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Optical Networks

Optical Networks. Rainbow for Communications. Medium Sharing. Time Division Multiplexing (TDM) Frequency Division Multiplexing In the optical domain, Wavelength Division Multiplexing. Time Division Multiplexing. Wavelength Division Multiplexing. Principle. Shared Medium. Potential.

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Optical Networks

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  1. Optical Networks Rainbow for Communications

  2. Medium Sharing • Time Division Multiplexing (TDM) • Frequency Division Multiplexing • In the optical domain, • Wavelength Division Multiplexing

  3. Time Division Multiplexing

  4. Wavelength Division Multiplexing

  5. Principle Shared Medium

  6. Potential • Today: each wavelength may carry data rates from 2.5 to 10 Gbps. Commercial systems support up to 160 wavelengths on one strand. • Soon, 1000 ?

  7. Wavelength Routing • For any two communicating nodes, establish a lightpath (using the same wavelength all along the path).

  8. The Routing and Wavelength Assignment Problem (RWA) NP Problem!

  9. RWA For Different Networks • Wavelength-continuity constraint: lightpath with the same wavelength from source to destination • Wavelength-convertible networks: All or some nodes are allowed to convert wavelengths (switch wavelength).

  10. RWA Types of Problems • Static RWA • Sequential RWA • Dynamic RWA

  11. Strategy to Solve RWA • Break RWA: • Routing problem : Dijkstra or Bellman-Ford • Wavelength assignment: a suggestion?

  12. How About Grooming? • Grooming adds another dimension to the problem: • Mix together some low rate traffic flows into one flow to occupy one wavelength.

  13. Switching in Optical Networks Based on “Techniques for Optical Packet Switching and Optical Burst Switching”, L. Xu, H.G. Perros, and G. Rouskas

  14. Packet Coding Techniques • Bit serial coding • Bit parallel: • Out of band signalling

  15. Bit Serial Coding • Optical code-division multiplexing (each bit carries routing information) • Optical pulse interval : header and payload are separate, but transmitted at same rate • Mixed rate techniques: header and payload are separate, but header transmitted slower

  16. Bit Parallel and Out of band Sig. • Bit parallel: bits are sent in parallel on different wavelength • Out-of-band signalling: • SCM (Subcarrier Multiplexing): header is sent on electrical carrier. • Dual wavelength: header and payload are sent on different wavelength

  17. How to Solve Contention?

  18. Optical Storing • Optical Buffering : using optical delay lines • Wavelength Domain: Packet scheduling becomes similar to multiprocessor scheduling • Deflection routing: send out on any available output port

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