383934148-DWDM-101-Introduction-to-DWDM-2-pdf.pdf

Cisco Confidential
© 2013 Cisco and/or its affiliates. All rights reserved. 1
APJC Optical Sales
DWDM introduction
IntroductiontoDWDM,baseapplicationsandarchitectures

© 2013 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 2
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Agenda
 Why DWDM?
 Optical Basics
 DWDM Technology
 Optical Transmission
Systems Network Design
 Reference architectures

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• Bit-rate and protocol independent transport
• Extremely high bandwidth
Bit-rate X no. of channels
10 Gbps  10G X 80  0.8 Tbps
40 Gbps  40G X 80  3.2 Tbps
100 Gbps  100G X 80  8 Tbps
Scales beyond efficiently too : 96 channels ; 400 Gbps ; 1 Tbps
• Fiber plant investment is preserved – add capacity to lit fiber thru equipment
upgrades; graceful growth
• Highly scalable – leverage abundance of dark fiber; convert existing spans of
SONET / SDH rings
• Dynamic provisioning – service availability in hours / days compared to months in a
purely TDM world; wavelength on demand
• Convergence Layer – Creates the optical superhighway IP and Ethernet
• Spans from access to the core
• Relevant in access, metro, regional, and long haul networks
• An established field, well aided by frequent innovations

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• Transport of bandwidths beyond available interface rates (GE, 10G,
40G, 100G) requires multiple channels.
• With standard interfaces, multiple channels requires multiple fiber pairs.
Fiber is a scarce resource, and can be costly.
• xWDM allows multiple channels over a single fiber pair, and is often
more cost effective than using multiple fiber pairs.
• Each channel physically separated and don’t have common data plane
path with the rest of the channels in the system
Without DWDM
N fiber pairs
With DWDM
One fiber pair
N wavelengths

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• With standard interfaces, distance is limited to the reach of the specified
interface (e.g. LX, EX, ZX – 10 km, 40 km, 80 km – depends on fiber).
• Exceeding these distances requires regeneration of each channel
(typically with router/switch interfaces).
• With DWDM, single span distances can reach 250 km.
• Amplified, multiple span DWDM distances can reach 1000’s of km, with
no ‘electrical’ regeneration and can have more than 80 channels today.
Optical
Amplifier
Without DWDM
up to 80km
With DWDM
1000’s of km

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• With standard interfaces, the physical (layer 1) network topology is
restricted to the fiber topology.
• Fiber is expensive, and availability is limited. Metro / regional fiber is
most cost effectively deployed to multiple sites in a ring.
• DWDM, specifically ROADM, allows any L1 topology (hub and spoke,
mesh) over any fiber topology – typically a ring.

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• Without DWDM (or TDM), service protection must be provided by an
upper layer protocol. This can be complicated and slow.
• DWDM provides the ability to protect individual channels at layer 1, with
sub 50 ms switching times.
• Bandwidth is reserved, with no oversubscription or contention in a failure
scenario.
• Multiple levels of resiliency are available, at varying cost points.
Transport Section Protection Multiplex Section Protection
(Splitter Protection)
Optical Channel Protection
(Trunk Protection)

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Agenda
 Why DWDM?
 Optical Basics
 DWDM Technology

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Optical communication wavelength bands in the InfraRed:
• 850 nm over Multimode fiber
• 1310 nm over Singlemode fiber
• C-band:1550 nm over Singlemode fiber
• L-band: 1625 nm over Singlemode fiber
UltraViolet InfraRed
850 nm 1310 nm 1550 nm 1625 nm
l
Visible

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• Wavelength (Lambda l) of light: in optical communications normally
measured in nanometers, 10–9m (nm)
• Frequency () in Hertz (Hz): normally expressed in TeraHertz (THz),
1012 Hz
• Converting between wavelength and frequency:
Wavelength x frequency = speed of light  l x  = C
C = 3x108 m/s
For example: 1550 nanometers (nm) = 193.41 terahertz (THz)

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• The optical power of a signal can be measured in milliwatts (mW)
• dBm is the optical power expressed in decibels relative to one milliwatt
• Power in dBm = 10 log10 [Optical power (mW)/1mW]
• Examples:
Optical Power mW Optical Power dBm
0.1 mW -10 dBm
1.0 mW 0 dBm
2.0 mW +3 dBm
10 mW +10 dBm
100 mW +20 dBm

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Invention of
first
low-loss
optical fiber
1970
Introduction
of Corning
62.5/125 um
multimode
fiber
1976
1983
1985
1986
Introduction
of Corning
SMF-21 fiber
Introduction
of Corning
SMF/DS
dispersion
shifted fiber
Introduction of
Corning SMF-
28 fiber
1986
Introduction
of Corning
50/125 um
fiber
1994
Introduction of
Corning SMF-
LS non-zero
dispersion
shifted fiber
1998
Introduction of
Corning LEAF
non-zero
dispersion
shifted fiber
with large
effective area
Introduction
of Lucent
TrueWave
non-zero
dispersion
shifted fiber
1993
Introduction of
Lucent TrueWave
RS reduced
slope non-zero
dispersion
shifted fiber
1998

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• The core carries the light signals
• The refractive index difference
between core & cladding confines
the light to the core
• The coating protects the glass
Coating
250 microns
An optical fiber comprises of three sections:
Cladding
125 microns
Core
SMF 8 microns

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n2
n1
Cladding
Core
• Light is weakly guided through index difference between core and cladding
n2-n1
• Single mode is transmitted
• Mode field travels in core and cladding
Intensity Profile

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• Attenuation, two primary loss mechanisms
Absorption loss due to impurities
Scattering loss due to refractive index fluctuations
• Chromatic dispersion:
Wavelengths travel at different speeds (refractive index function of l)
Smears pulses because lasers are not perfectly monochromatic
• Polarization mode dispersion (PMD):
Light travels in two orthogonal modes
If core is nonsymmetric, different modes travel at different speeds
Issue at high bit rates such as 10 Gbps and higher
• Nonlinear effects
Prevalent at higher signal powers

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• The Insertion Loss or Attenuation between transmitter and receiver is
expressed by the difference between the transmitted and received power
• Attenuation expressed in decibels (dB) is a negative gain, calculated by
10 x log10 Prx/Ptx (dB)
• If half the power is lost, this is 3 dB
• Example: Attenuation = 30 dB means transmitter power is 1000 times the
receive power
Transmitter Receiver
Transmit Power = Ptx (mW) Receive Power = Prx (mW)
Lossy optical
component

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• Fiber attenuation expressed in dB/km, calculated by
10 log10 (Ptx/Prx)/L
• Example:
A fiber of 10 km length has Pin = 10 μW and Pout = 6 μW
Its loss expressed in dB is
Fiber loss = 10 log10(10/6) = 2.2 dB
And expressed in dB/km = 0.22 dB/Km
Transmitter Receiver
Transmit Power = Ptx (μW or mW) Receive Power = Prx (μW or mW)
Length = L km

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• Attenuation specified in loss per kilometer (dB/km)
0.40 dB/km @ 1310 nm, 0.25 dB/km @ 1550 nm
• Loss due to absorption by impurities, 1400 nm peak due to OH (water) ions
• Rayleigh scattering loss, fundamental limit to fiber loss
1550
window
1310
window
Rayleigh scattering loss
Fundamental mode
Bending loss
OH Absorption Loss

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Wavelength l
Dispersion
ps/nm-km
20
0
1310 nm 1550nm
• Chromatic dispersion causes a broadening in time of the input signal as it
travels down the length of the fiber.
• The phenomenon occurs because the optical signal has a finite spectral
width, and different spectral components will propagate at different speeds
along the length of the fiber.
• The cause of this velocity difference is that the index of refraction of the fiber
core is different for different wavelengths.
• This is called material dispersion and it is the dominant source of chromatic
dispersion in single-mode fibers.
Variation of Chromatic
Dispersion with
wavelength for Standard
SingleMode fiber
(>95% of installed fiber)

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Standard SingleMode Fiber
>95% installed fiber
Non-zero dispersion shifted fibers (NZDSF)
Lower dispersion in 1550nm window
Wavelength l
Dispersion
ps/nm-km
20
0
1310 nm 1550nm
1530 1540 1550 1560nm
+2
+4
- 2
- 4
Corning LS
Corning DSF
Dispersion
(ps/nm
-km)
Lucent TW+
Corning Leaf

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• Dispersion limitation is defined by the dispersion tolerance of the transmitter
and the receiver
• Total dispersion is calculated from the fiber dispersion characteristics and the
fiber length for any channel or traffic path
• The effect of fiber dispersion should be taken into account in the power
budget as the dispersion penalty budget
• If any channel hit the dispersion limit, the dispersion should be compensated
or the channel signal should be regenerated (O-E-O)
• Doubling of bit rate results in an increase of dispersion penalty of up to four
times

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Distance (Km) =
Dispersion Tolerance of Transponder (ps/nm)
Coefficient of Dispersion of Fiber (ps/nm*km)
Transmission Rate Modulation format
Dispersion
Tolerance
Distance
2.5 Gb/s
External
Modulation
20,000 ps/nm/km ~ 1,100 km
2.5 Gb/s Direct Modulation 2,400 ps/nm/km 140 km
10 Gb/s
External
Modulation
1,200 ps/nm/km 70 km
40 Gb/s
External
Modulation
200 ps/nm/km 12 km
• Dispersion limited transmission distances over SMF fiber (17 ps/nm/km):

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• In fiber the different frequency components of the signal propagate at different speeds
• The effect is signal distortion and intersymbol Interference, the penalty is “eye-closure”
• Can be compensated for by the use of Dispersion Compensation
Eye opening
FOLDING

Tx bit sequence Eye diagram
no dispersion

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• Dispersion generally not an issue below 10Gbps
• Narrow spectrum laser sources (external modulation) and low chirp*
laser sources reduce dispersion penalty. With broad/chirped sources
the different spectral components of the source will see different
dispersions thus broadening the pulse in time
• New fiber types (NZ-DSF) greatly reduce effects
• Dispersion compensation techniques
• Dispersion compensation fiber
• Dispersion compensating optical filters
• Dispersion Compensating Units (DCU) generally placed in mid-
stage access of EDFA to alleviate DCU insertion loss
• *Chirp: frequency of launched pulse changes with time

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• Dispersion Compensating Fiber:
DCUs use fiber with chromatic dispersion of opposite sign/slope and of
suitable length to bring the average dispersion of the link close to zero.
The compensating fiber can be several kilometers in length, the DCU are
typically inserted after each span

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• PMD causes a broadening in time of the optical signal
• In an ideal optical fiber, the core has a perfectly circular cross-section. In this
case, the fundamental light mode has two orthogonal polarizations (orientations
of the electric field) that travel at the same speed through the fiber
• Birefringence (index of refraction variation between two polarization axis) arises
due to random imperfections and asymmetries, causes broadening of the optical
pulse due to the two orthogonal polarization states traveling at different speeds
n1
n2
n1 > n2 refractive index difference due
to mechanical stress

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• The “PMD coefficient”, with units of ps/km1/2, indicates the rate
at which PMD builds up along the fiber length
• Limits optical reach in high-speed transmission systems
• Typical PMD tolerance
2.5 Gbps: typically 40 ps
10 Gbps: typically 10 ps
40 Gbps: typically 2.5 ps (can be larger dependant on
modulation format)
• Power penalty due to PMD (1-2 dB)

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Link PMD:
• Individual fibers have higher PMD values than when concatenated in a link
• The PMD link value determines the statistical upper limit for system PMD
Transmission Rate Distance
2.5 Gb/s 1,000,000 km
10 Gb/s 62,500 km
40 Gb/s 3,906 km
Transmission Rate Distance
2.5 Gb/s 40,000 km
10 Gb/s 2,500 km
40 Gb/s 156 km
ELEAF: PMD spec <0.1 ps/km1/2, PMD Link Value of <0.04 ps/km1/2
Leads to PMD limited system length of:
Old SMF: PMD spec <0.5 ps/km1/2, PMD link value of <0.2 ps/km1/2
Leads to PMD limited system length of:
Examples:

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• Not an issue at 2.5 Gbps
• 2000+ Km at 10 Gbps on typical fiber
• Increase system robustness with Forward Error Correction (FEC) and
optimized transmitter modulation formats
• Deploy PMD-optimized fibers
• Use PMD Compensation (PMDC) (e.g. electronic post processing in
40/100G Optical Module DSP)

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• As long as the optical power density within the optical fiber core is
low, the fiber can be considered a linear medium
• Loss and refractive index are independent of the signal power
• When optical power levels gets fairly high, the fiber becomes a
nonlinear medium
• Loss and refractive index are dependent on the optical power
• High channel count, high bit rate, long reach systems require
higher per channel powers making them susceptible to non-linear
effects

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• Single channels non-linear effects
• Self Phase Modulation (SPM)
• Stimulated Brilliouin Scattering (SBS)
• Multi channel effects
• Four Wave Mixing (FWM)
• Cross Phase Modulation (XPM)
• Stimulated Raman Scattering (SRS)

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Intensity
Time
Slow Phase
Velocity
Fast Phase
Velocity
Optical Pulse
n = n0 + N2
Index of
Refraction
Nonlinear
Coefficient
Light
Intensity
• Non-linearity arises (excluding scattering NLEs) from the
modulation of the refractive index of the fiber through the
interaction of the high optical power
• Intensity of an optical pulse modulates the index of refraction
• Nonlinearity scales as (channel power)2

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• Self Phase Modulation is a single channel effect
• Through the non-linear index, as earlier mentioned, the signal
intensity variation of a channel modulates the fiber’s local refractive
index
• Therefore different parts of the optical signal see different refractive
indexes, and therefore different phase velocities
• The resultant effect on the signal depends on fiber dispersion
• For Dispersion < 0, SPM can add on to chromatic dispersion and
increase temporal broadening of the optical pulses, thus reducing the
dispersion tolerance of the system
• For Dispersion > 0, SPM can narrow the optical pulse and thus
alleviate chromatic dispersion pulse broadening

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No SPM, just Dispersion
SPM + Dispersion < 0
SPM + Dispersion > 0

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• Cross Phase Modulation is a multi-channel effect
• Through the non-linear index adjacent channels also modulate the
fiber’s local refractive index and therefore modulate the phase of the
channel under consideration
• The effect of XPM is to act as a crosstalk penalty
• Increasing channel spacing reduces XPM because dispersion
increases and the individual pulse streams “walk away” from each
other
• Optimized dispersion compensation mapping can also reduce the
effect.

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Out of Fiber
1 2
21-2 22-1
1 2
Into Fiber
• Channels beat against each other to form intermodulation products
• Creates in-band crosstalk that can not be filtered (optically or
electrically)

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Output Spectrum after 25 km of Dispersion Shifted Fiber
Wavelength (nm)
-5
-10
-15
-20
-25
-30
-35
-40
1542 1543 1544 1545 1546 1547 1548
Input Power = +4 dBm/ch
Power
(dBm)

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Channel Spacing (nm)
FWM
Efficiency
(dB)
0.0 0.5 1.0 1.5 2.0 2.5
-50
-30
-10
0
-20
-40
D= 0 ps/nm
D= 17 ps/nm
D= 2 ps/nm
D= 0.2 ps/nm
• FWM effect efficiency strongly dependant on dispersion
• With higher dispersion and greater channel spacing effect negated
• Dispersion Shifted fiber with disp zero in C-band exhibits high FWM penalty
• Uneven channel spacing can reduce effect because intermodulation products
do not fall on channels
2
( )
*
( )
*
FWM
eff
P n
P
A D


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• Effect and consequences
• SRS causes a signal wavelength to behave as a “pump” for longer
wavelengths. Energy is transferred from the shorter to longer wavelengths
• Thus the shorter wavelengths are attenuated by this process and longer
wavelengths amplified
• SRS takes place in the transmission fiber
• SRS (Raman) Amplification
• SRS can be used for amplification in the transmission fiber. Using Raman
pumps it is possible to implement a distributed Raman amplifier
f f
Transmission Fiber

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-50
-45
-40
-35
-30
-25
-20
-15
-10
1528 1532 1536 1540 1544 1548 1552 1556 1560
Wavelength (nm)
Spectrum
(dB)
• Impact of SRS in a DWDM system

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Fabry-Perot Laser
• Spectrally broad linewidth
• Unstable center/peak wavelength
• Characteristic of low-cost SR/IR optics
Distributed Feedback Laser (DFB)
• Dominant single wavelength
• Tighter wavelength control
• Can be externally modulated
• Necessary for DWDM transmission
lc
l
Power
l
Power
lc
Non-DWDM Laser
Characteristic
DWDM Laser
Characteristic

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• Direct modulation
• Directly varying the laser drive current with the information stream to
produce a varying optical output power, “1” and “0”
• Thermal difference between “1” and “0” state creates wavelength shift,
induces spectral broadening of the laser spectrum… “Chirping”
• Spectrally broad, chirped signal has low dispersion tolerance
• External modulation
• High-speed system to minimize undesirable effects, such a chirping
• Modulation achieved through
• separate device, for example Lithium Niobate Mach-Zehnder
interferometer
• or integral part of the laser transmitter, electro-absorption
• Spectrally narrow signal has high dispersion tolerance

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Each modulation format has advantages and disadvantages.
• IM-OOK NRZ: Intensity Modulation – On Off Keying Non Return to Zero
• RZ: return to Zero
• ODB: Optical Duobinary
• (D)PSK: (Differential) Phase Shift Keying
• (D)QPSK: (Differential) Quadrature Phase Shift Keying
• PM-(D)QPSK: Polarization Multiplexing (D)QPSK
0 1 0 1 1 0
0 0 0
Time
NRZ
RZ
( )
Rx
E t
( )
Ix
E t
x̂
0
1
( )
Rx
E t
00
11
10 01
( )
Ix
E t
(D)QPSK
(D)PSK
IM-OOK

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• Measures the degree of impairment when the optical signal is
carried by an optical transmission system that includes optical
amplifiers.
• Optical Signal to Noise Ratio, expressed in dB, is given by the
following:
OSNR=10 x log(Psig/N) + log (Bm/ Br )
• where:
Psig is the optical signal power (mW)
Bm is the resolution bandwidth (nm)
N is the noise power measured in Bm (mW)
Br is the reference optical bandwidth, typically
chosen to be 0.1 nm
• Typical OSNR value in 0.5 nm resolution bandwidth is >10 dB

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TX RX
 With no noise
 With no Inter Symbol Interference
 BER=0 independent of power
• BER is a key objective of Optical System Design
BER is the number of erroneous bits received divided by the total number
of bits transmitted over a stipulated period
• Goal is to get from the Tx to Rx with a BER less than the BER
threshold of the Rx
• Typical minimum acceptable system BER is 10-12 (10-15 with
Forward Error Correction)

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Optical Budget is affected by:
Fiber attenuation
Splices
Patch Panels/Connectors
Optical components (filters, amplifiers, etc)
Bends in fiber
Contamination/dirt on connectors
Link Optical Budget = Ptx – Prx
Where: Ptx = Transmitter output power
Prx = Receiver input sensitivity to achieve required BER performance
Ptx = +3 dBm Prx = -26 dBm
Budget = 29 dB

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• The vertical eye opening shows the ability to distinguish between a
1 and a 0 bit
• The horizontal opening gives the time period over which the signal
can be sampled
FOLDING

Tx bit sequence

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Decision Threshold
“1” Level
“0” Level
What causes bit errors:
• Noise introduced through receivers and amplifiers
• Pulse shape distortion introduced through dispersion and non-linear effects
These contribute to errors in bit detection when determining if a bit is a “1” or a “0”

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• Erbium Doped Fiber Amplifiers (EDFA)
• Operating range: C-band: 1530 to 1565 nm
L-band: 1605 to 1625nm
• Gain up to 30 dB, 1000x amplification for small signals
• High output saturation power up to +27 dBm, 500 mW
• Low signal distortion and cross-talk
• Optically Transparent
 Signal format and Bit rate independent

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Energy = h . 
Fundamental State
Excited State
Pump Photon
at 980 nm
Fundamental State
Transition to a lower energy state
Metastable State
Telecom signal
photon at 1550 nm
Energy = h . 
• The photon generated by the decay of the
Erbuim ion back to Its fundamental state is in
phase with the signal photon that initiated the
Stimulated Emission
+ =
Amplified Telecom
Signal
Photon at 1550 nm
= Erbium Ions

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Signal
Input
980 or 1480 nm
Pump Laser
Erbium
Doped
Fiber
Amplified
Signal
Output
Isolator
WDM Coupler
for pump and
signal
Isolator
• Gain though high power pump laser(s) at either 980nm or 1480nm pumping
into the absorption bands of the erbium ions
• Input and output isolators stop the EDFA “lasing” due to reflected power
passing back through EDFA
• WDM coupler efficiently combines pump and signal wavelengths
Basic EDFA
configuration

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• Gain can be expressed by the ratio of Pout/Pin
• Gain is measured more conveniently in dB , calculated by
10 log10 Pout/Pin
• If the power is doubled by an amplifier, this is +3 dB
• Example: Pout/Pin = 50, Gain = 17 dB
Amplifier
Pin
Pout

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AMP
Gain 14dB
Total Output Power : +2dBm
Per channel
output power
-1dBm
Per channel
input power
-15dBm
AMP
Total Output Power Constant : +2dBm
Total Output
Power +2dBm
Per channel
power -4dBm
Per channel
power -15dBm
AMP
Gain Stays Constant : Gain 14dB
Total Output
Power +5dBm
Per channel
power -1dBm
Per channel
power -15dBm
Constant Gain Mode Constant Power Mode
Total Input Power : -12dBm

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• Automatically corrects amplifier gain for capacity change, ageing
effects, operating conditions
• Keep traffic working after network failures
• Prevent BER degradation due to network degrade
• For DWDM applications Constant Gain mode is preferred
• Constant Power mode suitable for single channel applications

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Ch1
Channel
Power
Ch40
EDFA non-flat
gain spectrum
Non-flat amplified
signal spectrum
Pump bands
Gain band
• Erbium absorption and
emission lines.
• The multiple emission
lines gives rise to the
broad spectrum of the
EDFA

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• EDFAs are the source of noise, Amplified Spontaneous Emission noise
(ASE) in a system
• The difference between the optical power of a channel and the noise
power is called the Optical Signal to Noise Ratio, OSNR
• Between EDFAs, the OSNR stays constant
• The lower the input power to the EDFA the lower the OSNR at the output
• The only way to recover OSNR is via an OEO Regeneration.
• OSNR is tracked on a per channel basis, each channel will have a
different OSNR
Every optical interface (line card, Transponder etc) has a minimum
OSNR specification that must be met

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Agenda
 Why DWDM?
 Optical Basics
 DWDM Technology

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• One traffic channel per fiber pair
• 40 x 2.5 Gbps channels, 80 fibers
STM-16 Tx
STM-16 Rx
STM-16 Tx STM-16 Rx
STM-16 Tx
STM-16 Rx
STM-16 Tx STM-16 Rx
STM-16 Tx
STM-16 Rx
STM-16 Tx STM-16 Rx
STM-16 Tx
STM-16 Rx
STM-16 Tx STM-16 Rx
STM-16 Tx
STM-16 Rx
STM-16 Tx STM-16 Rx
STM-16 Tx
STM-16 Rx
STM-16 Tx STM-16 Rx
STM-16 Tx
STM-16 Rx
STM-16 Tx STM-16 Rx
STM-16 Tx
STM-16 Rx
STM-16 Tx STM-16 Rx

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• DWDM systems use optical devices to combine the output of several
optical transmitters
Optical
fiber pair
TX
Optical
transmitters
Optical
receivers
TX
TX
TX
RX
RX
RX
RX
Transmission
DWDM devices

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• Multiple traffic channels on a fiber pair
• Each channel transmitted on a different wavelength/color prevents
channel interference and allows them to be separated at the receiving end
• 40 x 2.5 Gbps channels, 2 fibers
STM-16 Tx
STM-16 Tx
STM-16 Tx
STM-16 Tx
STM-16 Tx
STM-16 Tx
STM-16 Tx
STM-16 Tx
STM-16 Rx
STM-16 Rx
STM-16 Rx
STM-16 Rx
STM-16 Rx
STM-16 Rx
STM-16 Rx
STM-16 Rx
STM-16 Tx
STM-16 Tx
STM-16 Tx
STM-16 Tx
STM-16 Tx
STM-16 Tx
STM-16 Tx
STM-16 Tx
STM-16 Rx
STM-16 Rx
STM-16 Rx
STM-16 Rx
STM-16 Rx
STM-16 Rx
STM-16 Rx
STM-16 Rx
STM-16 Tx
STM-16 Tx
STM-16 Tx
STM-16 Tx
STM-16 Tx
STM-16 Tx
STM-16 Tx
STM-16 Tx
STM-16 Rx
STM-16 Rx
STM-16 Rx
STM-16 Rx
STM-16 Rx
STM-16 Rx
STM-16 Rx
STM-16 Rx
STM-16 Rx
STM-16 Rx
STM-16 Rx
STM-16 Rx
STM-16 Rx
STM-16 Rx
STM-16 Rx
STM-16 Rx
STM-16 Tx
STM-16 Tx
STM-16 Tx
STM-16 Tx
STM-16 Tx
STM-16 Tx
STM-16 Tx
STM-16 Tx

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DWDM CWDM
Application Long Haul Metro
Amplifiers Typically EDFAs Almost Never
# Channels Up to 80 Up to 8
Channel Spacing 0.4 nm 20nm
Distance Up to 3000km Up to 80km
Spectrum 1530nm to 1565nm 1270nm to 1610nm
Filter Technology Intelligent Passive

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1530.33 nm 1553.86 nm
0.80 nm
195.9 THz 193.0 THz
100 GHz
1530.33 nm 1553.86 nm
0.40 nm
195.9 THz 193.0 THz
50 GHz
• ITU-T l grids are based on 191.7 THz + 100 GHz or + 50 GHz
• It is a standard for the channels in DWDM systems
l
Wavelength

Frequency
100GHz Grid
50GHz Grid
l
Wavelength

Frequency

APJC Optical Sales
Transponder
(O-E-O)
ROADM
OADM OA
OA
Rx Tx
Direct interface
(IPoDWDM)
To client devices
Mux/Demux Mux/Demux
Transponder
(O-E-O)
Animated slide

APJC Optical Sales
Commons
Chassis
Power Supplies
Processors
Optical Service Channel
Layer 0 Transport
ROADMs
Multiplexers / Demultiplexers
Amplifiers, DCU
Layer 1+ Transport
Transponders
Muxponders
Xponders (L2)

APJC Optical Sales
• 40/80 Wavelength DWDM
Metro, Regional, Long Haul scalability
Widely deployed across Carrier, Enterprise, Government, & Education customers
• ROADM Leadership
Leader Worldwide Market Share
Any Fiber Topology (mesh, ring, linear, etc…)
Any-to-Any Wavelength Provisioning
• Service Flexibility
Transponder based Wavelengths
Router/Switch based Wavelengths
Muxponder L1 Aggregation
Xponder L2 Aggregation and Services
• Automation and Intelligence
Automated turn-up, Automated Power Control
Advanced GUI, feature rich performance monitoring

APJC Optical Sales
Point to Point
Physical Ring
Wavelength Mesh
Physical Ring
Wavelength Hub & Spoke
Protected
Point to Point
Physical Mesh
Wavelength Mesh
Dark Fiber
DWDM
Wavelengths
Animated slide

APJC Optical Sales
Client
(router, switch, etc.)
Multiplexer /
Demultiplexer
RX
TX
to next site
This is a simple and effective solution if…
 Distance is less than ~60km
 Client devices support DWDM interfaces
 Client protection (layer 2, layer 3 failover mechanism) is acceptable
 Topology is point-to-point only

APJC Optical Sales
Client
Multiplexer /
Demultiplexer
RX
TX
TX
RX
TX
RX
‘Sponder
Services require
Transponding,
Muxponding, or Xponding
ONS Chassis
Amplifier(s)
Distance and/or loss is
too high for passive
ONS Chassis
same chassis
Services Require Layer 1 (sub-50ms) Protection
One ONS 15454 chassis handles any or all of these features
RX
TX
to next site
Animated slide

APJC Optical Sales
Point to Point
Physical Ring
Wavelength Mesh
Physical Ring
Wavelength Hub & Spoke
Protected
Point to Point
Physical Mesh
Wavelength Mesh
Dark Fiber
DWDM
Wavelengths
Animated slide

APJC Optical Sales
Client
Multiplexer /
Demultiplexer
RX
TX
TX
RX
TX
RX
‘Sponder
Services require
Transponding,
Muxponding, or Xponding
ONS Chassis
ROADM
Physical Network
Topology is a Ring
(3+ nodes) or a Mesh
ONS Chassis
Amplifier(s)
Distance and/or loss is
too high for passive
ONS Chassis
same chassis
Services Require Layer 1 (sub-50ms) Protection
One ONS 15454 chassis handles any or all of these features
to next site
Animated slide

APJC Optical Sales
Traditional OADM Reconfigurable OADM
pass-thru path
add/drop path
A fixed number of channels
A fixed set of channels
Any number of channels (0 to 40/80)
Any set of channels, directional
Physical Ring Only (2 Degree) Physical Ring (2D) or Mesh (Multi-Degree)
Animated slide

APJC Optical Sales
Fixed or Banded Filter Architecture
Traffic Topology is Fixed
Difficult to Upgrade
?
ROADM Architecture
Traffic Topology is Fully Flexible (Any-to-Any)
Non-Disruptive Service Additions
Animated slide

APJC Optical Sales
40ch 2-Degree
• iPLC Technology
• 40 Channels
• Lower insertion loss than 32WSS
32ch 2-Degree
• iPLC Technology
• 32 Channels
• Industry’s first widely deployed
ROADM
Legacy
Two Degrees
80-WXC
• 9x1 3D MEMS WSS
• Core of Mesh ROADM Node
• 80 Channels – 8 Degrees
• Add degrees in-service
40-WXC
• 9x1 3D MEMS WSS
• Core of Mesh ROADM Node
• Add degrees in-service
Multi-Degree
SMR-2
• ROADM + Integrated Pre & Post Amp
• Significant Cabling Reduction
• 50% Space & Power Reduction
SMR-1
• ROADM & Integrated Pre-Amp
• Significant Cabling Reduction
• 45% Space & Power Reduction
Single Module
Animated slide

APJC Optical Sales
8 Degrees
• 40 Channels
• 80 Channels
• Colorless A/D option
4 Degrees
• 40 Channels
• Extremely compact, single slot
• Integrated Pre/Post EDFAs
2 Degrees
• 40 Channels
• Very compact, single slot
• Integrated Pre-EDFA
Animated slide

APJC Optical Sales
• EDFA, ROADM, OSA
combined
• Only one slot required per
degree
• 4-Degree and cost-
optimized 2-Degree
versions
• Very few fibers required,
minimize complexity
• Thousands in service
EDFA
ROADM
OSA

APJC Optical Sales
• Form Factor
40ch ROADM + Amplifiers in a single slot card
Leaves room for service line cards and for ROADM in
smaller footprints
• Price-Point
Allows for ROADM anywhere (and everywhere)
Pay-As-You-Grow pricing option
• Simplicity
Very few fibers required
• Two Versions:
40ch 4-Degree ROADM
ROADM + Pre + Booster Amplifiers
40ch 2-Degree ROADM
ROADM + Pre-Amplifier

APJC Optical Sales
• Total number of line cards for 40ch ROADM 2D Optical Layer: 2
• Total number of cables for 40ch ROADM Optical Layer*: 6
• Total number of optical layer devices (line card + passive): 4
15454-M6
MD-40
15454-M6
MD-40
outside plant
outside plant
All amplifiers are internal to the ROADM

APJC Optical Sales
Local Add/Drop
Direction B
To Next Site
Direction B
To Next Site
Direction A
MD-40
Express
Wavelengths
MD-40
MD-40 MD-40
To Next Site
Direction D
To Next Site
Direction C
Local Add/Drop
Direction A
Mesh Patch Panel

APJC Optical Sales
Omni-Directional – ROADM ports
are not direction specific (re-route
does not require fiber move)
Colorless – ROADM ports are not
frequency specific (re-tuned laser
40-WXC
80-WXC
SMR-2
80-WXC

APJC Optical Sales
15454 MSTP
Embedded Optical
Intelligence
Tunable Laser – Transmit laser
can be provisioned to any frequency
in the C-band (96 channels)
Colorless – ROADM ports are
not frequency specific (re-tuned
laser does not require fiber move)
Tunable Receiver – Coherent
receiver can select one wavelength
among a composite signal (no demux
needed)
Omni-Directional – ROADM ports
are not direction specific (re-route
Contention-less - Same frequency
can be added/dropped from multiple
ports on same device.
Flex Spectrum – Ability to
provision the amount of spectrum
allocated to wavelength(s) allowing
for 400G and 1T channels.
WSON
Wavelength Switched Optical Network
Complete Control in Software, No Physical Intervention Required

APJC Optical Sales
Agenda
 Why DWDM?
 Optical Basics
 DWDM Technology

APJC Optical Sales
0dBm
–5dBm
–25dBm
–30dBm
Transponder Spec
Speed 2.5G
Transmit Power 0 dBm
Receive Power -28 dBm
Dispersion Tolerance 1600 ps/nm
OSNR Tolerance 21dB
Fiber
Type SMF-28
Distance 120 km
Loss per KM .25 dB
Dispersion 16.7 ps/nm*km
Outside of spec

APJC Optical Sales
0dBm
–20dBm
–25dBm
-9dBm
+5dBm
Transponder Spec
Speed 2.5G
OSNR Tolerance 21dB
Fiber
Type SMF-28
Distance 120 km
Loss per KM .25 dB
EDFA
Input Power -9 dBm
Output Power +5 dBm
Gain 11 dB
Noise Figure 6 dB

APJC Optical Sales
0ps/nm
334ps/nm
1670ps/nm
2004ps/nm
Transponder Spec
Speed 2.5G
OSNR Tolerance 21dB
Fiber
Type SMF-28
Distance 120 km
Loss per KM .25 dB
Outside of spec

APJC Optical Sales
DCF
Compensation 1950 ps/nm
Loss 10 dB
+0dBm
334ps/nm
–20dBm
1670ps/nm
–9dBm
+5dBm
0ps/nm
–25dBm
2004ps/nm
–35dBm
54ps/nm
Transponder Spec
Speed 2.5G
OSNR Tolerance 21dB
Fiber
Type SMF-28
Distance 120 km
Loss per KM .25 dB
EDFA
Input Power -9 dBm
Output Power +5 dBm
Gain 11 dB
Noise Figure 6 dB

APJC Optical Sales
DCF
Loss 10 dB
+0dBm
334ps/nm
–20dBm
1670ps/nm
–9dBm
+5dBm
0ps/nm
–25dBm
2004ps/nm
–15dBm
54ps/nm
Transponder Spec
Speed 2.5G
OSNR Tolerance 21dB
Fiber
Type SMF-28
Distance 120 km
Loss per KM .25 dB
EDFA 2
Input Power -35 dBm
Output Power -15 dBm
Gain 20 dB
Noise Figure 6 dB
Noise
OSNR
16.9 dB
Outside of spec

APJC Optical Sales
DCF
Loss 10 dB
Option #1
+0dBm
334ps/nm
–20dBm
1670ps/nm
–9dBm
+5dBm
0ps/nm
–20dBm
2004ps/nm
–15dBm
54ps/nm
Transponder Spec
Speed 2.5G
OSNR Tolerance 21dB
Fiber
Type SMF-28
Distance 120 km
Loss per KM .25 dB
RAMAN
Gain 5 dB
Noise Figure 0 dB
Noise
OSNR
21.9 dB
Add RAMAN

APJC Optical Sales
DCF
Loss 10 dB
Option #2
+0dBm
334ps/nm
–20dBm
1670ps/nm
–9dBm
+5dBm
0ps/nm
–25dBm
2004ps/nm
–15dBm
54ps/nm
Transponder Spec
Speed 2.5G
OSNR Tolerance (E-FEC) 12 dB
Fiber
Type SMF-28
Distance 120 km
Loss per KM .25 dB
Noise
OSNR
16.9 dB
Add FEC to Transponder to
improve ONSR Tolerance

APJC Optical Sales
Agenda
 Why DWDM?
 Optical Basics
 DWDM Technology

APJC Optical Sales
• Following options are available today:
 Passive Point-to-Point Architecture (CWDM or DWDM)
 Active* Point-to-Point Architecture (DWDM only)
 Active* Ring and Mesh Architectures (DWDM only)
• CWDM systems usually limited to passive solutions and short spans due
to performance limitation, protections usually performed on client side
• DWDM systems provide much better performance and scalability,
protection and restoration capabilities is available in DWDM system
* Active mean’s management and control capability
** Reference values as actual performance depends on configuration and performance of optical interfaces
Topology Mode Technology
Single span
Optical budget **
Single span
distance **
System capacity Traffic protection
P2P Passive CWDM 20 dB 80 Km 8 x 2.5G only on client equipment
P2P Passive DWDM 15 dB 60 Km 4 x 100G 1+1, Y-cable, PSM
P2P Passive DWDM 12.5 dB 50 Km 8 x 100G 1+1, Y-cable, PSM
P2P Passive DWDM 8 dB 30 Km 40 x 100G 1+1, Y-cable, PSM
P2P Active DWDM > 30 dB > 130 Km 80 x 100G 1+1, Y-cable, PSM
Ring / Mesh Active DWDM > 30 dB > 130 Km 80 x 100G 1+1, Y-cable, PSM, Restoration

APJC Optical Sales
• DataCenter / SAN extension uses dedicated optical fibers
• Scale limited to optical fiber availability, as separate pair of fiber required to add additional
capacity
• Protection performed at application level and need to have diverse optical paths
• Distances are usually short due to optical performance limitations
Core Site Remote Site
Metro Area
Campus Network
Control and Legacy
TDM,
Voice,
Etc.
TDM,
Voice,
Etc.
Control and Legacy
Branch Network
Service Provider
Direct fiber connection is required.
The same optical cable or diverse paths are used.
Data Center Data Center

APJC Optical Sales
• CWDM or DWDM passive devices can be used to improve optical fiber use, as many
channels can be transported in single optical fiber at the same time
• Distances are limited by optical performance of optical interfaces
• Interface protection can be done, path protection require diverse optical path
Metro Area
Campus Network
Control and Legacy
TDM,
Voice,
Etc.
Branch Network
Service Provider
TDM,
Voice,
Etc.
Control and Legacy
Single pair of optical fiber
CWDM or DWDM optical MUX/DEMUX
Colored interfaces are used on client equipment

APJC Optical Sales
• In DWDM systems Optical Service Channel (OSC) can be added to control optical fiber
loss, perform management automation as well to provide management access to remote
site
Metro Area
Campus Network
Control and Legacy
TDM,
Voice,
Etc.
Branch Network
Service Provider
TDM,
Voice,
Etc.
Control and Legacy
Optical Service Channel perform
span loss measurement and enable
management connectivity between nodes
O
S
C
O
S
C

APJC Optical Sales
• PSM module measure power level of signal and perform protection switching in case if
power level falls beyond specified threshold.
• Provide simplest optical protection solution
• Unit introduce significant amount of attenuation as result in many cases optical
amplification is required
Metro Area
Campus Network
Control and Legacy
TDM,
Voice,
Etc.
Branch Network
Service Provider
TDM,
Voice,
Etc.
Control and Legacy
PSM Provide simplest protection against fiber cuts
O
S
C
O
S
C
P
S
M
P
S
M

APJC Optical Sales
• CWDM or DWDM passive devices can be used to improve optical fiber use, as many
channels can be transported in single optical fiber at the same time
• Distances are limited by optical performance of optical interfaces
• Both port protection and part protection are available, protection switching performed on
client side
Metro Area
Campus Network
Control and Legacy
TDM,
Voice,
Etc.
Branch Network
Service Provider
Data Center
TDM,
Voice,
Etc.
Control and Legacy
Data Center
Diverse optical paths can be used for
protection, protection switching performed
on client equipment
O
S
C
O
S
C
O
S
C
O
S
C

APJC Optical Sales
• WDM Transponders can be used to:
 Connect devices which doesn’t support CWDM or DWDM interfaces
 Aggregate multiple client signals into single optical channel
 Gain improvement in optical performance (extend reach)
 Perform optical protection switching with guaranteed sub 50 ms connection recovery
Metro Area
Campus Network
Control and Legacy
TDM,
Voice,
Etc.
Branch Network
Service Provider
TDM,
Voice,
Etc.
Control and Legacy
Transponder’s can be used to achieve
sub 50ms protection switching between
two optical paths
T
X
P
T
X
P
T
X
P
T
X
P
O
S
C
O
S
C
O
S
C
O
S
C

APJC Optical Sales
• Optical amplification can be added to extend distance between sites in cases when
distance or fiber loss are too high for passive system.
• Together with OSC amplifiers are able to automatically adjust to changes in fiber loss
without need to manually change settings in the system
Metro Area
Campus Network
Control and Legacy
TDM,
Voice,
Etc.
Branch Network
Service Provider
TDM,
Voice,
Etc.
Control and Legacy
Optical amplification can significantly
extend reach of DWDM systems.
Single span can reach 250-300km.
T
X
P
T
X
P
T
X
P
T
X
P
O
S
C
O
S
C
O
S
C
O
S
C

APJC Optical Sales
• Use of ROADM allow to support ring architectures and most used configuration today in
DWDM networks due to simplicity and easy to use together with scale options
• High level of integration allow to have all necessary components (OPM, Amplifiers) in
single card, providing compact and simple for management solution
• Can be upgraded/extended to cover more advanced configurations or topologies
Metro Area
Campus Network
Control and Legacy
TDM,
Voice,
Etc.
Branch Network
Service Provider
TDM,
Voice,
Etc.
Control and Legacy
ROADM allow to support ring
topologies with possibility to
bypass channels without patching
T
X
P
T
X
P
T
X
P
T
X
P
O
S
C
O
S
C
O
S
C
O
S
C

APJC Optical Sales
• In Regional / LH DWDM networks Transponders or IPoDWDM cards are used to meet
performance requirements and support error-free transmission on long distances
• OSC is required to provide access to intermediate optical amplification (OLA) sites
• EDFA and Raman amplifiers are used for optical signal amplification
• No generic designs as any design is unique and depends on specific customer requirements
Metro Area
Campus Network
Control and Legacy
TDM,
Voice,
Etc.
Branch Network
Service Provider
TDM,
Voice,
Etc.
Control and Legacy
Intermidiate amplification sites are
controlled via OSC and support
efficient transmission of the signal
T
X
P
T
X
P
T
X
P
T
X
P
O
S
C
O
S
C
O
S
C
O
S
C
O
S
C
O
S
C
O
S
C
O
S
C
O
S
C
O
S
C

APJC Optical Sales
• Flexible Optical Transport
Flexible Service Options – Any Service, Anywhere
Low Latency Optical Network Architecture
L2+ Services, L1 Wavelength Services, Encryption
Carrier Class Quality and Reliability
Simplified Management and Planning Tools
Virtually Unlimited Bandwidth & Scale
• Industry leading 100G Solution
• Industry Leader in Packet + DWDM Convergence
• Industry’s Most Compact ROADM Solution
• End to End Management with Cisco Prime

APJC Optical Sales
Closing
Today we have discussed
 Why DWDM?
 Optical Basics
 DWDM Technology

383934148-DWDM-101-Introduction-to-DWDM-2-pdf.pdf

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