1. INTRODUCTION TO DWDM
19-Nov-18
ALTTC/TX-I/DWDM

2. CONTENTS The need for DWDDM Fibre exhaust- alternatives The challenge:
Tapping the unlimited fibre bandwidth
Achieving the networking functions in the optical domain
Wdm approach to fibre exhaust
Wdm functional block schematic
Differences from conventional system: the amplifier
Dwdm systems at present
Optical amplifiers
Dwdm components
Optical bands
Standard wavelengths: ITU grid
Dwdm applications :
Benefit to operators
New issues before planners
19-Nov-18
ALTTC/TX-I/DWDM

3. FIBRE EXHAUST INSTAL HIGHER BITRATE TDM EXPENSIVE, NEW FIBRE NEEDED
2.5- Gbit/s
transmitter
2.5-Gbit/s
2.5 Gbit/s
reciever
10-Gbit/s
10-Gbit/s
10-Gbit/s
transmitter
regenerator
reciever
INSTAL HIGHER BITRATE TDM
EXPENSIVE, NEW FIBRE NEEDED
19-Nov-18
ALTTC/TX-I/DWDM

4. FIBRE EXHAUST DEPLOY DWDM DEMUX MUX 10-Gbit/s transmitter regenerator
reciever
2.5- Gbit/s
transmitter
2.5-Gbit/s
2.5 Gbit/s
reciever λ1
2.5-Gbitt/s
transmitter λ1
MUX
DEMUX
2.5- Gbit/s
reciever λ2 λ2
2.5-Gbitt/s
transmitter
2.5- Gbit/s
reciever λ3 λ3
2.5-Gbitt/s
transmitter
2.5- Gbit/s
reciever λ4 λ4
2.5-Gbitt/s
transmitter
2.5- Gbit/s
reciever
DEPLOY DWDM
19-Nov-18
ALTTC/TX-I/DWDM

5. EVOLUTION OF DWDM Late 1990’s 64-160 channels 25-50 GHZ spacing Mid
Dense WDM, integrated systems with
Network Management, add-drop functions.
Early
1990’s
2-8 channels passive
WDM GHz spacing
WDM components/parts
Late
1980’s
2 channels Wideband
WDM 1310 nm, 1550 nm
19-Nov-18
ALTTC/TX-I/DWDM

6. THREE POSSIBLE SOLUTIONS
ACHIEVING HIGHER BANDWIDTH
THREE POSSIBLE SOLUTIONS
INSTAL NEW FIBRE
INVEST IN NEW TDM
TECHNOLOGIES TO
ACHIEVE HIGHER
BANDWIDTH.
DEPLOY DWDM
EXPENSIVE
VERY
REQUIRE NEW
TYPE FIBRE
ECONOMICAL
19-Nov-18
ALTTC/TX-I/DWDM

7. THE CHALLENGE:Continuous growth in traffic…
Calls for tapping the unutilized bandwidth of the media
ACHIEVE NETWORKING FUNCTIONS (ROUTING etc) IN OPTICAL DOMAIN
JUST LIKE WIDENING OF ROAD USING AVAILAB.E LAND TO MEET INCREASED TRAFFIC
19-Nov-18
ALTTC/TX-I/DWDM

8. DWDM BASICS NEW REQUIREMENTS: MULTIPLEXER DWDM SDH OPTICAL SIGNALS
SINGLE FIBRE
SDH OPTICAL SIGNALS
NEW REQUIREMENTS:
19-Nov-18
ALTTC/TX-I/DWDM

9. BLOCK SCHEMATIC Tx Rx OFA DEMUX MUX W D M W D M OPTICAL SIGNALS. 1
STM-1
STM-4
STM-16
ATM IP W D M 2 . 1 16 W D M
TRANSPONDERS
19-Nov-18
ALTTC/TX-I/DWDM

10. Wayside Optical Add/Drop MultiplexerTM TM
WDM MUX
WDM DEMUX  2 15 16 1 
1-4
5-8 OA
19-Nov-18
ALTTC/TX-I/DWDM

11. Optical Add/Drop Multiplexing
Terminal Equipt
In-Line Amplifier
Terminal Equipt
fixed OADM: 2 l1 l2 l2
Configurable OADM : 1 or 2 l1 l2
OADM : Optical Add/Drop Multiplexer
19-Nov-18
ALTTC/TX-I/DWDM

12. OADM Connectivity Omnibus From terminal to OADM, or from OADM to OADM
29 express ch
32 ch WDM
Omnibus
From terminal to OADM, or from OADM to OADM
19-Nov-18
ALTTC/TX-I/DWDM

13. DIFFERENCES FROM OLD SYSTEM
REGs
FIBRES REQUIREMENT
LASERS
TYPES OF COMPONENTS
CAPACITY
FIBRE TRANSMISSION BEHAVIOUR
19-Nov-18
ALTTC/TX-I/DWDM

14. ADVANTAGES OF DWDM
19-Nov-18
ALTTC/TX-I/DWDM

15. Why Optical (DWDM) Networking?
Fibre Exhaust : Unlimited bandwidth on a fibre pair
Bit Rate Transparency
Format/Protocol Transparency : IP, ATM etc.
Efficient use and rearrangement of embedded optical capacity as per demand.
Minimal Capital Expenditure : Capacity Expansions Demand
Simpler Operations : Embedded DCC
19-Nov-18
ALTTC/TX-I/DWDM

16. Economics of WDM Saving of regeneration costs:
one optical amplifier for many channels regeneration cost per channel drastically reduced
Saving of fibres/fibre shortage
Cost effective compared to laying new fibres
19-Nov-18
ALTTC/TX-I/DWDM

17. DWDM Components Transmit Receive Repeater Add Drop
Distribution: Cross connects
19-Nov-18
ALTTC/TX-I/DWDM

18. OPTICAL NETWORK ELEMENTS
OADM
OXC
OMUX
ODEMUX TP OA
19-Nov-18
ALTTC/TX-I/DWDM

19. TRANSPONDER / TRANSLATOR / WAVELENGTH CONVERTOR
OPTIONAL
REGENERATOR
Electrical
REGENERATION
O/E
E/O
TRANSPONDER / TRANSLATOR / WAVELENGTH CONVERTOR
19-Nov-18
ALTTC/TX-I/DWDM

20. Optical Multiplexers & Filters
W\L FILTER
W\L
MULTIPLEXER
W\L ROUTER
19-Nov-18
ALTTC/TX-I/DWDM

21. OPTICAL ADD DROP MUX M D
COUPLER
CIRCULATOR
19-Nov-18
ALTTC/TX-I/DWDM

22. WAVELENGTH ADAPTATION
OPTICAL CROSSCONNECT T
SWITCH
MATRIX T T T
INPUT FIBRE
LINKS
OUTPUT FIBRE
LINKS T T T T
WAVELENGTH ADAPTATION
TRIBUTARY LINKS
19-Nov-18
ALTTC/TX-I/DWDM

23. OPTICAL AMPLIFIERS Pump Pump laser laser Isolator Isolator Coupler
Erbium-doped
Fiber-(10-50 m)
Pump
laser
Pump
laser
19-Nov-18
ALTTC/TX-I/DWDM

24. NMS FOR DWDM SYSTEMS NMS IN CONVENTIONAL SDH SYSTEMS:
DCC: TIME SLOTS
DWDM – NO TIME SLOTS
WAVELENGTH SLOTS
ONE WAVELENGTH IS DEDICATED FOR N.M.S.
OPTICAL SUPERVISORY CHANNEL
OSC needs to be accessed at all points in the network
19-Nov-18
ALTTC/TX-I/DWDM

25. Line Terminal Equipment
Optical Supervisory Channel (OSC)
Line Terminal Equipment
In-line Amplifier
Tx 1
Tx 2
Tx 3
Tx 4
Tx 5
Tx 6
Tx 7
Tx 8
DATA IN 1 2 3 4 5 6 7 8 Rx
DATA OUT
Tx sup
System Control Processor
Rx Tx
OSC
System Control Processor
Rx sup
 + supervisory
Network Management
19-Nov-18
ALTTC/TX-I/DWDM

26. OPTICAL BANDS EXTENSIVE USE OF WAVELENGTHS ITU Classification of bands
DIFFERENT VENDORS:INTEROPERABILITY ISSUES
NEED FOR STANDARD WAVELENGTH VALUES
ITU Classification of bands
Standard values : ITU Grid
Center frequency: THz ( nm)
Standard spacing of 200, 100, 50 GHz for different applications
19-Nov-18
ALTTC/TX-I/DWDM

27. C BAND PRODUCTS ARE COMMERCIALLY AVAILABLE.
ITU-T BAND ALLOCATION
C BAND
L BAND
Optical
Supervisory
channel
BLUE
BAND
RED
BAND
C BAND PRODUCTS ARE COMMERCIALLY AVAILABLE.
ERBIUM DOPED FIBRE AMPLIFIERS SUITABLE FOR
‘C’ BAND.
GAIN IN RED BAND FLATTEST FOR EDFA.
SOME MANUFACTURERS PROVIDE 16 CHANNELS IN
RED BAND ONLY. OTHERS USE BOTH RED
& BLUE BANDS.
19-Nov-18
ALTTC/TX-I/DWDM

28. ITU –T G.692 Frequency Grid Nominal Central  (THz) Central  (nm)
196.1
194.7
193.3
196.0
194.6
193.2
195.9
194.5
193.1
195.8
194.4
193.0
195.7
194.3
192.9
195.6
194.2
192.8
195.5
194.1
192.7
195.4
194.0
192.6
195.3
193.9
192.5
195.2
193.8
192.4
195.1
193.7
192.3
195.0
193.6
192.2
194.9
193.5
192.1
194.8
193.4
19-Nov-18
ALTTC/TX-I/DWDM

29. LIMITATIONS DWDM TRANSMISSION IS ANALOG. THE IN LINE AMPLIFIERS ARE
ALSO ANALOG.
THIS IMPLIES THAT THE SIGNAL TO
NOISE RATIO WORSENS WITH
DISTANCE.
TO KEEP THE BER WITHIN LIMITS,
THE SIGNALS ARE REQUIRED TO BE
3R PROCESSED IN ELECTRICAL
DOMAIN.
FIBRE DISPERSION IS ANOTHER
LIMITATION.
19-Nov-18
ALTTC/TX-I/DWDM

30. LIMITATIONS THE MAXIMUM DISTANCE IS 640 Kms
MADE OF 8 SPANS OF 80 Kms. THE
ASSUMPTIONS ARE:
* FIBRE ATT INCLUDING SPLICE
LOSS IS dB/km
* SPAN LOSS OF 22 dB.
* TOTAL DISPERSION IS LESS
THAN ps/nm.
19-Nov-18
ALTTC/TX-I/DWDM

31. New Applications with DWDM
Long Distance
Longer Regenerator spacing: Hundreds to Thousands of Kilometers
Saving of Regenerators
Very Low Bandwidth Cost
Scalability
Very Fast Commissioning of Optical Paths: Within a week as compared to several months/ year with old technologies
Advanced Networking Capabilities
19-Nov-18
ALTTC/TX-I/DWDM

32. New Applications with DWDM
Metropolitan Area Network
Unlimited Bandwidth, bit rate and format transparency
Efficient Bandwidth use and Management
19-Nov-18
ALTTC/TX-I/DWDM

33. New Applications with DWDM
High speed parallel Data Transport
Certain Computer Applications Require that Computer Centers be interconnected with multiple high speed channels that have capacity and availability requirements, as well as interlink delay restrictions that can not be met by TDM Transport Systems.
In General, DWDM Optical Transport Benefits all Delay Sensitive Applications
19-Nov-18
ALTTC/TX-I/DWDM

34. New Applications with DWDM
Wavelength Leasing
Network Customers are beginning to demand high capacity Network Transport that affords high reliability and security, as well as segmentations from the providers Network
A spare Wavelength (Leased ) is used to provide clear-channel transport to a customer
The Customer’s Bandwidth requirements are cleanly separated from the providers core Network Needs.
19-Nov-18
ALTTC/TX-I/DWDM

35. Thank You
19-Nov-18
ALTTC/TX-I/DWDM