Optical Networks

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Optical Networks

• Rainbow for Communications

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Medium Sharing

• Time Division Multiplexing (TDM)
• Frequency Division Multiplexing
• In the optical domain,
• Wavelength Division Multiplexing

3
Time Division Multiplexing
4
Wavelength Division Multiplexing
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Principle

• Shared Medium

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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 ?

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Wavelength Routing

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

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

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RWA Types of Problems

• Static RWA
• Sequential RWA
• Dynamic RWA

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Strategy to Solve RWA

• Break RWA
• Routing problem Dijkstra or Bellman-Ford
• Wavelength assignment a suggestion?

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How About Grooming?

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

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Switching in Optical Networks

• Based on
• Techniques for Optical Packet Switching and
  Optical Burst Switching,
• L. Xu, H.G. Perros, and G. Rouskas

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Packet Coding Techniques

• Bit serial coding
• Bit parallel
• Out of band signalling

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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

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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

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How to Solve Contention?
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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