LISTS OF FIGURES
Figure 1: Coaxial cable 6
Figure 2: Fiber optic 7
Figure 3 : Basic structure of an optical fiber 9
Figure 4 : Principle of optical transmission 10
Figure 5 :Total internal reflection 11
Figure 6 : Emission block of fiber optical signal and laser
diodes as the source 13
Figure 7 : Block scheme of fiber optic receiver 14
Figure 8 : Single mode fiber optic 16
Figure 9 : Multimode step index fiber optic 16
Figure 10: Acceptance cone and acceptance angle in an optic fiber
17
Figure 11: Multimode graded index fiber optic 17
Figure 12 : Fiber optic multiplexing (WDM Point to Point). 19
Figure 13 : Basic Optical System 22
Figure 14 : General structure of a PON 23
Figure 15 : Downstream Traffic Flow in an Ethernet PON 25
Figure 16 : Upstream Traffic Flow in an Ethernet PON 26
Figure 17 : Active optical network 28
Figure 18 : Absorption loss 30
Figure 19 : Rayleigh Scatter loss, 31
Figure 20 : Bending loss 31
Figure 21 : Uplink bandwidth connectivity assigned to NUR 35
Figure 22 : Downlink bandwidth connectivity assigned to NUR 35
Figure 23 : The traffic internet link 36
LIST OF SYMBOLS
A/N: Analogue to Digital AON:
Active Optical Network
BPON: Broadband Passive Optical Network
CATV: Cable Television DMUX:
Demultiplexing DWDM: Dense Wavelength Division Multiplexing
EMI: Electromagnetic Interference
EPON: Ethernet Passive Optical Network
FTTB: Fiber To The Building
FTTC: Fiber To The Cabinet GPON :Gigabyte
Passive Optical Network
GPS :Global Positioning System
HDTV: High Definition Television
ICT: Information and Communication Technology
ISP: Internet Service Provider
LASER : Light Amplification by Stimulated
Emission Radiation LED: Light Emitting Diode
MTN: Mobile Telephone Network
MUX: Multiplexing
NA: Numerical Aperture
NT: Network Terminal
NUR: National University of Rwanda
OA: Optical Amplifier
ODN: Optical Distribution Network
OLT: Optical Line Terminal
ONT: Optical Network Terminal
ONU: Optical Network Unit
PON: Passive Optical Network
RCV: Receiver
RDB: Rwanda Development Board
SONET: Synchronous Optical Networking
STC: Standard Telephone and Cable
STP: Shield Twisted Pair
TDMA: Time Division Multiple Access
TRM: Transmitter
TV: Television
UTP: Unshielded Twisted Pair
VLAN: Virtual Local Access Network VSAT: Very
Small Aperture Terminal WDM: Wave Division Multiplexing
CHAPTER ONE: GENERAL INTRODUCTION
1.1 BACKGROUND
An optical fiber is a flexible and transparent fiber made of
very pure glass (silica) not much bigger than a human hair that acts as a
waveguide or light pipe to transmit light between the two ends of the fiber.
Fiber optics though used extensively in the modern world is a
fairly simple and old technology, of guiding light by refraction this principle
makes fiber optics possible.
The laser was introduced as an efficient source of light and
the concept was to show that masers could be made to operate in optical and
infrared regions. Basically, light is reflected back and forth in an energized
medium to generate amplified light as opposed to excited molecules of gas
amplified to generate radio waves as is the case with the maser. Laser stands
for light amplification by stimulated emission of radiation.
When the light passes from air into water, the refracted ray
is bent towards the perpendicular, When the ray passes from water to air it is
bent from the perpendicular if the angle which the ray in water encloses with
the perpendicular to the surface be greater than 48 degrees, the ray will not
quit the water at all, it will be totally reflected at the surface, The angle
which marks the limit where total reflection begins is called the limiting
angle of the medium, For water this angle is 48°27', Unpigmented human
hairs have also been shown to act as an optical fiber.
Modern optical fibers, where the glass fiber is coated with a
transparent cladding to offer a more suitable refractive index appeared later
in the decade Development then focused on fiber bundles for image
transmission.[1]
In the late 19th and early 20th centuries, light was guided
through bent glass rods to illuminate body cavities also the Photophone was
invented for transmission of voice signals over an optical beam.
The British company Standard Telephones and Cables (STC) was
the first to promote the idea that the attenuation in optical fibers could be
reduced below 20 decibels per kilometer (dB/km), making fibers a practical
communication medium, he proposed that the attenuation in fibers
available at the time was caused by impurities that could be
removed, rather than by fundamental physical effects such as scattering, he
correctly and systematically theorized the light-loss properties for optical
fiber, and pointed out the right material to use for such fibers, silica glass
with high purity, attenuation in modern optical cables is far less than in
electrical copper cables, leading to long-haul fiber connections with repeater
distances of 70-150 kilometers.[2]
Today , Fiber optic systems have many attractive features that
are superior to electrical systems, These include improved system performance,
immunity to electrical noise, signal security, and improved safety and
electrical isolation that why we encourage each Telecommunications services
provider of network in Rwanda to implement fiber optics in their services for
better communication.
In Rwanda we have five available fiber optics network such as:
RDB Fiber ,MTN Fiber ,TIGO fiber, EWSA Fiber and Rwandatel fiber.
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