1. Optical communications & networking - an Overview
By:
Mr. Gaurav Verma
Asst. Prof.
ECE
NIEC

2. Communication Systems
Basic Blocks
Coverage and Topology
Three basic components
Source and Transmitter
Destinations and Receiver
Communication channel (medium)
Communication channel
Wired
Wireless
Glass
Water and or materials
Coverage (public network)
LAN
MAN
WAN
Topology
Bus
Ring
Mesh
Star

3. Changing Service Landscape
Network characteristics
Full redundancy
Fast restoration
High availability ( %)
Low latency
High bandwidth
Dynamic allocation and high bandwidth efficiency
Support various services
More providers and equipment builders (due to Deregulation of the telecom industry)
Providers are expected to provide more services at higher capacity at lower prices!
A positive feedback business model!
Need for high capacity network
More users

4. Service Types Two basic service types (switching technologies)
Connection-oriented
Connectionless
Based on circuit switching (setup, connect, tear-down)
Example: Public Switching Telephone Network (PSTN)
Originally only supported voice
Not good for bursty traffic
Based on sending datagrams
Examples: Packet, massage, burst switching
Improves bandwidth and network utilization

5. Multiplexing
Transmitting several signals over a single communications channel
Multiplexing technologies
Frequency Division Multiplexing (modulating data into different carrier frequencies)
Wavelength Division Multiplexing
Time division Multiplexing (dividing available time among various signals)
Statistical Multiplexing (dynamic allocation of time spaces depending on the traffic pattern)
Statistical Multiplexing
Requires buffering resulting in variable delay
Many packets will have to be buffered
Packets will have to be delayed
Some packets may be lost
Guarantee of Service (QoS)

6. Multiplexing

7. Optical Fiber
Allowing transmission of information using pulses of light
Advantages
High bandwidth
Low noise
Low interference (electromagnetic)
Optical fiber installation
Measured in fiber sheath-miles (or fiber miles)
Example: we install 3 fiber cable within 10 mile long route; each fiber cable has 20 fibers  we have 600 fiber miles 30 cables
Currently more than 1.5 billion kilometers of optical fiber is deployed around the world [1]
The circumference of earth is 40,000 Km!
[1]

8. Evolution of Optical Networks – First Generation
Started in 1980
Limited to fiber optic transmission systems – the rest of the system was electrical
Thus, the electronic was the major bottleneck!
The received optical data had to be dropped and then transmitted – this was a point-to-point system
Example: Synchronous Optical Network (SONET) and Synchronous Digital Hierarchy (SDH), Fiber Distributed Data Interface (FDDI), Fiber Channel
These systems where based on Optical TDM (10Gb/s and 40Gb/s)
Higher capacity systems were build using WDM technology (1 Tb/s) – remember a single phone line is only 60 Kb/s!)

9. Evolution of Optical Networks – Second Generation
WADM
Incoming optical signals could be switched in optical domain (optical switching)
No longer limited to point-to-point
Underlying technologies included
Optical Add-Drop Multiplexers (OADM)
Optical crossconnets (OXC)
Optical line terminals (OLT)
Wavelength Add/Drop Multiplexer (WADM)
Dense WDM (DWDM)
Examples
FTTH, FTTC, ROADM
OXC

10. Evolution of Optical Networks – Third Generation
All optical packet switching
All packets are processed in optical domain
Transparent to the service
Handle any arbitrary bit rate
Underlying technologies
Optical buffering!
Fast switching
So far, no optical networks have been available!

11. Optical Networking

12. Comparing Different Optical Nodes
Optical Packet Switching

13. Layering Model The layering Model for the IP
Open Systems Interconnection (OSI) Seven-Layer Reference Model
The layering Model for the IP

14. Protocol Suites and Layering Models
Physical Layer (Layer 1)
specify details about the underlying transmission medium and hardware
all specifications related to electrical properties, radio frequencies, and signals belong in layer 1
Network Interface (or Data Link) Layer (Layer 2)
Network (physical) addresses
maximum packet size that a network can support
protocols used to access the underlying medium 14 14

15. Protocol Suites and Layering Models
Internet Layer (Layer 3)
protocols specifying communication across the Internet & routing specifications (spanning multiple interconnected networks)
Logical addressing and path determination
Transport Layer (Layer 4)
Includes specifications on
controlling the maximum rate a receiver can accept data (flow control)
mechanisms to avoid network congestion
techniques to insure that all data is received in the correct order
Remember: Each layer contains its own specifications & protocols! 15 15

16. Protocol Suites and Layering Models
Application Layer (Layer 5)
specify how a pair of applications interact when they communicate
specify details about
the meaning of messages that applications can exchange
the procedures to be followed to execute the application
Some examples of network applications in layer 5
exchange
file transfer
web browsing
telephone services
and video teleconferencing 16 16

17. How Data Passes Through Layers
Each computer has a
layered protocols

18. IP over ATM over SONET

19. IP over SONET

20. IP over WDM