Dense Wavelength Division
Multiplexing
Theory
What we will cover
•
•
•
•
WDM Overview
Optical Fiber Transmission Characteristics
Key technologies of DWDM
Technical Specifications
Background
WDM
TDM
SDM
PDH, SDH and DWDM
G.692
DWDM
G.957
G.691
SDH
155M
PDH
622M
2.5G
10G
Relationship between DWDM and Other Services
IP
ATM
SDH
ATM
IP
Other
Open Optical Interface
SDH
DWDM
Physical Fiber
WDM Definition
• WDM enables transmitting multiple optical
carriers with information (analog or digital) on
one fiber
l1 l2
lN
l1
l1
l2
l2
lN
lN
OA
OMU
ODU
DWDM Concept
Dense wavelength division multiplexing
(DWDM)
Power (dBm)
wavelength interval ：0.8～2nm
1529 - 1560nm
λ(nm)
DWDM System
Optical Transmitter
Ch 1
OTU1
┇
OTUn
λ1
BA
λs
λ
s
LA
λs
PA
λs
λn
ODU
Ch N
λ1
OMU
Input
Optical Receiver
OLA
OSC
OSC
EMS
OTU1
┇
Output
Ch N
λn
OSC
Ch 1
OTUn
Common Network Elements in DWDM
• Optical Terminal Multiplexer (OTM)
• Optical Line Amplifier (OLA)
• Optical Add/Drop Multiplexer (OADM)
Optical Terminal Multiplexer (OTM)
At the transmitter end, the OTM:
Multiplexes the STM-N signals of “N”
wavelengths λ1~λN into a DWDM main
optical channel
Amplifies the optical power of the main
channel via the multiplexer
Adds 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 STMN signals of the N different wavelengths
Client side
Line side
λ1
λn
λ1
λn
OTM
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 side
Line side
OLA
Optical Add/Drop Multiplexer (OADM)
• OADM performs add/drop of wavelengths
Line side
Line side
λ1 λn
λ1 λn
Client side
OADM
Operational Wavelength Range
3.0
~140THz
2.5
~50THz
OH- absorption peak
2.0
OH- absorption
peak
Loss (dB/km)
1.5
OH- absorption
peak
1.0
0.5
O
E
S C L
0
800
1000
1200
1400
1600
Wavelength (nm)
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
3.0
~140THz
2.5
~50THz
OH- absorption
peak
OH- absorption peak
2.0
Loss (dB/km)
1.5
I
II
V
III IV
OH- absorption
peak
1.0
0.5
O
E
S C L
0
800
1000
1200
1400
1600
Wavelength (nm)
Feature Comparison between Low-Loss Windows
Window
I
II
III
IV
V
Mark (nm)
850
1310 (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-Band
40 Channels / 100 GHz interval
No.
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
Wavelength Allocation On C-Band
40 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
DWDM vs. SDH
• TDM
• DWDM
• Electrical Regenerator • Multi-wavelength on
for Single Wavelength Single Fiber, for Optical
Amplification
Electrical
Regenerator
Transmitter
l1
T
l1 l2 lN
Receiver
R
l1
l2
lN
Electrical Multiplex
Electrical Demultiplex
Optical Multiplexer
l1
l2
OA
lN
Optical Demultiplexer
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 Regenerator
Light Amplifier
DWDM Features
32*10G
32*2.5G
16*2.5G
8*2.5G
Key technologies of DWDM
DWDM System
Optical Transmitter
Ch 1
┇
OTUn
λ1
BA
λ
s
λ
s
LA
λ
s
PA
λ
s
λn
ODU
Ch N
λ1
OMU
Input
OTU1
Optical Receiver
OLA
OSC
OSC
EMS
OTU1
┇
Output
Ch N
λn
OSC
Ch 1
OTUn
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
Demultiplexer
Fiber
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
OBA
OSC
OLA
OSC
OLA
OLA
OPA
OSC
OSC
OSC
ODU
ODU
OMU
OPA
OLA
OLA
OLA
OBA
Optical Supervision Control (OSC)
•
•
•
•
1510nm
Signal speed : 2.048Mb/s
Receiving sensitivity :
-48dbm
Transmission power :
0 ~ -7 dbm
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