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

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