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An see there is increase in clients day by

An optical network provides a typical
infrastructure over that a verity of services may be delivered. These networks
are also capable of delivering bandwidth in a versatile manner, supports
capability up gradation and transparency in information transmission. It
consists of optical supply (LED, LASER) as transmitter and optical fibre as
transmission medium with alternative connectors and photo detector, receiver
set. However owing to limitation of electronic processing speed, it’s impossible
to use all the BW of an optical fibre employing a single high capacity channel
or wavelength. The first drawback in a very WDM network design is to search out
the simplest attainable path between a source-destination node pair and assign
available wavelength to this path for data transmission. To see the simplest
path a series of measurements are performed which that are refereed as
performance matrices. From these performance matrices, the Quality of Service
parameters are determined.In this  digital  era  the  communication  demand
 has
 increased
 from
 previous
 eras  due
 to introduction of new communication  techniques. As we can see there is increase in clients day by
day, so we need huge bandwidth and high speed networks to deliver good quality of service to clients. Fiber optics communication is one of the major communication systems in modern
 era,  which
 meets  up
 the  above  challenges.   This
 utilizes
 different
 types
 of multiplexing techniques to maintain good quality of
service without traffic, less complicated
instruments with good utilization of
available resources .Wavelength Division Multiplexing (WDM) is one of them with good efficiency. It is based on dynamic light-path allocation. Here we have to take into consideration the physical topology of the WDM network and the traffic. We have taken performance analysis as parameter to analyse which type of topology is best suited  to 
implement  in real life application
 without  degrading
 quality  of service (QoS). Depending on the type of the
optical network considered, this problem may require the consideration of
various restrictions on the physical and logical topology. The restrictions
related to the physical topology of WDM optical networks usually depend on the
type of node equipment used and the capacity of the optical fibers available in
the network. The WDM optical network design problem studied in this paper deals
with an all-optical (also referred to as transparent) architecture. Current
trends in optical networks indicate they are gradually moving from an opaque
architecture (i.e., an architecture where the optical signal carrying traffic
undergoes an optical-electronicoptical (OEO) conversion at each node) to a
transparent one. There are several design choices in the deployment of
transparent optical networks. First, in WDM networks a lightpath is required to
use the same wavelength (this is referred to as a wavelength continuity
constraint in the literature) across the entire path unless intermediate nodes
are equipped with wavelength convertors. Currently, commercially available
wavelength convertor technology uses OEO conversion. Thus, currently
transparent optical networks must explicitly address the wavelength continuity
constraint. Alternatively, wavelength convertors are placed selectively at some
of the nodes in the network (such an architecture where OEO conversion only
takes place at a subset of nodes is called translucent) allowing the wavelength
continuity constraint to be relaxed somewhat. One advantage of networks with
wavelength convertor is some modest improvement in network throughput.
Currently, there is considerable focus on the development of optical wavelength
converters. All optical devices allow for the design of optical networks with
lower power consumption (which is a very important area of research). Thus,
some advantages of a transparent optical architecture with optical wavelength
convertors are (i) significantly lower power consumption, and (ii) increased
network throughput. Our paper focuses on transparent optical networks and
assumes the availability of optical wavelength convertors. Thus the wavelength
continuity constraint can be relaxed.In
optical communication, WDM is a technology that carries a variety of optical
carrier signals on one fibre by using completely different wavelengths of laser
light. This enables bifacial communication over one customary fibre with in
inflated capacity. As optical network supports huge bandwidth; WDM network split
this into a variety of small bandwidths optical channel. It permits multiple
data stream to be transferred along a same fibre at the same time. A WDM system
uses a variety of multiplexers at the transmitter end, which multiplexes over
one optical signal onto one fibre and demultiplexers at the receiver to separate
them apart. Usually the transmitter consists of an optical laser and modulator.
The light supply generates an optical carrier signal at either fixed or a
tuneable wavelength. The receiver consists of photodiode detector which
converts an optical signal to electrical signal. This new technology allows
engineers to increase the capacity of network without laying more fibre. It has
more security compared to other types of communication from tapping and also
immune to crosstalk. In this digital era the communication demand has increased
from previous eras due to introduction of new communication techniques. As we
can see there is increase in clients day by day, so we need huge bandwidth and
high speed networks to deliver good quality of service to clients. Fiber optics
communication is one of the major communication systems in modern era, which
meets up the above challenges. This utilizes different types of multiplexing
techniques to maintain good quality of service without traffic, less complicated
instruments with good utilization of available resources .Wavelength Division
Multiplexing (WDM) is one of them with good efficiency. It is based on dynamic
light-path allocation. Here we have got to take into consideration the physical
topology of the WDM network and the traffic. We have taken performance analysis
as parameter to analyse which type of topology is best suited to implement in
real life application without degrading quality of service (QoS). Wavelength Channel Multiplexing (WDM) is important technology used in today’s telecommunication systems. It has better features than other types of communication with client satisfaction. It has several benefits that make famous among clients such as WDM  networks  supports  data  to  be  transmitted
 at  different  bit  rates.  It also
supports  a number of protocols. So there is not much constraint in how we want to send the data. So it can be used for various very high speed data transmission applications. WDM  networks
 allows
 for
 wavelength  routing.
 So
 in  different
 fibre
 links
 the  same wavelength can be used again and again. This allows for wavelength reuse which in turn helps in increasing capacity. WDM networks are also very flexible in nature. As per requirement we can    make changes to the network. Extra processing units can be added to both transmitter and receiver ends. By this infrastructure can redevelop to serve more number of people. WDM  networks
 are extremely reliable  and secure.  Here chance of trapping the data and crosstalk is very low. It also can recover from network failure in a very efficient manner. There is provision for rerouting a path between a source-destination node pair. So in case of link failure we will not lose any data.

 

The optical network has huge bandwidth and capacity can be as high as 1000 times the entire RF spectrum. But this is not the case due to attenuation of
signals, which is a function of its wavelength and some
other fibre limitation factor like imperfection and refractive index
fluctuation.  So 1300nm
(0.32dB/km)-1550nm (0.2dB/km)
window with low attenuation is generally used. According to different wavelength there are three
existing types namely- Wavelength Channel Multiplexing (WDM), Coarse Wavelength
Division Multiplexing (CWDM), Dense Wavelength Division Multiplexing (DWDM).

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The paper
2
says designed the Mat Plan WDM software for topology design, multi hour analysis &
performance analysis. It is
a MATLAB-based publicly available network planning tool  for  Wavelength-Routing
 (WR)  optical
 networks,
 and
 it  was  fully developed  by our research group. His paper describes the multi-hour planning analysis extension included into the  Mat
 Plan  WDM
 version
 3.It’s  novel  functionality
 allows  the
 user  to  test  planning algorithms
 which  react
 under
 changes
 in the
 traffic  demands.
 Multi-hour  traffic  patterns appear typically in
backbone WR networks that span over large geographical areas, where network  nodes  are situated  in different  time zones.
 A case study example
 is included
 to illustrate the merits of the tool. The articles 16 discuss the routing and wavelength assignment (RWA) problem in optical networks employing wavelength division multiplexing (WDM) technology. Two variants of the problem are studied: static RWA, whereby the traffic requirements are known in advance, and dynamic RWA in which connection requests arrive in some random fashion. Both point- to-point and multicast traffic demands are considered. Input data
for communication network design/optimization problems involving multi-hour or uncertain traffic can consist of
a largest of
traffic matrices 17. These matrices are explicitly
considered in problem formulations for link dimensioning. However, many of these matrices are  usually
 dominated
 by others
 so  only a relatively  small subset  of  matrices
 would  be sufficient to obtain proper link capacity reservations, supporting all
original traffic matrices. Thus, elimination of
the dominated matrices leads to substantially smaller optimization
problems, making them treatable by contemporary solvers. In their paper they
discussed the issues behind detecting domination of one traffic matrix over another.
 They consider  two basic cases of domination: (i) total domination when the same traffic routing must be used for both matrices, and   (ii) ordinary domination when traffic dependent routing can be used. The paper is
based on
our original results and generalizes the domination results known for fully connected networks. Due to power considerations 18, it is possible that not all wavelengths available in a fiber can be used at a given time. In his paper, an
analytical model is proposed to evaluate the blocking performance of wavelength-routed  optical networks with and without wavelength
conversion where the usable wavelengths in a fiber is limited to a certain maximum number, referred to as wavelength usage constraint. The effect of the wavelength usage constraint is studied on ring and mesh-torus networks. It is shown that the analytical model closely approximates the simulation results. It is observed that increasing the total number of wavelengths in a fiber is an attractive alternative to wavelength conversion when the number of usable wavelengths in a fiber is maintained the same. The paper 19 says while optical-transmission techniques have been researched
 for quite some time, optical “networking” studies have been conducted only over the past dozen years or so. The field has matured enormously over this time: many papers and Ph.D. dissertations have been produced, a number of prototypes and test beds have been built, several books have
 been  written,
 a
 large
 number  of  start-ups  have
 been  formed,  and  optical  WDM technology is being deployed in the marketplace at a very rapid rate. The objective of this paper is
to summarize the basic optical-networking approaches, briefly report on the WDM deployment strategies of
two major U.S. carriers, and outline the current research and development trends on WDM optical networks.

In WDM technology to be deployed we
require a physical topology. After topology designing we require routing and
wavelength task to make it fully functional. Here we have taken three drawback
statements as: To design 60 Gbps capacity topology and compare performance
matrices and, to design 100 Gbps capacity topology and compare the performance
matrices with 60 Gbps topology. A connection needs to be setup in the optical
layer so as to carry the data between the clients of the network. The optical
connection that is maintained between a source node, s and destination node, d
is known as an optical path or light path. The difficulty of finding a path for
a light path and assigning a wavelength to the light path is referred to as the
routing and wavelength assignment problem (RWA). The problem of RWA is divided
into two parts namely routing and wavelength assignment. We designed four
different mesh network topologies (fully connected) having 6, 9, 12 and 15
nodes.

Also we have further added to design two
9-nodes networks to analyse the link failure case. We designed an .xml code to
design each network. The .xml contains the list of nodes and fibre links in the
network. Per node information is composed by the X and Y coordinates of the
node measured in kilometres over a Euclidean plane, number of E/O transmitters,
O/E receivers, node population, node type (or node level), number of nodes and
the name of each node. Per link information is the maximum number of
wavelengths per link and the number of optical fibres. MatPlan WDM is a good
simulation tool to analyse different network topologies and performance
matrices. With this we can use different types of designing algorithm like MILP
(Mixed integer Linear Programming). For this we need TOMLAB (require
registration) which allows many more Functions like wavelength
conversion/without wavelength conversion, with traffic losses/without traffic
losses, losses cost per Gbps, cost per electronically switched Gbps, maximum
light path distances. 

Its GUI (Graphic User Interface) allows
the user to carry out full multi-hour test for a prebuilt or user defined
multi-hour planning algorithm and virtual topology analysis. We can work
towards dynamic Analysis which allows GUI to test online optimization
algorithms to react to high level traffic connections arrivals, terminations
and to do high level of performance analysis with good accuracy.

In such an optical WDM network architecture, the
failure of a network component such as a fiber can lead to the failure of all
of the light paths that traverse the failed fiber. Since each light path is
expected to operate at a rate of few Gb/s, a fiber failure can lead to a
significant loss of bandwidth and revenue. For an IP-over-WDM network, two
methods for providing protection are as follows: 1) provide protection at the
WDM layer (i.e., set up a backup light path for every primary light path), or
2) provide restoration at the IP layer (i.e., overprovision the network so
that, after a fiber cut, the network should still be able to carry the same
amount of traffic as it was carrying before the fiber cut). The
two problems are how to interconnect WDM ring networks as well as how to groom
the traffic in interconnected rings.

Here
we have used MatPlanWDM0.61 as a stimulation tool to simulate our topologies.
It takes physical topologies and traffic data for different network topologies.
Here performance analysis of the four topologies has been done using MatPlanWDM0.61
simulator. We have to give topologies in .xml and traffic file in .traff
format. The algorithm we used here is shortest path algorithm. After that we
have selected sweep parameters with lower and upper limits and number of sweep
points to start simulation. We have then compared the results of the four 60
gbps network topologies and analysed them based on different parameters to
conclude which network topology suits best to provide best quality of service. Number of light path increases with increase in traffic demand as light paths are created as per demand. It decreases with increase in
WCC, because as the capacity for each channel increases, the number of
light path will decrease to maintain the total offered traffic. More number of light paths are desirable for better routing. Therefore network having more number of nodes is preferable.

For a topology to be implemented in real
life application it has to have minimum delay, low network congestion rate,
maximum number of possible light paths and high Single Hop Traffic/Offered
Traffic. In case of normal assumption one can think that delay will increase
with increase in number of nodes. It depends upon number of light paths. So
with increase in number of nodes, the number of light paths increases from
source node to destination node in shortest path algorithm. So the queuing
delay decreases, decreasing the overall delay. Since we can get more light
paths, so delay decreases with increase in nodes. We can see the network
congestion, number of light paths, single hop traffic/offered traffic increases
with increase in number of nodes.

Recent advances in the field of optical
communication have opened the way for the practical implementation of WDM
networks. After going through several papers we have found out that for
determining Quality of Service the effect of network architecture is not taken
into account. So we have studied and planned to design four different networks
and simulate them with different scenario to determine the performance
matrices, which are called QoS (Quality of Service) parameters. In this work,
we have decided of using the simulation tool MatPlanWDM0.61, to study WDM
networks and their performance analysis, which is freely available. It is an
excellent framework for designing & development of topology with various
features. Studying different research papers we have concluded that if there is
less number of nodes with high capacity, then delay will be more. If number of
nodes is more as well as high capacity then network congestion will be more. So
we have to choose a minimized output to maintain a better QoS. 

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