Light tree is a point to multi point all optical channel which may span multiple fiber links Enables single-hop communication between a source node and a set of destination nodes

1. WELCOME
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2. LIGHT TREES
SEMINAR COORDINATORS
Mr. UNNIKRISHANAN.P
Mrs. CHAITHANYA RAJ
PRESENTED BY
GAYATHRI DEVI.K.V
S7 ECE
ROLL NO : 22
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3. CONTENTS
 INTRODUCTION
 BLOCK DIAGRAM
 TYPES OF WDM
 COMPARISON BETWEEN CWDM AND DWDM
 LIGHT PATH
 LIGHT TREE
 ARCHITECTURE OF WAVELENGTH ROUTED OPTICAL NETWORKS
 MUTICAST SWTICHED ARCHITECTURES
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4. CONTINUATION…
 OPTICAL LAYER
 TRAFFIC MECHANISMS
 LIGHT TREE PROBLEM FORMULATIONS
 ADVANTAGES
 DISADVANTAGES
 APPLICATIONS
 CONCLUSION
 REFERENCE
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5. INTRODUCTION
 In near future wide area networks(WAN) will be based on Wavelength Division
Multiplexed(WDM) optical networks
 Physical topology networks can be classified into three generations
 1st generation: Networks employs copper-based or microwave technology
E.g. : Ethernet
 2nd generation: Networks use optical fibres for data transmission but switching is
performed in electronic domain
E.g.: FDDI
 3rd generation :Networks with both data transmission and switching is performed in
optical domain
E.g.: WDM14 July 2017 DEPT OF ECE 5

6. BLOCK DIAGRAM
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7. CONTINUATION…
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8. TYPES OF WDM
 Coarse Wavelength Division
Multiplexing(CWDM)
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9. CONTINUATION…
 Dense Wavelength Division
Multiplexing(DWDM)
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10. COMPARISON BETWEEN CWDM AND
DWDM
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11. LIGHT PATH
 Optical channel which may be used to carry circuit switched traffic
 May span multiple fibre links
 Can create logical(or virtual) neighbours
 Light path carries direct traffic between nodes it interconnects
 Major objective of light path communication is to reduce the number of hops
 Under light path communication the network employs an equal number of
transmitters and receiver because light path operates on point to point basis
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12. LIGHT TREE
 Light tree is a point to multipoint all optical channel which may span multiple
fibre links
 Enables single-hop communication between a source node and a set of destination
nodes
 Light tree based network topology can reduce the hop distance, thereby increasing
the network through put
 In general light tree is a point to multipoint extension of light path
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13. ARCHITECTURE OF WAVELENGTH-
ROUTED OPTICAL NETWORKS
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14. LIGHT TREE EXAMPLE
Architecture of wavelength-routed
network and layered graph
representation
 (a) represents a light path on
wavelength λ1 from node A to node
C, and a light path on wavelength
λ2 from node A to node F
 (b) represents layered-graph model
with three wavelength layers
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15. CONTINUATION…
 WDM network requires efficient delivery of broadcast and multicast
applications
 Modelled as a layered graph which represents a wavelength
 Each physical fibre has a corresponding link on each layer
 Switching state of each wavelength-routing switch(WRS) is managed by
controller
 Employ tuneable lasers and filters at access nodes and optical/electronic
switches at routing nodes
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16. MULTICAST SWITCHED
ARCHITECTURES
LINEAR DIVIDER COMBINER(LDC)
 Two input fibres(Pi’s) and two output
fibres (Po’s) two dividers and two
combiners
 Power of one output signal is less than or
equal to 1/n of input signal
 Acts as generalised optical switch with the
added function of multicasting and
broadcasting
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17. MWRS BASED ON A SPLITTER
BANK
 Optical splitter is a passive device
 Splits input signal to multiple identical
output signals
 Support four wavelengths on each fibre
link
 Information on each incoming link is first
demultiplexed into separate wavelengths
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18. CONTINUATION ……
 Separate signals each on separate wavelengths are switched by the optical switch
(OSW)
 Signals that do not need duplication are sent directly to output ports
 Signals that need to be duplicated are sent to a port connected to a splitter bank.
 Provide optical signal amplification, wavelength conversion and signal
regeneration for multicast as well as unicast applications
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19. MWRS BASED ON A
“DROP AND CONTINUE” SWITCH
 Light path can be terminated at node
 Identical copy of light path allowed to continue in another node
Constructed a chain of node connected by a drop and continue light path
All nodes on the chain will receive transmissions on a drop and continue light
path where light is dropped
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20. OPTICAL LAYER
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 Optical layer provides light paths to the higher layers
 Have the following features
• Transparency
• Reliability
• Wavelength reuse
• Virtual topological network
• Circuit switching

21. TRAFFIC MECHANISMS
 Unicast traffic
 Broadcast traffic
 Multicast traffic
UNICAST TRAFFIC
Sent from a single source to single destination IP address
Used by IP/TV on demand
Each user request program at different time
Limited by band width
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22. CONTINUATION....
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23. BROADCAST TRAFFIC
 Uses a special IP address to sends data,
sends single stream data to all machines
in local network
 Broadcast address typically ends in 255
e.g.: 192.0.2.255
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24. MULTICAST TRAFFIC
 Used by IP/TV scheduled programs
 Reach unlimited number of users
 No overloading of network
 User can decide to receive or ignore
data
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25. LIGHT TREE PROBLEM
FORMULATIONS
Here a problem formulation of a light tree based on unicast traffic it requires following inputs:
 Physical topology Gp=(V,Ep) consisting of a weighted undirected graph
Where,
V is the set of network nodes
Ep is the set of links connecting nodes
Undirected means that each link in the physical topology is bi-directional
 Number of wavelength channels carried by each fibre =W
 NxN traffic matrix, where N is the number of network nodes
 (i,j)th element is the average rate of traffic flow from node i to node j
 Number of wavelength tuneable lasers as (Ti) and wavelength tuneable filters as (Ri) at each node
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26. ADVANTAGES
 Data security
 Ease of installation
 Eliminating spark hazards
 High Bandwidth(up to 50 terabits per second) over long distances
 Significantly reduce hop distance
 Minimize total number of transceivers in a network
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27. DISADVANTAGES
 Difficulties arising from limited number of wavelengths
 Requires special skills
 Fragile
 Opaqueness
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28. APPLICATIONS
 Teleconferencing
 Video conferencing
 Internet NEWS distribution
 Internet television
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29. FUTURE ENHANCEMENT
Wavelength cost could be minimized
Wavelength assignment algorithm should be explored in future
research
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30. CONCLUSION
 Novel WDM architecture based light tree are capable of supporting broadcasting
and multicasting
 Employing minimum number of optoelectronic devices
 Can provide very high bandwidth optical layer which efficiently routes unicast ,
broadcast and multicast packet switch traffic
 If we employ a set of light trees, then significant savings can be achieved in terms
of number optoelectronic devices in the network
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31. REFERENCE
 Laxman H. Sahasrabudhe and Biswanth Mukherjee, Light trees :Optical
Multicasting For Improved Performance in Wavelength-Routed networks,IEEE
Communication Magazine. February pp.67-73
 Biswanth Mukherjee, Dhritiman Banerjee, S. Ramamurthy And Amaranth
Mukherjee, The Principles for Designing a wide-area WDM Optical Network,
IEEE/ACM
 Laxman H. Sahasrabudhe, Light trees: An Optical Layer for Tomorrow’s IP
Networks, Rajiv Ram swami and kumara N. Sivarajan Optical Networks. Pp.333-
336.
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32. THANK YOU ……
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33. QUERIES ????
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