Dense Wavelength Division Multiplexing

Muhammad Ayub Tareen

Theory

What we will cover

• WDM Overview• Optical Fiber Transmission Characteristics• Key technologies of DWDM• Technical Specifications

Background

WDM

TDM

SDM

PDH

SDH

DWDM

155M 622M 2.5G 10G

G.957 G.691

G.692

PDH, SDH and DWDM

IPIP

ATMATM

SDHSDH

DWDMPhysical Fiber

DWDMPhysical Fiber

Open Optical InterfaceOpen Optical Interface

SDHSDH ATMATM IPIP OtherOther

Relationship between DWDM and Other Services

WDM Definition

• WDM enables transmitting multiple optical carriers with information (analog or digital) on one fiber

N

2

1

N

2

1

N21

OMU ODU

OA

DWDM Concept

Dense wavelength division multiplexing (DWDM)

Power (dBm)

1529 - 1560nm λ(nm)

wavelength interval ： 0.8 ～ 2nm

DWDM System

OTU1OTU1OTU1OTU1

┇Input

Ch 1

Ch N

Ch 1

Ch N

λλ11

λλn n

OTUnOTUnOTUnOTUn

OM

UO

MU BABA LALA PAPA

OD

UO

DU

λλ11

λλn n

OTU1OTU1OTU1OTU1

┇

OTUnOTUnOTUnOTUnλsλs λsλs λsλs λsλs

OSCOSC

OSCOSC OSCOSC

Output

EMS

Optical Transmitter OLA Optical Receiver

Common Network Elements in DWDM

• Optical Terminal Multiplexer (OTM)• Optical Line Amplifier (OLA)• Optical Add/Drop Multiplexer (OADM)

Optical Terminal Multiplexer (OTM)

Client sideLine side

λ1

λn

λ1

λn

OTM

At the transmitter end, the OTM:

Multiplexes the STM-N signals of “N” wavelengths λ1~λN into a DWDM main optical channelAmplifies the optical power of the main channel via the multiplexerAdds an optical supervisory channel λs

At the receiving end, the OTM:Extracts the optical supervisory channel λs

DWDM main optical channel is amplified and de-multiplexed into STM-N signals of the N different wavelengths

Optical Line Amplifier (OLA)• OLA is configured in each

direction of the fiber link• OLA extracts the optical

supervisory channel (OSC) and processes it

• It then amplifies the main optical channel signals, multiplexes them with the optical supervisory channel and sends them onto the fiber

Line sideLine side

OLA

Optical Add/Drop Multiplexer (OADM)

• OADM performs add/drop of wavelengths

Client side

Line side Line side

λ1 λn λ1 λn

OADM

Operational Wavelength Range

0

0.5

1.0

1.5

2.0

2.5

3.0

800 1000 1200 1400 1600

Wavelength (nm)

Loss (dB/km)

~140THz

~50THzOH- absorption peak

OH- absorptionpeak

OH- absorptionpeak

O E S C L

O Band Original 1260-1360 nm

E Band Extended 1360-1460 nm

S Band Short 1460-1530 nm

C Band Conventional 1530-1565 nm

L Band Long 1565-1625 nm

U Band Ultralong 1625-1675 nm

Division Of Low-Loss Window

0

0.5

1.0

1.5

2.0

2.5

3.0

800 1000 1200 1400 1600Wavelength (nm)

Loss (dB/km)

~140THz

~50THzOH- absorption peak

OH- absorptionpeak

OH- absorptionpeak

O E S C L

III III IVV

Feature Comparison between Low-Loss Windows

Window I II III IV V

Mark (nm) 8501310 (O

band)1550 (C band) 1600 (L band)

1360 ~ 1530 (E + S bands)

Wavelength range (nm)

600~900 1260~1360 1530~1565 1565~1625 1360~1530

Fiber type MMF MMF/

G.652/G.653

G.652/G.653/G.655

G.652/G.653/G.655

Full-wave fiber

Applications

Short distance and low

rate

Short distance and low

rate

Long distance and high rate

Wavelength Allocation On C-BandNo. Central Frequency (THz) Wavelength (nm)

1 192.1 1560.61

2 192.2 1559.79

3 192.3 1558.98

4 192.4 1558.17

5 192.5 1557.36

6 192.6 1556.55

7 192.7 1555.75

8 192.8 1554.94

9 192.9 1554.13

10 193.0 1553.33

11 193.1 1552.52

12 193.2 1551.72

13 193.3 1550.92

14 193.4 1550.12

15 193.5 1549.32

16 193.6 1548.51

17 193.7 1547.72

18 193.8 1546.92

19 193.9 1546.12

20 194.0 1545.32

40 Channels / 100 GHz interval

Wavelength Allocation On C-Band40 Channels / 100 GHz interval

21 194.1 1544.53

22 194.2 1543.73

23 194.3 1542.94

24 194.4 1542.14

25 194.5 1541.35

26 194.6 1540.56

27 194.7 1539.77

28 194.8 1538.98

29 194.9 1538.19

30 195.0 1537.40

31 195.1 1536.61

32 195.2 1535.82

33 195.3 1535.04

34 195.4 1534.25

35 195.5 1533.47

36 195.6 1532.68

37 195.7 1531.90

38 195.8 1531.12

39 195.9 1530.33

40 196.0 1529.55

• TDM

• Electrical Regenerator for Single Wavelength

• DWDM• Multi-wavelength on Single Fiber, for Optical Amplification

DWDM vs. SDH

TTRR

1

Electrical Multiplex Electrical Demultiplex

Transmitter ReceiverElectrical

Regenerator

N

2

1

N

2

1

N21

Optical Multiplexer Optical Demultiplexer

OA

DWDM Features

Large transparent transmission capacity greatly saves fiber resources

Each wavelength can carry different signal: SDH 2.5Gbps, 10 Gbps, ATM, IP

DWDM technology provides multiple virtual fiber channels in one physical fiber channel

SDH DWDM

DWDM Features

Through super-long distance transmission technologies, the transmission cost is reduced

SDH

DWDM

Electrical RegeneratorLight Amplifier

DWDM Features

8*2.5G

32*2.5G

16*2.5G

32*10G

Key technologies of DWDM

DWDM System

OTU1OTU1OTU1OTU1

┇Input

Ch 1

Ch N

Ch 1

Ch N

λλ11

λλn n OTUnOTUnOTUnOTUn

OM

UO

MU BABA LALA PAPA

OD

UO

DU

λλ11

λλn n

OTU1OTU1OTU1OTU1

┇

OTUnOTUnOTUnOTUnλsλs λsλs λsλs λsλs

OSCOSC

OSCOSC OSCOSC

Output

EMS

Optical Transmitter OLA Optical Receiver

Key Technologies Of DWDM

• Optical Source

• Optical Multiplexer And De-multiplexer

• Optical Amplifiers

• The Supervision Of WDM System

Optical Source

Requirements of optical sources:Larger dispersion tolerance value

Standard and stable wavelength

Types of optical sources:Light Emitting Diode (LED)

Laser Diode (LD)

Optical Multiplexing and De-multiplexing Technology

Optical Multiplexer and Demultiplexer

Multiplexer

Fiber

Demultiplexer

Supervision System Technology

Supervision System• Detection, control and management are basic

requirements of all network operations• To ensure secure operation of DWDM system,

physically, the monitoring system is designed as an independent system separated from working channels and devices

• Used to transmit the NE management and supervision information related to DWDM system

Functions• Fault alarm• Fault location• Quality parameter supervision in the

operation• Control over backup line upon line

interruption• EDFA supervision

Optical Supervision Control (OSC)

OMU ODU

OBA

OPA

OPA

OBA

ODU OMU

OLA

OLA

OLA

OLA

OLA

OLA

OSC OSC OSC OSC OSC OSC OSC OSCOSCOSC

Optical Supervision Control (OSC)• 1510nm• Signal speed : 2.048Mb/s• Receiving sensitivity : -48dbm• Transmission power : 0 ~ -7 dbm

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