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class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Manipulates DWDM channel contents</div> <style data-mw-deduplicate="TemplateStyles:r1236090951">.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}</style><div role="note" class="hatnote navigation-not-searchable">Not to be confused with <a href="/wiki/Optical_add-drop_multiplexer" title="Optical add-drop multiplexer">optical add-drop multiplexer</a>.</div> <style data-mw-deduplicate="TemplateStyles:r1251242444">.mw-parser-output .ambox{border:1px solid #a2a9b1;border-left:10px solid #36c;background-color:#fbfbfb;box-sizing:border-box}.mw-parser-output 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//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/100px-Question_book-new.svg.png 2x" data-file-width="512" data-file-height="399" /></a></span></div></td><td class="mbox-text"><div class="mbox-text-span">This article <b>needs additional citations for <a href="/wiki/Wikipedia:Verifiability" title="Wikipedia:Verifiability">verification</a></b>.<span class="hide-when-compact"> Please help <a href="/wiki/Special:EditPage/Add-drop_multiplexer" title="Special:EditPage/Add-drop multiplexer">improve this article</a> by <a href="/wiki/Help:Referencing_for_beginners" title="Help:Referencing for beginners">adding citations to reliable sources</a>. Unsourced material may be challenged and removed.<br /><small><span class="plainlinks"><i>Find sources:</i> <a rel="nofollow" class="external text" href="https://www.google.com/search?as_eq=wikipedia&q=%22Add-drop+multiplexer%22">"Add-drop multiplexer"</a> – <a rel="nofollow" class="external text" href="https://www.google.com/search?tbm=nws&q=%22Add-drop+multiplexer%22+-wikipedia&tbs=ar:1">news</a> <b>·</b> <a rel="nofollow" class="external text" href="https://www.google.com/search?&q=%22Add-drop+multiplexer%22&tbs=bkt:s&tbm=bks">newspapers</a> <b>·</b> <a rel="nofollow" class="external text" href="https://www.google.com/search?tbs=bks:1&q=%22Add-drop+multiplexer%22+-wikipedia">books</a> <b>·</b> <a rel="nofollow" class="external text" href="https://scholar.google.com/scholar?q=%22Add-drop+multiplexer%22">scholar</a> <b>·</b> <a rel="nofollow" class="external text" href="https://www.jstor.org/action/doBasicSearch?Query=%22Add-drop+multiplexer%22&acc=on&wc=on">JSTOR</a></span></small></span> <span class="date-container"><i>(<span class="date">July 2007</span>)</i></span><span class="hide-when-compact"><i> (<small><a href="/wiki/Help:Maintenance_template_removal" title="Help:Maintenance template removal">Learn how and when to remove this message</a></small>)</i></span></div></td></tr></tbody></table> <figure typeof="mw:File/Thumb"><a href="/wiki/File:Add-drop-multiplexer-SONET-SDH.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/6/6b/Add-drop-multiplexer-SONET-SDH.jpg/300px-Add-drop-multiplexer-SONET-SDH.jpg" decoding="async" width="300" height="400" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/6/6b/Add-drop-multiplexer-SONET-SDH.jpg/450px-Add-drop-multiplexer-SONET-SDH.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/6/6b/Add-drop-multiplexer-SONET-SDH.jpg/600px-Add-drop-multiplexer-SONET-SDH.jpg 2x" data-file-width="2112" data-file-height="2816" /></a><figcaption>An add-drop multiplexer.</figcaption></figure> <p>An <b>add-drop multiplexer</b> (<b>ADM</b>) is an important element of an <a href="/wiki/Optical_fiber" title="Optical fiber">optical fiber</a> network. A <a href="/wiki/Multiplexer" title="Multiplexer">multiplexer</a> combines, or <a href="/wiki/Multiplexing" title="Multiplexing">multiplexes</a>, several lower-<a href="/wiki/Bandwidth_(computing)" title="Bandwidth (computing)">bandwidth</a> streams of data into a single beam of <a href="/wiki/Light" title="Light">light</a>. An <i>add-drop</i> multiplexer also has the capability to <i>add</i> one or more lower-bandwidth signals to an existing high-bandwidth data stream, and at the same time can extract or <i>drop</i> other low-bandwidth signals, removing them from the stream and redirecting them to some other network path. This is used as a local "on-ramp" and "off-ramp" to the high-speed network.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> </p><p>ADMs can be used both in long-haul core networks and in shorter-distance <a href="/wiki/Metropolitan_area_network" title="Metropolitan area network">metro networks</a>, although the former are much more expensive due to the difficulty of scaling the technology to the high data rates and <a href="/wiki/Wavelength_division_multiplexing" class="mw-redirect" title="Wavelength division multiplexing">dense wavelength division multiplexing</a> (DWDM) used for long-haul communications. The main optical filtering technology used in add-drop multiplexers is the <a href="/wiki/Fabry%E2%80%93P%C3%A9rot_etalon" class="mw-redirect" title="Fabry–Pérot etalon">Fabry–Pérot etalon</a>. </p><p>Newer "multi-service <a href="/wiki/SONET/SDH" class="mw-redirect" title="SONET/SDH">SONET/SDH</a>" (also known as a <a href="/w/index.php?title=Multi-service_provisioning_platform&action=edit&redlink=1" class="new" title="Multi-service provisioning platform (page does not exist)">multi-service provisioning platform</a> or MSPP) equipment has all the capabilities of legacy ADMs, but can also include cross-connect functionality to manage multiple fiber rings in a single chassis. These devices can replace multiple legacy ADMs and also allow connections directly from <a href="/wiki/Ethernet" title="Ethernet">Ethernet</a> <a href="/wiki/LAN" class="mw-redirect" title="LAN">LANs</a> to a service provider's optical backbone. At the end of 2003, sales of multiservice ADMs exceeded those of legacy ADMs for the first time, as the change to next-generation SONET/SDH networks accelerated. </p><p>An emerging variety of ADMs that is becoming popular as the carriers continue to invest in metro optical networks are <a href="/wiki/Reconfigurable_optical_add-drop_multiplexer" title="Reconfigurable optical add-drop multiplexer">reconfigurable optical add-drop multiplexers</a> (ROADMs). </p> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Add-drop_multiplexer&action=edit&section=1" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Optical_add-drop_multiplexer" title="Optical add-drop multiplexer">Optical add-drop multiplexer</a></li> <li><a href="/wiki/Drop_and_insert" title="Drop and insert">Drop and insert</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Add-drop_multiplexer&action=edit&section=2" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="mw-references-wrap"><ol class="references"> <li id="cite_note-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20080304030505/http://www.maxim-ic.com/glossary/index.cfm/Ac/V/ID/8/Tm/ADM">"Electrical Engineering Glossary Definition for ADM"</a>. 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