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 ndiOLT(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 zama netiweki zogwira ntchito zimaphatikizapo zida zapakati paofesi (OLT) ndi optical network unit (ONU). The Optical network unit (ONU) imapatsa ogwiritsa ntchito mawonekedwe pakati pa data, makanema, ndi maukonde amafoni ndi PON. Udindo woyamba waONUndikulandira chizindikiro cha kuwala ndikusintha kukhala mawonekedwe omwe wogwiritsa ntchito amafunikira (Efaneti, IP kuwulutsa, foni, T1/E1, etc.).OLTzida 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. TheOLTimayikidwa mu ofesi yapakati kuti igawire ndikuwongolera kulumikizidwa kwa njirayo, ndipo imakhala ndi ntchito zowunika, kuyang'anira ndi kukonza nthawi yeniyeni. TheONUimayikidwa kumbali ya wogwiritsa ntchito, ndiOLTndiONUamalumikizidwa mu njira ya 1:16/1:32 kudzera pa netiweki yogawa yamagetsi. 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 kuOLTku angapoONUimatumizidwa ndi data broadcasting. Deta imawulutsidwa pansi kuchokera kuOLTku angapoONUm'mapaketi a chidziwitso cha kutalika kosiyana. Phukusi lililonse lazidziwitso lili ndi mutu wa paketi ya EPON, yomwe imazindikiritsa ngati paketiyo yatumizidwa kuONU-1,ONU-2 kapenaONU-3. Itha kuzindikirikanso ngati paketi yazidziwitso zowulutsidwa yotumizidwa kwa onseONUkapena ku zenizeniONUgulu (paketi yazidziwitso zambiri). Pamene deta ifika paONU, ndiONUimalandira ndikuzindikira mapaketi azidziwitso omwe amatumizidwa kwa iwo kudzera mu kufananiza ma adilesi, ndikutaya mapaketi azidziwitso omwe amatumizidwa kwa ena.ONU. LLID yapadera imaperekedwa pambuyo paONUzalembedwa; ndiOLTamafanizitsa mndandanda wolembetsa wa LLID mukalandira deta, komanso pomweONUimalandira deta, imangolandira mafelemu kapena mafelemu owulutsa omwe amafanana ndi LLID yake.
(2) Kuthamanga kwa data kumtunda kumatengera luso la TDMA. TheOLTamafanizira mndandanda wa zolembera za LLID musanalandire deta; aliyenseONUimatumiza chimango cha data mu nthawi yoperekedwa mofanana ndi zida zapakati paofesiOLT; nthawi yoperekedwa (kudzera mu teknoloji yoyambira) imabwezera kusiyana kwa mtunda wa iliyonseONUndipo amapewa aliyenseONUKugundana pakati.
