS
7. MILITARY APPLICATION
8. NON-COMMUNICATION APPLICATIONS (sensors etc…)
COMPARISION WITH OTHER MEDIA /
TECHNOLOGIES
VARIOUS TYPES OF OPTICAL FIBER CABLES
1. OPGW Cable
2. ADSS type OF Cable
3. Self-Support AERIAL figure 8 type OF Cable
4. LASHED type OF Cable
5. UNDERGROUND / BURRIED type OF Cables
6. DUCT Type OF Cable
Thank You
Submitted forwww.mycollegebag.in