Page 81 - DLIS408_INFORMATION_TECHNOLOGY-APPLICATIONSL SCIENCES

Information Technology and Application

Notes Figure 6.7: A bundle of fiber optic cables (End view)

Jacket
Cladding
Core
Sheath

Fiber Optic Cables
Transmission of Data through Fiber Optic Cables. Twisted-pair and coaxial cables contain copper
conductors and hence data is transmitted through them in the form of electrical signals (streams of
electrons). However, through fiber optical cables, data is transmitted in the form of photons by
following procedure:
(i) Digital electronic pulses at one end of the cable are translated into light pulses either by a
laser or a light-emitting diode.
(ii) The light pulses travel along the core of the fiber and are kept there by the cladding which
reflect the light back to the core.
(iii) When light pulses are reached at the other end of cable, a photo detector transforms the
light pulses back into electrical pulses.

Advantages of Fiber Optical Cables
Fiber optic cables offer the following advantages over both Twisted-pair and Coaxial cables:
A signal sent through fiber optic cable can travel to longer distances (about 30 km) without
amplification. The coaxial cable, on the other hand, needs repeaters to amplify signals after
every 1 Km and so.
Fiber optic cables are free from interference by electromagnetic fields. Thus they provide
better quality transmissions than both Twisted-pair and Coaxial cables.
Fiber optic cables provide very high hand width (upto 1000 billion bps).
Fibers do not leak light and are difficult to tap. Hence, they provide excellent security to
data against potential wire tappers.

Disadvantages of Fiber Optic Cables

Fiber optic cables also have some disadvantages, which are discussed below:
Fiber optic cables are more expensive to install than copper wire cables.
They are difficult to maintain as they are mechanically weaker.
It is difficult to make joints in fiber optic cable as joining requires special connector units.
Uses of Fiber Optic Cables. Fiber optic cables are now being used in telephone networks by
replacing coaxial cables in the major lines. As fiber optic cables provide high quality transmissions
at very high hand width, they are being used for broadband services like thousands of television
stations, videoconferencing and on-demand video.

6.6 Wireless Communication

Data can be transmitted between commuters and other electronic devices as electromagnetic
signals through the air or empty space. Such transmission using electromagnetic signals such as
radio waves microwaves or infrared waves is called Wireless communication. Various types of
waves in an electromagnetic spectrum operate at different frequencies of transmission as shown in
figure 6.8.

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