Post on 21-Apr-2015
PRESENTED BY:
ACHYUTH REDDY K
What Actually Is MULTIPLEXING ?
MULTIPLEXING (also known as muxing) is a method by which multiple analog message signals or
digital data streams are combined into one signal over a shared medium.
A device that performs the multiplexing is called
a multiplexer (MUX), and a device that performs the reverse process is called a demultiplexer (DEMUX).
Types of MULTIPLEXING
Wavelength Division Multiplexing
(WDM)
TYPES OF WDM
Two main types of WDM: Coarse Wavelength Division Multiplexing (CWDM)
Dense Wavelength Division Multiplexing (DWDM)
Feature CWDM DWDM
Wavelengths per fiber 8 – 16 40 – 80
Wavelength spacing 2500GHz (20nm) 100 GHz (0.8nm)
Wavelength capacity Up to 2.5 Gbps Up to 10 Gbps
Aggregate fiber capacity 20 – 40 Gbps 100 – 1000 Gbps
Overall cost Low Medium
Applications Enterprise, metro-access Access, metro-core,
regional
O - band E - band S - band C - band L - band
1280 1320 1360 1400 1440 1480 1520 1560 16001552Wavelength
(nm)
C Band Range : 1530 – 1560
L Band Range : 1560 – 1600
Dense Wavelength Division Multiplexing
Late 1990
1996
DWDM
Early
1990’s
Narrowband WDM
1980’s
Wideband WDM
16+ channels
100~200 GHz spacing
2~8 channels
200~400 GHz spacing
2 channels
1310nm, 1550nm
64+ channels
25~50 GHz spacing
Definition : • Dense wavelength division multiplexing (DWDM) is a fiber-optic
Transmission technique that employs light wavelengths to transmit
data parallel-by-bit or serial-by-character
Multiple channels of information carried over the same fibre, each using an individual
wavelength
Dense WDM is WDM utilising closely spaced channels
Channel spacing reduced to 1.6 nm and less
Cost effective way of increasing capacity without replacing fibre
Commercial systems available with capacities of 32 channels and upwards; > 80 Gb/s
per fibre
Wavelength
Division
Multiplexer
Wavelength
Division
Demultiplexer l1
A l2
l3 B
C
l1 X
l3 Y
Z l1 + l2 + l3
Fibre
l2
DWDM System
Block Diagram of DWDM System
DWDM Components
Transmitter : Laser with precise stable waveleng-th.
Link: Optical fiber that exhibits low loss and transmission performance in relevant wavelength spectra.
Receiver:Photo detectors and Optical demultiple-xers using thin film filters or diffractive elements.
Optical add/drop multiplexers and optical
cross connect components.
Dense WDM is WDM utilising closely spaced channels
Channel spacing reduced to 1.6 nm and less
Cost effective way of increasing capacity without replacing fibre
Commercial systems available with capacities of 32 channels and
upwards; > 80 Gb/s per fibre
Allows new optical network topologies, for example high speed
metropolitian rings
Optical amplifiers are also a key component
DWDM: Key Issues
Why DWDM?
Unlimited Transmission Capacity
Transparency
Scalability
Dynamic Provisioning
Principles of DWDM
BW of a modulated laser: 10-50 MHz 0.001
nm
Typical Guard band: 0.4 – 1.6 nm
80 nm or 14 THz @1300 nm band
120 nm or 15 THz @ 1550 nm
Discrete wavelengths form individual channels
that can be modulated, routed and switched
individually
These operations require variety of passive
and active devices
2
c l
l
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 expansion
DWDM Advantages and Disadvantages
Greater fibre capacity
Easier network expansion
No new fibre needed
Just add a new wavelength
Incremental cost for a new channel is low
No need to replace many components such as optical amplifiers
DWDM systems capable of longer span lengths
TDM approach using STM-64 is more costly and more susceptible to chromatic
and polarization mode dispersion
Can move to STM-64 when economics improve
DWDM Advantages
Not cost-effective for low channel numbers
Fixed cost of mux/demux, transponder, other system components
Introduces another element, the frequency domain, to
network design and management
SONET/SDH network management systems not well
equipped to handle DWDM topologies
DWDM performance monitoring and protection
methodologies developing
DWDM Disadvantages
Applications of DWDM
DWDM is ready made for long-distance telecommunications operators that use either point-to-point 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
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
References
http://www.cisco.com/univercd/cc/td/doc/product/mels/cm1500/dwdm/dwdm_ovr.htm
http://www.cis.ohio-state.edu/~jain/cis788-99/ftp/dwdm/index.html
http://www.iec.org
http://www.igigroup.com/st.html
http://www.cisco.com/univercd/cc/td/doc/product/mels/dwdm/dwdm_fns.pdf
http://www.ee.ucl.ac.uk/lcs/papers99/dbojic.pdf