Nrog rau kev txhim kho kev sib txuas lus, cov ntaub ntawv yuav tsum tau xa tawm tsis yog lub suab nkaus xwb, tab sis kuj yog cov ntawv nyeem, cov ntaub ntawv, duab, thiab video.Ua ke nrog kev txhim kho kev sib txuas lus digital thiab khoos phis tawj thev naus laus zis, hauv xyoo 1970s thiab 1980s, T1 (DS1) / E1 cab kuj systems (1.544/2.048Mbps), X.25 ncej relay, ISDN (Integrated Services Digital Network) thiab FDDI (Optical fiber) faib cov ntaub ntawv interface) thiab lwm yam network technologies.Nrog rau kev tshwm sim ntawm cov neeg zej zog cov ntaub ntawv, tib neeg cia siab tias cov xov xwm niaj hnub kis tau tus mob tuaj yeem muab ntau yam circuits thiab kev pabcuam sai, kev lag luam, thiab ua tau zoo.Txawm li cas los xij, vim yog monotonicity ntawm lawv cov kev pabcuam, qhov nyuaj ntawm kev nthuav dav, thiab kev txwv ntawm bandwidth, cov thev naus laus zis tau hais los saum toj no tsuas yog nyob rau hauv cov kev hloov pauv qub lossis kev txhim kho hauv lub moj khaum tsis muaj txiaj ntsig ntxiv lawm.SDHtau tsim nyob rau hauv keeb kwm yav dhau no.Ntawm ntau yam broadband optical fiber nkag network technologies, kev nkag tau network system siv SDH technology yog siv dav tshaj plaws.Kev yug los ntawm SDH daws qhov teeb meem ntawm kev tsis tuaj yeem ua raws li kev txhim kho ntawm cov pob txha caj qaum thiab cov neeg siv cov kev xav tau vim yog qhov txwv bandwidth ntawm cov xov xwm inbound, thiab qhov teeb meem ntawm kev nkag mus rau "bottleneck" ntawm tus neeg siv thiab cov tub ntxhais network. , thiab tib lub sijhawm, nws tau nce ntau ntawm bandwidth ntawm kev sib kis network.Kev siv tus nqi.Txij li thaum pib ntawm SDH thev naus laus zis hauv xyoo 1990, nws tau ua cov cuab yeej paub tab thiab qauv.Nws yog dav siv hauv cov pob txha caj qaum thiab tus nqi tau txais qis dua thiab qis dua.Daim ntawv thov ntawm SDH thev naus laus zis hauv kev nkag mus rau hauv lub network tuaj yeem txo qhov bandwidth loj hauv cov tub ntxhais network.Cov txiaj ntsig zoo thiab cov txiaj ntsig tau raug coj mus rau hauv kev nkag mus rau hauv kev sib koom tes, ua kom tag nrho kev siv SDH synchronous multiplexing, standardized optical interfaces, muaj peev xwm tswj hwm lub network muaj peev xwm, hloov tau yooj yim network topology muaj peev xwm thiab muaj kev ntseeg siab los coj cov txiaj ntsig, thiab cov txiaj ntsig ntev hauv kev tsim kho thiab txoj kev loj hlob ntawm kev siv network.