3.4 ACTIVE OPTICAL NETWORK
An active optical network (AON) is a system that uses
electrical powered switching equipment such as router and switch to manage
signal distribution and direct signals to specific customers.
At the termination point of the fiber at the NUR ICT CENTER
there is a semiconductor which converts optical signal into electrical signal
then a signal amplifier which increase the amplitude of the signal in order to
avoid signal attenuation that can cause the data to be loss hence comes switch
which divide the network into different parts depending on how they wants to
use it .
The most common type of active optical networks are called
active Ethernet this Active Ethernet uses optical Ethernet switches to
distribute the signal means that the internet network all over it is needed at
Ruhande.
This switch opens and closes in various ways to direct the
incoming and outgoing signals to the proper place in such a system a customer
may have a dedicated fiber running to his building.
Figure 17 : Active optical network
Active optical network is a fiber to the building, this is NUR
ICT CENTER as optical network termination where all fibers connections ends
from the operators offices OLT before being distributed to the users of the
internet connections. User can also download and upload depending on his
need.[17]
3.5 SONET TECHNOLOGY
When data is transmitted over a communications medium a number
of things must be provided on the link including framing of the data, error
checking and the ability to manage the link. for optical communications these
functions have been standardized by the ANSI T1X1.5 committee as Synchronous
Optical Networking (SONET)
The information is sent over an optical fiber by turning the
light off and on in the fiber suppose that the presence of light is indicated
by «1» while the absence of light is indicates by «0» we
can
send and receive bits across an optical link and extract the
information from those bits by using SONET .
SONET is defined as the low level framing , rules which
governs the optical links By framing this means a block of bits (or octets)
that have a structure and which utilizes some technique to allow us to find the
boundaries of that frame structure ,Same parts of the block may be devoted to
overhead the network in order to provide the use of network management and
another parts will be dedicated to carrying payload or information we want to
communicate. [18]
3.6 FIBER OPTIC LOSSES 3.6.1 TYPES OF LOSSES
The word loss means attenuation or loss of optical power in
fiber optic itself, losses is valuable in designing and choosing components in
a fiber optic communications system, losses are also important variables in the
network design phase. There are different reasons for light losses which may
occur during transmission of light signal inside the fiber or during the
interconnection process of two fibers. [19]
Losses are expressed in decibels per kilometer (dB/km), in terms
of particular length L of a fiber the loss is expressed as:
Po=Pin10-áL/10 (3.1)
Where Po: The Power at a distance L from the input.
Pin: The Amount of Power coupled in the
fiber.
á: The fiber attenuation expressed in dB/km. Hence
attenuation in the fiber is
á=10[log(Pout /Pin )] /L expressed in dB/km (3.2)
The loss may be arise from different sources same are fiber
intrinsic loss which means that they occur due to the nature of the core
material and others are attenuation losses which may be caused by different
reasons.
We can explain same of the losses in the following paragraphs
3.6.1.2 Absorption Loss
This is due to the impurity such as metal particles or
moisture in the fiber and it can block some of the light energy which caused
absorption loss. it absorbs light and dissipate it in the form of heat
energy
The solution to this problem is to use ultra pure glass and add
Impurity chemicals to minimize impurities manufacturing so that Light can
travels best in clear substance .
light transmitted
Cladding fiber core connection
Figure 18 . Absorption loss
Absorption loss are due to the absorption of energy by
impurity ions that forms the core and hydroxyl radicals present in the core in
addition this causes the loss of signal means information along the
transmission.[19]
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