1. EPON network introduction
EPON(Ethernet Passive Optical Network) ndiukadaulo waukadaulo waukadaulo wolumikizira maukonde, womwe umatengera mawonekedwe a point-to-multipoint, passive optical fiber transmission mode, kutengera nsanja ya Ethernet yothamanga kwambiri komanso gawo la TDM nthawi ya MAC (MediaAccessControl) njira yowongolera media, Perekani matekinoloje osiyanasiyana amtundu wa Broadband pazantchito zophatikizika.Zomwe zimatchedwa "passive" zimatanthawuza kuti ODN ilibe zipangizo zamagetsi zamagetsi ndi magetsi, ndipo zonse zimakhala ndi zipangizo zopanda kanthu monga optical splitters (Splitter).Imagwiritsa ntchito ukadaulo wa PON pagawo lakuthupi, Ethernet protocol pagawo lolumikizana, ndipo imagwiritsa ntchito PON topology kuti ikwaniritse Efaneti.Chifukwa chake, imaphatikiza zabwino zaukadaulo wa PON ndi ukadaulo wa Efaneti: mtengo wotsika, bandwidth yayikulu, scalability yamphamvu, kusinthika komanso kukonzanso kwautumiki, kuyanjana ndi Ethernet yomwe ilipo, kasamalidwe kosavuta, ndi zina zotero.
EPON imatha kuzindikira kuphatikiza kwa mawu, data, makanema, ndi ntchito zamafoni.Dongosolo la EPON limapangidwa makamaka ndi OLT (optical line terminal),ONU(optical network unit), ONT (optical network terminal) ndi ODN (optical distribution network).Ili pamlingo wofikira pa netiweki ndipo ndiyoyenera kwambiri kulumikizana ndi ma fiber opangidwa ndi ma burodibandi.Ku.
Zida zamagetsi zogwira ntchito zimaphatikizapo zida zapakati paofesi (OLT) ndi optical network unit (ONU).Optical network unit (ONU) imapatsa ogwiritsa ntchito mawonekedwe pakati pa data, makanema, ndi maukonde amafoni ndi PON.Ntchito yoyamba ya ONU ndiyo kulandira chizindikiro cha kuwala ndikuchisintha kukhala mawonekedwe ofunikira ndi wogwiritsa ntchito (Ethernet, IP broadcast, telefoni, T1 / E1, etc.).Zida za OLT zimalumikizidwa ndi netiweki ya IP core kudzera mu fiber optical.Kukhazikitsidwa kwa netiweki ya optical access kumafikira mpaka 20km, zomwe zimatsimikizira kutiOLTatha kukwezedwa ku chikhalidwe cha metropolitan convergence node kuyambira gawo loyambirira la zomangamanga zolumikizira maukonde, motero kumathandizira mawonekedwe a netiweki a gawo lolumikizana la netiweki yofikira ndikupulumutsa Chiwerengero cha maofesi omaliza.Kuphatikiza apo, mawonekedwe amtundu waukulu wa netiweki yofikira, kuchuluka kwa bandwidth, kudalirika kwakukulu, komanso kuthekera kothandizira kwamagawo angapo a QoS apangitsanso kusinthika kwa netiweki kupita ku nsanja yolumikizana, yophatikizika, komanso yogwira ntchito bwino.
2. Mfundo Zazikulu za EPON Network
Dongosolo la EPON limagwiritsa ntchito ukadaulo wa WDM kuti uzindikire kufalikira kwa fiber imodzi, pogwiritsa ntchito mafunde a 1310nm kumtunda ndi kumunsi kwa 1490nm mafunde kuti atumize deta ndi mawu, ndipo ntchito za CATV zimagwiritsa ntchito kutalika kwa 1550nm kunyamula.OLT imayikidwa mu ofesi yapakati kuti igawire ndikuwongolera kulumikizidwa kwa njirayo, ndipo ili ndi nthawi yeniyeni yowunika, kuyang'anira ndi kukonza ntchito.ONU imayikidwa kumbali ya wogwiritsa ntchito, ndipo OLT ndi ONU zimagwirizanitsidwa mu 1:16 / 1:32 njira kudzera mu network yogawa yogawa.Pofuna kulekanitsa zizindikiro kuchokera kwa ogwiritsa ntchito angapo pamtundu womwewo, njira ziwiri zotsatirazi zochulukitsa zingagwiritsidwe ntchito.
(1) Kutsikira kwa data kumatengera ukadaulo wowulutsa.Mu EPON, njira yotumizira deta yotsika kuchokera ku OLT kupita ku ma ONU angapo imatumizidwa ndi kuwulutsa kwa data.Deta imawulutsidwa pansi kuchokera ku OLT kupita ku ma ONU angapo mu mawonekedwe a mapaketi azidziwitso akutali.Phukusi lililonse lazidziwitso lili ndi mutu wa paketi ya EPON, yomwe imazindikiritsa mwapadera ngati paketiyo itumizidwa ku ONU-1, ONU-2 kapena ONU-3.Itha kuzindikirikanso ngati paketi yazidziwitso zowulutsa zomwe zimatumizidwa ku ma ONU onse kapena kugulu linalake la ONU (paketi yazidziwitso zambiri).Deta ikafika ku ONU, ONU imalandira ndikuzindikira mapaketi azidziwitso omwe amatumizidwa kwa iyo kudzera mu ma adilesi ofananira, ndikutaya mapaketi a chidziwitso omwe amatumizidwa ku ma ONU ena.LLID yapadera imaperekedwa pambuyo polembetsa ONU;OLT imafanizira mndandanda wa zolembera za LLID polandira deta, ndipo ONU ikalandira deta, imangolandira mafelemu kapena mafelemu owulutsa omwe amafanana ndi LLID yake.
(2) Kuthamanga kwa data kumtunda kumatengera luso la TDMA.OLT ikufanizira mndandanda wolembetsa wa LLID musanalandire deta;aliyense ONU amatumiza chimango deta mu nthawi kagawo uniformly kuperekedwa ndi chapakati ofesi zida OLT;nthawi yomwe yaperekedwa (kudzera mu teknoloji yoyambira) imabwezera kusiyana kwa mtunda wa ONU iliyonse ndikupewa Kugundana kulikonse kwa ONU pakati.
