SONET Second Generation Optical Network
Wavelength Routing Network
WRA Prole! Ne"t Generation Optical Networks Optical Packet Switching Network
Elastic Optical Network
which transmission links are made up optical
fibers, and its architecture is designed to exploit
the optical fiber advantages
s!stems
 
n most existing networks optical technolog! is used onl! to transport  
signals across links and most processing  is carried out electricall! %emands man! expensive Optical to Electronic to Optical -OEO.
conversions Not bit rate transparent Classic example is an S%/ -S!nchronous %igital /ierarch!. ring
0ibre 1inks
 
NETWORKING
 6        
Shifting to the Cloud… Enterprise and personal IT are moving to
the cloud computing
Service Providers become
“All Play” providers…
-+./ 0 IP at 1" -++2 levels with *+, 'ideo
#3na!ic Tra))ic
S%/ " Sonet Networks
ncrease capacit! 5oint$to$point C7%2"%7%2 8p to 9) channels :;"&)< channels
2.5G CWDM, DWDM
10G 40 Channels
OA%2 7%2 over OTN &)< channels
40G 80 Channels
5 over 7%2 2esh topolog!  ASON <251S$based O%8 basednetworks &)<"9)< channels,
read! for &))< coherent
5lug and pla!
N=2 3OA%2 configuration
<ridless 3OA%2 9))<"&T
transceivers 0ull! automated
History and roadmap
Optical Network Architecture
5etropolitan network > consists of a metro access network and a metro
interoffice network > The access network extends from a central office to
individual businesses or homes > ts reach is t!picall! a few kilometers > Traffic is collected from customer premises and
hubbed into the central office > The intero))ice network connects groups of central
offices within a cit! or region > spans a few kilometers to several tens of kilometers
between offices
regions and spans hundreds to thousands of kilometers
between nodes
metro interoffice and long$haul networks is based on a
meshed topolog!
T%2= Time %ivision 2ultiplexing -eg car traffic.
SC2= Sub$Carrier 2ultiplexing -eg 3adio"T@ channels.
S20= Single$2ode 0iber -core6µm.
220= 2ulti$2ode 0iber -core;)µm.
1750= 1ow$7ater$5eak 0iber  
%0'= %istributed 0eedback 1aser  
Niagara Falls…
transmission and to provide capacity
 All the switching and other intelligent network
functions were handled by electronics
  e.g SONET, SDH, FDDI, fiber channel
 
well defined standards and bit rates up *9 Tb"s
These s!stems where based on Optical T%2 -&)<b"s and
9)<b"s.
 pleiosynchronous digital hierarchy (PDH)
FEAT8RES OF SONET
/igh$speed optical transport network 2ultiplexing in electrical level using T%2  All the clocks in the network are perfectl!
s!nchroniBed Eas! to extract low stream data 'it rates are integral multiples of basic bit rate
Efficient protection and restoration 2ulti$vendor networks Transmission bandwidth management
 
 
the  photonic(/ optical  ), the section , the line , and the
 path  layer. They correspond to both the physical and
the data link layers.
Each synchronous transfer signal STS-N  is composed of 8000
frames. Each frame is a two-dimensional matrix of bytes with 9
rows by 90 N columns.
SONET frames
signal labeling& tracing
Transport o%erhead bytes that carry networ' management information
(ser data information plus 9 bytes
of path o%erhead
STS-1, like other STS signals, sends 8000 frames per second.
Each STS-1 frame is made of 9 by (1 × 90) bytes. Each byte is
made of 8 bits. The data rate is
 
STS-3, like other STS signals, sends 8000 frames per second.
Each STS-3 frame is made of 9 by (3 × 90) bytes. Each byte
is made of 8 bits. The data rate is
Data rate for STS*+ signals
 
9IT RATE STAN#AR# 0 SONET
The basic building block of SONET is called STS0.  -S!nchronous Transport Signal. with ;&+9 2bps data rate
  /igher$rate SONET signals are obtained b! b!te$
interleaving N  STS$& frames, which are scrambled converted to an Optical Carrier 1evel N  -O$0N. signal
SONET basic bit rate STS$&  ;&+9 2b"s
STS $D   &;;;: 2b"s -;&+9 D.
STS$&:  *::)+ 2b"s -;&+9 &: .
 
&;99 2b"s
 
lower$speed streams
>  8ser pa!load is mapped in S5E in a hierarchical and
organiBed manner  >  Several siBes of blocks of columns are known as @irtual
Tributaries
 
> Number of @Ts ma! fit in a S5E > @Ts are mapped in larger containers known as groups
9 @T&;
D @T: : @TD
 @T defines a maximum bit rate for a clientHs pa!load, as an example,
a @T&; contains :G b!tes transmitted in &:; µs, resulting to bit rate up
to &G:+ 2b"s
Prole! .:
0ind the number of voice channels that could be multiplexed to STS I
&6: SONET signal
%S& &;99 kb"s :9 voice channel
@T&; :9 @oice channel
  G
&6*
 
Prole! -=
*9 AT2 streams at 9+D+9 2b"s and D: AT2 streams at &96G*) 2b"s are mapped into STS$&6: SONET stream The rest of the SONET stream is mapped with %S& streams carr!ing voice channels /ow man! voice channels are transmitted b! the %S& stream
Ans:
 *9 AT2 streams at 9+D+9 2b"s occup! *9 STS$& stream
D: AT2 streams at &96G*) 2b"s occup! D: STS$D stream
  or D:JD ( 6* STS$&
Total STS$& stream ( *9F6* ( &*) STS$&
&*) STS$& are occupied b! AT2 streams - mapped into STS$&6: SONET stream.
0ree space ( &6: I &*) ( D: STS$& streams
Each STS$& stream can carr! 9JG(:+ %S& signal
Each %S& signal carries :9 voice channels
So, Total voice channel transmitted b! the %S& signal
:+J:9JD: ( :&;)9 voice channels
@T group
 
Objetives:
–To provide a resilient network against failures. It becomes an essential requirement during the design of high speed optical networks
– To offer a reliable service when large volume of traffic is transmitted even in the presence of failures and anomalous operation.
Frequently faults:
– Disruption of service (software)
– Catastrophic events (flooding, fire)
is assigned its own dedicated bandwidth in the
network over which it can be rerouted in case of a
failure.
fail
can share protection their bandwidth. This helps
reduce the amount of bandwidth needed in the
network for protection.
  the traffic remains on the protect path until it is
manually switched back onto the original working
path, usually by a user through the network
management system.
automatically switched back from the protect path
onto the working path.
> unidirectional protection switching:  each direction of traffic is handled independent of the other.
in the event of a single fiber cut, only one direction of traffic is switched over to the protection fiber, and the other direction remains on the original working fiber.
> bidirectional protection switching:  both directions are switched over to the protection fibers.
 the switching becomes bidirectional by default because both directions of traffic are lost when a fiber is cut
PROTECTION SCHEMES
In the event of failure the traffic is routed by
path switching:the connection is rerouted
end to end from its source to its destination
along an alternate path.
a spare link between the nodes adjacent to the
failure.
a ring between the nodes adjacent to the
failure.
protection from the source to the destination.
If that fiber is cut, the destination simply switches over to
the other fiber and continues to receive data.
very fast and requires no signaling protocol between the two
ends.
traffic is transmitted over only one fiber at a time,
through the working fiber.
If that fiber is cut, the source and destination both
switch over to the other protection fiber.
 APS protocol is required for signaling between the
source and destination. This is added overhead which
slows down the process.
they incorporate protection mechanisms that
automaticallydetect failures and reroute traffic
away from failed links and nodes onto other
routes rapidly.
add/drop multiplexers
the ring as well as protect the traffic against
failures.
Types of ring architectures
 Aunidirectional ring carries workingtraffic in only one direction of the ring.
  two-fiber unidirectional path-switched rings (UPSR)
 Abidirectional ring carries working traffic in both directions.
  four-fiber bidirectional line-switched rings (BLSR/4),
two-fiber bidirectional line-switched rings (BLSR/2).
 
-T&o fi0er PSR/
> One of the fibers is considered the working fiber and the other the protection fiber >Traffic is transmitted simultaneousl! on the working fiber in the clockwise direction
.
-
/
;
-T&o*fi0er or four*fi0er 1LSR/
 
NETWORKSNETWORKS
networks performs switching and routing in optical
domain.
considers the introduction of a new level in a
layered network model:the optical layer
Second-generation optical networks have routing,
switching and intelligence in theoptical layer.
 
key network elements  optical line terminals
multiplexes multiple wavelengths into a single fiber and demultiplexes a set of wavelengths on a single fiber into separate fibers.
OLTs are used at the ends of a point-to-point WDM link.
optical add/drop multiplexers (OADMs) takes in signals at multiple wavelengths and selectively drops some of these wavelengths and let others pass through.
It also selectively adds wavelengths to the composite outbound signal.
 
optical crossconnects(OXCs)  An OXC essentially performs a similar function as OADM
but at much larger sizes.
OXCs have a large number of ports (ranging from a few
tens to thousands) and are able to switch wavelengths
from one input port to another.
Both OADMs and OXCs may incorporate wavelength
conversion capabilities.
 
) The state of the art is to use 80 wa%elengths on one fiber& but
systems using from *+ to ,0 wa%elengths are more common
) ith each wa%elength capable of carrying 0 /bs& the increase
in capacity of 112 is impressi%e& though costly
1ense a%elength 1i%ision 2ultiplexing
 
defined as follows:
lightpath requests,determine a routeand
possible number of wavelengths.
(RWA)
To establish a lightpath, need to determine:  A route Corresponding wavelengths on the route
RWA problem can be divided into two sub- problems: Lightpath Routing (LR) Wavelength Assignment (WA)
Static vs. dynamic lightpath establishment
 
advance
needed for the traffic when setting up the
network
connection in an off-line manner
 
DYNAMIC LIGHTPATH
ESTABLISHMENT (DLE)
Suitable for dynamic traffic Traffic matrix is not known in advance while network topology is known
 
 
The LR problem is to find routes for a collection of
lightpaths The objective of the LR problem is to minimize the
maximum, over all fiber links, of the number of lightpaths
using a fiber link.
 An alternative objective of the LR problem is to minimize
some network cost such as bandwidth, ports, switching, or
regenerator cost.
The WA problem is, given a collection of lightpaths and
their routes, to assign wavelengths to the lightpaths.
The objective is to minimize, over all fiber links, the
maximum wavelength used on a fiber link.
 
ROUTING AND WAVELENGTH ASSIGNMENT
To solve the LR problem, route the lightpaths one at a
time in some order. Routes can be computed by using shortest path routing
algorithms on the network topology.
The network topology has weights assigned to each link, so
that the shortest path is the least-weight path.
The link weights are chosen so that the resulting lightpath
routes meet the objective of the LR problem.
 
 ASSIGNMENT For the WA problem, the assignments must obey the
following constraints:
wavelength on a given link.
 2. If no wavelength conversion is available through a
switch, then a lightpath must be assigned the same
wavelength on the links through the switch.
 3. If no wavelength conversion is available in the network,
then a lightpath must be assigned the same wavelength all
along its route.
lightpath connection
each lightpath connection and choose one of them
Exhaust routing: use all the possible paths
 
network state
capability, wavelength assignment is trivial
For the network with wavelength continuity
constraint, use heuristics approach
integer numbers
assigned
each wavelength
each wavelength
maximize the possibility of future connections.
RCL will choose the wavelength which minimize
the relative capacity loss.
Random-1. For a lightpath request between two nodes, choose at
random one of the available wavelengths on a fixed shortest
path between the two nodes.
Random-2. Fix two shortest paths between every pair of nodes. For a
lightpath request between two nodes, choose at random one
of the available wavelengths on the first shortest path
between the two nodes. If no such wavelength is available,
choose a random one of the available wavelengths on the
second shortest path.
Construct a graph G(V, E), so that each lightpath in
the system is represented by a node in graph G.
There is an undirected edge between two nodes in
graph G if the corresponding lightpaths pass through a
common physical fiber link.
Color the nodes of the graph G such that no two
adjacent nodes have the same color.
 
 
0uture applications with unknown reKuirements
0lexible and efficient optical networks to support existing, emerging and
future applications
 
3EL83E2ENTS
C833ENT SO18TON 0O3 'AN%7%T/$
NTENS@E A551CATONS Optical virtual concatenation -O@C. for high capacit! end$to$end connection -super$wavelength.
%emultiplex  the demand to smaller ones such as &)) or 9) <b"s, which can still fit in the fixed grid -nverse multiplexing.
Several wavelengths are grouped and allocated end$to$end according to the application bandwidth reKuirements
<rouping occurs at the client la!er without reall! affecting the network
 
 
%3@E3S 0O3 %E@E1O5N< T/E EONS
Support for 9)) <b"s, &Tb"s and other high bit rate demands
%isparate bandwidth needs= properl! siBe the spectrum for each
demand based on its bit rate the transmission distance
Tighter channel spacing= freeing up spectrum for other demands
 
3each vs spectral efficienc! trade$off= bandwidth variable transmitter
can adust to a modulation format occup!ing less optical spectrum for
short EO5 and still perform error$free due to the reduced impairments
%!namic networking= the optical la!er can now response directl! to
variable bandwidth demands from the client la!ers
 
The optical spectru! can e divided up )le"il3
Courtes!= Ori <erstel, EEE Comm 2ag :)&:
 
The transceivers can generate elastic optical paths -EO5s. that is,
paths with variable bit rates
E1ASTC O5TCA1 NET7O34N<
 
EMA251E
400 !"s 200 !"s 400 !"s#00 !"s #00 !"s
#$000 km #$000 km #$000 km
0ixed format, grid
5ath length
'it rate
Conventional   design
-3SA. Input: Network topolog3> tra))ic !atri"> ph3sical la3er !odels
Output: Routes and spectru! allocation RSA
2inimiBe utiliBed spectrum and"or number of transponders, and"orP
Satisf! ph!sical la!er constraints
utilizes slots around reference frequency
 expands /contractsits spectrum to follow the traffic variations
 A slot is assigned to only one connection at a given time instant
Slots are shared among connections at different time instants
Spectrum Expansion/Contraction(SEC) policy
Next Generation Access Networks (NGANs) Long-Reach Passive Optical networks for Metropolitan network consolidation
Optical Wireless networks convergence Optical network architectures and protocols design for wireless backhauling
Medium Access Control (MAC) protocols and algorithms for NGPONs
System Level design for centralised Optical Wireless networks
 
dynamic spectrum allocation in elastic optical networks
Design of low power, low latency, high throughput,
optical interconnect network architectures connecting
racks within data centres and high performance
computers
 
NETWORKS
optical network evolves to the ultimate goal of end-to-end wavelength services.
Impact can be measured in two ways   -economic impact