Dwdm Basics 4m74f
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Contents
Introduction Definition of DWDM Why we choose DWDM? Discrete transmission vs DWDM Types of Multiplexing Optical Network components Optical Fiber Interfaces to DWDM
ethio telecom
UIL Program
2
Introduction The demand for internet services and the growth of
data traffic has devoured more and more bandwidth. Multiple forms of traffic place increasingly heavy
burdens on fiber networks, pushing carriers look for innovative ways to send more data through existing fiber.
ethio telecom
UIL Program
3
Dense Wave Division Multiplexing (DWDM) is one of
the several key developments that have emerged to exploit and extend the capability of current fiber optic systems in significant ways.
ethio telecom
UIL Program
4
Contents
Introduction Definition of DWDM Why we choose DWDM? Discrete transmission vs DWDM Types of Multiplexing Optical Network components Optical Fiber Interfaces to DWDM
ethio telecom
UIL Program
5
Definition of DWDM Dense wavelength division multiplexing (DWDM) is a
fiber – optic transmission technique that employs light wavelengths to transmit different types of traffic at the same time through a single fiber line. introduced in 1995, splits light waves into different frequencies of infrared light, with each frequency capable of transmitting data at high speeds.
ethio telecom
UIL Program
6
Many systems in use today have reached 80 different
wavelengths (hence the term 'dense'), per fiber, which effectively multiplies the capacity of the network by 80 fold. Current newest equipment splits light waves into as many as 160 channels, carrying on each channel up to 40 Gb/s of traffic.
ethio telecom
UIL Program
7
Content
Introduction Definition of DWDM Why we choose DWDM? Discrete transmission vs DWDM Types of Multiplexing Optical Network components Optical Fiber Interfaces to DWDM
ethio telecom
UIL Program
8
Why we choose DWDM? The challenges of Today’s Telecom. Network Requirement of enormous amount of bandwidth capacity to provide the services demanded by consumers. Coping with fiber exhaust in major portions of networks. Challenge of deploying and integrating diverse technologies in one physical infrastructure.
ethio telecom
UIL Program
9
Resolving capacity crisis One way to alleviate fiber exhaust is to lay more fiber. The second one is to increase the bit rate using time
division multiplexing (TDM), i.e. increases the capacity of a fiber by slicing time into
smaller intervals so that more bits (data) can be transmitted per second ( STM1, STM4,… STM 64)
ethio telecom
UIL Program
10
ethio telecom
UIL Program
11
The third choice to solve the problem is dense
wavelength division multiplexing (DWDM). which increases the capacity of embedded fiber by first
asg incoming optical signals to specific frequencies (wavelength, lambda) within a designated frequency band and then multiplexing the resulting signals out onto one fiber.
ethio telecom
UIL Program
12
DWDM combines multiple optical signals so that they
can be amplified as a group and transported over a single fiber to increase capacity. Each signal carried can be at a different rate (STM-1, STM-4, STM-16, etc.) and in a different format (SDH, ATM, data, etc.)
ethio telecom
UIL Program
13
ethio telecom
UIL Program
14
Consider a highway analogy where one fiber can be
thought of as a multilane highway. Traditional TDM systems use a single lane of this
highway and increase capacity by moving faster on this single lane. DWDM is analogous to accessing the unused lanes on the highway
ethio telecom
UIL Program
15
ethio telecom
UIL Program
16
Capacity Expansion Potential Using DWDM service providers can establish a grow-
as-you-go infrastructure gives service providers the flexibility to expand capacity
in any portion of their networks - an advantage no other technology can offer.
ethio telecom
UIL Program
17
Incremental growth DWDM provides a graceful network evolution for
service providers who seek to address their customers' ever-increasing capacity demands. service providers to reduce their initial costs significantly while deploying the network infrastructure (DWDM) that will serve them in the long run.
ethio telecom
UIL Program
18
Content
Introduction Definition of DWDM Why we choose DWDM? Discrete transmission vs DWDM Types of Multiplexing Optical Network components Optical Fiber Interfaces to DWDM
ethio telecom
UIL Program
19
Discrete Transmission vs DWDM Traditional SDH, T/IP, ATM, and voice over
Internet Protocol (VoIP) are transmitted over discrete channels, each requiring a fiber pair between the end points. This traditional SDH method requires ‘n’ regenerators to condition the signals across each fiber path between each of the ‘m’ nodes, a total of ‘m x n’ regenerators.
ethio telecom
UIL Program
20
Discrete transmission
ethio telecom
UIL Program
21
DWDM Dense wavelength division multiplexing systems
allow many discrete transport channels to be carried over a single fiber pair.
ethio telecom
UIL Program
22
Service Provider Advantages The service provider uses an existing installed fiber
plant more effectively by incorporating DWDM systems. The service provider reduces the cost per bit sent and received over the network by reducing the number of regenerators. DWDM infrastructure can carry multi-service traffic of all types over a single fiber line
ethio telecom
UIL Program
23
Content
Introduction Definition of DWDM Why we choose DWDM? Discrete transmission vs DWDM Types of Multiplexing Optical Network components Optical Fiber Interfaces to DWDM
ethio telecom
UIL Program
24
Types of Multiplexing Multiplexing is sending multiple signals or streams of
information through a circuit at the same time in the form of a single, complex signal and then recovering the separate signals at the receiving end. FDM
TDM WDM
ethio telecom
UIL Program
25
Time Division Multiplexing It is a method of combining multiple independent
data streams into a single data stream by merging the signals according to a defined sequence. Each independent data stream is reassembled at the receiving end based on the sequence and timing. SDH, ATM, IP are based on TDM
ethio telecom
UIL Program
26
TDM
Time Division multiplexing ethio telecom
UIL Program
27
Wavelength Division Multiplexing WDM combines multiple optical TDM data streams
onto one fiber through the use of multiple wavelengths of light. Each individual TDM data stream is sent over an individual laser transmitting a unique wavelength of light.
ethio telecom
UIL Program
28
WDM
Wavelength Division multiplexing ethio telecom
UIL Program
29
Types of WDM CWDM (Coarse Wavelength Division Multiplexing) CWDM typical uses 20 nm spacing and multiplexes up to 18 channels It is used for lower bit rate short distance metropolitan area application (50 Km) It uses range of wavelengths specified in ITU-T Reco. G.694.2
ethio telecom
UIL Program
30
ITU-T G.694.2
ethio telecom
UIL Program
31
DWDM DWDM (Dense Wavelength Division Multiplexing) It multiplexes up to 160 wavelengths with 0.4 nm channel spacing It is used for high bit rate long distance back bone transmission It uses range of wave lengths stipulated in the ITU-T Recom. G.692
ethio telecom
UIL Program
32
ITU-T G.692 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 ethio telecom
UIL 1545.32 Program
33
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
ethio telecom Program
UIL
34
Integrated vs Open DWDM System 155MSDH 622MSDH 2.5G SDH 10G SDH PDH IP ATM 155MSDH 622MSDH 2.5G SDH 10G SDH PDH IP ATM
Open
O T U G.692
G.692
O M U
Integrated
OTU: Optical Transponder Unit OMU: Optical Multiplexing Unit ethio telecom
UIL Program
35
Operating 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
ethio telecom
1200
1400
UIL Program
1600 Wavelength (nm) 36
Operating windows 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
ethio telecom
UIL Program
37
Working wavelength in 1550 nm window
C Band: 1530nm~1565nm L Band: 1565nm~1625nm
ethio telecom
UIL Program
38
40λ DWDM System Working wavelength range: C band (1530 nm ~ 1565 nm) Frequency range: 192.1 THz ~ 196.0 THz Channel interval: 100 GHz Central frequency offset: ±20 GHz (at rate lower than 2.5
Gbit/s); ±12.5 GHz (at rate 10 Gbit/s)
ethio telecom
UIL Program
39
80λ DWDM System Working wavelength range: C band (1530 nm ~ 1565 nm) Frequency range: C band (192.1 THz ~ 196.0 THz) Channel interval: 50 GHz Central frequency offset: ±5 GHz
ethio telecom
UIL Program
40
160λ DWDM System Working wavelength range: C band (1530 nm ~ 1565 nm)
+ L band (1565 nm ~ 1625 nm) Frequency range: C band (192.1 THz ~ 196.0 THz) + L band (190.90 THz ~ 186.95 THz) Channel interval: 50 GHz Central frequency offset: ±5 GHz
ethio telecom
UIL Program
41
Content
Introduction Definition of DWDM Why we choose DWDM? Discrete transmission vs DWDM Types of Multiplexing Components of optical Network Optical Fiber Interfaces to DWDM
ethio telecom
UIL Program
42
Components of Optical networks
ethio telecom
UIL Program
43
Components of Optical networks Transmitter (Transmit transponder) Multiplexer/de-multiplexer Amplifiers Optical fiber (media) Receiver (receive transponder)
ethio telecom
UIL Program
44
Transmitter and receivers Light emitters and light detectors are active devices at opposite ends of an optical transmission network. Light detectors perform the opposite function of light emitters. They are receive-side opto-electronic devices that convert light pulses into electrical signals.
ethio telecom
UIL Program
45
Optical multiplexing/de-multiplexing Optical multiplexer takes optical wavelengths from multiple light sources and converges them into one beam. De-multiplexers separate the received beam into its wavelength components and coupling them to individual light detectors.
ethio telecom
UIL Program
46
Optical Multiplexing/De-multiplexing Techniques A simple form of multiplexing or de-multiplexing of light can be done using a prism.
ethio telecom
UIL Program
47
Optical Multiplexing/De-multiplexing Techniques Another technology is based on the principles of diffraction and of optical
interference.
ethio telecom
UIL Program
48
Optical Multiplexing/De-multiplexing Techniques Arrayed waveguide gratings (AWGs) are also based on diffraction principles.
ethio telecom
UIL Program
49
Optical Multiplexing/De-multiplexing Techniques A different technology uses interference filters in devices called thin film filters or
multilayer interference filters.
ethio telecom
UIL Program
50
Optical Add/Drop Multiplexer An optical add/drop multiplexer (O) performs drop or
insert of one or more wavelengths at some point along the transmission span, rather than combining or separating all wavelengths, the O can drop some while ing others on. Os are similar in many respects to SDH , except that only optical wavelengths are added and dropped, and no conversion of the signal from optical to electrical takes place.
ethio telecom
UIL Program
51
O
ethio telecom
UIL Program
52
Optical Amplifier (OA) The OA has made it possible to amplify all the
wavelengths at once and without optical-electricaloptical (OEO) conversion. Optical amplifiers also can be used to boost signal power after multiplexing or before de-multiplexing
ethio telecom
UIL Program
53
Erbium Doped Fiber Amplifier Erbium is a rare-earth element that, when excited, emits light
around 1.54 micrometers—the low-loss wavelength for optical fibers used in DWDM. A weak signal enters the erbium-doped fiber, into which light at 980 nm or 1480 nm is injected using a pump laser. This injected light stimulates the erbium atoms to release their stored energy as additional 1550-nm light. As a result down the fiber the signal strength grows stronger.
ethio telecom
UIL Program
54
EDFA (Erbium Doped Fiber Amplifier)
ethio telecom
UIL Program
55
Content
Introduction Definition of DWDM Why we choose DWDM? Discrete transmission vs DWDM Types of Multiplexing Components of optical Network Optical Fiber Interfaces to DWDM
ethio telecom
UIL Program
56
Optical Fiber The main job of optical fibers is to guide light waves
with a minimum of attenuation (loss of signal). Optical fibers are composed of fine threads of glass in layers, called the core and cladding that can transmit light at about two-thirds the speed of light in a vacuum.
ethio telecom
UIL Program
57
Optical Fiber Coat i ng
Cl addi ng
Cor e
n1
n2 n1: refractive index of core n2: refractive index of cladding n1>n2 ethio telecom
UIL Program
58
Propagation of light through fiber The transmission of light in optical fiber is commonly explained using the principle of total internal reflection. Light is either reflected (it bounces back) or refracted
(its angle is altered while ing through a different medium) depending upon the angle of incidence (the angle at which light strikes the interface between an optically denser and optically thinner material).
ethio telecom
UIL Program
59
Total Internal Reflection Total internal reflection happens when the following
conditions are met: Beams from a more dense to a less dense material. The incident angle is less than the critical angle (the critical angle is the angle of incidence at which light stops being refracted and is instead totally reflected).
ethio telecom
UIL Program
60
Reflection vs Refraction
ethio telecom
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61
Principle of Total Internal reflection
ethio telecom
UIL Program
62
Multimode and single-mode fiber
Multimode fiber, has a larger core than single-
mode. It gets its name from the fact that numerous modes, or light rays, can be carried simultaneously through the waveguide.
ethio telecom
UIL Program
63
single-mode, has a much smaller core that allows only
one mode of light at a time through the core As a result, the fidelity of the signal is better retained over longer distances, and modal dispersion is greatly reduced.
ethio telecom
UIL Program
64
Types of single mode fiber Non-dispersion-shifted fiber (NDSF), G.652 Dispersion-shifted fiber (DSF), G.653 Non-zero dispersion-shifted fiber (NZ-DSF), G.655
ethio telecom
UIL Program
65
Transmission Challenges Transmission of light in optical fiber presents several
challenges that must be dealt with. These fall into the following three broad categories: Attenuation—decay of signal strength or loss of light power,
as the signal propagates through the fiber Chromatic dispersion—spreading of light pulses as they travel down the fiber Nonlinearities—cumulative effects from the interaction of light with the material through which it travels
ethio telecom
UIL Program
66
Attenuation
ethio telecom
UIL Program
67
Dispersion Dispersion is the spreading of light pulses as they
travel down optical fiber.
ethio telecom
UIL Program
68
Chromatic Dispersion Chromatic dispersion occurs because different
wavelengths propagate at different speeds. chromatic dispersion has two components, material
dispersion and waveguide dispersion.
ethio telecom
UIL Program
69
Chromatic Dispersion
ethio telecom
UIL Program
70
Polarization mode Dispersion Polarization mode dispersion (PMD) is caused by non circular (oval) shape of the fiber during manufacturing or from external stressors.
Most single-mode fibers two perpendicular polarization modes,
a vertical one and a horizontal one. Due to geometrical and pressure asymmetry, two polarization modes have different transmission rates, resulting in delay and PMD. PMD is generally not a problem at speeds below 10 Gb/s (STM-64).
ethio telecom
UIL Program
71
Non-Linear Effects Nonlinear effects tend to manifest themselves when
optical power is goes beyond some level. The most important types of nonlinear effects are
stimulated Brillouin scattering, stimulated Raman scattering, self-phase modulation, and four-wave mixing.
ethio telecom
UIL Program
72
Stimulated Brillouin Scattering Output Power
Scattering Power Input Power ethio telecom
UIL Program
73
Stimulated Raman scattering
SRS affect results in attenuation of signals with short
wavelength and reinforcement of signals with long wavelength. P
P
Input
Output
ethio telecom
UIL Program
74
Self Phase Modulation (SPM) Due to dependency relationship
between refractive index and light intensity, refractive index changes during optical pulse continuance, with pulse peak phase delayed for both front and rear edges. With more transmission distance, phase shift is accumulated continuously and represents large phase modulation upon certain distance. As a result, spectrum spreading results in pulse spreading, which is called SPM.
Intensity
Pulse width before transmission
Intensity
Pulse width after transmission
ethio telecom Program
Optical spectrum before transmission
UIL
Optical spectrum after transmission
75
Four wave Mixing (FWM)
FWM refers to a physical process of energy exchange between
multiple optical carriers caused by the non-linear effect of fiber, when multiple frequencies of optical carriers with high power are simultaneously transmitted in the fiber. FWM results in optical signal energy attenuation in multiplexing channels and channel crosstalk.
ethio telecom
UIL Program
76
Content
Introduction Definition of DWDM Why we choose DWDM? Discrete transmission vs DWDM Types of Multiplexing Components of optical Network Optical Fiber Interfaces to DWDM
ethio telecom
UIL Program
77
Interfaces to DWDM DWDM systems
Standard SDH/SONET IP ATM signals
By converting incoming optical signals into the precise
ITU-standard wavelengths to be multiplexed, transponders are currently a key determinant of the openness of DWDM systems.
ethio telecom
UIL Program
78
Integrated vs Open DWDM sys. Integrated DWDM system Within the DWDM system a transponder converts the
client optical signal from optical back to an electrical signal and converts its client's signal to ITU-T standard stable wavelength to be multiplexed optically.
ethio telecom
UIL Program
79
155MSDH 622MSDH 2.5G SDH 10G SDH PDH IP ATM
O T U
155MSDH 622MSDH 2.5G SDH 10G SDH PDH IP ATM
G.692
G.692
O M U
Integrated Intfc
Open (ive Intfc.)
ethio telecom
UIL Program
80
Integrated vs Open DWDM sys. Open DWDM System Open DWDM system designs include ive interfaces,
which accept the ITU-compliant light directly from an attached switch or router with an optical interface without being interfaced the transponder interface.
ethio telecom
UIL Program
81
ethio telecom
UIL Program
82
Introduction Definition of DWDM Why we choose DWDM? Discrete transmission vs DWDM Types of Multiplexing Optical Network components Optical Fiber Interfaces to DWDM
ethio telecom
UIL Program
2
Introduction The demand for internet services and the growth of
data traffic has devoured more and more bandwidth. Multiple forms of traffic place increasingly heavy
burdens on fiber networks, pushing carriers look for innovative ways to send more data through existing fiber.
ethio telecom
UIL Program
3
Dense Wave Division Multiplexing (DWDM) is one of
the several key developments that have emerged to exploit and extend the capability of current fiber optic systems in significant ways.
ethio telecom
UIL Program
4
Contents
Introduction Definition of DWDM Why we choose DWDM? Discrete transmission vs DWDM Types of Multiplexing Optical Network components Optical Fiber Interfaces to DWDM
ethio telecom
UIL Program
5
Definition of DWDM Dense wavelength division multiplexing (DWDM) is a
fiber – optic transmission technique that employs light wavelengths to transmit different types of traffic at the same time through a single fiber line. introduced in 1995, splits light waves into different frequencies of infrared light, with each frequency capable of transmitting data at high speeds.
ethio telecom
UIL Program
6
Many systems in use today have reached 80 different
wavelengths (hence the term 'dense'), per fiber, which effectively multiplies the capacity of the network by 80 fold. Current newest equipment splits light waves into as many as 160 channels, carrying on each channel up to 40 Gb/s of traffic.
ethio telecom
UIL Program
7
Content
Introduction Definition of DWDM Why we choose DWDM? Discrete transmission vs DWDM Types of Multiplexing Optical Network components Optical Fiber Interfaces to DWDM
ethio telecom
UIL Program
8
Why we choose DWDM? The challenges of Today’s Telecom. Network Requirement of enormous amount of bandwidth capacity to provide the services demanded by consumers. Coping with fiber exhaust in major portions of networks. Challenge of deploying and integrating diverse technologies in one physical infrastructure.
ethio telecom
UIL Program
9
Resolving capacity crisis One way to alleviate fiber exhaust is to lay more fiber. The second one is to increase the bit rate using time
division multiplexing (TDM), i.e. increases the capacity of a fiber by slicing time into
smaller intervals so that more bits (data) can be transmitted per second ( STM1, STM4,… STM 64)
ethio telecom
UIL Program
10
ethio telecom
UIL Program
11
The third choice to solve the problem is dense
wavelength division multiplexing (DWDM). which increases the capacity of embedded fiber by first
asg incoming optical signals to specific frequencies (wavelength, lambda) within a designated frequency band and then multiplexing the resulting signals out onto one fiber.
ethio telecom
UIL Program
12
DWDM combines multiple optical signals so that they
can be amplified as a group and transported over a single fiber to increase capacity. Each signal carried can be at a different rate (STM-1, STM-4, STM-16, etc.) and in a different format (SDH, ATM, data, etc.)
ethio telecom
UIL Program
13
ethio telecom
UIL Program
14
Consider a highway analogy where one fiber can be
thought of as a multilane highway. Traditional TDM systems use a single lane of this
highway and increase capacity by moving faster on this single lane. DWDM is analogous to accessing the unused lanes on the highway
ethio telecom
UIL Program
15
ethio telecom
UIL Program
16
Capacity Expansion Potential Using DWDM service providers can establish a grow-
as-you-go infrastructure gives service providers the flexibility to expand capacity
in any portion of their networks - an advantage no other technology can offer.
ethio telecom
UIL Program
17
Incremental growth DWDM provides a graceful network evolution for
service providers who seek to address their customers' ever-increasing capacity demands. service providers to reduce their initial costs significantly while deploying the network infrastructure (DWDM) that will serve them in the long run.
ethio telecom
UIL Program
18
Content
Introduction Definition of DWDM Why we choose DWDM? Discrete transmission vs DWDM Types of Multiplexing Optical Network components Optical Fiber Interfaces to DWDM
ethio telecom
UIL Program
19
Discrete Transmission vs DWDM Traditional SDH, T/IP, ATM, and voice over
Internet Protocol (VoIP) are transmitted over discrete channels, each requiring a fiber pair between the end points. This traditional SDH method requires ‘n’ regenerators to condition the signals across each fiber path between each of the ‘m’ nodes, a total of ‘m x n’ regenerators.
ethio telecom
UIL Program
20
Discrete transmission
ethio telecom
UIL Program
21
DWDM Dense wavelength division multiplexing systems
allow many discrete transport channels to be carried over a single fiber pair.
ethio telecom
UIL Program
22
Service Provider Advantages The service provider uses an existing installed fiber
plant more effectively by incorporating DWDM systems. The service provider reduces the cost per bit sent and received over the network by reducing the number of regenerators. DWDM infrastructure can carry multi-service traffic of all types over a single fiber line
ethio telecom
UIL Program
23
Content
Introduction Definition of DWDM Why we choose DWDM? Discrete transmission vs DWDM Types of Multiplexing Optical Network components Optical Fiber Interfaces to DWDM
ethio telecom
UIL Program
24
Types of Multiplexing Multiplexing is sending multiple signals or streams of
information through a circuit at the same time in the form of a single, complex signal and then recovering the separate signals at the receiving end. FDM
TDM WDM
ethio telecom
UIL Program
25
Time Division Multiplexing It is a method of combining multiple independent
data streams into a single data stream by merging the signals according to a defined sequence. Each independent data stream is reassembled at the receiving end based on the sequence and timing. SDH, ATM, IP are based on TDM
ethio telecom
UIL Program
26
TDM
Time Division multiplexing ethio telecom
UIL Program
27
Wavelength Division Multiplexing WDM combines multiple optical TDM data streams
onto one fiber through the use of multiple wavelengths of light. Each individual TDM data stream is sent over an individual laser transmitting a unique wavelength of light.
ethio telecom
UIL Program
28
WDM
Wavelength Division multiplexing ethio telecom
UIL Program
29
Types of WDM CWDM (Coarse Wavelength Division Multiplexing) CWDM typical uses 20 nm spacing and multiplexes up to 18 channels It is used for lower bit rate short distance metropolitan area application (50 Km) It uses range of wavelengths specified in ITU-T Reco. G.694.2
ethio telecom
UIL Program
30
ITU-T G.694.2
ethio telecom
UIL Program
31
DWDM DWDM (Dense Wavelength Division Multiplexing) It multiplexes up to 160 wavelengths with 0.4 nm channel spacing It is used for high bit rate long distance back bone transmission It uses range of wave lengths stipulated in the ITU-T Recom. G.692
ethio telecom
UIL Program
32
ITU-T G.692 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 ethio telecom
UIL 1545.32 Program
33
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
ethio telecom Program
UIL
34
Integrated vs Open DWDM System 155MSDH 622MSDH 2.5G SDH 10G SDH PDH IP ATM 155MSDH 622MSDH 2.5G SDH 10G SDH PDH IP ATM
Open
O T U G.692
G.692
O M U
Integrated
OTU: Optical Transponder Unit OMU: Optical Multiplexing Unit ethio telecom
UIL Program
35
Operating 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
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Operating windows 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
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Working wavelength in 1550 nm window
C Band: 1530nm~1565nm L Band: 1565nm~1625nm
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40λ DWDM System Working wavelength range: C band (1530 nm ~ 1565 nm) Frequency range: 192.1 THz ~ 196.0 THz Channel interval: 100 GHz Central frequency offset: ±20 GHz (at rate lower than 2.5
Gbit/s); ±12.5 GHz (at rate 10 Gbit/s)
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80λ DWDM System Working wavelength range: C band (1530 nm ~ 1565 nm) Frequency range: C band (192.1 THz ~ 196.0 THz) Channel interval: 50 GHz Central frequency offset: ±5 GHz
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160λ DWDM System Working wavelength range: C band (1530 nm ~ 1565 nm)
+ L band (1565 nm ~ 1625 nm) Frequency range: C band (192.1 THz ~ 196.0 THz) + L band (190.90 THz ~ 186.95 THz) Channel interval: 50 GHz Central frequency offset: ±5 GHz
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Content
Introduction Definition of DWDM Why we choose DWDM? Discrete transmission vs DWDM Types of Multiplexing Components of optical Network Optical Fiber Interfaces to DWDM
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Components of Optical networks
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Components of Optical networks Transmitter (Transmit transponder) Multiplexer/de-multiplexer Amplifiers Optical fiber (media) Receiver (receive transponder)
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Transmitter and receivers Light emitters and light detectors are active devices at opposite ends of an optical transmission network. Light detectors perform the opposite function of light emitters. They are receive-side opto-electronic devices that convert light pulses into electrical signals.
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Optical multiplexing/de-multiplexing Optical multiplexer takes optical wavelengths from multiple light sources and converges them into one beam. De-multiplexers separate the received beam into its wavelength components and coupling them to individual light detectors.
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Optical Multiplexing/De-multiplexing Techniques A simple form of multiplexing or de-multiplexing of light can be done using a prism.
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Optical Multiplexing/De-multiplexing Techniques Another technology is based on the principles of diffraction and of optical
interference.
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Optical Multiplexing/De-multiplexing Techniques Arrayed waveguide gratings (AWGs) are also based on diffraction principles.
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Optical Multiplexing/De-multiplexing Techniques A different technology uses interference filters in devices called thin film filters or
multilayer interference filters.
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Optical Add/Drop Multiplexer An optical add/drop multiplexer (O) performs drop or
insert of one or more wavelengths at some point along the transmission span, rather than combining or separating all wavelengths, the O can drop some while ing others on. Os are similar in many respects to SDH , except that only optical wavelengths are added and dropped, and no conversion of the signal from optical to electrical takes place.
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O
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Optical Amplifier (OA) The OA has made it possible to amplify all the
wavelengths at once and without optical-electricaloptical (OEO) conversion. Optical amplifiers also can be used to boost signal power after multiplexing or before de-multiplexing
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Erbium Doped Fiber Amplifier Erbium is a rare-earth element that, when excited, emits light
around 1.54 micrometers—the low-loss wavelength for optical fibers used in DWDM. A weak signal enters the erbium-doped fiber, into which light at 980 nm or 1480 nm is injected using a pump laser. This injected light stimulates the erbium atoms to release their stored energy as additional 1550-nm light. As a result down the fiber the signal strength grows stronger.
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EDFA (Erbium Doped Fiber Amplifier)
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Content
Introduction Definition of DWDM Why we choose DWDM? Discrete transmission vs DWDM Types of Multiplexing Components of optical Network Optical Fiber Interfaces to DWDM
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Optical Fiber The main job of optical fibers is to guide light waves
with a minimum of attenuation (loss of signal). Optical fibers are composed of fine threads of glass in layers, called the core and cladding that can transmit light at about two-thirds the speed of light in a vacuum.
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Optical Fiber Coat i ng
Cl addi ng
Cor e
n1
n2 n1: refractive index of core n2: refractive index of cladding n1>n2 ethio telecom
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Propagation of light through fiber The transmission of light in optical fiber is commonly explained using the principle of total internal reflection. Light is either reflected (it bounces back) or refracted
(its angle is altered while ing through a different medium) depending upon the angle of incidence (the angle at which light strikes the interface between an optically denser and optically thinner material).
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Total Internal Reflection Total internal reflection happens when the following
conditions are met: Beams from a more dense to a less dense material. The incident angle is less than the critical angle (the critical angle is the angle of incidence at which light stops being refracted and is instead totally reflected).
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Reflection vs Refraction
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Principle of Total Internal reflection
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Multimode and single-mode fiber
Multimode fiber, has a larger core than single-
mode. It gets its name from the fact that numerous modes, or light rays, can be carried simultaneously through the waveguide.
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single-mode, has a much smaller core that allows only
one mode of light at a time through the core As a result, the fidelity of the signal is better retained over longer distances, and modal dispersion is greatly reduced.
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Types of single mode fiber Non-dispersion-shifted fiber (NDSF), G.652 Dispersion-shifted fiber (DSF), G.653 Non-zero dispersion-shifted fiber (NZ-DSF), G.655
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Transmission Challenges Transmission of light in optical fiber presents several
challenges that must be dealt with. These fall into the following three broad categories: Attenuation—decay of signal strength or loss of light power,
as the signal propagates through the fiber Chromatic dispersion—spreading of light pulses as they travel down the fiber Nonlinearities—cumulative effects from the interaction of light with the material through which it travels
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Attenuation
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Dispersion Dispersion is the spreading of light pulses as they
travel down optical fiber.
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Chromatic Dispersion Chromatic dispersion occurs because different
wavelengths propagate at different speeds. chromatic dispersion has two components, material
dispersion and waveguide dispersion.
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Chromatic Dispersion
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Polarization mode Dispersion Polarization mode dispersion (PMD) is caused by non circular (oval) shape of the fiber during manufacturing or from external stressors.
Most single-mode fibers two perpendicular polarization modes,
a vertical one and a horizontal one. Due to geometrical and pressure asymmetry, two polarization modes have different transmission rates, resulting in delay and PMD. PMD is generally not a problem at speeds below 10 Gb/s (STM-64).
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Non-Linear Effects Nonlinear effects tend to manifest themselves when
optical power is goes beyond some level. The most important types of nonlinear effects are
stimulated Brillouin scattering, stimulated Raman scattering, self-phase modulation, and four-wave mixing.
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Stimulated Brillouin Scattering Output Power
Scattering Power Input Power ethio telecom
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Stimulated Raman scattering
SRS affect results in attenuation of signals with short
wavelength and reinforcement of signals with long wavelength. P
P
Input
Output
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Self Phase Modulation (SPM) Due to dependency relationship
between refractive index and light intensity, refractive index changes during optical pulse continuance, with pulse peak phase delayed for both front and rear edges. With more transmission distance, phase shift is accumulated continuously and represents large phase modulation upon certain distance. As a result, spectrum spreading results in pulse spreading, which is called SPM.
Intensity
Pulse width before transmission
Intensity
Pulse width after transmission
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Optical spectrum before transmission
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Optical spectrum after transmission
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Four wave Mixing (FWM)
FWM refers to a physical process of energy exchange between
multiple optical carriers caused by the non-linear effect of fiber, when multiple frequencies of optical carriers with high power are simultaneously transmitted in the fiber. FWM results in optical signal energy attenuation in multiplexing channels and channel crosstalk.
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Content
Introduction Definition of DWDM Why we choose DWDM? Discrete transmission vs DWDM Types of Multiplexing Components of optical Network Optical Fiber Interfaces to DWDM
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Interfaces to DWDM DWDM systems
Standard SDH/SONET IP ATM signals
By converting incoming optical signals into the precise
ITU-standard wavelengths to be multiplexed, transponders are currently a key determinant of the openness of DWDM systems.
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Integrated vs Open DWDM sys. Integrated DWDM system Within the DWDM system a transponder converts the
client optical signal from optical back to an electrical signal and converts its client's signal to ITU-T standard stable wavelength to be multiplexed optically.
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155MSDH 622MSDH 2.5G SDH 10G SDH PDH IP ATM
O T U
155MSDH 622MSDH 2.5G SDH 10G SDH PDH IP ATM
G.692
G.692
O M U
Integrated Intfc
Open (ive Intfc.)
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Integrated vs Open DWDM sys. Open DWDM System Open DWDM system designs include ive interfaces,
which accept the ITU-compliant light directly from an attached switch or router with an optical interface without being interfaced the transponder interface.
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