PON yog dab tsi? Kev siv thev naus laus zis dav dav tau nce ntxiv, thiab nws yog lub hom phiaj los ua kev sib ntaus sib tua uas cov pa luam yeeb yuav tsis ploj mus. Tam sim no, cov khoom siv hauv tsev tseem yog ADSL thev naus laus zis, tab sis ntau thiab ntau cov khoom lag luam thiab cov tswv lag luam tau tig lawv lub ntsej muag rau optical network access technology.
Cov nqi tooj liab txuas ntxiv nce ntxiv, cov nqi cable txuas ntxiv poob qis, thiab qhov kev thov nce ntxiv rau IPTV thiab kev pabcuam video game yog tsav kev loj hlob ntawm FTTH. Lub zeem muag zoo nkauj ntawm kev hloov cov tooj liab cable thiab cov xaim coaxial cable los ntawm optical cable, xov tooj, cable TV, thiab cov ntaub ntawv broadband triple ua kom pom tseeb.
Daim duab 1: PON topology
PON (Passive Optical Network) passive optical network yog lub ntsiab thev naus laus zis kom paub FTTH fiber ntau rau hauv tsev, muab kev nkag mus rau point-to-multipoint fiber ntau, raws li qhia hauv daim duab 1, nws yogOLT(optical kab davhlau ya nyob twg) thiab cov neeg siv sab ntawm lub chaw ua haujlwm sab. CovONU(Optical Network Unit) thiab ODN (Optical Distribution Network) yog tsim. Feem ntau, cov downlink txais TDM tshaj tawm hom thiab cov uplink txais TDMA (Time Division Multiple Access) hom los tsim ib qho point-to-multipoint ntoo topology.The Qhov tseem ceeb tshaj plaws ntawm PON li optical access technology yog "passive". ODN tsis muaj cov khoom siv hluav taws xob thiab cov khoom siv hluav taws xob hluav taws xob. Tag nrho cov ntawm lawv yog tsim los ntawm passive Cheebtsam xws li splitters, uas muaj kev tswj tsis tshua muaj nqi thiab kev khiav hauj lwm nqi.
PON Kev Txhim Kho Keeb Kwm
Kev tshawb fawb PON thev naus laus zis tau pib xyoo 1995. Lub Kaum Hli 1998, ITU tau txais ATM-raws li PON thev naus laus zis tus qauv, G, tawm suab los ntawm FSAN lub koom haum (tag nrho cov kev pabcuam nkag mus rau hauv network). 983. Kuj hu ua BPON (BroadbandPON). Tus nqi yog 155Mbps thiab tuaj yeem xaiv 622Mbps.
EFMA (Ethernetin the First Mile Alliance) tau qhia txog lub tswv yim ntawm Ethernet-PON (EPON) thaum kawg ntawm xyoo 2000 nrog kev sib kis ntawm 1 Gbps thiab txheej txheej txuas raws li Ethernet encapsulation yooj yim.
GPON (Gigabit-CapablePON) tau thov los ntawm lub koom haum FSAN thaum lub Cuaj Hlis 2002, thiab ITU tau txais G hauv lub Peb Hlis 2003. 984. 1 thiab G. 984. 2 kev pom zoo. G. 984.1 Tag nrho cov yam ntxwv ntawm GPON nkag system yog teev.G. 984. 2 qhia txog lub cev kev faib tawm cuam tshuam txog sublayer ntawm ODN (Optical Distribution Network) ntawm GPON.Lub Rau Hli 2004, ITU dhau G dua. 984. 3, uas qhia meej txog qhov yuav tsum tau ua rau Transmission Convergence (TC) txheej.
Kev sib piv ntawm EPON thiab GPON cov khoom
EPON thiab GPON yog ob tus tswv cuab tseem ceeb ntawm kev nkag mus rau qhov muag pom, txhua tus muaj nws tus kheej tsim nyog, sib tw nrog ib leeg, ua kom muaj kev sib koom ua ke thiab kev kawm ntawm ib leeg. Cov hauv qab no sib piv lawv hauv ntau yam:
Tus nqi
EPON muab kev ruaj ntseg uplink thiab downlink ntawm 1.25Gbps, siv 8b/10b kab coding, thiab tus nqi tiag tiag yog 1Gbps.
GPON txhawb nqa ntau qib ceev thiab tuaj yeem txhawb nqa uplink thiab downlink asymmetric speeds, 2.5Gbps lossis 1.25Gbps downstream, thiab 1.25Gbps lossis 622Mbps uplink. Raws li qhov xav tau tiag tiag, tus nqi uplink thiab downlink tau txiav txim siab, thiab cov khoom siv kho qhov muag raug xaiv los ua kom cov khoom siv kho qhov muag ceev tus nqi sib piv.
Qhov kev txiav txim siab no: GPON zoo dua EPON.
Split ratio
Qhov sib cais yog pes tsawgONUs(cov neeg siv) nqa los ntawm ib tusOLTchaw nres nkoj (office).
Tus qauv EPON txhais tau tias qhov sib faib ntawm 1:32.
Tus qauv GPON txhais qhov sib faib piv rau hauv qab no 1:32; 1:64; 1:128
Qhov tseeb, cov txheej txheem EPON tseem tuaj yeem ua tiav qhov sib faib ntau dua, xws li 1: 64, 1: 128, EPON tswj raws tu qauv tuaj yeem txhawb nqa ntau dua.ONUs.Txoj kev sib piv yog tsuas yog txwv los ntawm kev ua tau zoo ntawm cov khoom siv kho qhov muag, thiab qhov sib faib loj loj yuav ua rau cov nqi kho qhov muag tau nce siab. Tsis tas li ntawd, PON qhov kev poob qis yog 15 mus rau 18 dB, thiab qhov sib cais loj txo qhov kev sib kis. Ntau tus neeg siv kev sib koom bandwidth kuj yog tus nqi ntawm qhov sib faib loj.
Qhov kev txiav txim siab no: GPON muab ntau yam kev xaiv, tab sis tus nqi txiav txim siab tsis pom tseeb. Qhov siab tshaj plaws lub cev nyob deb uas GPON system tuaj yeem txhawb nqa. Thaum lub optical split ratio yog 1:16, qhov siab tshaj plaws lub cev nyob deb ntawm 20km yuav tsum tau txais kev txhawb nqa. Thaum lub optical split ratio yog 1:32, lub siab tshaj plaws lub cev nyob deb ntawm 10km yuav tsum tau txais kev txhawb nqa. EPON yog tib yam,qhov xaus no: sib npaug.
QOS (Kev Pabcuam Zoo)
EPON ntxiv 64-byte MPCP (multi point control protocol) rau MAC header Ethernet header.MPCP tswj kev nkag mus rau P2MP point-to-multipoint topology los ntawm cov lus, lub xeev cov tshuab, thiab timers los siv DBA dynamic bandwidth faib.The MPCP koom nrog. faib ntawmONUkis tau tus mob lub sij hawm slots, tsis siv neeg nrhiav thiab koom ntawmONUs, thiab tshaj tawm ntawm kev sib tsoo mus rau cov khaubncaws sab nraud povtseg ntau dua rau kev faib cov bandwidth.MPCP muab kev txhawb nqa yooj yim rau P2MP topology. Txawm li cas los xij, txoj cai tsis tau faib cov kev pabcuam tseem ceeb. Txhua qhov kev pabcuam random sib tw rau bandwidth. GPON muaj qhov ua tiav DBA ntau dua thiab muaj peev xwm ua tau zoo QoS.
GPON faib cov kev pabcuam bandwidth faib ua plaub hom. Qhov tseem ceeb tshaj plaws yog tsau (Fixed), Assured, Non-Assured, thiab BestEffort. Lub DBA ntxiv txhais lub thawv tsheb (T-CONT) raws li qhov chaw sib tw tsheb thauj mus los, thiab txhua T-CONT raug txheeb xyuas los ntawm Alloc-ID. Txhua T-CONT tuaj yeem muaj ib lossis ntau dua GEMPort-IDs.T-CONT muab faib ua tsib hom kev pabcuam. Ntau hom T-CONTs muaj ntau hom kev faib cov bandwidth, uas tuaj yeem ua tau raws li QoS cov kev cai sib txawv ntawm cov kev pabcuam sib txawv rau kev ncua sijhawm, jitter, thiab pob ntawv poob tus nqi.T-CONT Hom 1 yog tus cwj pwm los ntawm lub sijhawm ruaj khov-bandwidth taag lub sijhawm, sib xws rau ib tug ruaj-bandwidth (Fixed) faib, haum rau ncua-sensitive kev pab cuam, xws li cov kev pab cuam lub suab. Hom 2 yog tus cwj pwm los ntawm kev ruaj khov bandwidth tab sis lub sijhawm tsis paub meej. Qhov sib txuas tau lees paub bandwidth (Assured) faib yog tsim rau cov kev pabcuam bandwidth ruaj khov uas tsis tas yuav muaj kev ntxhov siab, xws li video ntawm kev thov kev pabcuam. Hom 3 yog tus cwj pwm los ntawm qhov tsawg kawg nkaus bandwidth lav thiab dynamic sib koom ntawm redundant bandwidth, thiab muaj qhov txwv ntawm qhov siab tshaj plaws bandwidth, sib haum mus rau qhov tsis muaj kev ruaj ntseg bandwidth (Tsis yog-Assured) faib, haum rau cov kev pab cuam nrog cov kev pab cuam lav yuav tsum thiab loj tawg tsheb. Xws li rub tawm ua lag luam.Type 4 yog tus cwj pwm los ntawm BestEffort, tsis muaj bandwidth lav, haum rau cov kev pabcuam uas tsis tshua muaj latency thiab jitter, xws li WEB browsing service. Hom 5 yog hom kev sib xyaw ua ke, tom qab faib cov kev lees paub thiab tsis muaj kev lav phib xaub, ntxiv Cov kev xav tau bandwidth raug faib raws li qhov zoo tshaj plaws.
Cov ntsiab lus: GPON zoo dua EPON
Ua haujlwm thiab tswj OAM
EPON tsis muaj kev txiav txim siab ntau dhau rau OAM, tab sis tsuas yog txhais tau tias ONT tej thaj chaw deb qhov teeb meem txhaum cai, rov qab rov qab thiab txuas txuas, thiab yog kev txhawb nqa.
GPON txhais PLOAM (PhysicalLayerOAM) ntawm lub cev txheej, thiab OMCI (ONTManagementandControlInterface) yog txhais rau ntawm txheej sab sauv los ua OAM tswj ntawm ntau theem.PLOAM yog siv los siv cov ntaub ntawv encryption, kev tshawb pom, thiab kev saib xyuas yuam kev. OMCI channel raws tu qauv yog siv los tswj cov kev pabcuam uas tau teev tseg los ntawm txheej txheej sab saud, suav nrog cov txheej txheem kev ua haujlwm ntawmONU, hom thiab ntau npaum li cas ntawm T-CONT cov kev pabcuam, QoS tsis muaj, cov ntaub ntawv thov kev teeb tsa thiab cov ntaub ntawv txheeb xyuas kev ua haujlwm, thiab cia li ceeb toom cov xwm txheej khiav ntawm lub kaw lus txhawm rau ua raws li kev teeb tsa.OLTmus rau ONT. Kev tswj xyuas qhov txhaum, kev ua haujlwm thiab kev nyab xeeb.
Cov ntsiab lus: GPON zoo dua EPON
Txuas txheej encapsulation thiab kev pabcuam ntau yam
Raws li pom hauv daim duab 2, EPON ua raws li Ethernet cov ntaub ntawv yooj yim, tab sis ntxiv 64-byte MPCP point-to-multipoint tswj raws tu qauv rau Ethernet header los siv bandwidth faib, bandwidth round-robin, thiab nrhiav tsis siv neeg hauv EPON system. Kev sib tw thiab lwm yam haujlwm. Tsis muaj kev tshawb fawb ntau txog kev txhawb nqa ntawm cov kev pabcuam uas tsis yog cov kev pabcuam cov ntaub ntawv (xws li TDM synchronization cov kev pabcuam). Ntau tus neeg muag khoom EPON tau tsim qee cov khoom tsis yog qauv los daws qhov teeb meem no, tab sis lawv tsis zoo tagnrho thiab nws nyuaj rau ua kom tau raws li cov neeg nqa khoom-chav QoS cov cai.
Daim duab 2: Kev sib piv ntawm GPON thiab EPON raws tu qauv pawg
GPON yog ua raws li cov txheej txheem thauj tshiab tag nrho (TC), uas tuaj yeem ua tiav qhov kev hloov pauv ntawm cov kev pabcuam muaj ntau haiv neeg. Raws li pom nyob rau hauv daim duab 2, nws txhais lub ATM encapsulation thiab GFP encapsulation (general framing raws tu qauv). Koj tuaj yeem xaiv ob qho tib si. Ib qho yog rau kev lag luam encapsulation. Raws li qhov kev nyiam ntawm cov ntawv thov ATM tam sim no, GPON tsuas yog txhawb nqa GFP encapsulation muaj. Cov cuab yeej lite tau los ua, tshem ATM los ntawm pawg txheej txheem kom txo cov nqi.
GFP yog txheej txheem txuas txheej txheej txheej txheem rau ntau yam kev pabcuam, txhais los ntawm ITU raws li G. 7041.Ib tug me me ntawm kev hloov kho tau ua rau GFP hauv GPON, thiab PortID tau qhia ntawm lub taub hau ntawm GFP thav duab los txhawb ntau qhov chaw nres nkoj multiplexing. Ib qho Frag (Fragment) segmentation qhia kuj tau qhia los ua kom cov bandwidth zoo ntawm qhov system. Thiab nws tsuas yog txhawb cov ntaub ntawv ua hom rau cov ntaub ntawv ntev kuj sib txawv thiab tsis txhawb cov ntaub ntawv pob tshab ua hom rau cov ntaub ntawv thaiv. GPON muaj peev xwm nqa tau ntau yam kev pabcuam. GPON's TC txheej yog qhov tseem ceeb synchronous, siv tus qauv 8 kHz (125μm) thav duab ntev-ntev, uas tso cai rau GPON los txhawb lub sijhawm kawg-rau-kawg thiab lwm yam kev pabcuam quasi-synchronous, tshwj xeeb tshaj yog rau kev txhawb nqa ncaj qha TDM cov kev pabcuam, lub npe hu ua NativeTDM. GPON muaj "natural" kev txhawb nqa rau TDM cov kev pabcuam.
Qhov kev txiav txim siab no: TC txheej txhawb GPON rau ntau qhov kev pabcuam muaj zog dua li MPCP ntawm EPON.
Xaus
EPON thiab GPON muaj lawv tus kheej zoo. GPON zoo dua EPON nyob rau hauv cov nqe lus ntawm kev ua tau zoo ntsuas. Txawm li cas los xij, EPON muaj qhov zoo ntawm lub sijhawm thiab tus nqi. GPON tab tom ntes. Nrhiav rau pem hauv ntej mus rau yav tom ntej broadband nkag lag luam tej zaum yuav tsis yog ib tug hloov, nws yuav tsum tau complementary. Rau bandwidth, ntau qhov kev pabcuam, siab QoS thiab kev ruaj ntseg, thiab ATM thev naus laus zis raws li tus neeg siv khoom qaum, GPON yuav tsim nyog dua. Rau cov neeg siv khoom nrog tus nqi qis, QoS thiab kev ruaj ntseg, EPON tau dhau los ua qhov tseem ceeb.