1 Isingeniso
Ngokuthuthuka okusheshayo kobuchwepheshe bokufinyelela ku-broadband, ubuchwepheshe obuhlukahlukene obuvelayo bokufinyelela be-broadband buvele ngemva kwemvula. Ngemva kobuchwepheshe be-PON ubuchwepheshe be-DSL kanye nobuchwepheshe bekhebula, enye inkundla yokufinyelela ekahle, i-PON ingahlinzeka ngokuqondile ngezinsizakalo zokubona noma izinsizakalo ze-FTTH. I-EPON iwuhlobo olusha lobuchwepheshe benethiwekhi yokufinyelela ifayibha, kusetshenziswa amaphuzu esakhiweni samaphuzu amaningi, ukudlulisa ukukhanya okungenamthombo, ukuhlinzeka ngezinsizakalo ezihlukahlukene ze-Ethernet. Isebenzisa ama-topology e-PON ukuze isebenzise ukufinyelela kwe-Ethernet, futhi ubuchwepheshe be-PON busetshenziswa kusendlalelo esibonakalayo kungqimba olubonakalayo. Ngakho-ke, ihlanganisa izinzuzo zobuchwepheshe be-PON nobuchwepheshe be-Ethernet: izindleko eziphansi; umkhawulokudonsa ophezulu; ukuqina okunamandla, ukuhlelwa kabusha kwesevisi okuvumelana nezimo nokushesha; ukuhambisana ne-Ethernet ekhona; ukuphathwa okulula, njll. Ukuhlolwa kwe-EPON kuhluke kakhulu kumishini ye-Ethernet evamile. Lesi sihloko sigxile kubuchwepheshe bokuhlola be-EPON.
2 Isingeniso sobuchwepheshe be-EPON kanye nenselelo yokuhlola
II-EPONuhlelo luqukethe ubuningi bamayunithi enethiwekhi ye-optical, itheminali yokukhanya (OLT), kanye ne-spectra eyodwa noma ngaphezulu (bona Umfanekiso 1). Esiqondisweni se-downlink, isignali ethunyelwe i-OLT isakazwa kuwo wonke ama-ONU. Esiqondisweni se-uplink, kusetshenziswa amasu e-TDMA eziteshi eziningi, futhi ulwazi lwe-uplink lwama-ONU amaningi lwenza ulwazi lwe-TDM ku-OLT. 802.3AH Lungisa ifomethi yozimele we-Ethernet, chaza kabusha ingxenye echazayo, engeza izitembu zesikhathi nezihlonzi zesixhumanisi esinengqondo (LLID). I-LLID ikhomba i-ONU ngayinye yesistimu ye-PON futhi icacisa i-LLID phakathi nenqubo yokutholwa.
3 Ubuchwepheshe obubalulekile ohlelweni lwe-PON
Kusistimu ye-EPON, ibanga elibonakalayo phakathi kwe-ONU ngayinye ne-OLT endaweni yokudlulisela ulwazi ekhuphukayo alilingani. Ngokuvamile, uhlelo lwe-EPON lubeka ukuthi ibanga elide ukusuka ku-ONU ukuya ku-OLT ngu-20km, futhi ibanga elifushane kakhulu ngu-0km. Lo mehluko ebangeni udala ukubambezeleka kwehluke phakathi kuka-0 no-200 us. Uma lingekho igebe elanele lokuzihlukanisa, amasiginali asuka kuma-ONU ahlukahlukene angase afinyelele ekugcineni kokwamukela kwe-OLT ngesikhathi esifanayo, okubangele ukungqubuzana kwamasignali akhuphuka nomfula. Ukungqubuzana kungabangela inani elikhulu lamaphutha nokulahlekelwa kokuvumelanisa, njll., okuholela ekutheni isistimu ingasebenzi kahle. Usebenzisa indlela yokuhlukanisa, qala ngokukala ibanga elibonakalayo, bese ulungisa wonke ama-ONU ebangeni elinengqondo elifanayo njenge-OLT, bese usebenzisa indlela ye-TDMA ukuze ugweme ukungqubuzana. Izindlela ezihlukene ezisetshenziswayo njengamanje zifaka phakathi ukuhlukahluka kwe-spectrum, ukuphuma kwebhendi kanye nokuvulwa kwamawindi okungaphakathi kwebhendi. Isibonelo, usebenzisa indlela yesikali sesikhathi, qala ngokukala isikhathi sokulibaziseka kweluphu yesiginali ukusuka ku-ONU ngayinye ukuya ku-OLT, bese ufaka ukubambezeleka okuthile kokulinganisa kwe-Td kwe-ONU ngayinye, ukuze ukubambezeleka kweluphu yawo wonke ama-ONU ngemva kokufaka i-Td ingakwazi. ukutholwa Isikhathi (okubhekiselwa kuso njengevelu yokulibaziseka kweluphu ye-equalization Tequ) siyalingana, futhi umphumela ufana nokuhambisa i-ONU ngayinye ebangeni elinengqondo elifanayo njenge-OLT, bese ithumela ifremu ngendlela efanele ngokobuchwepheshe be-TDMA ngaphandle kokungqubuzana.
I-OLT ithola ukuthi i-ONU ohlelweni lwe-PON ngezikhathi ezithile ithumela imilayezo yeSango MPCP. Ngemva kokuba i-ONU engabhalisiwe ithola umlayezo weSango, izolinda isikhathi esingahleliwe (ukugwema ukubhaliswa kanyekanye kwama-ONU amaningi), bese ithumela umlayezo Wokubhalisa ku-OLT. Ngemva kokubhalisa ngempumelelo, i-OLT yabela i-LLID ku-ONU.
Ngemva kokubhaliswa kwe-ONU ne-OLT, i-Ethernet OAM ku-ONU iqala inqubo yokutholwa bese isungula ukuxhumana ne-OLT. I-Ethernet OAM isetshenziselwa ukuthola amaphutha akude kusixhumanisi se-ONU/OLT, icuphe i-loopback yesilawuli kude, futhi ithole ikhwalithi yesixhumanisi. Nokho, i-Ethernet OAM ihlinzeka ngosekelo lwama-OAM PDU angokwezifiso, amayunithi olwazi, nemibiko yesikhathi. Abakhiqizi abaningi be-ONU/OLT basebenzisa izandiso ze-OAM ukusetha imisebenzi ekhethekile yama-ONU. Uhlelo lokusebenza olujwayelekile ukulawula umkhawulokudonsa wabasebenzisi bokugcina ngokusebenzisa imodeli yomkhawulokudonsa enwetshiwe ku-ONU. Lolu hlelo lokusebenza olungajwayelekile luwukhiye wokuhlolwa futhi luba isithiyo ekuxhumaneni phakathi kwe-ONU ne-OLT.
Uma i-OLT inethrafikhi yokuthumela i-ONU, izophatha imininingwane ye-LLID yendawo okuyiwa kuyo i-ONU kuthrafikhi. Ngenxa yezici zokusakaza ze-PON, idatha ethunyelwe yi-OLT izosakazwa kuwo wonke ama-ONU. Ikakhulukazi, isimo lapho ithrafikhi engezansi idlulisela ukusakazwa kwesevisi yevidiyo kufanele kucatshangelwe. Ngenxa yezici zokusakaza zohlelo lwe-EPON, uma umsebenzisi enza ngendlela oyifisayo uhlelo lwevidiyo, luzosakazwa kubo bonke abasebenzisi, olusebenzisa umkhawulokudonsa ongezansi womfula. I-OLT ivamise ukusekela i-IGMP Snooping. Ingakwazi ukuqapha imilayezo ye-IGMP Joyina Yesicelo futhi ithumele idatha yokusakaza okuningi kubasebenzisi abahlobene neqembu esikhundleni sokusakaza kubo bonke abasebenzisi, ngaleyo ndlela yehlise ithrafikhi.
I-ONU eyodwa kuphela engathumela ithrafikhi ngesikhathi esithile. I-ONU inolayini abaningi ababalulekile (umugqa ngamunye uhambisana nezinga le-QoS. I-ONU ithumela umlayezo Wombiko ku-OLT ukuze icele ithuba lokuthumela, echaza isimo somugqa ngamunye. I-OLT ithumela umlayezo weSango ku-ONU ukutshela i-ONU isikhathi sokuqala sokudluliswa okulandelayo ku-OLT Kumele ikwazi ukuphatha izidingo zomkhawulokudonsa wawo wonke ama-ONU, futhi kufanele inikeze kuqala igunya lokudlulisela phambili Ngokuhambisana nokuhamba phambili komugqa, bhalansisa izicelo zama-ONU amaningi ikwazi ukuphatha izidingo zomkhawulokudonsa wawo wonke ama-ONU futhi yabele umkhawulokudonsa okhuphukayo okhuphukayo (okungukuthi i-algorithm ye-DBA).