This document discusses dense wavelength division multiplexing (DWDM) technology. It begins with an overview of DWDM, describing how it multiplexes multiple optical carrier signals onto a single optical fiber using different laser light wavelengths. It then provides details on DWDM network architecture, including optical transponders, multiplexers/demultiplexers, optical add-drop multiplexers, optical fiber amplifiers, and the optical supervisory channel. The document also discusses optical frequency bands defined by the ITU and advantages and limitations of DWDM networks.

1. MADE BY :-
SHUCHISHMAN BURMAN
090103508
ECE-D

2. Introduction
 Multiplexing
 a process where multiple analog message signals or
digital data streams are combined into one signal over a
shared medium
 Types
 Time division multiplexing
 Frequency division multiplexing
 Optically
 Time division multiplexing
 Wavelength division multiplexing

3. •WDM is a technology which multiplexes multiple optical
carrier signals on a single optical fiber by using different
wavelengths of laser light to carry different signals.
• There are two types of WDM—
> Coarse WDM
> Dense WDM

4. Evolution of DWDM
Late
1990’s
1996
DWDM
Early
1990’s
Narrowband WDM
1980’s
Wideband WDM
16+ channels
100~200 GHz spacing
2~8 channels
200~400 GHz spacing
2 channels
1310nm, 1550nm
64+ channels
25~50 GHz spacing

5.  Dense wavelength division multiplexing (DWDM) is a
fibre-optic transmission technique that employs light
wavelengths to transmit data parallel-by-bit or serial-
by-character.
dense wavelength division multiplexing
(dwdm)

8. The following steps describe the system :-
1. The transponder accepts input in the form of standard single mode laser. The input can
come from different physical media and different protocols and traffics types.
2. The wavelength of each input signal is mapped to a DWDM wave length.
3. DWDM wave length from the transponders are multiplexed into single optical signal
and launched into fiber
4. A post amplifier boosts the strength of the optical signal as it leaves the system
5. Optical amplifier are used along the fiber span as needed
6. A pre amplifier boosts the signal before it enter the end system
7. The incoming signal is de multiplexed and fed to respective receiver
8. From receiver they are transmitted to different system according to requirement

9. OVERVIEW OF DWDM NETWORK
ARCHITECTURE
Optical Transponder Unit (OTU):
The major function of the OTU board is to employ the Optical
/electrical/ optical conversion made to realize wave length conversion.
OTU includes transmission OTU and receiver OTU.

10. Optical Multiplexers and De-multiplexers Unit (OMU & ODU):-
As DWDM system send signal from several source over a single fiber, they must include some
means to combine the incoming signal. This is done with multiplexers, which take optical
wavelength from multiple fiber and converge them into one beam
Multiplexing & Demultiplexing using Prism and Lens De multiplexing Using Array of Wave Guide
Optical Add Drop Multiplexers (OADM):
This is the area in which multiple wave length exist .It is often desirable to be able
to remove or insert one or more wavelength at some point along this spans. An
OADM performs this function. Rather than combining and separating all wave
length, the OADM can remove some while passing others.

11. Optical Fiber Amplifier (OBA, OLA, OPA):
Optical amplifiers also can be used to boost signal power after multiplexing or
before de multiplexing By making it possible to carry large loads that DWDM is
capable of transmitting over long distance, the EDFA (Erbium Doped Fiber
Amplifier) was key enabling technology
Optical Supervisory Channel (OSC):
It is used for supervision of DWDM networks and its components. It works
on wave length of 1510 nm and speed of 2.048 Mb/s .It is use in Network
Monitoring System.

12. 2-May-15 12
OPTICAL BANDS
 EXTENSIVE USE OF WAVELENGTHS
 DIFFERENT VENDORS:INTEROPERABILITY ISSUES
 NEED FOR STANDARD WAVELENGTH VALUES
 ITU Classification of bands
 Standard values : ITU Grid
 Center frequency: 193.10THz (1552.52 nm)
 Standard spacing of 200, 100, 50 GHz for different applications

13. 2-May-15 ALTTC/TX-I/DWDM 13
ITU-T BAND ALLOCATION
Optical
Supervisory
channel
1500 1520 1530 1542 1547 1560 1620
RED
BAND
C BAND L BAND
BLUE
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.

14. • Capacity increase : Large aggregate transmission capacity.
• Upgradability : Customer growth without requiring additional
fiber to be laid.
• Flexibility : Optical Add/Drop Multiplexing (OADM)
Optical Cross connect (OXC)
• Scalability : The possibility to add new nodes to the network.
• Network Transparency : Independence of data rate, format &
protocols.

15. ADVANTAGES OF DWDM

16. 2-May-15 ALTTC/TX-I/DWDM 16
LIMITATIONS
• DWDM TRANSMISSION IS ANALOG.
THE IN LINE AMPLIFIERS ARE
ALSO ANALOG.
THIS IMPLIES THAT THE SIGNAL TO
NOISE RATIO WORSENS WITH
DISTANCE.
• FIBRE DISPERSION IS ANOTHER
LIMITATION.