WDM Basics

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1·1 Module 1WDM Transmission Basics

3JK10358AAAAWBZZA Edition 01

Section 1WDM Technology -

Fundamentals

Transmission NetworksWDM Technology - Fundamentals

WDM Technology - Fundamentals · WDM Transmission Basics 1 · 1 · 3

Objectives

Explain the reasons for deploying a WDM network.Describe the basic WDM technology and the

operational concepts.Describe the functions of the major components used

in WDM.

1 Introduction

1.1 Network Hierarchy

Inter-metroconnection

Point-to-point

Residential networks:

- DSL- Cable modem

SDH/SONET:

- POTS- Wireless

ISP POP:- IP services

Enterprise:- Frame Relay - ESCON- Fiber Channel- Gigabit

Ethernet

Long-haul

networks

Metro-politannetworks

Accessnetwork

1 Introduction

1.2 Bandwidth Demand

Voice-centric

Data-centric

Trafficvolume

1996 1997 1998 1999 2000 2001

1 Introduction

1.3 Options for Increasing Carrier Bandwidth

Space Division Multiplexing (SDM) increasing the number of fibers

Time Division Multiplexing (TDM) increasing the bit rate

Wavelength Division Multiplexing (WDM) increasing the number of wavelengths

Complementarysolutions

1.3.1 Time Division Multiplexing

Concept

Bits of information

Transmission link

1.3.1 Time Division Multiplexing

SDH Standard

Incoming streams

Link rate =(2.5Gbps x 4 =

10Gbps)

Outgoing

stream

Bit rate = 2.5Gbps

1.3.2 Wavelength Division Multiplexing

Concept

TRANSMITTERS

Separating

signals

Optical fiber

RECEIVERS

Combining

signals

1.3.2 Wavelength Division Multiplexing

Input Format Independence

Leased line

1.3.3 TDM versus WDM

Network Evolution

16 x STM-1

N channels

Colored signals with specific wavelengths

16 x STM-1

N terminals

WDMSTM-16terminal

STM-16terminal

1R 1R 1R 1R

N terminals

16 x STM-1

3R 3R 3R

REGENERATOR REGENERATOR REGENERATOR

16 x STM-1

16 x STM-116 x STM-1

16 x STM-1

STM-16terminal

N terminals

1.3.3 TDM versus WDM

Unlimited Transmission Capacity

WDM + TDM

N x 2.5Gbps

TDMSingle Channel

128 x 2.5Gbps

64 x 2.5Gbps

32 x 2.5Gbps

16 x 25Gbps

8 x 25Gbps

4 x 25Gbps

2 x 25Gbps

8 x 10Gbps

16 x 10Gbps

40 x 10Gbps

N x 10Gbps

200Gbps

100Gbps

10Gbps

140Mbps

565Mbps

2.5Gbps

10Gbps

40Gbps

Global capacity

per fiber (Gbps)

2 Varieties of WDM

2.1 WDM Evolution

64 channels50GHz spacing

64 channels 100-200GHz spacingDense WDM, integrated systems with network management, add-drop functions

2-8 channelsNarrowband WDM 200-400Ghz spacing Passive WDM components

2 channels Wideband WDM 1310nm, 1550nm

Evolution of WDM

Late1990’s

Early1990’s

1980’s

2 Varieties of WDM

2.2 Conventional WDM Definition

Transmit

Receive

End system End system

(1310nm + 1550nm)

2.3 DWDM Definition

Absorption Spectrum of the Optical Fiber

Wavelength (nm)

Loss (dB/km

800 1000 1200 1400 1600 1800

2.3 DWDM Definition

C Band

BLUE BAND RED BAND

1528nm 1546nm 1564nm

C Band

2.3 DWDM Definition

ITU-T Standard for 100GHz Spacing in C Band

Nominal Frequencies Allocation Plan (Red Band)

Channel Central Central frequency (THz) number wavelength (nm)

20 1561.42 192.000

21 1560.61 192.100

22 1559.79 192.200

23 1558.98 192.300

25 1557.36 192.500

26 1556.55 192.600

27 1555.75 192.700

28 1554.94 192.800

30 1553.33 193.000

31 1552.52 193.100

32 1551.72 193.200

33 1550.92 193.300

35 1549.32 193.500

36 1548.51 193.600

37 1547.72 193.700

38 1546.92 193.800

Nominal Frequencies Allocation Plan (Blue Band)

Channel Central Central frequency (THz) number wavelength (nm)

42 1543.73 194.200

43 1542.94 194.300

44 1542.14 194.400

45 1541.35 194.500

47 1539.77 194.700

48 1538.98 194.800

49 1538.19 194.900

50 1537.40 195.000

52 1535.82 195.200

53 1535.04 195.300

54 1534.25 195.400

55 1533.47 195.500

57 1531.90 195.700

58 1531.12 195.800

59 1530.33 195.900

60 1529.55 196.000

2 Varieties of WDM

2.4 CWDM Definition

ChannelWaveleng

thFrequen

cyChann

elWavelengt

hFrequen

1 1470nm203.94TH

z5 1550nm

193.41THz

2 1490nm201.20TH

z6 1570nm

190.95THz

3 1510nm198.54TH

z7 1590nm

188.55THz

4 1530nm195.94TH

z8 1610nm

186.21THz

3 DWDM Basic Components

3.1 DWDM Network

Post-amplifier

Pre-amplifier

In-line amplifiers

Transponderinterfaces

Directconnection

Terminal A Terminal B

Transponderinterfaces

Directconnection

… …

3.2 Transponder

StandardReceiver

Client Interface

DWDM Interface

3RRegenerati

ColoredInterface

B&WInterface

3RRegenerati

OptimizedReceiver

OpticalSignal

ElectricalSignal

3.3 Multiplexer/Demultiplexer

Multiplexing and demultiplexing in a bidirectional communication

Optical fiber

3.4 Optical Amplifier

Applications

Post-amplifier

In-line Amplifier

Pre-amplifier

TRANSMITTER

RECEIVER

GS-TDFA

GS-EDFA

L BandC Band

162015601530

S BandS+ Band

14801420Waveleng

th(nm)

Erbium-Doped Fiber Amplifier

Active fiber doped with Erbium ions

Ground state

Excited state

Energy supply(pumping)

Spontaneousemission

Stimulatedemission

electron

Noisegenerati

Opticalamplification

photon Signal in

Signal in Signal outPump

coupler

Pumplaser diode

ERBIUM-DOPEDFIBER AMPLIFIER

Raman Amplification Principle

1450 1470 1490 1510 1530 1550 1570 1590 1610 1630 1650

@1455nm @1480nm

Gain spectrumversus pump wavelength

Gain(relative)

(gain)=(pump)+100nm

Transmitter Receiver

1455nm pump

Optical fiber

3.5 OADM Concept

Optical fiber

1 , 2 , … , n

AmplifierOptical fiber

Amplifier

1 , 2 , … , n

4 Module Evaluation

Answer the Questions (1/8)

Is the following statement true or false?WDM systems cost more than installing more fibers.

Select the correct answer.

What is the multiplexing concept used for SDH?

Is the following statement true or false?WDM systems are input format independent.

Which band is in the third optical window?

Associate each wavelength spacing to the correct multiplexing technology.To do this, draw a line between each wavelength spacing from the list on the left and the appropriate technology from the list on the right.

100GHz

3000GHz

400GHz

Fill in the blanks in the figure below to situate each element that makes up a DWDM network.

The elements are: MUX (multiplexer) PreA (pre-amplifier) ILA (In-line amplifier) Receiver

Transmitter DEMUX (demultiplexer) PostA (post-amplifier)

Is the following statement true or false?The main function of the transponder is to convert theB&W wavelength to a colored wavelength.

What is the amplification range for an EDFA?

1530-1610nm

1490-1530nm

1530-1565nm

Summary (1/2)

Options for increasing carrier bandwidth:Space Division Multiplexing (SDM)Time Division Multiplexing (TDM)Wavelength Division Multiplexing (WDM)

Varieties of WDM:Conventional WDM:

2 wavelengths: 1310nm and 1550nm Or 400 GHz spacing around 1550nm

Dense WDM (DWDM): Range: 1460nm-1565nm S, C, L bands Spacing: 200, 100, 50, 25GHz

Coarse WDM (CWDM): Range: 1270nm-1610nm Spacing: 3000GHz

Summary (2/2)

A DWDM network is made up of:a transmitter, also called transmit transponder,a multiplexer and a demultiplexer,amplifiers:

a post-amplifier, also called booster, In-Line Amplifiers (ILAs), also called repeaters, a pre-amplifier,

an optical fiber,an Optical Add-Drop Multiplexer (OADM) which is optional,a receiver, also called receive transponder.

Self-Assessment on the Objectives

Please be reminded to fill in the formSelf-Assessment on the Objectivesfor this module

The form can be found in the first partof this course documentation

End of ModuleWDM Transmission Basics

WDM Basics

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