Page 162 - Physics 10_Float

INFORMATION TECHNOLOGY

of glass fibres with thickness of a human hair. For your information
Light that enters the core at one end of the optical fibre goes Microwave, digital and optical
fibre technologies are
straight and hits the inner wall (the cladding) of fibre optics. If
combined to give us today's
the angle of incidence with cladding is less than the critical telecommunication systems.
angle, some of the light will escape the fibre optics and is lost Microwaves travel in straight
(Fig. 17.9). However, if the angle of incidence is greater than lines through the space and
the critical angle, light is totally reflected into the fibre optics. give a very strong signal. We
can connect to the other side
Then the totally reflected beam of light travels in a straight
of the world in milliseconds.
line until it hits the inner wall again, and so on. The advantage Communication satellites
of optical fibre is that it can be used for sending very high data including INTELSAT and
rates over long distances. This feature of fibre optics SATCOM are geostationary
distinguishes it from wires. When electrical signals are satellites that stay over the
same position above the Earth
transmitted through wires, the signal lost increases with surface and receive and
increasing data rate. This decreases the range of the signal. transmit digital signals across
Lost Lost the world.

Cladding Do you know?
Reflected

Axis

Core
Critical Normal
Angle
Cell phone transmissions are
Fig. 17.9: Light entering a glass rod at greater than the made with microwaves.
critical angle is trapped inside the glass
Each optical fibre in a multi-mode cable is about 10 times
Transmission
thicker than fibre optics used in a single-mode cable. This of digital voice
means light beams can travel through the core by following data by
fibre optics
different paths, hence the name multiple-mode. Multi-mode Glass Fibre
cables can send information only over relatively short
distances and are used to link computer networks together. Input Output

Most of the data transmitted
COMPUTER across the Internet is also
Computer (Fig. 17.10) is an electronic computing machine carried by light. A network of
used for adding, subtracting or multiplying. Computers work fibre optic cables across the
through an interaction of hardware and software. Hardware country carrying data from one
computer to another.

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