Ngokuthuthuka kokuxhumana, ulwazi oludingekayo ukuze ludluliselwe akulona izwi kuphela, kodwa futhi umbhalo, idatha, izithombe, nevidiyo.Ngokuhambisana nokuthuthukiswa kokuxhumana kwedijithali nobuchwepheshe bekhompyutha, ngeminyaka yawo-1970 nawo-1980, i-T1 (DS1)/E1 yezinkampani zenethiwekhi (1.544/2.048Mbps), i-X.25 frame relay, ISDN (Integrated Services Digital Network) kanye ne-FDDI ( Optical fibre i-interface yedatha esabalalisiwe) nobunye ubuchwepheshe benethiwekhi.Ngokufika komphakathi wolwazi, abantu bathemba ukuthi amanethiwekhi okudlulisa ulwazi esimanje angahlinzeka ngamasekethe namasevisi ahlukahlukene ngokushesha, ngokwezomnotho, nangempumelelo.Kodwa-ke, ngenxa ye-monotonicity yezinsizakalo zabo, inkimbinkimbi yokunwetshwa, kanye nomkhawulo womkhawulokudonsa, ubuchwepheshe benethiwekhi obubalulwe ngenhla bukhona kuphela Ukuguqulwa kwasekuqaleni noma ukuthuthukiswa ngaphakathi kohlaka akusasizi.I-SDHyathuthukiswa ngaphansi kwalesi sizinda.Phakathi kobuchwepheshe obuhlukahlukene benethiwekhi ye-broadband optical fiber access, uhlelo lwenethiwekhi yokufinyelela olusebenzisa ubuchwepheshe be-SDH yilona olusetshenziswa kakhulu.Ukuzalwa kwe-SDH kuxazulula inkinga yokungakwazi ukuhambisana nokuthuthukiswa kwenethiwekhi yomgogodla kanye nezidingo zesevisi yomsebenzisi ngenxa yomkhawulo womkhawulokudonsa wemidiya engenayo, kanye nenkinga yokufinyelela "ibhodlela" phakathi komsebenzisi nenethiwekhi eyinhloko. , futhi ngesikhathi esifanayo, ikhulise inani elikhulu lomkhawulokudonsa kunethiwekhi yokudlulisela.Izinga lokusetshenziswa.Kusukela kwethulwa ubuchwepheshe be-SDH ngeminyaka yawo-1990, kube ubuchwepheshe obuvuthiwe nobujwayelekile.Isetshenziswa kakhulu kumanethiwekhi omgogodla futhi intengo iyancipha futhi yehla.Ukusetshenziswa kobuchwepheshe be-SDH kunethiwekhi yokufinyelela kunganciphisa umkhawulokudonsa omkhulu kunethiwekhi eyinhloko.Izinzuzo kanye nezinzuzo zezobuchwepheshe zilethwa emkhakheni wokufinyelela amanethiwekhi, ukusetshenziswa ngokugcwele kwe-SDH synchronous multiplexing, ukuxhumana optical standardized, amandla okuphatha inethiwekhi enamandla, flexible network topology amakhono kanye nokuthembeka okuphezulu ukuletha izinzuzo, kanye nezinzuzo zesikhathi eside ekwakheni kanye ukuthuthukiswa kwamanethiwekhi okufinyelela .