Gii thiu v mng quang th ng GPON

- 1 -Table of ContentsKhi nim v GPON FTTH3Nhng ni dung chnh ca GPON4Kin trc ca GPON4K thut truy nhp TDMA5Phng thc ng gi d liu5Phng thc cp pht bng thng ng (hng ln)6Cc m hnh trin khai GPON FTTx84 m hnh trin khai FTTx83 m hnh bo v tuyn trong GPON9Thng s k thut10Kh nng cung cp dch v11Mng phn phi quang(ODN): Cc ni dung chnh v gi xy dng mng12Cc thnh phn mng phn phi quang (ODN)12Qu suy hao cng sut quang trong GPON v tnh ton suy hao ton tuyn13Vi gi trong vic xy dng mng phn phi quang ODN15Mt vi im ni bt ca mng GPON16V d v mt s thit b GPON (miniOLT, ONT, splitter )18miniOLT18Mt s mu ONT19Mt s loi Splitter21

1. Khi nim v GPON FTTHMng FTTH bao gm cc ng quang i t nh cung cp dch v c dng chung cho mt s khch hng. S c mt ng quang i n mt nhm khch hng gn nhau v mt a l. Ti y ng quang dng chung ny s c chia tch thnh cc ng quang ring bit i n tng khch hng.Mng truy nhp quang th ng PON l kiu mng im-a im. Mi khch hng c kt ni ti mng quang thng qua mt b chia quang th ng, v vy khng c cc thit b in ch ng trong mng phn chia v bng thng c chia s t nhnh n ngi dng. Tn hiu ng xung c pht qung b ti cc thu bao, tn hiu ny c m ha trnh vic xem trm. Tn hiu ng ln c kt hp bng vic s dng giao thc a truy nhp phn chia theo thi gian (TDMA), OLT s iu khin cc ONU s dng cc khe thi gian cho vic truyn d liu ng ln.Trong mng PON, OLT l thnh phn chc nng chnh ca h thng thng t phng my chnh. ONU/ONT l thit b t pha ngi dng.ONU/ONT kt ni ti OLT bng cc si quang v khng c cc thnh phn ch ng gia (mt ONU/ONT ch dng 1 si quang ni ln splitter v OLT). B chia tn hiu (splitter) l thnh phn rt quan trng cua h thng, mt b chia s dng ti a cho 64 khch hng.B khuyn ngh G.984 ca ITU a ra tiu chun cho mng PON tc gigabit (GPON). Mng GPON c dung lng mc gigabit cho php cung cp cc ng dng video, truy nhp internet tc cao, multimedia, v cc dch v bng thng rng. Cng vi dung lng mng gia tng, tiu chun mi ny a ra kh nng x l IP v Ethernet hiu qu hn.

2. Nhng ni dung chnh ca GPONKin trc ca GPON

Figure 1: Kin trc mng GPON

H thng G-PON bao gm 3 thnh phn chnh: OLT, ONT/ONU, ODN (splitter )Thit b kt cui quang (Optical Line Terminator) OLT (thng t ti phng my CO)Cc thit b u cui quang (Optical Network Terminer = ONT) hoc Khi mng quang (Optical Network Unit=ONU) t ti pha khch hng. ONU (Optical Network Unit): thit b kt cui mng cp quang tch cc, kt ni vi OLT thng qua mng phn phi quang (ODN) thng dng cho trng hp kt ni ti buiding hoc ti cc va h, cabin (FTTB, FTTC, FTTCab)Mng phn phi quang (Optical Distribution Network = ODN). ODN gm c 2 thnh phn chnh l b chia quang (Splitter) v cc si quang, ngoi ra cn c cc ph kin khc nh t phn phi quang (ODF), mng xng, t ngoi tri.B chia/ghp quang th ng (Splitter): Dng chia/ghp th ng tn hiu quang t nh cung cp dch v n khch hng v ngc li gip tn dng hiu qu si quang vt l. Splitter thng c t ti cc im phn phi quang (DP) v cc im truy nhp quang (AP). B chia/ghp quang s c 2 loi, mt loi t ti cc nh trm vin thng s dng cc t kiu indoor, loi th 2 s l loi thit b c bc kn c th m ra c khi cn thit v t ti cc im mng xng hay t phi quang t ngoi tri

Trong mng GPON ch c 2 loi phn t l thit b tch cc (yu cu phi c ngun in) l OLT, ONT/ONU. Cc thnh phn khc trong mng (splitter, ph kin quang) u l thit b th ng (khng yu cu phi cp ngun) do gim thiu c rt nhiu s c c th c i vi mt phn t tch cc.K thut truy nhp TDMAK thut truy nhp c s dng ph bin trong cc h thng GPON hin nay l a truy nhp phn chia theo thi gian (TDMA).TDMA l k thut phn chia bng tn truyn dn thnh nhng khe thi gian k tip nhau. Nhng khe thi gian ny c th c n nh trc cho mi khch hng hoc c th phn theo yu cu tu thuc vo phng thc chuyn giao ang s dng. Hnh di y l mt v d v vic s dng TDMA trn GPON hnh cy. Mi thu bao c php gi s liu ng ln trong khe thi gian ring bit. B tch knh sp xp s liu n theo v tr khe thi gian ca n hoc thng tin c gi trong bn thn khe thi gian. S liu ng xung cng c gi trong nhng khe thi gian xc nh.

Figure 2: K thut a truy nhp TDMA trong GPON

GPON s dng k thut TDMA c u im rt ln l cc ONU c th hot ng trn cng mt bc sng, v OLT hon ton c kh nng phn bit c lu lng ca tng ONU. OLT cng ch cn mt b thu, iu ny s d dng cho vic trin khai thit b, gim c chi ph cho cc qu trnh thit k, sn xut, hot ng v bo dng. Ngoi ra, vic s dng k thut ny cn c mt u im l c th lp t d dng thm cc ONU nu c nhu cu nng cp mngPhng thc ng gi d liuGPON nh ngha hai phng th c ng gi ATM v GEM (GPON Encapsulation Method). Cc ONU v OLT c th h tr c T-CONT nn ATM hoc GEM.Phng thc ng gi d liu GPON (GPON Encapsulation Method - GEM) s dng ng gi d liu qua mng GPON. GEM cung cp kh nng thng tin kt ni nh hng tng t ATM. GPON cho php h tr nhiu loi hnh dch v khch hng khc nhau. Khch hng ATM c sp

xp trong sut vo khung GEM trn c hai hng. Khch hng TDM c sp xp vo khung GEM s dng th tc ng gi GEM. Cc gi d liu bao gm c cc khung Ethernet cng c sp xp s dng th tc ng gi GEM. GEM cng h tr vic phn mnh hoc chia nh cc khung ln thnh cc phn mnh nh v ghp li u thu nhm gim tr cho cc lu lng thi gian thc. Lu lng d liu bao gm cc khung Ethernet, cc gi tin IP, IPTV, VoIP v cc loi khc gip cho truyn dn khung GEM hiu qu v n gin. GPON s dng GEM mang li hiu qu cao trong truyn dn ti tin IP nh s dng ti 95% bng thng cho php trn knh truyn dnPhng thc cp pht bng thng ng (hng ln)Ti hng ln bng thng c s dng bi cc ONU khng ch ph thuc vo bi cnh lu lng ti cc ONU c lin quan m ng thi lin quan n lu lng ti cc ONU khc trong mng. V s dng mi trng chia s bng thng nn lu lng truyn bi mi ONU c kh nng b xung t v qu trnh truyn li lm gim hiu sut. Do hng ln GPON s dng phng thc cp pht bng thng ng DBA (Dynamic Bandwidth Assignment). Cc khung truyn dn hng ln c chia thnh 5 loi TCONT (Transmission Container) s dng qun l vic cp pht bng thng hng ln.Loi I - TCONT: trn c s c cp pht bng thng c nh hay l dch v yu cu bng thng c nh, khng c phc v bi DBA.Loi II - TCONT cho dch v c tc bit thay i vi yu cu v tr v jitter nh truyn hnh v VoIP.Loi III - TCONT cho cc dch v c m bo v tr. Loi IV - TCONT cho lu lng best-effort.Loi V - TCONT l kt hp ca hai hay nhiu loi x - TCONT trn. Bo co mu lu lng gi ti OLT bi mi ONU bao gm mu ca mi loi TCONT v ch s cp pht t pha OLT. OLT s da vo loi TCONT ra quyt nh cp pht bng thng hng ln cho ONU.

Figure 3: Bo co vo phn b bng thng trong GPON

Th tc cp pht ni chung gm cc bc sau: ONU lu d liu thu bao cho lu lng hng ln vo b m Khi d liu cha trong b m c bo ti OLT nh mt yu cu ti mt thi im quy nh bi OLT OLT xc nh thi gian bt u truyn dn v khong thi gian truyn cho php (1/4 ca s truyn dn) ti ONU nh mt s cp php ONU nhn s cp php v truyn khi d liu xc nh

Figure 4: Th tc cp pht bng thng trong GPON

Cc m hnh trin khai GPON FTTx

4 m hnh trin khai FTTxCn c vo vn xa ca cp quang t OLT ti ONT/ONU m chia thnh 4 m hnh trin khai FTTx in hnh: FTTH, FTTB/FTTO, FTTC

Figure 5: Cc m hnh trin khai FTTx s dng GPON

Figure 6: Cc m hnh trin khai FTTx s dng GPON

2.5.2. 3 m hnh bo v tuyn trong GPONType A: d phng cp quang gia OLT v splitter

Figure 7: M hnh bo v Type A

Type B: d phng cp quang gia OLT v splitter, d phng cng GPON trn OLT , splitter c 2 u vo.

Figure 8: M hnh bo v type B

Type C: d phng cp quang gia OLT v splitter, d phng cng GPON trn OLT , d phng splitter, d phng ONU/ONT. M hnh ny an ton nht nhng c chi ph cao.

Figure 9: M hnh bo v Type C

M hnh bo v tuyn type B, trong 2 tuyn gia OLT v Splitter i theo 2 hng cp vt l khc nhau l m hnh cn bng gia an ton ca mng v chi ph u t.

Thng s k thut(wave length, bitrate, logical distance, physical distance, splitting ratio)Bc sng hot ng ng xungDi bc sng hot ng cho ng xung s dng mt si quang l 1480-1500 nm. (thng gi l bc sng quanh 1490nm)Ngoi ra, khi tn hiu analog CATV c ghp trn cng 1 si quang, CATV s ng truyn theo hng t xung ONTs bng di bc sng quanh 1550 nm (1535-1600 nm) ng lnDi bc sng hot ng cho ng ln l 1260-1360 nm (thng gi chung l bc sng quanh 1310 nm)Tc bitGPON nh ngha nhng dng tc bit nh sau: ng ln 155 Mbit/s, ng xung 1.25 Gbit/s; ng ln 622 Mbit/s up, ng xung 1.25 Gbit/s; ng ln 1.25 Gbit/s up, ng xung 1.25 Gbit/s; ng ln 155 Mbit/s up, ng xung 2.5 Gbit/s; ng ln 622 Mbit/s up, ng xung 2.5 Gbit/s; ng ln 1.25 Gbit/s up, ng xung 2.5 Gbit/s;Ph bin nht hin ny l ng ln 1.25 Gbit/s up, ng xung 2.5 Gbit/s;Khong cch logicKhong cch logic l khong cch ln nht gia ONU/ONT v OLT m cha tnh n cc yu t gy suy hao cng sut quang trn tuyn. Trong mng GPON, khong cch logic ln nht l 60 km.Khong cch vt lKhong cch vt l l khong cch vt l ln nht gia ONU/ONT v OLT. Trong mng GPON khong cch vt l ti a l 20 km.Khong cch si quang chnh lchL khong cch gia si quang ngn nht v xa nht. Trong mng GPON khong cch si quang chnh lch l 20 km. Thng s ny c nh hng n kch thc vng ph mng v cn tng thch vi tiu chun ITU-T Rec. G.983.1.

T l chia ca splitteri vi nh khai thc mng th t l chia cng ln cng tt. Tuy nhin t l chia ln th i hi cng sut quang pht cao hn h tr khong cch vt l ln hn. T l chia 1:64 l t l l tng cho lp vt l vi cng ngh hin nay. Tuy nhin trong cc bc pht trin tip theo th t l 1:128 c th c s dng.

3. Kh nng cung cp dch vGPON c xy dng cung cp tt c cc dch v hin c v c cc dch v mi cho cc thu bao gia nh v doanh nghip s dng do kh nng truyn bng rng ca mng. Cc dch v c th do cc nh khai thc mng cung cp s ty thuc vo cc iu kin quy ch ring ca tng th trng i vi nh khai thc mng.c im dch v: GPON c trin khai p ng t l dung lng dch v/chi ph khi so snh vi mng cp ng/DSL v mng HFC c dung lng nh v cc mng SDH/SONET cng nh gii php quang Ethernet im - im c chi ph cao. V vy n ph hp vi cc h gia nh, doanh nghip va v nh, chnh ph v cc c quan cng s.Cc dch v b ba dnh cho h gia nh: GPON c pht trin mang n cc dch v th h mi nh IPTV, truyn hnh theo yu cu, game trc tuyn, Internet tc cc cao v VoIP vi chi ph hiu qu, bng thng ln v cht lng m bo cho cc thu bao h gia nh.IP qung b qua cu hnh im - a im cho php mt lung video c th truyn ti nhiu thu bao mt cch ng thiKh nng cp pht bng thng ng v phc v qu ti cho php cc nh cung cp dch v ti u ha bng thng quang, to ra nhiu li nhun hn. Bng thng ln v dch v linh hot ca GPON gip cho GPON tr thnh mt s la chn hon ho cho vic cung cp dch v ti nhiu h thu bao MDU (Multiple Dwelling Units) nh cc ta nh, khch sn, chung c. GPON ONU c th phc v nh cc DSLAM.Vi cc doanh nghip va v nh: GPON l s la chn hon ho cho cc doanh nghip va v nh c yu cu v thoi, truy nhp Internet, VPN vi chi ph hp l. GPON c bng thng ln v c tnh nng QoS cho php cc dch v lp doanh nghip c th c cung cp trn cng c s h tng nh cc dch v h gia nh nhm loi tr yu cu xy dng c s h tng mi.Vi Chnh ph, Gio dc v Y t: Th trng cc c quan chnh ph yu cu cc dch v d liu v thoi c cht lng cao v bng thng ln vi chi ph thp. Kh nng ca GPON cho php phc v hiu qu mt s lng ln thu bao cc khu vc trung tm vn phng chnh ph, cc trng hc, bnh vin cng nh cc khu vui chi gii tr, khu cng nghip.Khong cch OLT - ONU: Gii hn c ly ca cng ngh GPON hin ti c quy nh trong khong 20 km v cung cp t l chia ln ti 1:64.

Cc ng dng c bn trong mng: GPON c ng dng ch yu trong cc mng sau: GPON c ng dng trong cc mng truy nhp quang FTTx cung cp cc dch v nh IPTV, VoD, RF Video (chng ln), Internet tc cao, VoIP, h tr QoS y . Thng tin lin lc - Cc ng thoi, thng tin lin lc, Truy cp internet, intranet tc cao, Truy cp internet khng dy ti nhng a im cng cng, ng bng thng ln v lm backhaul cho mng khng dy Bo mt - Camera, Bo chy, bo t nhp, Bo ng an ninh, trung tm iu khin 24/7 vi kh nng gim st, backup d liu

4. Mng phn phi quang(ODN): Cc ni dung chnh v gi xy dng mngCc thnh phn mng phn phi quang (ODN)Mng cp thu bao quang c xc nh trong phm vi ranh gii t giao tip si quang gia thit b OLT n thit ONU/ONT.

Figure 10: Cu trc c bn mng phn phi quang (ODN)

Mng cp quang thu bao c cu thnh bi cc thnh phn chnh nh sau:Cp quang gc (Feeder Cable): xut pht t pha nh cung cp dch v (hay cn gi chung l Central Office) ti im phn phi c gi l DP (Distribution Point).im phn phi si quang (DP): l im kt thc ca on cp gc. Trn thc t trin khai, im phn phi si quang thng l mng xng quang, hoc cc t cp quang phi, u tin dng mng xng quang.Cp quang phi (Distribution Optical Cable): xut pht t im phi quang (DP) ti cc im truy nhp mng (AP - Access Point) hay t cc t quang phi ti cc tp im quang.Cp quang thu bao (Drop Cable): xut pht t cc im truy nhp mng (AP) hay l t cc tp im quang n thu bao.

Figure 11: Mng phn phi quang (ODN) v cc thnh phn ca n

Qu suy hao cng sut quang trong GPON v tnh ton suy hao ton tuynTheo chun G.984.2 Qu suy hao cng sut quang trong G-PON c m t nh sau

ItemsUnitSingle fibre

Minimum optical loss at 1490 nmdB13

Minimum optical loss at 1310 nmdB13

Maximum optical loss at 1490 nmdB28

Maximum optical loss at 1310 nmdB28

Suy hao ton tuyn t OLT ti ONU/ONT khng c vt qu 28dB (gi tr ny l Qu Suy hao cng sut quang)-Tng suy hao trn tuyn c hp thnh t cc yu t sau: Suy hao trn si quang (ph thuc chiu di cp)Suy hao khi i qua SplitterSuy hao mi hn (Splice Attenuation) (ph thuc s mi hn)Suy hao gic ni (Adapter Connectors Attenuation) (ph thuc s connectors) Qu cng sut D phng

ItemsSuy hao (dB)

Suy hao s quang0.35dB/km

Suy hao mi hn0.1dB/point

Suy hao do Adaptor0.3dB/point

D phng1~3dB

T l chia ca SplitterSuy hao (dB)

1:23.5 dB

1:47.2 dB

1:810.5 dB

1:1613.5 dB

1:3217.0 dB

1:6419.7 dB

Figure 12: S kt ni mt tuyn ODN

Total Loss =Fiber Attenuation x (Length of Cable)+Splitter Attenuation Losses+Splice Attenuation x (No. of splice)+Connectors Attenuation x (No. of connectors)+Safety Margin=0.35*4.5 + 19.7 + 0.1*7 +0.3*5 + 2=25.48 dB

ContentUnitAttentuationRemark

Fiber attenuationdB1.580.35dB/km, L=3.5km

Splicing attenuationdB0.70.1dB/pcs, as 7 fixed connector

Adapter connector attenuationdB1.50.2~0.3dB/pcs, as 5 active connector

Splitter attenuationdB19.71:64 splitter

Safety MargindB2

Total AttenuationdB25.48GPON allowed attenuation 10, v s ko thng cp quang ti tng thu bao thuc cm thu bao < 10 t splitter cp 1.Trin khai mi ton b cc si cp da trn cc cng b sn c, hn ch ti a vic xy dng cng b mi. Trong trng hp khong cch t OLT n cc Splitter >10km th u tin s dng si cp cn trng trn tuyn cp c.S lng cp quang gc: Thng thng cc si cp quang gc c dung lng ti thiu t 48 i si quang tr lnCc im phn phi cp (DP) u tin s dng mng xng quang, trong cc trng hp tht cn thit c th dng ODF. Nu dng ODF th yu cu cu trc Module lp trong cc Rack tiu chun ETSI, c t ngoi tri hoc trong nh tu theo a bn, phi c kho ca bo v, t phi phi c kh nng lp t b chia/ghp (Splitter) cho mng GPON, hp ph kin quang (cassette, chuyn i quang, suy hao, dy nhy ...)S lng cp quang phi: thng thng si cp quang phi c dung lng t 24 i si quang tr ln.Cc im truy nhp/kt cui (AP) c s dng l ODF loi nh, c dung lng t 24 FO n 48 FO treo trn tng/ct, trong b cp hoc lp trn b bc ngoi tri, trong nh, phi c kho bo v v phi c kh nng lp t b chia/ghp (Splitter).S lng cp quang thu bao: thng thng cc si cp quang thu bao c dung lng nh 4 si.Chun u ni quang: cn thng nht chun u ni quang gim thiu suy hao.Cc bc xy dng cu hnh mng: La chn hnh thc cung cp FTTx La chn khu vc trin khai D bo s lng thu bao. Tnh ton s lng thit b Tnh ton dung lng kt ni ln mng MAN Xc nh a im lp t thit b Xy dng cu hnh mng

5. Mt vi im ni bt ca mng GPONPON l mng truy nhp c nhiu u im trin khai cc dch v bng rng (thoi, d liu, video) gia cc khi kt cui ng dy xa (ONUs) v kt cui mng (OLT). Khng nh mng quang tch cc AON cn cc b chuyn i quang in ti mi nt, mng quang th ng PON s

dng cc b ghp v chia quang th ng phn b lu lng quang. Mt cng PON c th tp trung lu lng t 64 ONU n mt OLT c t tng i ni ht (CO) theo kin trc hnh cy, bus, hoc vng ring chng li.Mng PON ngoi vic gii quyt cc vn v bng thng, n cn c u im l chi ph lp t thp do n tn dng c nhng si quang trong mng c t trc. PON cng d dng v thun tin trong vic ghp thm cc ONU theo yu cu ca cc dch v, trong khi vic thit lp thm cc nt trong mng tch cc kh phc tp do vic cp ngun ti mi nt mng, v trong mi nt mng u cn c cc b pht li.Cng ngh GPON gii quyt c vn tc nghn bng thng trong mng truy nhp, cho php trin khai cc dch v bng rng v c tnh tng tc. Vi vic a ra mt gii php vi gi thnh h, bng tn cao, c kh nng chng li, cng ngh PON s l gii php tt nht cho mng th h sau, cng nh cho mng truy nhp bng rng.

6. V d v mt s thit b GPON (miniOLT, ONT, splitter )6.1.miniOLT

Cch thc lp t: Indoor/Outdoor

Mt s mu ONT

Mt s loi Splitter

Loi 1: splitter dng m-un

Splitter dng m-un thng c lp vo ODF, OCC (Optical Cross- Connection Cabinet, ODB (Optical Distribution Box)

Loi 2: Splitter dng hp, km t lp ngoi tri

Loi 3: Khay splitter lp vo Rack 19"

Loi 4: Splitter trn, hn trc tip

Dng trong iu kin khong khng hp, t trong khay hn hoc Mng Xng, u vo v u ra ca splitter khng c connector m c hn trc tip vo si quang.

Loi 5: Splitter mini

Splitter loi ny c kch thc nh, u input v output c connector, ph hp vi khong trng cho lp t nh hp