Okokuqala, iyiphi inkinga i-PON esetshenziselwa ukuyixazulula?
● Ngokuvela kwezinsizakalo zomkhawulokudonsa ophezulu njengevidiyo efunwayo, imidlalo ye-inthanethi ne-IPTV, abasebenzisi banesidingo esiphuthumayo sokwandisa umkhawulokudonsa wokufinyelela.Izindlela ezikhona zokufinyelela i-broadband ezisekelwe ku-ADSL ziya ngokuya ziba nzima ukuhlangabezana nezidingo zomsebenzisi zomkhawulokudonsa ophezulu, ezimbili- indlela yokudlulisa amandla, nokuphepha.
● Ngenxa yebanga elide lokudlulisela, ikhono eliqinile lokulwa nokuphazamiseka kanye nomthamo omkhulu, i-fiber optical isetshenziswe kabanzi kunethiwekhi yomgogodla.Eminyakeni yamuva, ngokuncipha kwezindleko zedivayisi yokubona, i-fiber optical kancane kancane isibe yinketho yokuqala yendlela yokudlulisela yenethiwekhi yokufinyelela.
● Inethiwekhi ye-Passive Optical (PON) iyindleko ephansi kumodi yokufinyelela ifayibha futhi ingathuthukiswa ngokushelela.Iya ngokuya ithandwa ngabasebenza ngocingo futhi ithathwa njengesixazululo esifanelekile sokuxazulula inkinga “yemayela lokugcina”.
Okwesibili, ukwakheka kwe-PON
I-PON iqukethe izingxenye ezintathu: i-optical line termination (OLT), i-optical network unit (ONU), kanye ne-passive optical splitter (POS).
I-PON iyi-asymmetric, i-point-to-multipoint (P2MP) isakhiwo.Izindima ezidlalwa i-OLT kanye ne-ONU zihlukile.I-OLT ilingana nendima yeNkosi, futhi i-ONU ilingana nendima yeSigqila.
Okwesithathu, izinzuzo ze-PON:
● Iyalondoloza
I-P2P - Ayikho imicu ye-optical;I-2N i-optical transceiver
I-P2PCurb - i-fiber engu-1;2N+2 i-transceiver ebonakalayo;idinga ugesi wendawo;yonga i-fiber eningi
I-P2MP (PON) - i-fiber engu-1;i-transceiver ye-N+1;inani elikhulu lemicu ye-optical elondoloziwe;inani elikhulu lama-transceiver optical
● Uthembekile
Isignali ayidluli kudivayisi ye-elekthronikhi esebenzayo phakathi nenqubo yokudlulisa i-PON, inciphisa kakhulu iphuzu elingase lihluleke;
Ukusetshenziswa kwemishini yokwenziwa kwenza kube lula ukulandelana kwenethiwekhi, futhi isakhiwo senethiwekhi esicaba kulula ukusinakekela nokuphatha.
● Ibanga elide
Ibanga lokudlulisela le-PON liyi-10 ukuya ku-20km, elinqoba ngokuphelele umkhawulo webanga phakathi kwe-Ethernet kanye nezindlela zokufinyelela ze-xDSL, futhi lithuthukisa kakhulu ukuguquguquka kokuthunyelwa kwehhovisi lokugcina lomsebenzisi.
● Umkhawulokudonsa ophezulu
Uma kuqhathaniswa ne-xDSL, i-PON inomkhawulokudonsa ophezulu futhi ihlangabezana ngokugcwele nezidingo zezinsizakalo zokusakaza ku-inthanethi ze-HDTV zesikhathi esizayo.
● Uyavumelana nezimo
Imodeli yenethiwekhi ye-PON ayikhawulelwe, futhi inethiwekhi ye-topology yesihlahla nenkanyezi ingakhiwa ngendlela evumelana nezimo.
I-PON ifaneleke ikakhulukazi izikhathi lapho izindawo zolwazi lokufinyelela komsebenzisi zihlakazeka khona, kanye ne-trunk optical fiber ingenelisa ukufinyelela kwabo bonke abasebenzisi ukuze bafinyelele amaphuzu olwazi.
Okwesine, izinga eliyinhloko le-PON
● I-GPON – I-GigabitPON, iphrothokholi ejwayelekile ye-ITUG.984, ukuthuthukiswa nokunwetshwa kwe-APON, kusetshenziswa ifomethi yozimele evamile ukuze kuhlinzekwe usekelo lwezinsiza ezihlukahlukene.Isilinganiso esiphezulu singu-2.5Gbps.I-GPON inezinzuzo ngesivinini esikhulu nokusekelwa kwezinsizakalo eziningi, kodwa ubuchwepheshe bunzima, izindleko ziphezulu, futhi ukuvuthwa komkhiqizo akuphakeme.
● I-EPON——Ethernetover PON, IEEE802.3ah ejwayelekile yephrothokholi, ethumela amaphakethe efomethi ye-Ethernet kunethiwekhi ye-PON futhi engasekela isilinganiso se-symmetric esingu-1.25Gbps.I-EPON isuselwe kubuchwepheshe be-Ethernet futhi umthetho olandelwayo ulula futhi uyasebenza.Uma kuqhathaniswa ne-APON, i-GPON inezinzuzo ezisobala ngokwezindleko.
Okwesihlanu, Ubuchwepheshe Obubalulekile be-EPON
● Ukuphindaphinda kwesiteshi
Uhlelo lwe-EPON lwamukela ubuchwepheshe be-WDM ukuze bubone ukudluliswa kwe-bidirectional ye-fiber eyodwa;
Izinga lesiteshi ngu-1.25 Gbps phezulu nomfula.
● Imodi yokudlulisela ye-EPON downlink – imodi yokusakaza
● Imodi yokudlulisa ye-EPON uplink – Imodi ye-TDMA
● I-Multipoint Control Protocol – MPCP
Ngokungafani nesakhiwo se-Ethernet P2P, i-PON iyisakhiwo se-P2MP.I-ONU iqhudelana ngezinsiza zesiteshi se-uplink, futhi kudingeka indlela yokulamula ukuze kugwenywe ukungqubuzana kwedatha ye-uplink kanye nokwaba izinsiza zesiteshi ngendlela efanele.Iphrothokholi ye-802.3ah icacisa iphrothokholi yokulawula ehambisanayo, i-Multi-point MAC Control Protocol (MPCP);
I-lMPCP ichaza kakhulu i-Multi-point MAC Control sublayer ukuze inwebe futhi imiselele isendlalelo esingaphansi sokulawula kwe-MAC esichazwe yiphrothokholi engu-802.3.Uhlaka lokulawula lwephrothokholi ye-MPCP lubaluleke kakhulu kunohlaka lwedatha ye-MACClient.
● Isinxephezelo esilinganisa nokubambezeleka
I-EPON uplink transmission isebenzisa imodi ye-TDMA.I-OLT inquma isikhathi sokuthi i-ONU ithumele idatha.Njengoba i-ONU ngayinye ihlukile ku-OLT, kuzoba khona umehluko wokulibaziseka.Uma ingekho indlela esebenzayo yesinxephezelo sokulibaziseka, ukungqubuzana kokudluliswa kwedatha ye-uplink kusazokwenzeka.
Ukulinganisa kwe-EPON nesinxephezelo sokubambezeleka kuwubuchwepheshe obuyinhloko bokuphindaphindeka kwesiteshi se-uplink.Ø Kunqubo ye-DiscoveryProcessing, i-OLT ibala inani le-RTT (RoundTrip Time) le-ONU ngayinye ngokulinganisa i-ONU esanda kubhaliswa.
I-OLT isebenzisa i-RTT ukulungisa isikhathi sokugunyazwa se-ONU ngayinye.
I-OLT ingase futhi iqale ukusuka lapho ithola i-MPCP PDU.
Isibalo se-RTT:
Uhlaka lwe-GATE luqukethe inkambu “yesitembu sesikhathi” i-ONU eyisebenzisela ukuvuselela irejista yesikhathi sasendaweni.I-OLT ingabala i-RTT ngohlaka olutholiwe lwe-REPORT ukuze yenze isinxephezelo sokuhlola.
● I-Dynamic Bandwidth Allocation (DBA)
Ukuqhathaniswa kwezikhala zesikhathi esimisiwe kanye nezikhala zesikhathi eziguqukayo:
