Lec-13 WDM Network Elements(22-3-2011)

Lec-13 WDM Network Elements(22-3-2011) - WDM Network...

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1 WDM Network Elements A lightpath consists of an optical channel, or wavelength, between two network nodes that is routed through multiple intermediate nodes. Intermediate nodes may switch and convert wavelengths. Networks may thus be thought of as wavelength- routing networks. Lightpaths are set up and taken down as dictated by the users of the network. Network consists of optical line terminals (OLTs), optical add/drop links.
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2 OADMs, and OXCs may themselves incorporate optical amplifiers to make up for losses. As of this writing, OLTs are widely deployed, and OADMs are deployed to a lesser extent. OXCs are just beginning to be deployed. Architecture (Fig7.1) supports a variety of topologies, including ring and mesh topologies. OLTs multiplex multiple wavelengths into a single fiber and also demultiplex a composite WDM signal into individual wavelengths. WDM Network Elements
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3 Figure: 7.1
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4 OLTs are used at either end of a point-to-point link. OADMs are used at locations where some fraction of the wavelengths need to be terminated locally and others need to be routed to other destinations. Network provides lightpaths to its users, such as SONET boxes and IP Routers. Lightpath is carried on a wavelength between its source and destination but may get converted from one wavelength to another along the way. WDM Network Elements
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5 They are typically deployed in linear or ring topologies. OXCs perform a similar function but on a much larger scale in terms of number of ports and wavelengths involved, and are deployed in mesh topologies or in order to interconnect multiple rings. The users (or clients) of this network are connected to the OLTs, OADMs, or OXCs. Network supports a variety of client types, such as IP routers, ATM switches, and SONET terminals and ADMs. WDM Network Elements
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6 Each link can support a certain number of wavelengths. Number of wavelengths that can be supported depends on the component and transmission-imposed limitations. Several noteworthy features of this architecture: WDM Network Elements
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7 Multiple lightpaths in the network can use the same wavelength, as long as they do not overlap on any link. This spatial reuse capability allows the network to support a large number of lightpaths using a limited number of wavelengths. Wavelength reuse
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8 Lightpaths may undergo wavelength conversion along their route. One such lightpath that uses wavelength λ 2 on link EX, gets converted to λ 1 at node X, and uses that wavelength on link X F. Wavelength conversion can improve the utilization of wavelengths inside the network. Wavelength conversion is also needed at the boundaries of the network to adapt signals from outside the network into a suitable wavelength for use inside the network. Wavelength Conversion
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9 Transparency Transparency refers to the fact that the lightpaths can carry data at a variety of bit rates, protocols, and so forth and can, in effect, be made protocol insensitive.
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  • Spring '11
  • Mr.Tayyab
  • Network topology, Wavelength-division multiplexing, optical add/drop multiplexers, Optical Line Terminals, optical line, WDM Network Elements

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