Introduction to Optical Networks

1. Introduction to Optical Networks Ajmal Muhammad, Robert Forchheimer Information Coding Group ISY Department

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

3. Changing Service Landscape • Network characteristics • Full redundancy • Fast restoration • High availability (99.999 %) • 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 • Connection-oriented • Based on circuit switching (setup, connect, tear-down) • Example: Public Switching Telephone Network (PSTN) • Originally only supported voice • Not good for bursty traffic • Connectionless • Based on sending datagrams • Examples: Packet, message, burst switching • Improves bandwidth and network utilization

5. Optical Fiber • Allowing transmission of information using light • Advantages • High bandwidth • Low noise • Low interference (electromagnetic) • Optical fiber installation • Measured in fiber sheath-km (or fiber km) • Example: we install 3 fiber cable within 10 km long route; each fiber cable has 20 fibers  we have 600 fiber km • 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] http://www.corning.com/opticalfiber/innovation/futureoffiber/index.aspx

6. Multimedia over Fiber • Fiber carries various media • Voice(SONET/Telephony) - The largest traffic • Video (TV) over • Hybrid Fiber Coaxial (HFC) or • Fiber-Twisted Pair/Digital Subscriber Loops (DSL) • Data – Internet traffic ‘Triple Play’ The Information Revolution would not have happened without the Optical Fiber

7. Network Architecture

8. Elements of a Fiber Optic Link

9. Elements of OPTICOM System • The Fiber – that carries the light • Single Mode Fiber (only one EM mode exists), offers the highest bit rate, most widely used • Multi Mode Fiber (multiple EM modes exist), hence higher dispersion (due to multiple modes) cheaper than SMF, used in local area networks • Step Index Fiber – two distinct refractive indices • Graded Index Fiber – gradual change in refractive index

10. Elements of OPTICOM System • Optical Transmitter converts the electrical information to optical format (E/O) • Light Emitting Diode (LED): cheap, robust and used with MMF in short range applications • Surface emitting and edge emitting LED • LASER Diode: high performance and more power, used with SMF in high speed links • Distributed Feedback (DFB) Laser – high performance single mode laser • Fabry-Perot (FP) lasers – low performance multimode laser

11. Elements of OPTICOM System • Optical Receiver convertsthe optical signal into appropriate electrical format (E/O) • PIN Photo Diode: Low performance, no internal gain, low cost, widely used • Avalanche Photo Diode (APD): High performance with internal (avalanche) gain • Repeater: receives weak light signal, cleans-up, amplifies and retransmits (O/E/O) • Optical Amplifier: Amplifies light in fiber without O/E/O

12. Development of Optical Networks • First-generation optical networks • Transmission in the optical domain (to provide capacity) • Example: SONET network (Synchronous Optical Network) • Second-generation optical networks • Wavelength routed network (Optical Circuit Switching OCS) • More functionality in the optical domain (optical networking) Some of the routing, switching and intelligence is moving into the optical domain • Third-generation: optical networks (?)

13. Optical Networks

14. Transmission Window

15. Transmission Bands & Capacities Shannon theorem

16. WDM Grids ITU-T G.694.1

17. Overview of WDM • A characteristic of WDM is that the discrete wavelengths form an orthogonal set of carriers that can be separated, routed, and switched without interfering with each other. • WDM networks require a variety of passive and active devicesto combine, distribute, isolate, and amplify optical power at different wavelengths.

18. Optical Amplifier and EDFA

19. Inside an EDFA

20. Layered Model for Today’s Networks Current protocol stacks

21. Current Multiple Protocol Stacks 22% bandwidth used for protocol overhead

22. Towards a two Layer Network Architecture A perfect combination Flexibility Capacity Less latency Higher bandwidth utilization

23. The optical layer provides lightpath service to it’s client layers • Lightpath: optical connection • An optical channel trail between two nodes that carries the entire traffic within a wavelength The Optical Layer Client layers

24. Optical Layer Service: Providing Lightpaths • Bandwidth • Adaptation to and from client layers • Performance • Bit error rate (BER) Optical signal quality (OSNR, impairments) • Jitter • Maximum delay • Protection • Fault management

25. Layers within the Optical Layer Optical Transport Network protocol layers • Optical channel sublayer (OCh) • Optical multiplex section (OMS) • Optical transmission section (OTS) • Physical media layer: fiber-type specification

26. Simplified view of an Optical Connection