1. Intshayelelo
Ngophuhliso olukhawulezayo lwetekhnoloji yokufikelela kwibroadband, ubugcisa obahlukeneyo obuvelayo bokufikelela kwibroadband buvele emva kwemvula.Emva kokuba iteknoloji ye-PON iteknoloji ye-DSL kunye ne-cable technology, enye i-platform yokufikelela efanelekileyo, i-PON inokubonelela ngokuthe ngqo ngeenkonzo ze-optical okanye iinkonzo ze-FTTH.I-EPON luhlobo olutsha lweteknoloji yokufikelela kwi-fiber network, usebenzisa amanqaku kwisakhiwo samanqaku amaninzi, ukuhanjiswa kokukhanya okungenamthombo, ukubonelela ngeenkonzo ezahlukeneyo ze-Ethernet.Isebenzisa i-PON's topology ukuphumeza ukufikelela kwe-Ethernet, kwaye iteknoloji ye-PON isetyenziswa kumaleko womzimba kumaleko womzimba.Ngoko ke, idibanisa iingenelo zeteknoloji yePON kunye neteknoloji ye-Ethernet: ixabiso eliphantsi;i-bandwidth ephezulu;ukuqina okunamandla, ukuguquguquka kunye nohlengahlengiso olukhawulezayo lwenkonzo;ukuhambelana ne-Ethernet ekhoyo;ulawulo olulula, njl uvavanyo lweEPON lwahluke kakhulu kwizixhobo ze-Ethernet zemveli.Eli nqaku ligxile kwitekhnoloji yovavanyo lwe-EPON.
I-2 EPON isingeniso sobuchwepheshe kunye nomngeni wokuvavanya
IEPONinkqubo iqulethe ubuninzi beeyunithi zenethiwekhi ye-optical, i-terminal yokukhanya (OLT), kunye ne-spectra enye okanye ngaphezulu (jonga uMfanekiso 1).Kwisalathiso se-downlink, isignali ethunyelwe yi-OLT isasazwa kuzo zonke ii-ONU.Kwi-uplink direction, i-TDMA i-multi-channel techniques isetyenzisiweyo, kunye nolwazi oluphezulu lwe-ONU ezininzi zenza ulwazi lwe-TDM kwi-OLT.I-802.3AH Guqula ifomathi yesakhelo se-Ethernet, chaza kwakhona isahlulo se-predefinctive, yongeza izitampu zexesha kunye ne-logical link identifiers (LLID).I-LLID ichonga i-ONU nganye ye-PON inkqubo kwaye ichaze i-LLID ngexesha lenkqubo yokufumanisa.
3 Itekhnoloji ephambili kwinkqubo yePON
Kwinkqubo ye-EPON, umgama womzimba phakathi kwe-ONU nganye kunye ne-OLT kwindlela yokuhambisa ulwazi oluphezulu alulingani.Ngokubanzi, inkqubo ye-EPON imisela ukuba owona mgama mde ukusuka kwi-ONU ukuya kwi-OLT yi-20km, kwaye owona mgama umfutshane yi-0km.Lo mahluko kumgama ubangela ukulibaziseka kwahluka phakathi kwe-0 kunye ne-200 yethu.Ukuba akukho msantsa waneleyo wokuzihlukanisa, iimpawu ezivela kwii-ONU ezahlukeneyo zinokufikelela ekupheleni kokufumana i-OLT ngaxeshanye, kubangele ukungqubana kweempawu ezisuka phezulu.Ukungqubuzana kunokubangela inani elikhulu leempazamo kunye nelahleko yongqamaniso, njl., okubangela ukuba inkqubo ingasebenzi kakuhle.Usebenzisa indlela yokusukela, qala ulinganise umgama womzimba, emva koko ulungelelanise zonke ii-ONU kumgama ofanayo wengqiqo njenge-OLT, uze wenze indlela ye-TDMA ukuphepha iingxabano.Iindlela ezisetyenziswayo ngoku zibandakanya ukusasazeka kwe-spectrum, ukuphuma kwe-band kunye ne-band-in-band-opening range.Umzekelo, usebenzisa indlela yokulinganisa ixesha, qala ukulinganisa ixesha lokulibaziseka kwe-loop ukusuka kwi-ONU nganye ukuya kwi-OLT, kwaye emva koko ufake ukulinganisa okuchanekileyo kwexabiso le-Td kwi-ONU nganye, ukwenzela ukuba ulibaziseko lwe-loop yazo zonke ii-ONU emva kokufaka i-Td ingakwazi. ukufunyanwa Ixesha (ekubhekiselwa kulo njengexabiso lolibaziseko lwe-loop yokulinganisa i-Tequ) iyalingana, kwaye umphumo ufana nokuhambisa i-ONU nganye kumgama ofanayo onengqondo njenge-OLT, kwaye emva koko ukuthumela isakhelo ngokuchanekileyo ngokweteknoloji ye-TDMA ngaphandle kokungqubana.
I-OLT ifumanisa ukuba i-ONU kwinkqubo ye-PON ithumela ngamaxesha athile iSango MPCP imiyalezo.Emva kokuba i-ONU engabhaliswanga ifumana umyalezo weSango, iya kulinda ixesha elingenammiselo (ukuphepha ukubhaliswa kwangaxeshanye kwee-ONU ezininzi), kwaye emva koko uthumele umyalezo weBhalisa kwiOLT.Emva kobhaliso oluyimpumelelo, iOLT yabela i-LLID kwi-ONU.
Emva kokuba iirejista ze-ONU kunye ne-OLT, i-Ethernet OAM kwi-ONU iqala inkqubo yokufumanisa kwaye iseke uxhulumaniso kunye ne-OLT.I-Ethernet OAM isetyenziselwa ukufumanisa iimpazamo ezikude kwikhonkco ye-ONU / OLT, iqalise i-loopback ekude, kwaye ibone umgangatho wekhonkco.Nangona kunjalo, i-Ethernet OAM inikezela ngenkxaso ye-PDU ye-OAM yesiko, iiyunithi zolwazi, kunye neengxelo zexesha.Abavelisi abaninzi be-ONU/OLT basebenzisa izandiso ze-OAM ukuseta imisebenzi ekhethekileyo yee-ONU.Isicelo esiqhelekileyo kukulawula i-bandwidth yabasebenzisi bokugqibela ngokusebenzisa imodeli yoqwalaselo olwandisiweyo lwe-bandwidth kwi-ONU.Esi sicelo esingenamgangatho sisitshixo sovavanyo kwaye sibe ngumqobo kwi-intercommunication phakathi kwe-ONU kunye ne-OLT.
Xa i-OLT inetrafikhi yokuthumela i-ONU, iya kuthwala ulwazi lwe-LLID yendawo ekuyiwa kuyo i-ONU kwi-traffic.Ngenxa yeempawu zosasazo lwe-PON, idatha ethunyelwe yi-OLT iya kusasazwa kuzo zonke ii-ONU.Ngokukodwa, imeko apho i-traffic traffic esezantsi ihambisa umjelo wenkonzo yevidiyo kufuneka ithathelwe ingqalelo.Ngenxa yeempawu zokusasazwa kwenkqubo ye-EPON, xa umsebenzisi elungiselela inkqubo yevidiyo, iya kusasazwa kubo bonke abasebenzisi, abasebenzisa i-bandwidth eninzi.I-OLT ihlala ixhasa i-IGMP Snooping.Inokubeka iliso kwi-IGMP Joyina imiyalezo yeSicelo kwaye ithumele idatha ye-multicast kubasebenzisi abanxulumene neqela endaweni yokusasaza kubo bonke abasebenzisi, ngaloo ndlela inciphisa i-traffic.
Inye kuphela i-ONU enokuthumela itrafikhi ngexesha elithile.I-ONU inemigca emininzi ebalulekileyo (umgca ngamnye uhambelana nenqanaba leQoS. I-ONU ithumela umyalezo weNgxelo kwiOLT ukucela ithuba lokuthumela, ichaza imeko yomgca ngamnye. I-OLT ithumela umyalezo weSango kwi-ONU ukuxelela i-ONU ixesha lokuqala lothumelo olulandelayo kwiOLT Kufuneka ikwazi ukulawula iimfuno zebhanwidth yazo zonke ii-ONU, kwaye kufuneka inike ingqwalaselo ephambili kugunyaziwe wothumelo.Ngokokubaluleka komgca, ukulinganisa izicelo zee-ONU ezininzi.I-OLT kufuneka ibe ekwaziyo ukulawula iimfuno zebhanwidth yazo zonke ii-ONU kunye nokwabela umda onyukayo womlambo (okt i-algorithm ye-DBA).