|
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.
 |
|
|
|
|
Operation of fibre optic system |
|
In a
fibre optic system, there are a
few major components to perform
the task of communication.
The Input Modulator is needed;
this modulates the incoming signal
with a light beam.
A light emitting device is used;
it can be either a light emitting
diode (LED) or a semiconductor
laser diode.
A fibre optic cable is used as a
transportation medium.
A fibre optic system converts an
electrical signal to an infrared
light signal, and then transmits
the signal onto an optical fibre.
An Output Modulator is used to
separate the signal from the light
beam.
Special connectors must be used to
couple the light from the source
to the fibre and from the fibre to
the detector.
|
|
|
|
Transmision Loss |
The
transmission loss or attenuation of an
optical fibre is perhaps the most
important characteristic of the fibre;
this determines if a system is
practical. It controls (1) spacing
between repeaters and (2) the type of
optical transmitter and receiver to be
used.
As light waves travel down an optical
fibre, they lose part of their energy
because of various imperfections in the
fibre. These losses are measured in
decibels per kilometers (dB/km).
 |
|
|
