Download ppt

Mahmoud Al-Saba – 223132
Majed Al-Bishi – 216423
1
History of Fiber Optic Technology
 People have used light to transmit info. for hundreds of years
 The invention of the laser prompted researchers to study the potential
of fiber optics
 send a much larger amount of data than telephone
 first experiment
 letting the laser beam transmit freely in air
& through different types of waveguides
 very large losses in the optical fibers prevented coaxial cables from
being replaced
 Decrease in the amount of light reaching the end of the fiber
Cont: History of Fiber Optic
Technology





Early fibers had losses around 1,000 dB/km
In 1969, several scientists concluded that impurities in the fiber material
caused the signal loss
 Researchers believed it was possible to reduce the losses
By removing the impurities
researchersobserve the improvement
In 1970,(corning glass works)* made a multimode fiber with losses under 20
dB/km.
in 1972, the company made a high silica-core multimode optical fiber
with 4dB/km.
Nowadays, multimode fibers can have losses as low as 0.5 dB/km at
wavelengths around 1300 nm
*company
Introduction
 Optical fiber has a number of advantages over the copper wire
 since it is made glass or plastic
 light has a much higher frequency than any radio signal
 we can generate, fiber has a wider bandwidth
To carry more information at one time
Transmitters
 transmitters  include an LED(Light-emitting diodes) or laser diode
 LED produce incoherent light
 have relatively large emitting areas and as a result are not as
good light source

 they are widely used for short distances because they are
much more economical

Cont: Transmitters
 Laser diode  produce coherent light
 used for applications that require the transmission of signals
over long distances
 Important performance specifications
 data rate
 transmitter rise time
 wavelength
 spectral width
 maximum optical output power
Receivers
 Receivers are instruments that convert light into
electrical signals.
 component of an optical receiver is a photo detector
that converts light into electricity
 use three types of photodiodes
 positive-negative (PN) junctions
 positive-intrinsic-negative (PIN) photodiodes
 avalanche photodiodes (APD)
Optical Fiber
 Fiber is the medium to guide the light form the
transmitter to the receiver.
 There are two types:
 Multimode Fiber
 Single-Mode Fiber
Multimode Fiber
 In multimode fibers more than one light transmitted
at a time.
 Fiber diameter ranges from 50-to-100 micron.
9
Multimode Fiber
 Multimode Fiber is divided into two types:
 Multimode Step-index Fiber
 Multimode Graded-index Fiber
Multimode Step-index Fiber
 Lights are sent at angles lower than the critical angle
or straight
 Any light angle exceed the critical angle will cause it to
penetrate through cladding.
 Obviously light with lower angle will reach the end
faster than others.
Multimode Step-index Fiber
 The difference in signals receiving time result in
unstable wave light at the receiver.
 To avoid this problem there should be spacing
between the light pulses  but this will limit the
bandwidth.
 Used for very short distance
Multimode Graded-index Fiber
 In this mode reduce the problem with Multimode
Step-Index.
 All the beams reaching the receiver almost at the same
time.
 This can be done by slowing down the ones with
shorter distance.
 This is done in fiber implementation by increasing its
refractive index at the center and gradually decreases
it toward the edges
Single-Mode Fiber
 Only one light is transmitted in the fiber.
 Diameter ranges from 8.3 to 10 microns.
 It has Higher transmission rate.
 it can be used for longer distance.
Fiber Cables
 Advantages of Cabling fiber:
 Ease of Handling
 Protection
 Crush Resistance
 Degradation
 Types of Fiber Cables:
 Loose Tube Cable
 Tightly Buffered Cable
 Ribbon Cables
Wave Division Multiplexing
(WDM)
 it is a way to send multiple optical signals from
deferent source at the same time on one optical fiber.
 Used with single mode fiber
 How it works:
 At the sender the data stream from each Source is
assigned an optical wavelength.
 The multiplexer modulates each data stream from each
Source.
 The resulted optical signal generated for each source
data stream is placed on its assigned wavelength.
Wave Division Multiplexing
(WDM)
 The resulted signals are simultaneously sent through
the fiber.
 At the receiver the signal is separated into the original
signals according to their different wavelengths by
using prisms.
 These signals are further demodulated.
 Then, The resulting separated data streams are
provided to the respective Users.
Some Application
 Long telecommunication systems on land and at sea




to carry many simultaneous telephone calls (or other
signals) over long distances.
Links among computers and high resolution videoterminals.
Local area Networks operating at high speeds.
Connections between the telephone N/W and
antennas for mobile telephone service.
Interoffice trunks that carry many telephone
conversations simultaneously between local and
regional switching facilities.
Thank you
Any Question please
19