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<span id="openzim-page-title" class="mw-page-title-main"><span class="mw-page-title-main">Optical buffer</span></span>

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</style><div role="note" class="hatnote navigation-not-searchable">For mechanical isolation and protection of optical fibers, see <a href="Buffer_(optical_fiber)" title="Buffer (optical fiber)">Buffer (optical fiber)</a>.</div>

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<p>In <a href="Telecommunications" title="Telecommunications">telecommunications</a>, an <b>optical buffer</b> is a device that is capable of temporarily storing light. Just as in the case of a regular <a href="Buffer_(telecommunication)" class="mw-redirect" title="Buffer (telecommunication)">buffer</a>, it is a <a href="Storage_medium" class="mw-redirect" title="Storage medium">storage medium</a> that enables compensation for a difference in time of occurrence of events.

</p><p>More specifically, an optical buffer serves to store data that was transmitted optically (i.e., in the form of light), without converting it to the electrical domain.<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>

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<div class="mw-heading mw-heading2"><h2 id="Optical_networks">Optical networks</h2></div>

<p>Today, <a href="Computer_networks" class="mw-redirect" title="Computer networks">computer networks</a> consist of <a href="Optical_fiber" title="Optical fiber">optical fiber</a> links, interconnected by electrical nodes. The data transport in the backbone is done in the form of light, typically from <a href="LED" class="mw-redirect" title="LED">LED</a> or <a href="Laser" title="Laser">laser</a>. <a href="DWDM" class="mw-redirect" title="DWDM">DWDM</a> technologies enable <a href="Bit_rate" title="Bit rate">bitrates</a> well beyond 1 <a href="Terabit" class="mw-redirect" title="Terabit">Tbit</a>/s. However, at the nodes, this light has to be converted to the electronic domain, in order to switch all data to their separate destinations. Due to rapidly increasing channel capacities, the switching capacity is becoming the bottleneck of the system. Currently, research activities focus on <a href="Optical_switching" class="mw-redirect" title="Optical switching">optical switching</a> technologies, that involve fewer or no conversions from the optical to the electronic domain. An important problem however, is the buffering.

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<div class="mw-heading mw-heading2"><h2 id="Contention_resolution">Contention resolution</h2></div>

<p>Whenever two or more data packets arrive at a network node at the same time and contend for the same output, external blocking occurs. All packets but one are perceived as superfluous, and have to be dealt with. Next to the obvious choice of dropping all excess packets, academic literature typically presents three solutions: buffering, deflection routing or wavelength conversion. Optical buffering uses fiber delay lines (FDLs) to delay the light, and is regarded as the most effective, but comes with the additional cost of the FDLs.

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<div class="mw-heading mw-heading2"><h2 id="Implementation_of_optical_buffers">Implementation of optical buffers</h2></div>

<p>As light cannot be frozen, an optical buffer is made of optical fibers, and is generally much larger than a <a href="RAM" class="mw-redirect" title="RAM">RAM</a> chip of comparable capacity. A single fiber can serve as a buffer. However, a set of more than one is usually used. A possibility, for example, is to choose a certain length <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle D}">

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<annotation encoding="application/x-tex">{\displaystyle D}</annotation>

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</math></span><img src="./f34a0c600395e5d4345287e21fb26efd386990e6.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.924ex; height:2.176ex;" alt="{\displaystyle D}" loading="lazy"></span> for the smallest fiber, and then let the second, third... have lengths <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle 2\cdot D,3\cdot D,\ldots }">

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<annotation encoding="application/x-tex">{\displaystyle 2\cdot D,3\cdot D,\ldots }</annotation>

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</math></span><img src="./b646bbe2d848f88d5dd854d58fedaeb9ed013833.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:14.323ex; height:2.509ex;" alt="{\displaystyle 2\cdot D,3\cdot D,\ldots }" loading="lazy"></span>. Another typical example is to use a single loop, in which the data circulates a variable number of times.

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<div class="mw-heading mw-heading2"><h2 id="Research">Research</h2></div>

<p>Currently, research on optical buffers is performed in two separate fields. One is to investigate on the technological implementation of this buffer, and try to reduce the size by using <a href="Slow_light" title="Slow light">slow-light</a> <a rel="nofollow" class="external text" href="http://www.physorg.com/news7839.html">devices</a>. The other is to better overall performance, by using <a href="Stochastics" class="mw-redirect" title="Stochastics">stochastics</a>. (Further detail on the latter approach can be found e.g. on the <a rel="nofollow" class="external text" href="http://telin.ugent.be/~wrogiest">author's homepage</a>.)

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<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>

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</style><cite id="CITEREFKhurgin2005" class="citation journal cs1">Khurgin, Jacob B. (2005-05-01). <span class="id-lock-subscription" title="Paid subscription required"><a rel="nofollow" class="external text" href="https://opg.optica.org/josab/abstract.cfm?uri=josab-22-5-1062">"Optical buffers based on slow light in electromagnetically induced transparent media and coupled resonator structures: comparative analysis"</a></span>. <i>JOSA B</i>. <b>22</b> (5): <span class="nowrap">1062–</span>1074. <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1364%2FJOSAB.22.001062">10.1364/JOSAB.22.001062</a>. <a href="ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/1520-8540">1520-8540</a>.</cite></span>

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This article is issued from <a class="external text" title="Last edited on 2025-05-28" href="https://en.wikipedia.org/wiki/?title=Optical_buffer&oldid=1292725993">Wikipedia</a>. The text is available under <a class="external text" href="https://creativecommons.org/licenses/by-sa/4.0/deed.en">Creative Commons Attribution-Share Alike 4.0</a> unless otherwise noted. Additional terms may apply for the media files.

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