gioi thieu ve cong nghe pon

Mc lc I. Gii thiu chung v cng ngh PON: .................................................................................................... 3

1. AON: .................................................................................................................................................. 3 2. PON: .................................................................................................................................................. 4 3. So snh PON v AON: ........................................................................................................................ 4 4. Cc bc sng s dng trong PON: .................................................................................................. 6

II. EPON v GPON: ..................................................................................................................................... 7 1. Cng ngh truyn dn: ...................................................................................................................... 7 2. EPON: ................................................................................................................................................ 9 3. GPON: .............................................................................................................................................. 14 4. So snh EPON, GPON: ..................................................................................................................... 17

III. M hnh trin khai: .......................................................................................................................... 18 1. Tng quan v m hnh: ................................................................................................................... 18 2. Cc phng php bo v trong PON: ............................................................................................. 20

2.1 Uplink protection: ................................................................................................................... 20 2.2 Gii php bo v cho PON (Downlink protection): ....................................................................... 20

3. M hnh d kin trin khai: ............................................................................................................ 23 4. Cc khi chc nng trong tng thit b........................................................................................... 24

4.1 OLT (Optical Line Terminal): .......................................................................................................... 24 4.2 Thit b u cui mng ONU/ONT: ............................................................................................... 26 4.3 Mng phn phi quang ODN: ....................................................................................................... 27 4.4 C bn v b thu-pht trong PON: ............................................................................................... 28 4.5 Phng trnh th hin mi lin h gia khong cch v suy hao: ....................................... 33

IV. Hng dn troubleshoot: ............................................................................................................... 35

Hnh v/Bng biu Hnh 1.1 Kin trc n gii ca mng AON .................................................................................................. 3 Hnh 1.2 Kin trc mng PON ....................................................................................................................... 4 Bng 1.1 So snh PON v AON ...................................................................................................................... 5 Hnh 1.3 Cc m hnh cung cp FTTx ............................................................................................................ 5 Hnh 1.4 c tuyn suy hao trong si quang ................................................................................................ 7 Hnh 2.1 Qu trnh t ng tm kim ........................................................................................................... 8 Hnh 2.2 S gi tin truyn trong mng PON ............................................................................................ 8 Hnh 2.3 S m t truyn gi tin da vo LLID ........................................................................................ 9 Hnh 2.4 Kin trc c bn ca EPON ........................................................................................................... 10 Hnh 2.5 Cu trc frame ethernet ............................................................................................................... 10 Hnh 2.6 Chn trng LLID vo Header ...................................................................................................... 10 Hnh 2.7 Giao thc MPCP-hot ng ca bn tin Gate .............................................................................. 11 Hnh 2.8 Giao thc MPCP-hot ng ca bn tin Report ........................................................................... 12 Hnh 2.9 Thi gian Round-trip ................................................................................................................... 13 Hnh 2.11 Kin trc c bn ca GPON ........................................................................................................ 14 Hnh 2.12 Cu trc phn lp ca mng GPON ............................................................................................ 16 Bng 2.1 So snh EPON v GPON ............................................................................................................... 17 Hnh 3.1 M hnh tng quan ....................................................................................................................... 18 Hnh 3.2 B chia cng sut quang............................................................................................................... 19 Hnh 3.3 Type A protection ......................................................................................................................... 20 Hnh 3.4 Type B protection ......................................................................................................................... 21 Hnh 3.5 Tpye C protection ......................................................................................................................... 21 Hnh 3.6 Type D protection ......................................................................................................................... 22 Hnh 3.7 M hnh d kin trin khai ........................................................................................................... 23 Hnh 3.8 Cc khi chc nng trong OLT ..................................................................................................... 24 Hnh 3.9 S khi chc nng ONU .......................................................................................................... 26 Hnh 3.10 Cc b ghp 8x8 c to ra t cc b 2x2 ............................................................................... 28 Hnh 3.11 Cc loi Transceiver .................................................................................................................... 29 Bng 3.1 Cc thng s ca Transceiver ...................................................................................................... 30 Bng 3.2 D tr cng sut [6] ..................................................................................................................... 31 Bng 3.3 Tnh cht lp vt l ca mng BPON [7] ...................................................................................... 32 Bng 3.4 Lp vt l mng EPON v GPON [8] ............................................................................................. 33

I. Gii thiu chung v cng ngh PON: Nh ta bit FTTH c xem nh l mt gii php hon ho thay th mng cp

ng hin ti nhm cung cp cc dch v triple play (bao gm thoi, hnh nh, truy nhp d liu tc cao) v cc cc ng dng i hi nhiu bng thng (nh l truy cp Internet bng rng, chi game trc tuyn v phn tn cc on video). Tuy nhin nhc im chnh ca FTTH l chi ph cho cc linh kin v cp quang tng i cao dn ti gi thnh lp t nhng ng quang nh vy l rt ln. C nhiu gii php khc phc nhc im ny v mt trong s l trin khai FTTH trn nn mng quang th ng PON (Passive Optical Network). Hu ht trong cc mng quang hin nay, mi ng cp quang t nh cung cp s c chia s cho mt s ngi s dng. Khi cc ng cp quang ny c ko ti pha ngi s dng, cn c 1 b chia quang tch tn hiu ti cc si quang ring bit ti tng ngi s dng khc nhau. Bi vy, xut hin 2 kin trc in hnh trong vic chia ng cp quang l mng quang tch cc AON (Active Optical Network) v mng quang th ng PON. c ci nhn r rt hn v FTTH, ta s tm hiu s lc 2 kin trc ny.

1. AON: Mng quang tch cc s dng mt s thit b quang tch cc phn chia

tn hiu l : switch, DSLAM. Mi tn hiu i ra t pha nh cung cp s c a trc tip ti khch hng yu cu. Di y l kin trc n gin ca mng AON.

Hnh 1.1 Kin trc n gii ca mng AON Mt nhc im rt ln ca mng quang tch cc chnh l thit b chuyn

mch. Thit b chuyn mch phi chuyn tn hiu quang thnh tn hiu in phn tch thng tin ri tip tc chuyn ngc li truyn i nn s lm gim tc truyn dn ti a c th trong h thng FTTH. Ngoi ra do y l nhng

chuyn mch c tc cao nn cc thit b ny rt t, khng ph hp vi vic trin khai i tr cho mng truy cp.

2. PON: PON passive optical network l mt h thng mng m cc thit b

truyn dn quang l cc thit b th ng.

Hnh 1.2 Kin trc mng PON u im ca PON l n s dng cc b tch/ghp quang th ng, c gi thnh r v c th t bt k u, khng ph thuc vo cc iu kin mi trng, khng cn phi cung cp nng lng cho cc thit b gia phng my trung tm v pha ngi dng. Ngoi ra, u im ny cn gip cc nh khai thc gim c chi ph bo dng, vn hnh. Nh m kin trc PON cho php gim chi ph cp si quang v gim chi ph cho thit b ti nh cung cp do n cho php nhiu ngi dng chia s chung mt si quang.

3. So snh PON v AON:

Index AON PON Ph hp vi FPT

1 Mi KH c cung cp mt ng truyn ring, mi KH cn mt module quang

Cc KH dng chung 1 ng truyn t OLT ti POS

PON gin lc ha c cable truyn, module quang

2

ng truyn cho mi KH c th up ln ti 100M

Cc KH chia s bng thng, do c th tn dng ti a bng thng, khng trng lng ph

Nhu cu Vit Nam v tc ng truyn vn thp, thng ch 30-60Mbps.

3

C th cung cp ng truyn xa ti 60km

Ch c th cung cp ng truyn khong 20km

Phm vi H Ni vi ng knh ch khong 15km, mt KH li ng nn khong cch truyn ngn (20km) khng nh hng ti vic trin khai dch v

4 Cc KH c lp nhau, m bo bo mt

Cc KH dng chung nn s dng m ha AES bo mt

5 D dng nng cp v thay i bng thng cho KH

Cc KH dng chung nn vic thay i cho tng KH l kh khn

6

Vic nng cp m rng h tng ng ngha vi tng thm thit b, tn km

Mi OLT c th gnh nhiu ONU, ph thuc vo POS. nng cp POS n gin v r hn

Tnh kinh t ca PON cao hn

7 Cc KH c lp nn vic bo tr s kh khn v n l

Bo tr mt ng dy duy nht, thun tin hn

Bng 1.1 So snh PON v AON Xt mt bi ton so snh gia PON v AON:

Hnh 1.3 Cc m hnh cung cp FTTx

phc v cho 32 khch hng, gi s khong cch t nh khch hng n nh cung cp dch v (CO) trung bnh l 200m. Khong cch t CO n POP l 1km th: Vi m hnh th nht (FTTH-AON) ta cn: 32 hoc 64 si quang di 200m. 64 module truyn nhn tn hiu quang (Transceiver)

Vi m hnh th 2 (FTTC): 1 ethernet switch hoc DSLAM. 1 hoc 2 si quang di 100m t CO n switch v 64 si quang 100m t

switch n tng nh khch hng 66 module

Vi m hnh th 3 (FTTH-PON): 1 splitter quang (khng tiu th in). 1 si quang 1 km t CO n switch v 32 si quang t switch n nh

khch hng. 33 module. M hnh th 3 tn thit b, thit b r v vn m bo cung cp dch v

cho KH.

4. Cc bc sng s dng trong PON: Tn hao truyn sng trn si quang gy nh hng ln ti d tr cng sut,

khong cch vt l, t s chia trong mng. Trong si quang, tn ti rt nhiu nguyn nhn gy ra suy hao tn hiu nhng ch yu bi 4 nguyn nhn chnh : suy hao do hp th vt liu, suy hao do tn x, suy hao do un cong v suy hao do ghp v chia si quang.

Tng hp cc loi suy hao trong si v biu din mt tng quan theo bc sng ngi ta nhn c ph suy hao ca si quang. Mi loi si c c tnh suy hao ring. Mt c tuyn in hnh ca loi si n mode nh Hnh 1.4.

Nhn vo Hnh 1.4 ta thy c ba vng bc sng suy hao thp nht, cn gi l ba ca s thng tin. * Ca s th nht: bc sng 850nm. Trong vng bc sng t 0.8m ti 1m, suy hao ch yu do tn x trong c mt phn nh hng ca suy hao hp th. Suy hao trung bnh trong ca s ny mc t (2-3)dB/Km. * Ca s th hai : bc sng 1310nm. bc sng ny tn sc rt thp, suy hao chnh do tiu hao tn x Rayleigh. Suy hao tng i thp khong t (0,4 - 0,5) dB/Km v tn sc nn c dng rng ri hin nay. * Ca s th ba : bc sng 1550nm. Suy hao thp nht cho n nay khong 0,3 dB/Km, vi si quang bnh thng tn sc bc sng 1550nm ln so vi bc sng 1310nm. Tuy nhin vi mt s loi si quang c dng phn b chit sut c bit c th gim tn sc bc sng 1550nm nh cc si quang DC, MC v si quang b tn sc. Lc vic s dng ca s th ba s c nhiu thun li : suy hao thp v tn sc nh.

Hnh 1.4 c tuyn suy hao trong si quang Hnh 1.4 trn ch ra ph suy hao trong si quang silicat. Thng thng, tn hao ln nht trn si quang bc sng 1,38 m gy ra bi hp th ca tp cht trong ion OH- do qu trnh sn xut cp quang. Thng qua cc tnh cht suy hao ca si quang, mng FTTH c trin khai da trn 3 vng bc sng chnh l 1310nm, 1490nm v 1550nm. Vng bc sng 1310nm truyn d liu tuyn ln, vng bc sng 1490nm c dng cho tuyn truyn dn quang tuyn xung cn vng bc sng 1550nm c s dng cho vic truyn tn hiu tng t trn cp truyn hnh CATV.

II. EPON v GPON: 1. Cng ngh truyn dn:

PON l mt mng point to multipoints. Cc thit b trong mng PON (OLT v ONU) truyn d liu lp 2. OLT v ONU nhn bit c nhau, OLT to ra mt trng LLID (Logic link ID) sau qu trnh Auto discovery process.

Hnh 2.1 Qu trnh t ng tm kim OLT v ONU trao i cc bn tin Discovery, Register nhn bit c a ch MAC ca nhau. Sau OLT s khi to cc LLID map vi mi ONU. LLID c dng xc thc a ch gi tin truyn trong mng. OLT dng TDM iu khin cc timeslots cp cho ONU.

Hnh 2.2 S gi tin truyn trong mng PON - Chiu Downstream: Chiu downstream trong mng PON theo kiu point to multi-point, OLT s truyn gi tin Broadcast ti tt c cc ONU. Gi tin mang thm trng gi tr LLID. LLID c cha a ch MAC ca port trn ONU.

- Chiu Upstream: Chiu upstream tun theo dng point to point. Cc ONU gi gi tin s chn vo LLID ch nh ca n.

Hnh 2.3 S m t truyn gi tin da vo LLID 2. EPON:

Nm 2004, Ethernet PON (EPON hoc GEPON) c chun ha theo tiu chun 802.3ah-2004 nh l mt phn ca Ethernet. EPON s dng tiu chun 802.3 cho php truyn cc khung Ethernet vi tc ln ti 1Gbps i xng c chiu Upstrem v Downstream. EPON c th p ng hu nh tt c cc dch v nh truyn ti d liu, thoi, video. 10Gbit / s EPON hoc 10G-EPON l mt chun mi ca IEEE 802.3 cho php truyn ti d liu vi tc ln ti 10 Gbps.. Hin nay trn th gii ang c khong trn 40 triu cng EPON, ch yu phn b Trung Quc, nht v cc nc ng , chim a s th phn chung ca mng PON trn th gii. EPON cng l nn tng cho cc dch v kinh doanh khai thc cp quang.

Hnh 2.4 Kin trc c bn ca EPON

Trong EPON d liu c ng Frame theo khun dng Ethernet. Frame EPON c thay i Header nhn dng c LLID.

Hnh 2.5 Cu trc frame ethernet Trng Preamble s c chn thm LLID xc thc a ch duy nht,

trnh vic cc ONU c th gi bn tin qua nhau

Hnh 2.6 Chn trng LLID vo Header Theo hng ln, trnh xung t bn tin v iu khin vic cp pht khe

thi gian, OLT v ONU s dng giao thc MPCP (Multipoint Controller Protocol) m phn vi nhau.

Giao thc ny da vo hai bn tin Ethernet: Gate v Report. Bn tin Gate c gi t OLT n ONU n nh mt khe thi gian truyn. Bn tin Report c ONU s dng truyn t cc thng tin v trng thi hin ti ca n (nh mc chim d ca b m) n OLT, gip OLT c th phn b khe thi gian mt cch hp l.

C hai m hnh hot ng ca MPCP: t khi to v hot ng bnh thng.

M hnh t khi to c dng d cc kt ni ONU mi, nhn bit tr Round-trip v a ch MAC ca ONU .

M hnh hot ng bnh thng c dng phn hoch timeslots cho tt c cc ONU c khi to. T nhiu ONU c th yu cu khi to cng mt lc, m hnh khi to t ng l mt th tc da vo s cnh tranh. lp cao hn n lm vic nh sau: OLT ch nh mt khe khi to, mt khong thi gian m khng c ONU khi

to trc no c php truyn. Chiu di ca khe khi to ny phi ti thiu l: + - ; vi l chiu di ca ca s truyn m mt ONU khng khi to c th dng.

OLT gi mt bn tin khi to Gate bo hiu thi gian bt u ca khe khi to v chiu di ca n. Trong khi chuyn tip bn tin ny t lp cao hn n lp MAC, MPCP s gn nhn thi gian c ly theo ng h ca n.

Hnh 2.7 Giao thc MPCP-hot ng ca bn tin Gate

Ch cc ONU cha khi to mi p ng bn tin khi to Gate. Trong lc nhn bn tin khi to Gate, mt ONU s thit lp thi gian ng h ca n theo nhn thi gian n trong bn tin khi to Gate.

Khi ng h trong ONU n thi gian bt u ca khe thi gian khi to (cng c phn phi trong bn tin Gate), ONU s truyn bn tin ca chnh n (khi to Report). Bn tin Report s cha a ch ngun ca ONU v nhn thi gian tng trng cho thi gian bn trong ca ONU khi bn tin Report c gi.

Hnh 2.8 Giao thc MPCP-hot ng ca bn tin Report Khi OLT nhn bn tin Report t mt ONU cha khi to, n nhn bit a ch

MAC ca n v thi gian Round-trip. Nh c minh ha Hnh 2.9, thi gian Round-trip ca mt ONU l thi gian sai bit gia thi gian bn tin Report c nhn OLT v nhn thi gian cha trong bn tin Report.

Hnh 2.9 Thi gian Round-trip Khi ng h trong ONU ch n thi im bt u ca khe thi gian truyn dn, ONU s bt u phin truyn dn. Qu trnh truyn dn ny c th cha nhiu khung Ethernet. ONU s m bo rng khng c khung no b truyn gin on. Nu phn cn li ca khe thi gian khng cho khung tip theo th khung ny s c li cho khe thi gian truyn dn tip theo v trng mt phn khng s dng trong khe thi gian hin ti.

Do khng c cu trc khung thng nht gia downstream v upstream nn trong cu trc ca EPON, cc khe thi gian v giao thc xc nh c ly khc so vi GPON. OLT v cc ONU duy tr cc b m cc b ring v tng thm 1 sau mi 16ns.

Mt chun khc cng cng h vi E-PON l chun Gbit/s Ethernet PON (IEEE 802.3av Gbit/s PON). Chun ny l pht trin ca E-PON ti tc 10Gbit/s v c ng dng ch yu trong cc mng qung b video s

3. GPON:

Hnh 2.11 Kin trc c bn ca GPON Gbit/s PON cho php phn phi nhiu dch v i hi bng thng ln,

phn gii cao, ng gi IP cc lung d liu video ngay c khi h s chia OLT/ONT l 1:64 hoc cao hn. Ti thi im hin ti, tc chiu xung ca GPON khong 2.5 Gbps, v chiu ln l 1.25 Gbps. Nu 1 OLT phc v duy nht mt thu bao th thu bao c th uc khai thc ton b bng thng nh trn, tuy nhin thng thng trong cc mng trin khai ti mt s nuc trn th gii, nh cung cp thng thit k tc cho mt thu bao s dng PON vo khong 100 Mbps cho chiu xung v 40 Mbps cho chiu ln. Vi tc truy nhp nh vy, bng thng tha mn cho hu ht cc ng dng cao cp nh HDTV (khong 10 Mbps, chiu ln chiu xung, chiu ln cho peer-to-peer HDTV).

Tuy nhin, GPON cng c nhc im chnh l : thiu tnh hi t IP; c mt kt ni duy nht gia OLT v b chia, nu kt ni ny mt ton b ONT khng c cung cp dch v.

Mc d G-PON h tr truyn ti tin ATM, nhng n cng a vo mt c ch thch nghi ti tin mi m c ti u ha cho truyn ti cc khung Ethernet c gi l phng thc ng gi GEM (GPON Encapsulation Method). GEM l phng thc da trn th tc ng khung chung trong khuyn ngh G.701 ngoi tr vic GEM ti u ha header phc v cho ng dng ca PON, cho php sp

xp cc d liu Ethernet vo ti tin GEM v h tr sp xp TDM. G-PON s dng cu trc khung GTC cho c hai hng xung v hng ln. Khung hng xung bt u vi mt t mo u PLOAM, tip sau l vng ti tin GEM v/hoc cc t bo ATM. PLOAM gm c thng tin cu trc khung v sp t bng thng cho ONT gi d liu trong khung hng ln tip theo. Khung hng ln bao gm cc nhm khung gi t cc ONT. Mi mt nhm c bt u vi t mo u lp vt l m c chc nng tng t trong B-PON, nhng cng bao hm tng hp cc yu cu bng thng ca cc ONT. Ngoi ra, cc trc PLOAM v cc yu cu bng thng chi tit hn c gi i km vi cc nhm hng ln khi c yu cu t OLT. OLT gn cc thi gian cho vic gi d liu hng ln t cho mi ONT.

V c bn, GPON hng ti tc truyn dn ln hn hoc bng 1.2 Gbit/s. GPOn nh ngha 7 dng tc bit nh sau: ng ln 155 Mbit/s, ng xung 1.2 Gbit/s; ng ln 622 Mbit/s up, ng xung 1.2 Gbit/s; ng ln 1.2 Gbit/s up, ng xung 1.2 Gbit/s; ng ln 155 Mbit/s up, ng xung 2.4 Gbit/s; ng ln 622 Mbit/s up, ng xung 2.4 Gbit/s; ng ln 1.2 Gbit/s up, ng xung 2.4 Gbit/s; ng ln 2.4 Gbit/s up, ng xung 2.4 Gbit/s.

Khong cch logic l khong cch ln nht gia ONU/ONT v OLT ngoi tr khong vt l. Trong mng GPON, khong cch logic ln nht l 60 km.

Khong cch vt l l khong cch vt l ln nht gia ONU/ONT v OLT. Trong mng GPON, c hai ty chn cho khong cch vt l l 10 km v 20 km. i vi vn tc truyn ln nht l 1.25 Gbit/s th khong cch vt l l 10 km.

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.

Cu trc phn lp ca mng GPON c cho trong bng sau:

Hnh 2.12 Cu trc phn lp ca mng GPON Lp ph thuc phng tin vt l PMD: Cc thng s ca lp PMD c ch ra sau y v c tham chiu ti

cc gi tr trong ph lc t A n F. Tc tn hiu danh nh: Tc ng truyn l cc tc bi s ca 8 kHz. H thng c chun

ha s c cc tc danh nh nh sau (ng xung/ng ln): 1244.16 Mbit/s/155.52 Mbit/s, 1244.16 Mbit/s/622.08 Mbit/s, 1244.16 Mbit/s/1244.16 Mbit/s, 2488.32 Mbit/s/155.52 Mbit/s, 2488.32 Mbit/s/622.08 Mbit/s, 2488.32 Mbit/s/1244.16 Mbit/s, 2488.32 Mbit/s/2488.32 Mbit/s.

Cc thng s trn l cc gi tr trong trng hp xu nht, gi thit hot ng trong nhiu loi iu kin mi trng (nhit , m) v chu nh hng ca yu t thi gian. Cc thng s ny tng ng vi vi cc thng s trong mng quang t c t l li bit BER 1 1010 trong trng hp iu kin suy hao v tn sc ng truyn ln nht.

Khi ang trng thi hot ng v c cp quyn, ONU s pht tn hiu vi chnh xc bng chnh xc ca tn hiu thu c ng xung.

Lp hi t truyn dn

(TC- Transmission convergence)

Phn lp tng tch hi t truyn dn (TC adaption sub- layer).

Phn lp ng khung GTC

(GTC framing sub- layer)

Lp ph thuc phng tin vt l (Physical Media Dependence)

4. So snh EPON, GPON: Item EPON GPON

Tc

Max downlink: 1.25 Gb/s Max downlink: 2.5 Gb/s Max Uplink: 1.25 Gb/s Max uplink: 1.25 Gb/s Bit rate after 8B/10B line coding

1Gbps/1Gb/s Bit rate after scrambling line coding

2.44Gbps/1.24416 Gb/s

Cng ngh Ch yu chy cng ngh IP, trin khai d dng. Frame truyn trong mng l Frame Ethernet

Chy trn nn cng ngh ATM v GEM Frame truyn l GEM frame, ATM cell

Gi thnh trin khai R t hn Trin khai Pht trin mnh m, ch yu Trung Quc v cc nc chu

Pht trin sau GPON, vn ang trong giai on nghin cu

Tnh tng thch, ng b

Tt. Cc thit b c th tng thch vi nhau tt, khng cn thit phi cng mt vendor

Khuyn co nn s dng cc thit b ca cng mt vendor

Tnh ph bin Hin rt ph bin ph bin, nhng mc ng dng cha bng EPON

Nhnh chia Max 64 branchs Max 128 branchs Khong cch truyn

10 / 20 km (1000Base PX10 / 1000base PX20) 0 ~ 20km

Dch v tch hp Full service ( Ethernet, TDM, POTS) Dch v ethernet Bng 2.1 So snh EPON v GPON

III. M hnh trin khai: 1. Tng quan v m hnh:

Hnh 3.1 M hnh tng quan Cu trc mng PON c bn gm cc thnh phn l OLT, splitter quang,

ONU/ONT. OLT chnh l thit b u cui pha nh sn xut, c nhim v kt ni tt c cc loi dch v li v truyn tn hiu thng qua si cp quang. Tn hiu t OLT s n cc splitter quang. Splitter quang c s dng phn chia bng thng t mt si duy nht n ngi s dng (c th l 128, 64, 32 hoc 16, iu ph thuc vo h s chia ca splitter) trn mt khong cch ti a l 20 km ??. thu c tn hiu t OLT, ti pha ngi s dng cn c cc ONU/ONT. Cc thit b ny c nhim v l bin i tn hiu in thnh tn hiu quang. S khc bit r nht gia ONU v ONT l ONU khng cn cp ngun cn ONT cn phi cp ngun v ch c ONU mi c kh nng h tr dch v IPTV.Trong s trn, cc thnh phn chnh ca mt mng PON l:

OLT (Optical Line Terminal): y l thit b kt cui knh quang t ti Center Office. N l thnh phn quan trng nht trong h thng FTTH, cung cp cc giao din truy nhp PON cho thit b ONU pha ngi s dng v cc giao din khc cho tn hiu pha uplink.

ONU (Optical Network Unit): ONU l thit b lp t ti pha khch hng. N l im cui ca mng quang FTTH. ONU c nhim v chuyn tn hiu quang t

giao din PON thnh cc chun tn hiu cho cc thit b mng, tn hiu truyn hnh, tn hiu thoi c s dng ti thu bao.

ONT (Optical Network Terminal):y l thit b u cui pha ngi s dng, l im cui cng ca ODN.

OND (Optical Network Distribution): H thng phn phi cp quang tnh t sau OLT n ONU/ONT. C th, h thng phn phi quang OND li bao gm cc thnh phn sau y: mng xng quang, dy nhy quang, hp phi quang ODF, splitter (b chia/ghp quang)

o y b chia/ghp quang chnh l b chia cng sut quang (Optical Power Splitter): dng chia mt tn hiu quang u vo thnh nhiu tn hiu u ra. Cc h s chia thng thng l 1:4, 1:8 y l b chia th ng tc l khng phi cp ngun. Suy hao trong b chia ph thuc vo h s chia. H s chia cng ln th suy hao cng ln. Vi h s chia l 1:2 th suy hao khong 3 dB, vi h s chia l1:32 th suy hao ti thiu l 15dB. Suy hao ny chnh l suy hao xen to ra bi s cha hon ho trong qu trnh x l.

Hnh 3.2 B chia cng sut quang Hnh 3.2 cho bit nguyn l chung ca b chia cng sut quang. Gi s ti u vo c 3 bc sng 1 hng ln, 2, 3 hng xung, vi b chia cng sut c h s chia l 1:2 th u ra c 2 ca ra, mt ca c bc sng vo l 2 v bc sng ra l 1, mt ca khc li c bc sng vo l 3 v bc sng ra l 1. B tch/ghp quang c s dng rng ri trong mng PON xy dng thnh 4 topo c bn nht v mng l : hnh cy, vng, bus v hnh cy & ng ti d phng.

2. Cc phng php bo v trong PON: 2.1 Uplink protection: Link aggregation:

Tp trung nhiu port vt l to ln mt port logic. o u im: Nhiu knh vt l c th chia s ti vi nhau. o Nhc im: Ch 1 + 1 : o 1 port uplink s l master v trng thi active, 1 port uplink khc l slave s

trng thi standby. Khi port master down, port slave s c active. o Nhc im: khng tn dng c ti nguyn (port, cp), do port slave ch chy

khi port active down.

2.2 Gii php bo v cho PON (Downlink protection): Trong ITU-T Recommendation G.983.1 chng IV c gii thiu 4 kiu bo v cho

mng PON

TYPE A:

Hnh 3.3 Type A protection o Ch c phn on F1 l c redundant. o Vi dng ny, mt s chuyn mch quang v cc giao thc TC PON, nh Ranging

(iu khin tr upstream) c iu khin mt cch c lp. Lp TC thc hin th tc re-ranging sau khi pht hin li v vic khi phc chuyn mch quang. Do cch ny ch a ra c s bo v b gii hn v s dng cc thnh phn quang hc (chi ph cn t) nn khng phi l la chn hp dn thi im hin ti.

TYPE B:

Hnh 3.4 Type B protection o Bo v c OLT port, phn on cp feed fiber gia OLT v Splitter u tin.

Do phn on mng ny c chia s rt ln nn y l mt m hnh kinh t, mc d vic bo v ca n cng l gii hn.

o Thng thng trong dng ny ch 1 primary PON port hot ng, cn slave PON port trng thi khng hot ng (cold standby). Nu on cp chung b li hoc primary port li, port slave s c active khi phc dch v. Vic iu khin chuyn knh c thc hin hon ton pha OLT, do khng cn phi s dng

o giao thc chuyn mch no c. TYPE C:

Hnh 3.5 Tpye C protection Type C l dng bo v y v c nhiu tnh nng hp dn. Khi nim c bn

l c giao tip primary v secondary u hot ng bnh thng (hot standby). iu ny gip cho vic chuyn mch c thc hin nhanh hn (50ms hoc t hn). Vic chuyn mch c thc hin lp TC cho mi ONU ring bit. N c th ph hp vi cu hnh hn hp gia cc ONU c bo v v khng c bo

v, v c th bo v khng ch vi li phn cp chung m cn vi c li ONU v cp nhnh.

o 2 PON interface trn ONU kt ni n 2 interface PON ca OLT 1 cch ring bit.

o C 2 interface PON u active v ONU s ng k vi chng. TYPE D:

Hnh 3.6 Type D protection Type D a ra s redundant c lp cho phn on cp chung v cp

nhnh. Tp trung vo OLT, cc c tnh ca kiu ny tng t Type B. Dng ny khng th chuyn mch nhanh, nhng li gip bo v cho tt c cc ONT mt vi cp bo v. Do s lng thit b ca kiu ny l bng hoc nhiu hn Type C nn n cng khng c chn la nhiu.

Bn dng m hnh l thuyt trn l nhng tng c bn v nn tng, pht trin mt c ch bo v r rng th Type B v Type C c khuyn co s dng nhiu hn. Vi Type B khng cn tnh nng c bit no ONU hay giao thc c bit no cho PON. OLT iu khin hon ton tnh nng la chn chn la port PON active, v tnh nng shut-down deactivate port PON stand-by. Vn chnh cn phi gii quyt trong c ch ny l phi m bo c tnh sn sng/kh nng hot ng c ca port secondary.

Vi quan im ca nh cung cp, cc tnh nng bt buc l: chuyn mch cng bc t OLT, chuyn mch t ng, v vic la chn ch phc hi / khng phc hi. Trong yu cu quan trng nht l thi gian chuyn mch, nu vic chuyn mch t ng nh hn 50ms th mng PON c th c s dng cho

tt c cc loi dch v, bao gm cc tnh nng kht khe nht trong iu khin cuc gi.

3. M hnh d kin trin khai:

Hnh 3.7 M hnh d kin trin khai Vi phn uplink: Cc OLT s c u thnh vng Ring m bo tnh Redundant cho thit b. Cc link ny s c to port-channel, khi cn tng bng thng th s thc hin

join thm knh vt l vo cc port-channel ny. Vi phn downlink: T OLT n ONU s chy kiu bo v l Type B 2 OLT port c u n 1

Splitter 2:N. Vi Type B th 1 knh chy active, 1 knh chy standby, khi knh chnh b down

knh standby s chuyn sang trng thi active. Yu cu i vi thi gian chuyn giao knh l

m rng vng ph ca PON c th chn thm cc Splitter vo pha sau: Khong cch t OLT n ONU ~ 20 30Km Vic chng bao nhiu tng Splitter cn m bo suy hao t OLT n ONU nm

trong ngng cho php ca thit b. Cch tnh ton suy hao tham kho mc 4.5 Vic chng tng Splitter khng nh hng n Delay t OLT n ONU, m delay

ny b tc ng bi cc thit b ch ng v khong cch truyn pht v do cng khng nh hng n vic gn timeslot ca OLT.

4. Cc khi chc nng trong tng thit b

4.1 OLT (Optical Line Terminal): OLT c kt ni ti mng chuyn mch thng qua cc giao din c

chun ha. pha phn tn, OLT a ra giao din truy nhp quang tng ng vi cc chun GPON nh tc bit, qu cng sut, jitter

OLT bao gm ba phn chnh: Chc nng giao din port dch v, chc nng kt ni cho v giao din mng phn tn quang.

Hnh 3.8 Cc khi chc nng trong OLT Pon core shell: khi ny gm hai phn, phn giao din ODN v chc nng

PON TC. Chc nng PON TC bao gm to khung, iu khin truy cp phng tin, OAM, DBA, v qun l ONU. Mi PON TC c th la chn hot ng theo mt ch ATM, GEM hoc c hai.

Cross-connect shell: cung cp ng truyn gia PON core shell v Serviceshell. OLT cung cp chc nng kt ni cho tng ng vi cc ch c la chn (ATM, GEM hoc c hai).

Service shell: phn ny h tr chuyn i gia cc giao din dch v v giao din khung TC ca phn PON.

Cc tnh nng thng dng ca OLT: System features Data rate 1.25Gbps MAC address 16k Transmission distance

20km Split ratio 1:64

PON interface 4 Support ONU 256 Switch capacity 16Gbps Back-plane

buss bandwidth 32Gbps

VLAN Support IEEE 802.1Q(VLAN) Support 4k VLAN Support IEEE 802.1ad (QinQ/ flexible QinQ) Support VLAN transparent transmission Support VLAN classification based on interface Support multicast VLAN

Layer-2 function

Support store-and-forward mode and layer-2 wire-speed forwarding Maximum frame: 9728 bytes Packet transmit rate: 35.7Mpps Support IEEE 802.1d (STP)/802.1w (RSTP)/802.1s(MSTP) Support broadcasting storm control Support port mirroring

Flow control Support IEEE 802.3x(full duplex flow control) and back pressure flow control (half duplex)

Link integrationSupport IEEE 802.3ad (Link integration) Support load equilibrium based on MAC and IP

Multicast Suport SCB (Single Copy Broadcast) Support IGMP V1/V2 Support IGMP Snooping and IGMP Proxy Support 1000 multicast groups Support multicast source port control Support multicast authority control Support joining and fast-leave function of IGMP member Support static multicast

QoS Support IEEE 802.1P(COS PRI) and DSCP Support service classification based on port, MAC address, IP address, TCP/UDP port number, ToS(Type of Service)/Diffserv Support queue schedule algorithms such as SP (Strict Priority), WRR (Weighted Round Robin), SP+WRR Support 8 priority queuing for each port Support Ingress/Egress CAR, 64kbps increment Support Traffic Shaping Support Tail-Drop

DBA Bandwidth increment is 64kbit/s Support fixed bandwidth/guaranteed bandwidth/maximal bandwidth, delay priority and etc SLA parameter

ACL Based on port, MAC, IP, TCP/UDP port number, ToS/Diffserv

Security Support interface isolation Support AES-128, data encryption for both upstream and downstream Support dynamic update of key.

Reliability SW module supports switch between main and spare module Support 11 trunk protection Power supply supports backup function

Management Support UniView DA NM platform based on SNMP V1/V2 Support Telnet management and local CONSOLE management Support in-band and out-of-band NM, and the management data configuration of VLAN and PRI

Maintenance Support alarm and capability statistic, flow inspection, loop-back test, remote power-fail inspection Support long-distance on line upgrade of timing automatism and batch. Support remote line inspection, such as short circuit, incomplete circuit, and the location of failure.

4.2 Thit b u cui mng ONU/ONT: Hu ht cc khi chc nng ca ONU/ONT tng t nh cc khi chc

nng ca OLT. Do ONU hot ng vi mt giao din PON (hoc ti a 2 giao din khi hot ng ch bo v), chc nng u ni cho (cross-connectfunction) c th c b qua. Thay vo l chc nng ghp v tch knh dch v (MUX v DMUX) x l lu lng. Cu hnh tiu biu ca ONU c th hin trong Hnh 3.9. S cc khi chc nng ONU. Mi PON TC s la chn mt ch truyn dn ATM, GEM hoc c hai

Hnh 3.9 S khi chc nng ONU

Cc tnh nng c bn ca 1 ONU:

System features Data rate Uplink/downlink 1.25Gbps MAC address 8k Transmission distance


Voice VoIP mode, it supports MGCPSIP protocol Support auto-switching function of soft-switch between master and spare

CATV function CATV function is optional One CATV optical interface is connected to the CATV transmission network One CATV electrical interface (RF

RJ11 interface for common phone Support Voice encoding / compression technologies such as G.711 A-Law/ u-Law, G.729A/B, G.723.1-5.3/6.3 and G.726. Encoding methods could be dynamically switched according to requirements.

interface) is connected to Video displays. Support Triple Play

VLAN Support IEEE 802.1Q (VLAN) Support 256 VLAN Support IEEE 802.1ad (QinQ) Support VLAN transparent transmission Support VLAN trunk Support VLAN translation

Layer-2 function

Support store and forward mode and layer-2 wire-speed forwarding Maximum frame: 1600 bytes Support broadcasting storm control Support port/flow mirroring Support rate-limiting of bi-direction interfaces

Flow control Support IEEE 802.3x(full duplex flow control) and back pressure flow control(half duplex)


Multicast Based on SCB(single copy broadcast) Support IGMP V1/V2 Support IGMP Snooping Support 256 groups at most Support multicast authority control Support fast-leave function of IGMP member Support static multicast Capacity of 8M bytes can support IPTV burst flow.

QoS Support IEEE 802.1P(COS PRI) and DSCP Support service classification based on port, MAC address, IP address, TCP/UDP port number, ToS(Type of Service)/Diffserv Support SP queue schedule algorithms Support 8 classes priority queuing for each port

Security Support AES-128, data encryption for both upstream and downstream Support dynamic update of key.

Maintenance Support centralized management of OLT based on OAM Support alarm and capability statistic, flow inspection, loop-back test, remote power-fail inspection Support long-distance on line upgrade of timing automatism and batch

4.3 Mng phn phi quang ODN:

Mng phn phi quang kt ni gia mt OLT vi mt hoc nhiu ONU s dng thit b tch/ghp quang v mng cp thu bao.

B tch/ghp quang: L thit b th ng chia tn hiu quang t mt si truyn i trn

nhiu si v ngc li, kt hp cc tn hiu quang t nhiu si thnh tn hiu trn mt si.

Dng n gin nht l b ghp quang bao gm hai si dnh vo nhau. Tn hiu nhn c bt k u no cng chia lm hai. Cc b tch/ghp NxN c ch to bng cch ghp nhiu b 2x2 vi nhau hoc s dng cng ngh ng dn sng.

Hnh 3.10 Cc b ghp 8x8 c to ra t cc b 2x2 Cc b tch ghp c c trng bi cc tham s:

Suy hao chia: l t l gia cng sut u ra v cng sut u vo ca b ghp, tnh theo dB. Vi mt b 2x2 l tng, gi tr ny l 3dB. Hnh trn biu din hai m hnh ca b 8x8 da trn cc b 2x2. Trong m Hnh 3.10a, ch c 1/16 cng sut u c a ti tng u ra. Hnh 3.10b biu din m hnh thit k hiu qu hn, mi u ra nhn c 1/8 cng sut u vo.

Suy hao ghp: y l cng sut b tn hao do qu trnh sn xut, gi tr ny thng thng khong 0.1 dB n 1dB.

Thng thng cc b tch/ghp ch ch to c mt u vo hoc mt u ra. B c mt u vo gi l b chia (tch), b c mt u ra gi l b ghp. Tuy nhin c nhng b 2x2 c ch to khng i xng (vi t s chia 5/95 hoc 10/90).

4.4 C bn v b thu-pht trong PON: B thu pht quang chim vai tr quan trng nht trong h thng thng tin

quang hin nay bi chng thc hin nhim v c bn nht trong mng quang l bin i tn hiu quang thnh tn hiu in. Cc b thu pht quang s dng laser bn dn v thit b nhn c kt hp trong mt linh kin tch hp lm gim

gi thnh thit b mang li ngha v cng quan trng trong vic truyn nhn tn hiu tng t v s thng qua si quang. Transceiver (l thut ng kt hp ca transmitter v receiver) c xem l thnh phn chnh lm gi thnh ca vic lp t mng quang tng ln kh cao. Chnh v vy, trn th gii c rt nhiu nghin cu thit k b thu-pht c gi thnh r, hiu sut cao v gn nh, d dng s dng trong thc t.

Cp quang c bit n t nhng nm 1990. Ban u, mng s dng cp quang ch c tc khong 100Mbps. Sau , mng ny c nng cp c th t ti tc t 150-600 Mbps da vo kin trc SDH. Sau , kin trc mng s dng cc gi ATM c thay th mng Ethernet trc nhm nng cao tc ca mng. T , chun u tin cho mng PON l G.893 c ITU-T a ra nm 1998. ng thi, h thng mng PON tc 100Mbps c pht trin v a vo s dng trong thng mi nhng ch trong mt s vng gii hn v gi thnh kh cao. Trong khong thi gian 3-4 nm sau, tc mng PON c ci thin ln ti hn 1Gbps v y ban IEEE a ra chun 802.3 ah (chun EPON) vo thng 6 nm 2004. Mt vi nh cung cp ti Nht Bn nh NTT xut mt h thng vi chun GPON dnh cho cc ng dng thc t. Cng trong thi gian ny, ITU-T a ra chun GPON vi tc lung ln 1,244 Gbps v tc lung xung ln ti 2,488 Gbps. Cc b thu pht quang tun theo nhng chun ny c a ra thnh cc chip v cc module cng vi s pht trin ca cc thit b truyn tn hiu quang nng cao tc ca cc ng dng trong mng FTTH.

Hnh 3.11 Cc loi Transceiver

Bng 3.1 Cc thng s ca Transceiver 4.4.1 Yu cu i vi mng PON:

Bng 3.2 di y a ra t s chia v d tr cng sut cho tng kin trc mng PON 3 chun khc nhau. BPON c th cung cp t 16 n 32 ONU v kh nng phn phi bng thng linh hot. C 2 mng BPON v GPON u tun th theo 3 lp A, B, C ca chun G.982 ca ITU-T vi d tr cng sut ln lt l 20, 25, 30 dB gia OLT v ONU. GPON c nng cp t BPON vi tc cao hn c th s dng chung cho n 128 node. ng thi, GPON cho php t s chia cao hn mang BPON kh nhiu tc l c th phc v s lng thu bao cao hn so vi BPON rt nhiu nhng n cng b hn ch bi d tr cng sut.

Chun 802.3 ah cng xc nh r khong cch truyn nhn ch t 10-20 km. Lp vt l cng s dng chun 1000BASE-TX10 hoc 1000BASE-TX20. EPON c th cung cp ti thiu 16 b chia quang ch cn hiu sut c th vt qua mt gi tr gii hn chp nhn c, t s chia cng khng c xc nh r rng bi n ph thuc chnh vo suy hao ca cp quang v kh nng thit b lp vt l trong thc t. Trong thc t, mng EPON c th cung cp t s chia 1:32 hoc 1: 64 ty thuc vo d tr cng sut trong thc t.

Bng 3.2 D tr cng sut [6] D tr cng sut quang trong tng c quyt nh bi cc nh cung cp

khc nhau do chng ph thuc trc tip vo cc linh kin tch cc ca nh sn xut nh laser, b thu v PON chip. Thng thng cc thit b trong mng BPON s dng theo chun lp B nhng mt vi tuyn truyn dn c di 20km trong thc t yu cu d tr cng sut cn thit cao hn. Chnh iu lm cho mt s thit b tch cc trong thc t phi c d tr cng sut ln ti 26,5dB; nh vy lm tng kh nng ghp vi cc thit b khc trong mng, tng t s chia ca mng BPON ng thi cho php mng c kh nng chp nhn d tr cng sut l 28dB. Do , lp B+ c a ra trong chun G.982.

Vi chun G.982 lp A thng c s dng cho cc ng dng ca mng FTTC th chun G.982 lp B v B+ c s dng trong mng FTTP ngy nay vi cht lng v t s chia tt nht. Hn na, mc d chun lp B+ c cht lng tt hn nhng n khng c gi thnh cao nh mng tun theo chun lp C (cung cp cht lng mng c d tr cng sut cao hn) nh cc IC c nhy cao v tp m nh. Trong thc t cc nh cung cp mng thng s dng chun B+ cung cp mng cho thu bao s dng. Trong tng lai, cc nh cung cp s a ti nhng thit b c th s dng cho tuyn truyn dn khong cch xa hn (t 30-40km) vi t s chia ln ti 1:128 nh chun lp C.

4.4.2 Lp vt l mng PON: c im lp vt l trong mng ph thuc trc tip vo tnh cht vt l ca

c s h tng mng m c th trong mng PON l kh nng bin i tn hiu quang-in v ngc li, kh nng khi phc nh thi cho xung clock v d liu c truyn trong mng. Lp vt l s trc tip mang dng d liu nhn c truyn ti ln cc lp trn v cng chu trch nhim bin i d liu t cc lp trn chuyn ti thnh cc tn hiu quang truyn i. V vy, c im vt l ca mng

PON s quyt nh bi cng sut pht, nhy thu cho tng mng vi d tr cng sut v tc truyn ti khc nhau. Bng 3.3 di y xc nh c im ca lp vt l trong mng BPON theo chun G.982.

Bng 3.3 Tnh cht lp vt l ca mng BPON [7] Sau khi a ra chun BPON, mng GPON c xut thay th BPON

bi kh nng truyn ti tc cao. Trong khi GPON c dng phc v tt c cc dch v khc nhau th mc ch thit k mng EPON ch dnh truyn ti cc gi d liu trong mng Ethernet. ITU-T c gng a ra mt chun chung cho lp vt l mng EPON nhng bi tnh cht khc nhau gia 2 mng ny nn c im lp vt l ca EPON v GPON c s khc bit theo Bng 3.4.

Bng 3.4 Lp vt l mng EPON v GPON [8] 4.5 Phng trnh th hin mi lin h gia khong cch v suy hao:

Lb = |Ps| - |Po| o Lb = link budget o Ps = Sensitivity o Po = Output power

Rb = (Lb SIL Lc) / Ol o Rb = range budget o SIL = splitter insertion loss o Lc = connector loss o Ol = Optical loss

V d:

M hnh:

Xt trng hp OLT kt ni qua 1 Splitter 1:32 n ONU, Power Budget = 26dB Khong cch cho php t OLT n ONU l:

Rb = (Lb SIL Lc) / Ol = (26 3 - 17.5 4*0.3) / 0.5 = 8.6 (km)

IV. Hng dn troubleshoot: STT Li c th xy ra Hng dn x l n v x l

Phn loi li ti nh khch hng.

1 1 vi k/h trn 1 Splitter khng s dng c mng (Internet, IPTV, VOD, Voice)

Kim tra n bo hiu trn ONU xem li t cp hay khng: o Nu khng t cp: kim tra CPE, ONU xem c

li khng. o Nu t cp: kim tra phn on cp t

Splitter n nh k/h.

TIN

2 Internet tt, dch v IPTV/VOD hoc Voice li Kim tra STB/Phone kim tra CPE, ONU kim tra trn h thng cc dch v tng ng xem c li thit b (Splitter, OLT, switch access, thit b NOC) hay li source khng.

TIN TIN INF, NOC, OneTV

3 Internet + VOD li, IPTV tt Do h thng IPTV chy h thng ring trn phn on NOC nn nu gp li ny cn bo NOC kim tra xem BRAS c nghn cc b khng.

NOC, OneTV

4 Cc dch v s dng c nhng cht lng khng tt (internet lag, IPTV, VOD v hnh, git hnh).

Kim tra xem li c tnh thi im hay b c ngy. o Nu c tnh thi im th cn kim tra xem

traffic ti thi im c nghn khng. o Nu b c ngy th cn kim tra cht lng cp

t OLT hoc Splitter xung k/h, ty theo phm vi li m khoanh vng.

o INF, NOC

o TIN

Li c th xy ra ti phn on OLT - Splitter

1 OLT b mt ngun cp, ngng hot ng. Ton b k/h thuc OLT ny s b li INF

2 Splitter li Ton b k/h thuc Splitter ny s b li TIN

3 t cp t OLT n Splitter. Ton b k/h thuc OLT ny s b li TIN