Ngophuhliso lonxibelelwano, ulwazi olufunekayo ukuba luhanjiswe alukho nje ilizwi, kodwa kunye nesicatshulwa, idatha, imifanekiso kunye nevidiyo. Idityaniswe nophuhliso lonxibelelwano lwedijithali kunye nobuchwepheshe bekhompyuter, kwiminyaka yee-1970 kunye ne-1980, i-T1 (DS1) / E1 i-carrier systems (1.544 / 2.048Mbps), i-X.25 frame relay, i-ISDN (i-Integrated Services Digital Network) kunye ne-FDDI (i-Optical fiber). ujongano lwedatha olusasaziweyo) kunye nobunye ubuchwepheshe benethiwekhi. Ngokufika koluntu lolwazi, abantu banethemba lokuba uthungelwano losasazo lolwazi lwanamhlanje lunokubonelela ngeesekethe ezahlukeneyo kunye neenkonzo ngokukhawuleza, ngokwezoqoqosho, nangempumelelo. Nangona kunjalo, ngenxa ye-monotonicity yeenkonzo zabo, ubunzima bokwandiswa, kunye nokunciphisa umda we-bandwidth, iteknoloji yenethiwekhi ekhankanywe ngasentla kuphela kwi-original Modifications okanye ukuphuculwa ngaphakathi kwesakhelo ayisancedi.SDHyaphuhliswa phantsi kwale mvelaphi. Phakathi kobuchwephesha be-broadband optical fiber network access network, inkqubo yokufikelela kwinethiwekhi esebenzisa iteknoloji yeSDH yeyona isetyenziswa kakhulu.Ukuzalwa kwe-SDH kusombulula ingxaki yokungakwazi ukuqhubeka nokuphuhliswa kwenethiwekhi ye-backbone kunye neemfuno zenkonzo yomsebenzisi ngenxa yokunciphisa umda we-bandwidth ye-media engenayo, kunye nengxaki yokufikelela "kwi-bottleneck" phakathi komsebenzisi kunye nenethiwekhi engundoqo. , kwaye ngexesha elifanayo, liye landa inani elikhulu le-bandwidth kwinethiwekhi yokudlulisa. Izinga lokusetyenziswa. Ukususela ekuqalisweni kweteknoloji ye-SDH kwiminyaka yee-1990, ibe yiteknoloji evuthiweyo kunye nesemgangathweni. Isetyenziswa ngokubanzi kuthungelwano lwe-backbone kwaye ixabiso liyancipha kwaye liphantsi. Ukusetyenziswa kweteknoloji ye-SDH kwinethiwekhi yokufikelela kunokunciphisa i-bandwidth enkulu kwinethiwekhi engundoqo. Izinto eziluncedo kunye neenzuzo zobugcisa zingeniswa kwintsimi yokufikelela kuthungelwano, ukusetyenziswa ngokupheleleyo kwe-SDH ye-synchronous multiplexing, i-standard optical interfaces, amandla okulawula inethiwekhi enamandla, i-flexible network topology capabilities kunye nokuthembeka okuphezulu ukuzisa izibonelelo, kunye neenzuzo zexesha elide kulwakhiwo kunye. uphuhliso lothungelwano lokufikelela .