Lub EPON network tau txais txoj hauv kev FTTB los tsim lub network, thiab lub hauv paus ntawm lub network yog OLT thiab ONU. OLT muab ntau qhov chaw nres nkoj PON rau cov khoom siv hauv chaw ua haujlwm txuas rau ONU cov cuab yeej; ONU yog cov neeg siv khoom siv uas muab cov ntaub ntawv sib xws thiab lub suab sib cuam tshuam kom paub cov neeg siv kev pabcuam nkag. Rau kev nkag mus rau kev siv cov kev pabcuam sib txawv, cov neeg siv sib txawv thiab cov kev pabcuam sib txawv raug cim nrog VLAN cov cim sib txawv kom pob tshab xa mus rau cov kev pabcuam nkag mus rau cov neeg siv khoom, thiab cov ntawv VLAN sib raug raug stripped thiab xa mus rau IP tus neeg nqa khoom network rau kev sib kis.
1. EPON network qhia
EPON (Ethernet Passive Optical Network) yog ib qho tshiab optical fiber nkag network technology. Nws txais cov qauv point-to-multipoint, passive optical fiber kis tau tus mob hom, raws li high-ceev Ethernet platform thiab TDM lub sij hawm faib MAC (Media Access Control) media access control mode. , Broadband access technology uas muab ntau yam kev pabcuam kev sib koom ua ke. Lub npe hu ua "passive" txhais tau hais tias ODN tsis muaj cov khoom siv hluav taws xob thiab cov khoom siv hluav taws xob, thiab muaj cov khoom siv tsis zoo xws li optical splitters (Splitter). Nws txais PON thev naus laus zis hauv txheej txheej lub cev, siv Ethernet raws tu qauv hauv txheej txuas, thiab paub txog kev nkag mus ntawm Ethernet los ntawm kev siv cov qauv topology ntawm PON. Yog li ntawd, nws muab cov txiaj ntsig zoo ntawm PON thev naus laus zis thiab Ethernet thev naus laus zis: tus nqi qis, siab bandwidth, muaj zog scalability, hloov tau yooj yim thiab ceev cov kev pab cuam reorganization, compatibility nrog Ethernet uas twb muaj lawm, yooj yim tswj thiab hais txog.
EPON tuaj yeem paub txog kev sib koom ua ke ntawm lub suab, cov ntaub ntawv, video thiab cov kev pabcuam txawb. EPON system yog tsim los ntawm OLT (optical kab davhlau ya nyob twg), ONU (optical network unit), ONT (optical network davhlau ya nyob twg) thiab ODN (optical distribution network). nkag.
Cov khoom siv hluav taws xob muaj xws li cov khoom siv hauv chaw ua haujlwm hauv nruab nrab (OLT) thiab chav tsev kho qhov muag (ONU). Optical Network Units (ONUs) muab cov neeg siv nrog kev sib txuas ntawm cov ntaub ntawv, video thiab xov tooj thiab PON. Lub luag haujlwm tseem ceeb ntawm ONU yog kom tau txais lub teeb liab txoj kev kho qhov muag thiab tom qab ntawd hloov nws mus rau hauv hom ntawv xav tau los ntawm tus neeg siv (Ethernet, IP tshaj tawm, xov tooj, T1 / E1, thiab lwm yam). Cov khoom siv OLT txuas nrog IP core network los ntawm fiber ntau optical. Kev taw qhia ntawm optical access network, nws cov kev pab them nqi mus txog 20km, xyuas kom meej tias OLT tuaj yeem hloov kho mus rau ib txwm metro convergence node los ntawm thawj theem ntawm optical access network tsim, yog li ua kom yooj yim lub network qauv ntawm cov txheej txheem nkag mus rau hauv network convergence thiab txuag. zog. tus naj npawb ntawm cov chaw ua haujlwm kawg. Tsis tas li ntawd, cov yam ntxwv ntawm lub peev xwm loj, kev nkag siab bandwidth, kev ntseeg siab, thiab ntau qhov kev pabcuam QoS qib kev txhawb nqa muaj peev xwm ntawm kev siv kho qhov muag network kuj ua rau cov kev hloov pauv ntawm kev nkag mus rau hauv kev sib koom ua ke, sib koom ua ke, thiab muaj txiaj ntsig cov kabmob muaj tseeb.
2. Lub hauv paus ntsiab lus ntawm EPON network
EPON system siv WDM thev naus laus zis kom paub txog ib leeg-fiber bidirectional kis tau tus mob, siv uplink 1310nm thiab downlink 1490nm wavelengths xa cov ntaub ntawv thiab lub suab, thaum CATV cov kev pabcuam siv 1550nm wavelength los nqa. OLT tau muab tso rau ntawm qhov chaw ua haujlwm hauv nruab nrab kom faib thiab tswj kev sib txuas ntawm cov channel, thiab muaj kev saib xyuas, kev tswj hwm thiab kev saib xyuas lub sijhawm. ONU tau muab tso rau ntawm tus neeg siv sab, thiab OLT thiab ONU txuas nrog hauv 1: 16 / 1: 32 hom los ntawm kev faib khoom siv kho qhov muag.
Txhawm rau cais cov kev sib tw mus ncig ntawm ntau tus neeg siv ntawm tib lub fiber ntau, ob txoj kev sib tw hauv qab no tuaj yeem siv tau.
1) Cov ntaub ntawv downlink kwj txais kev tshaj tawm tshuab. Nyob rau hauv EPON, cov txheej txheem ntawm downstream cov ntaub ntawv kis tau tus mob los ntawm OLT rau ntau ONUs yog xa los ntawm cov ntaub ntawv tshaj tawm. Cov ntaub ntawv tau tshaj tawm los ntawm OLT mus rau ntau ONUs nyob rau hauv daim ntawv ntawm cov pob ntawv sib txawv-ntev. Txhua pob ntawv cov ntaub ntawv muaj EPON header, uas tshwj xeeb txheeb xyuas seb cov ntaub ntawv pob ntawv raug xa mus rau ONU-1, ONU-2 lossis ONU-3. Nws tseem tuaj yeem raug txheeb xyuas tias yog pob ntawv tshaj tawm rau txhua ONUs lossis rau ib pawg ONU tshwj xeeb (cov pob ntawv ntau ntau). Thaum cov ntaub ntawv tuaj txog ntawm ONU, ONU tau txais thiab lees paub cov ntaub ntawv pob ntawv xa mus rau nws los ntawm qhov chaw nyob sib xws, thiab muab cov ntaub ntawv xa mus rau lwm cov ONUs. Tom qab ONU tau sau npe ua haujlwm, ib qho LLID tshwj xeeb raug faib; thaum OLT tau txais cov ntaub ntawv, nws muab piv rau daim ntawv teev npe LLID. Thaum ONU tau txais cov ntaub ntawv, nws tsuas yog tau txais thav duab lossis tshaj tawm cov thav duab uas phim nws tus kheej LLID.
2) Cov ntaub ntawv ntws ntws los siv TDMA thev naus laus zis. OLT piv cov npe LLID ua ntej tau txais cov ntaub ntawv; txhua ONU xa cov ntaub ntawv thav ntawv nyob rau hauv lub sij hawm slot uniformly faib los ntawm lub hauv paus chaw ua hauj lwm khoom OLT; lub sijhawm teem sijhawm (los ntawm kev siv thev naus laus zis) them nyiaj rau qhov sib txawv ntawm txhua ONU thiab zam txhua ONU kev sib tsoo ntawm.
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