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Wavelength Division Multiplexing(WDM)

40 - 120 km(80 km typically)

Up to 10,000 km(600 km in 2001 basic commercial products)

OA OA

1

2

3

N

WDMMux

R

R

R

R

WDMDeMux

Frequency-registeredtransmitters

Receivers

All-Optical AmplificationOf Multi-Wavelength Signal!!!

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wdm

wdm

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Mux/dx

Mux/dx

wgd

awg

WDM 2 canale

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EVOLUTION

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WDM Evolution

– Faster (higher speed per wave), • 40 Gb/s on the horizon

– Thicker (more waves), • 160 waves possible today

– Longer (link lengths before regeneration) • A few thousand km possible today

– 160 waves at 10 Gb/s = 1.6 Tb/s• 25 million simultaneous phone calls• 5 million books per minute

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Capacitatea Fibrei Optice

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Uni Versus Bi-directional DWDM (cont.)

32

32

Full band

Full band

ChannelSpacing100 GHz

16

16

Blue-band

Red-band

ChannelSpacing100 GHz

16

16

• Uni-directional 32 channels system

• Bi-directional 32 channels system

32 chfull

duplex

16 chfull

duplex

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Key components for WDM

Passive Optical Components• Wavelength Selective Splitters• Wavelength Selective Couplers

Active Optical Components• Tunable Optical Filter• Tunable Source• Optical amplifier• Add-drop Multiplexer and De-multiplexer

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Optical Amplifiers are key in DWDM systems

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Amplificatoare EDFA

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Multiplexer / Demultiplexer

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MUX-DX

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Drop Channel

Add Channel

Drop & Insert

Optical Add/Drop Filters (OADMs)

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WDM

Network Architecture

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Classes of WDM Networks

• Broadcast-and-select

• Wavelength routed

• Linear lightwave

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Broadcast-and-Select

Passive

Couplerw1

w0

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Wavelength Routed

• An OXC is placed at each node• End users communicate with one another

through lightpaths, which may contain several fiber links and wavelengths

• Two lightpaths are not allowed to have the same wavelength on the same link.

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A WR Network

B

A

CD

E

F

G

HI

J

K

L

M

N

O

1

2

32

1

1

1

OXC

IP SONET

SONET

IP

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WRN (cont’d)

• Wavelength converter can be used to convert a wavelength to another at OXC

• Wavelength-convertible network.– Wavelength converters configured in the network– A lightpath can occupy different wavelengths

• Wavelength-continuous network– A lightpath must occupy the same wavelength

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Routing and Wavelength Assignment (RWA)

• To establish a lightpath, need to determine:– A route– Corresponding wavelengths on the route

• RWA problem can be divided into two sub-problems:– Routing– Wavelength assignment

• Static vs. dynamic lightpath establishment

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Linear Lightwave Networks

• Granularity of switching in wave bands

• Complexity reduction in switches

• Inseparability– Channels belonging to the same waveband

when combined on a single fiber cannot be separated within the network

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