ROADM

Reconfigurable Optical Add/Drop Multiplexer -- 可配置光分插復用器

　　A reconfigurable optical add-drop multiplexer (ROADM) is a form of optical add-drop multiplexer that adds the ability to remotely switch traffic from a WDM system at the wavelength layer. This allows individual wavelengths carrying data channels to be added and dropped from a transport fiber without the need to convert the signals on all of the WDM channels to electronic signals and back again to optical signals.

　　The main advantages of the ROADM are:

　　The planning of entire bandwidth assignment need not be carried out during initial deployment of a system. The configuration can be done as and when required.

　　ROADM allows for remote configuration and reconfiguration.

　　In ROADM, as it is not clear beforehand where a signal can be potentially routed, there is a necessity of power balancing of these signals. ROADMs allow for automatic power balancing.

　　ROADM functionality originally appeared in long-haul DWDM equipment, but by 2005, it began to appear in metro optical systems because of the need to build out major metropolitan networks in order to deal with the traffic driven by the increasing demand for packet-based services.

　　The switching or reconfiguration functions of a ROADM can be achieved using a variety of switching technologies including MEMS, Liquid crystal, thermo optic and beam-steering switches in planar waveguide circuits, and tunable optical filter technology.

　　“ROADM”又稱可重構的光分插復用器，是指一種網(wǎng)絡元素（或稱節(jié)點），通過遠程的重新配置，可以動態(tài)上下業(yè)務波長，并且，業(yè)務波長的功率也是可以管理的。ROADM的組成模塊隨應用的不同而不同。不過大多數(shù)ROADM都具有這里列出的模塊。

　　ROADM節(jié)點的主要功能模塊包括：

　　1、前置和后置光放大器。

　　2、光業(yè)務信道（OSC）的生成和終結。

　　3、波長下路。

　　4、波長上路。

　　5、節(jié)點內(nèi)部聚合信道或單信道的功率監(jiān)控，可在節(jié)點內(nèi)多處進行。

　　6、可用/不可用和可選波長的監(jiān)測，整個節(jié)點內(nèi)的光信號的信噪比監(jiān)測。

　　7、上下路和直通波長的功率/衰減控制。

　　8、色散補償。

　　9、前置和后置放大器的增益均衡。

　　“ROADM”一段時間曾經(jīng)是通信產(chǎn)業(yè)中的一個“熱門”詞匯。網(wǎng)絡節(jié)點采用ROADM后，網(wǎng)管系統(tǒng)可以控制某個波長通過這個光節(jié)點或者從本地端口下路，終結于這個光節(jié)點的光轉發(fā)器。ROADM系統(tǒng)中，至少可以在兩個端口之間交換波長。直通口支持普通WDM信號，這時本地端口可以是任意波長或者某個已知波長。ROADM還有更多的功能，如可以連續(xù)控制每一個波長的光功率。

　　ROADM系統(tǒng)可以給服務提供商們提供一系列的好處：快捷的業(yè)務指配、更加自動化的處理、簡化的網(wǎng)絡規(guī)劃和施工，更為強大的網(wǎng)絡監(jiān)控能力和網(wǎng)絡擴展能力。然而，雖然人們預測它將成各種類型的通信網(wǎng)中的完整的網(wǎng)元，但是ROADM目前仍然處于二線位置。

　　網(wǎng)絡以及業(yè)務都需要考慮成本，正是在價格問題上，ROADM沒能過關。因此，服務提供商們目前還不愿投錢進去。

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