求翻译：SDH 以其明显的优越性已成为传输网发展的主流。SDH技术与一些先进技术相结合，如光波分复用（WDM）、ATM技术、Internet技术（IP over SDH）等，使SDH网络的作用越来越大。SDH已被各国列入21世纪高速通信网的应用项目，是电信界公认的数字传输网的发展方向，具有远大的商用前景。而掌握SDH的基本传输原理对于SDH的组网、应用与维护都有着重要的作用。是什么意思？

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The obvious to SDH superiority has become the mainstream in the development of transport network. Sdh technology and advanced technology, such as light-division multiplexing (WDM), ATM technology, internet technologies (IP over SDH), so that the role of the network in an increasingly SDH. Have been

SDH has become the transmission network development by its obvious superiority the mainstream.The SDH technology unifies with some vanguard technologies, like light wavelength division multiplying (WDM), the ATM technology, the Internet technology (IP over SDH) and so on, causes the SDH network the

SDH, with its obvious advantages have become the mainstream of transport network development. SDH technology combined with advanced technology, such as optical wavelength division multiplexing (WDM), ATM, Internet technologies (IP over SDH), SDH networks more and more important role. SDH has been ap

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