SDH network in Japan and SDH 52/156 Mbps (VC-3/4) digital cross-connect systems with hit-less switching function

Since 1989, NTT has been using the synchronous digital hierarchy (SDH) transmission system to create simplified, easy-to-operate transmission networks in Japan. This paper describes the SDH networks at NTT and the newly developed SDH 52M/156M digital cross-connect system (Module AX), which enables real-time VC-3/VC-4 path level network operation and hit-less switching, thus providing support for relocation of existing telecommunication cables through cross-connection at the VC-3/VC-4 level. It also supports a standard Q interface and synchronous equipment management function (SEMF), and is based on the telecommunication management network (TMN) principle.<
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