Ngophuhliso lonxibelelwano, ulwazi olufunekayo ukuba luhanjiswe alukho nje ilizwi, kodwa kunye nesicatshulwa, idatha, imifanekiso kunye nevidiyo.Idityaniswe nophuhliso lonxibelelwano lwedijithali kunye nobuchwepheshe bekhompyuter, kwi-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 neqhelekileyo.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 .