Basics of DWDM Technology

1) Introduction
2) Need of DWDM Transmission
technology
3) Types of DWDM
4)Basic components of DWDM
3)NE Type/Structure
5)Transmission quality parameters
4)Equipment Alarms of 1626 LM
5)Fault Troubleshooting of 1626 LM
6)Link Budget & Power loss designing

For singlemode fiber, the loss is about 0.5 dB per km for 1310 nm sources, 0.4 dB
per km for 1550 nm

Multiplexing techniques
1) Space Division Multiplexing
2) Time Division Multiplexing
3) Wavelength Division Multiplexing

Why we need DWDM?
Earlier we use SDH transmission technology where optical
signals transmitted through a optical fiber utilizing only single
dedication bandwidth like STM-1,4,16 & 64, by implementing
SDH technology we have wasted maximum amount of
bandwidth which we can utilize only by a technology known as
DWDM.
Definition of DWDM:-> DWDM is a transmission technology by
which we can transmit/multiplex/Demux different wavelengths on
a single fiber by which we can utilize maximum bandwidth via
optical fiber cable. OR
DWDM combines multiple optical signals so that they can
amplified as a group & transported over a single fiber to
increase capacity.

ITU-T BAND
Band Description Wavelength Range
O band original 1260 to 1360 nm
E band extended 1360 to 1460 nm
S band short wavelengths 1460 to 1530 nm
C band
conventional
("erbium
window")
1530 to 1565 nm
L band long wavelengths 1565 to 1625 nm
U band
ultralong
wavelengths
1625 to 1675 nm
Historically, there was a window used below the O band, called the first
window, at 800-900 nm; however, losses are high in this region so this window
is used primarily for short-distance communications. The current lower
windows (O and E) around 1300 nm have much lower losses. This region has
zero dispersion. The middle windows (S and C) around 1500 nm are the
most widely used. This region has the lowest attenuation losses and achieves
the longest range. It does have some dispersion, so dispersion compensator
devices are used to remove this.

• The minimum frequency separation between two different
multiplexed signals is known as the Channel Spacing. Since the
wavelength of operation is inversely proportional to the frequency,
a corresponding difference is introduced in the wavelength of each
signal.

C
M
D
X
B
M
D
X
L
O
F
A
D
C
U
T
R
A
N
S
P
O
N
D
E
R
96 TRBD/C CARD require to provide
full capacity of 96 Lamada
12*CMDX 1*BMDX

Late
1990’s
Mid
1990’s
Early
1990’s
1980’s
64 to 160 channels in 1550 nm window
Next generation DWDM system
Channel spacing of 0.2 to 0.4 nm
16 to 40 channels in 1550nm window
DWDM (Dense wdm)
Channel spacing of 0.8 to 1.6
2 to 8 channels in 1550nm window
Passive (or) 2nd generation WDM
Channel spacing of~ 3.2nm
2 channels WWDM (Wideband WDM)
1310nm & 1550nm

*A basic DWDM system contains several main
components:
(a) A DWDM terminal multiplexer
(b) An intermediate line repeater
(c) An intermediate optical terminal
(d) A DWDM terminal demultiplexer
(e) Optical Supervisory Channel (OSC)

•Wavelength converting transponders translate the transmitted
wavelength of a client-layer signal into one of the DWDM system's
equivalent internal wavelengths.
•In the mid-1990s,wavelength converting transponders rapidly took
on the additional function of signal regeneration.
Signal regeneration in transponders quickly evolved through 1R
to 2R to 3R .
1R 2R 3R
Retransmission Re-time,
Re-transmit
Re-time,
Re-transmit,
Re-shape

• 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.

Line Terminal MUX 1626 for LH App

1626 view as regional application

Between multiplexing and de-multiplexing points in a DWDM system, there is an area in which
multiple wavelengths exist. It is often desirable to be able to remove or insert one or more
wavelengths at some point along this span. An Optical Add-Drop Multiplexer (OADM) performs
this function. Rather than combining or separating all wavelengths, the OADM can remove some
while passing others on. OADMs are a key part of moving toward the goal of all-optical networks.

Types of OADMs
1)Conventional OADMs- Used to drop fixed wavelength/Lamda---
where optical signal transmitted from more than one directions.
2)ROADM-> Reconfigurable OADM—used where optical signal
transmitted from more than two directions.

Optical Spectrum Analyzer
An Optical Spectrum Analyzer (or OSA) is a precision instrument
designed to measure and display the distribution of power of an optical
source over a specified wavelength span. An OSA trace displays power in
the vertical scale and the wavelength in the horizontal scale.
Power
(dB)
Wavelength(nm)

1)Optical Transmit Power(Tx)-Optical Receive
Power(Rx)= is called a Total LOSS of a Link.
2) Planning team will define Beginning of Life (BOL) of
a link & End of life (EOL) based on the total distance of
a link and type of fiber quality.
3)FOR PROPER WORKING OF A DWDM NETWORK ONE
MUST HAVE TO BE MAINTAIN DWDM LINK LOSS BELOW
BOL & EOL.

Basics of DWDM Technology

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