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