DENSE WAVELENGTH
DIVISION MULTIPLEXING
PRESENTED TO
DR.SAPNA GAMBHIR
ASSOCIATE PROF.
CSE DEPTT.
YMCAUST.FBD.
PRESENTED BY
PRITI RANI
MNW-891-2K11
MTECH(CN)
YMCAUST.FBD
CONTENTS
INTRODUCTION
VARIETIES OF WDM
DWDM TECHNOLOGY
HISTORY OF DWDM
DWDM SYSTEM AND COMPONENTS
TOPOLOGY
CONT…
TRANSMISSION CHALLENGES
MARKET DYNAMIC
FUTURE
APPLICATIONS
BENEFITS
REFERNCES
INTRODUCTION
One of the major issues in the networking
industry today is tremendous demand for more
and more bandwidth.
With the development of Optical network and the
use Dense Wavelength Division Technology, a
new and probably, a very crucial milestone is
being reached network evaluation.
OPTICAL NETWORKING
Optical networks are high-capacity
telecommunications networks based on optical
technologies.
The origin of optical networks is linked to
Wavelength Division Multiplexing (WDM) which
arose to provide additional capacity on existing
fibers.
CLASSIFICATION OF OPTICAL
NETWORK
FIRST GENERATION: Networks use
microwave technology based.
SECOND GENERATION: Networks use
microwave links with optical fibers.
THIRD GENERATION: Networks employ
Wavelength Division Multiplexing technology.
What is DWDM?
Dense Wavelength Division Multiplexing
(DWDM) is a fiber-optic transmission
technique.
It involves the process of multiplexing many
different wavelength signals onto a single fiber.
So each fiber has a set of parallel optical
channels each using slightly different light
wavelengths.
CONT..
It employs light wavelengths to transmit data
parallel-by-bit or serial-by-character.
DWDM is a very crucial component of optical
networks that will allow the transmission of
data: voice, video over the optical layer.
CONT..
It transmits multiple data signals using
different wavelengths of light through a single
fiber.
Incoming optical signals are assigned to
specific frequencies within a designated
frequency band.
The capacity of fiber is increased when these
signals are multiplexed onto one fiber
CONT..
Transmission capabilities is 4-8 times of TDM
Systems with the help of Erbium doped
optical amplifier.
EDFA’s : increase the optical signal and don’t
have to regenerate signal to boost it strength.
It lengthens the distances of transmission to
more than 300 km before regeneration .
Why DWDM?
Unlimited Transmission Capacity
Transparency
Scalability
Dynamic Provisioning
Is DWDM Flexible?
DWDM is a protocol and bit rate independent
hence, data signals such as ATM, SONET and
IP can be transmitted through same stream
regardless their speed difference.
The signals are never terminated within the
optical layer allows the independence of bit
rate and protocols,allowing DWDM
technology to be integrated with existing
equipment in network.
Hence, there’s a flexibility to expand
capacity within any portion of their networks.
Is DWDM Expandable?
“ DWDM technology gives us the ability to
expand out fiber network rapidly to meet
growing demands of our customer”, said
Mike Flynn, group President for ALLTEL’s
communications operations.
DWDM coupled with ATM simplifies the
network, reduce network costs and provide
new services.
They can add current and new TDM systems
to their existing technology to create a
system with virtually endless capacity
DISADVANTAGES
Not cost effective for low channel numbers
Sonet/sdh network management system
Are not well equipped to handle dwdm
topologies
DWDM SYSTEM
Comparison of TDM, WDM,
and DWDM multiplexing
capabilities
Multiple
x
Scalable Protoco Bit rate
l
indepen
indepen dent
dent
Chann
els per
optical
fiber
Optical Equival
system ent DScapacity 3
connect
ions
TDM
No
No
No
1
2.5
Gbit/s
48
WDM
Yes
Yes
Yes
2
5 Gbit/s
96
DWDM
Yes
Yes
Yes
16
N/A at
publicati
on
N/A at
publicati
on
EVOLUTION OF DWDM
A picture representing the really
cool analogy
Before
After TDM (cars go faster)
After DWDM (all the lanes are used)
Example of Speeds

Currently Lucent DWDM systems
support transmissions of 160 separate
wavelengths. Each wavelength is
capable of supporting a signal of up to
10 Gbps.


The total combined bandwidth is
1.6 trillion bits per second.
This is greater than the speed of
one million T-1 connections.
How DWDM saves $$
In addition to saving money on fiber cables,
DWDM also saves money on optical repeating
equipment
 Because one fiber is used instead of many, one
repeater can be used in place of many
 For example: you need 16 OC-3 carrier lines to
go 1000 miles and repeaters are needed every
100 miles…
 If you didn’t use DWDM, you would need 16
thousand miles of fiber and 160 repeaters
 With DWDM, you need only 1 thousand
miles of fiber and 10 repeaters
A picture of How DWDM saves $$
Before DWDM
After DWDM
Signal Quality
Optical Signal to Noise Ratio
Optical Spectrum Analyzer
Optical
Signal
Noise
Floor
DWDM Components
Transmitter : - Changes electrical bits to optical
pulses
- Is frequency specific
- Uses a narrowband laser to generate the optical
pulse
5.2 Multiplexer/ Demultiplexer:
- Combines/separates discrete wavelengths
5.3 Amplifier:
- Pre-amplifier boosts signal pulses at the receive
side
- Post-amplifier boosts signal pulses at the transmit
side
CONT…
5.5 Receiver (receive transponder)
- Changes optical pulses back to electrical bits
- Uses wideband laser to provide the optical
pulse
DWDM Mesh Designs
Advantages of DWDM Point to
Point Systems
The DWDM point-to-point architecture is
simple to build and troubleshoot .
It enables protocol transparency, increme-ntal
growth, and capacity expansion over time,
while dramatically reducing start-up costs.
Point-to-point solutions are also extremely
efficient.
No amplifiers or additional equipment
required.
Transmission Challenges
Attenuation
Attenuation is caused by :
- intrinsic factors primarily scattering and
absorption
- extrinsic factors, including stress from the
manufacturing process, the environment, and
physical bending
Rayleigh scattering - is an issue at shorter
wavelengths
Rayleigh Scattering
CONT…
Attenuation due to absorption
- is an issue at longer wavelengths
- the intrinsic properties of the material
- impurities in the glass, and any atomic
defects
in the glass.
These impurities absorb the optical
energy, causing the light to become
dimmer.
Absorption
Dispersion
Dispersion is the spreading of light pulses as they travel
down optical fiber. Dispersion results in distortion of the
signal, which limits the bandwidth of the fiber.
Two general types of dispersion
Chromatic Dispersion - is linear
Chromatic dispersion occurs because different
wavelengths propagate at different speeds.
Increases as the square of the bit rate.
Polarization Mode Dispersion - is nonlinear.
Polarization mode dispersion (PMD) is caused by ovality
of the fiber shape as a result of the manufacturing
process or from external stressors.
CONT…
Changes over time
PMD is generally not a problem at speeds below OC-192.
Smearing of the signal
Fiber Non Linear ties
Because nonlinear effects tend to manifest themselves
when optical power is very high, they become important
in DWDM.
These nonlinearities fall into two broad groups:
- scattering phenomena
- refractive index phenomena
Future of DWDM
What the future holds
Two-way video communication
Digital video for our everyday use at home and at work.
Change from voice telephony to digital data heavy with
video to require multiplying backbone transmission
capacity.
The Ultimate Squeeze
- reducing the “space” between wavelengths
- expanding the range of transmission
wavelengths
- better EDFAs
Develop better equipment for switching and manipulating
the various wavelengths after the signal emerges from the
optical “pipe.”
WDM is creating huge new information pipelines that
will bring better service at lower cost. But the real
information revolution won’t come until cheap WDM
pipelines reach individual residences.
Applications of DWDM
DWDM is ready made for long-distance
telecommunications operators that use either point-topoint or ring topologies.
Building or expanding networks
Network wholesalers can lease capacity, rather than
entire fibers.
The transparency of DWDM systems to various bit rates
and protocols.
Utilize the existing thin fiber
DWDM improves signal transmission
Summary
DWDM was introduced to increase bandwidth by better
utilizing existing fiber optic cabling
DWDM is able to place many network formats of
different speeds on the same fiber optic cable
Optical Add-Drop Multiplexers and Cross Connects are
what places the digital signals on the fiber
Less cable and therefore less optical repeating equipment
is needed for DWDM
DWDM SAVES $$$
THANKYOU
FOR YOUR ATTENTION