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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
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Time Division Multiplexing
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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
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