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: ukunqanyulwa komugqa optical (OLT), iyunithi yenethiwekhi yokubona (I-ONU), kanye ne-passive optical splitter (POS).
I-PON iyi-asymmetric, i-point-to-multipoint (P2MP) isakhiwo. Izindima ezidlalwa yi-OLTkanye neI-ONUzihlukile. IOLTlilingana neqhaza leNkosi, kanye neI-ONUilingana 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 kuya 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. II-ONUiqhudelana nezinsiza 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. IOLTinquma isikhathi se-I-ONUukuthumela idatha. Kusukela ngamunyeI-ONUyehlukile ku-OLT, kuzoba nomehluko 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, iOLTibala inani le-RTT (I-RoundTrip Time) ngayinyeI-ONUngokulinganisa abasanda kubhaliswaI-ONU.
IOLTisebenzisa i-RTT ukulungisa isikhathi sokugunyazwa sayo ngasinyeI-ONU.
IOLTingase futhi iqale ukusukela lapho ithola i-MPCP PDU.
Isibalo se-RTT:
Uhlaka lwe-GATE luqukethe inkambu "yesitembu sesikhathi" laphoI-ONUisebenzisa ukuvuselela irejista yesikhathi sasendaweni. IOLTingabala i-RTT ngohlaka olutholiwe LWEMBIKO ukuze yenze isinxephezelo sokuhlola.
● I-Dynamic Bandwidth Allocation (DBA)
Ukuqhathaniswa kwezikhala zesikhathi esimisiwe kanye nezikhala zesikhathi eziguqukayo:
