tl mang tt quang (1) (1)

AON and PON

Nguyn Vn Dng Nguyn Th Thu H KTT K19 Page 1

MC LC CNG NGH MNG AON V PON 2

1.Gii thiu chung 2 2. Mng quang tch cc AON v mng quang th ng PON 2

2.1 Mng quang tch cc AON (Active Optical Network) ............................................... 3 2.2 Mng PON (Passive Optical Network) ....................................................................... 4 2.3 Cc chun trong mng PON ....................................................................................... 7 2.3.1 B-PON ....................................................................................................................... 7 2.3.2 EPON v Gigabit PON ............................................................................................... 8 2.3.3 WDM-PON .............................................................................................................. 11 2.3.4 CDMA-PON ............................................................................................................ 12 2.3.5 GEPON .................................................................................................................... 13

3. KT LUN 16 4. CHNH KIN V CNG NGH AON V PON 17

4.1 NGUYN VN DNG : V CNG NGH GPON 17 4.2 NGUYN TH THU H : V CNG NGH AON V PON 17

AON and PON


CNG NGH MNG AON V PON 1.Gii thiu chung

Ngy nay, s pht trin bng n ca mng Internet trn ton cu gy nh hng ln ti

cc nh cung cp mng trn ton cu trong vi chc nm gn y. S ph bin ca mng

Internet cng vi cc yu cu ngy cng tng ln v lnh vc multimedia, truyn hnh trc

tuyn, qua mng Internet yu cu mng phi phn phi bng thng rng cho nhiu ngi

s dng vi tin cy cao. Vi s lng ngi dng ngy cng ln v nhiu yu cu dch

v cht lng cao, hin tng thiu bng thng s l tng lai gn cho tt c cc nh cung

cp mng Internet nu nh cung cp vn s dng nhng thit b mng v hnh thc t chc

mng theo kiu truyn thng s dng cp in thng thng. Cng ngh cp quang tr

thnh mt gii php khng th trnh khi cho vn nan gii ny. Cp quang l mi trng

truyn dn cung cp bng thng rng, kh nng chng nhiu in t cao v t chu nh

hng ca mi trng cho php truyn dn d liu vi suy hao thp. Bi nhng c tnh

quan trng ny m tt c cc mng xng sng trong Internet hin nay u c xy dng

bng cp quang. Tuy nhin, vic kt ni trc tip t ngi dng ti mng Internet bng cp

quang mi ch bt u c thc hin trong nhng nm gn y. L do chnh gii thch cho

vn ny l h thng dch v multimedia cha pht trin ng thi nhng yu cu v dch

v bng rng cha tr nn ph bin. Mt l do khc l vic lp t cp quang c chi ph rt

cao cha tha mn c yu cu cn thit. Do , mng cp quang ti tn thu bao FTTH

(Fiber-to-the-Home) l mt bc tin vt bc trong cng nghip multimedia nh kh nng

cung cp cc dch v multimedia cht lng cao nh truyn hnh cht lng cao

HDTV(High-definition Television), download cc bn nhc v video.

2. Mng quang tch cc AON v mng quang th ng PON

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

AON and PON


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. Ta

s tm hiu s lc 2 kin trc ny.

2.1 Mng quang tch cc AON (Active Optical Network)

Mng quang tch cc s dng mt s thit b quang tch cc phn chia tn hiu l :

switch, router v multiplexer. Mi tn hiu i ra t pha nh cung cp ch c a trc tip

ti khch hng yu cu n. Do , trnh xung t tn hiu on phn chia t nh cung

cp ti ngi dng, cn phi s dng mt thit b in c tnh cht m cho qu trnh ny.

T nm 2007, mt loi mng cp quang ph bin ny sinh l Ethernet tch cc (Active

Ethernet). chnh l bc i u tin cho s pht trin ca chun 802.3ah nm trong h

thng chun 802.3 c gi l Ethernet in First Mile (EFM). Mng Ethernet tch cc ny s

dng chuyn mch Ethernet quang phn phi tn hiu cho ngi s dng; nh , c pha

nh cung cp v khch hng tham gia vo mt kin trc mng chuyn mch Ethernet

tng t nh mng my tnh Ethernet s dng trong cc trng hc. Tuy nhin, 2 mng ny

cng c s khc bit l Ethernet trong trng hc mc ch ch yu l lin kt gia my

tnh v my in cn mng chuyn mch Ethernet tch cc ny dng cho kt ni t pha nh

cung cp ti khch hng. Mi mt khi chuyn mch trong mng Ethernet tch cc c th

iu khin ln ti 1000 khch hng nhng thng thng trong thc t, 1 chuyn mch ch s

dng cho t 400 n 500 khch hng.Cc thit b chuyn mch ny thc hin chuyn mch

v nh tuyn da vo lp 2 v lp 3. Chun 802.3ah cng cho php nh cung cp dch v

cung cp ng truyn 100Mbps song cng ti khch hng v tin ti cung cp ng

truyn 1Gbps song cng. Hnh 1 di y l kin trc n gin ca mng AON.

AON and PON


Hnh 1.1 - Mng Active Ethernet (trn ) v mng AON (di)

Mt nhc im rt ln ca mng quang tch cc chnh l thit b chuyn mch. Vi

cng ngh hin ti, thit b chuyn mch bt buc phi chuyn tn hiu quang thnh tn hiu

in phn tch thng tin ri tip tc chuyn ngc li truyn i. iu ny 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.

2.2 Mng PON (Passive Optical Network)

Cc mng vin thng ngy nay u da trn cc thit b ch ng, ti thit b tng i ca

nh cung cp dch v ln thit b u cui ca khch hng cng nh cc trm lp, cc thit

b chuyn tip v mt s cc thit b khc trn ng truyn. Cc thit b ch ng l cc

thit b ny cn phi cung cp ngun cho mt s thnh phn, thng l b x l, cc chp

nh Vi mng PON, tt c cc thnh phn ch ng gia tng i CO v ngi s dng

s khng cn tn ti m thay vo l cc thit b quang th ng, iu khin lu lng

AON and PON


trn mng da trn vic phn tch nng lng ca cc bc sng quang hc ti cc im

u cui trn ng truyn. Vic thay th cc thit b ch ng s tit kim chi ph cho cc

nh cung cp dch v v h khng cn cn n nng lng v cc thit b ch ng trn

ng truyn na. Cc b ghp / tch th ng ch lm cc cng vic n thun nh cho

i qua hoc ngn chn nh sng V th, khng cn nng lng hay cc ng tc x l

tn hiu no v t , gn nh ko di v hn khong thi gian trung bnh gia cc ln li

truy cp MTBF (Mean Time Between Failure), gim chi ph bo tr tng th cho cc nh

cung cp dch v.

Mng quang th ng (PON) c xy dng nhm gim s lng cc thit b thu, pht

v si quang trong mng thng tin quang FTTH. PON l mt mng im ti a im,

mt kin trc PON bao gm mt thit b u cui knh quang c t ti trm trung

tm ca nh khai thc dch v v cc b kt cui mng cp quang ONU/ONT (Opt ica l

Network Unit /Optical Network Terminal) t ti gn hoc ti nh thu bao.

Gia chng l h thng phn phi mng quan ODN (Optical Distribution Network) bao

gm cp quang, cc thit b tch ghp th ng. Kin trc ca PON c m t nh

trong Hnh 1.2

Hnh 1.2 Mng PON

Trong h thng PON, kt ni mng quang ONT c kh nng h tr kt ni dch v in

thoi truyn thng qua giao din POTS (Plain Old Telephone Service) v cc giao tip

truyn d liu tc cao nh Ethernet v DSL. u cui ng dy quang OLT bao gm

cc khi giao tip PON, mt kt cu chuyn mch d liu v cc phn t iu khin NE

(Network Element). Thit b OLT (thit b kt cui knh quang) c t pha nh cung

AON and PON


cp dch v, cn cc thit b ONT (thit b kt cui mng quang) c t pha ngui s

dng. Thit b OLT cung cp nhiu knh quang, mi knh quang uc truyn trn mt tuyn

cp quang trn c b chia. Nhim v ca b chia l thu v nhn cc tn hiu quang uc

nhn v pht bi OLT.

Cp si quang truyn t OLT s tri di v kt ni ti mi ONT. Cc bc sng truyn

1490 nm (hoc 1550 nm ty theo la chn) uc dng cho bng thng chiu xung t OLT,

trong cc bc sng 1310 nm s uc truyn theo hung ln bi mi thit b ONT. H

thng cung cp a ch, cung cp bng thng mt cch t ng t ng cng nh vic m

ha c s dung truy tr v phn tch lu lng gia OLT v ONT.

Ti hng xung, OLT pht qung b d liu ti tt c cc ONU. Tn hiu hng xung

bao gm d liu cho cc ONT, t u Khai thc Qun l v Bo dng OAM

(Operation Administration and Maintenance) v cc tn hiu ng b cho cc ONT gi

d liu hng ln. Da vo cc thng tin v khe thi gian (knh), a ch gi/t

bo, bc sng, m CDMA m cc ONT tch d liu tng ng vi thu bao ca khch

hng.

Trong hng ln, mi mt ONU cn c giao thc iu khin truy nhp mi

trng MAC (Medium Access Control) chia s PON. Giao thc MAC thng c s

dng trong PON l a truy nhp phn chia theo thi gian TDMA, khi mi ONT c cp

mt khe thi gian (knh) gi d liu ca mnh ti OLT. Ngoi ra trong hng ln cn

phi c khong thi gian bo v gia cc nhm gi d liu ca cc ONT, khong thi gian

ny phi m bo sao cho ti b thu OLT d liu khng b trm ph ln nhau.

Thng thng cc h thng TDMA-PON gn trc mt t l phn chia c nh

bng thng hng ln cho cc ONT m khng quan tm c bao nhiu d liu c gi i.

Mt gii php phn b bng thng cho cc ONT l s dng giao thc phn b bng thng

ng DBA (Dynamic Bandwidth Allocation). DBA l giao thc cho php cc ONT gi yu

cu v bng thng ti OLT nhm s dng hiu qu bng thng hng ln. Cc thng tin yu

cu c th l cc mc y hng i u vo cho cc lp dch v khc nhau. OLT nh gi

cc yu cu t cc ONT v gn bng thng cho gi d liu hng ln ln k tip theo.

AON and PON


OLT cng c th tch hp chc nng tha thun mc dch v SLA (Service Level

Agreement) kt hp vi DBA trong vic phn b bng thng.

Thng thng cc h thng PON truyn d liu c hng xung v hng ln trong cng

mt si quang. Trn mi si mc d cc b ni nh hng cho php s dng cng mt

bc sng cho c 2 hng, tuy nhin i vi cc h thng truyn ti tc cao m bo

cht lng th thng thng mi hng s dng mt bc sng ring. Trong cc mng PON

cc bc sng c s dng l 1490nm hoc 1550nm cho hng xung v 1310nm cho tn

hiu ng ln.

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 (thng l 32) chia s chung mt si quang.

2.3 Cc chun trong mng PON

Cc chun mng PON c th chia thnh 2 nhm: nhm 1 bao gm cc chun theo phng

thc truy nhp TDMA-PON nh l B-PON (Broadband PON), E-PON (Ethernet PON),

G-PON (Gigabit PON) (c tnh cc ca chun TDMA-PON c so snh trong Bng 1.1);

nhm 2 bao gm chun theo cc phng thc truy nhp khc nh WDM-PON

(Wavelength Division Multiplexing PON) v CDMA-PON (Code Division Multiple Access

PON).

2.3.1 B-PON

Mng quang th ng bng rng B-PON c chun ha trong chui cc khuyn ngh

G.938 ca ITU-T. Cc khuyn ngh ny a ra cc tiu chun v cc khi chc nng ONT

v OLT, khun dng v tc khung ca lung d liu hng ln v hng xung, giao

thc truy nhp hng ln TDMA, cc giao tip vt l, cc giao tip qun l v iu khin

ONT v DBA.

Trong mng B-PON, d liu c ng khung theo cu trc ca cc t bo ATM. Mt

AON and PON


khung hng xung c tc 155Mbit/s (56 t bo ATM c khch thc 53byte), hoc

622 Mbit/s (4*56 t bo ATM) v mt t bo qun l vn hnh bo dng lp vt l

OAM (PLOAM Physical Layer OAM) c chn vo c mi 28 t bo trong knh.

PLOAM c mt bt nhn dng cc t bo PLOAM. Ngoi ra cc t bo PLOAM c kh

nng lp trnh c v cha thng tin nh l bng thng hng ln v cc bn tin OAM.

Cn c vo cc thng tin v m s nhn dng knh o v nhn dng ng o (VPI/VCI)

trong cu trc ATM, cc ONT nhn bit v tch d liu ng xung ca mnh.

Cu trc khung hng ln bao gm 56 t bo ATM (53 byte). Mi mt knh (time slot)

gm c mt t bo ATM/PLOAM v 24 bt t mo u. T mo u mang thng tin v

khong thi gian bo v (guard time), mo u cho php ng b v khi phc tn hiu ti

OLT, v thng tin nhn dng im kt thc ca t mo u. Chiu di ca t mo u v cc

thng tin cha trong c lp trnh bi OLT. Cc ONT thc hin gi cc t bo

PLOAM khi chng nhn c yu cu t OLT.

B-PON s dng giao thc DBA cho php OLT nhn bit lng bng thng cn thit

cp cho cc ONT. OLT c th gim hoc tng bng thng cho cc ONT da vo gi cc t

bo ATM ri hoc lm y tt c hng ln bi d liu ca ONT. OLT dng nh k vic

truyn hng ln do vy n c kh nng mi bt k ONT mi no tham gia vo hot ng

h thng. Cc ONT mi pht mt bn tin phc hi trong ca s ny vi thi gian tr ngu

nhin trnh xung t khi m c nhiu ONT mi mun tham gia. OLT xc nh khong

cch ti mi ONT mi bng vic gi ti ONT mt bn tin o c ly v xc nh thi gian bao

lu thu c bn tin phc hi. Sau OLT gi ti ONT mt gi tr tr, gi tr ny c

s dng xc nh thi gian bo v ng vi cc ONT.

2.3.2 EPON v Gigabit PON

E-PON l giao thc mng truy nhp y dch v FSAN (Full Service Access

Network) TDMA PON th nht c pht trin da trn khai thc cc u im ca cng

ngh Ethernet ng dng trong thng tin quang. E-PON c chun ha bi IEEE 802.3.

Trong E-PON d liu hng xung c ng khung theo khun dng Ethernet. Cc

khung E- PON c cu trc tng t nh cc lin kt Gigabit Ethernet im ti im ngoi

AON and PON


tr t mo u v thng tin xc nh im bt u ca khung c thay i mang trng

nhn dng knh logic LLID (Link logic ID) nhm xc nh duy nht mt ONU MAC. Trong

hng ln, cc ONU pht cc khung Ethernet trong cc khe thi gian c phn b.

ONU s dng giao thc iu khin a im MPCPDU (Multipoint Control Protocol Data

Unit) gi cc bn tin Report yu cu bng thng, trong khi OLT gi bn tin Gate

cp pht bng thng cho cc ONU. Cc bn tin Gate bao gm thng tin v thi gian bt

u v khong thi gian cho php truyn d liu i vi ONU. OLT cng nh k

gi cc bn tin Gate ti cc ONU hi xem chng c yu cu bng thng hay khng. Cc

ONU cng c th gi Report cng vi d liu c pht trong hng ln. Ngoi ra, giao

thc DBA cng c th c s dng trong E-PON thc hin c ch iu khin phn b

bng thng.

Do khng c cu trc khung thng nht i vi hng xung v hng ln, do vy trong

cu trc ca E-PON, cc khe thi gian v giao thc xc nh c ly l khc so vi B-PON v

G-PON. OLT v cc ONU duy tr cc b m cc b ring v tng thm 1 sau

mi 16ns. Mi mt MPCPDU mang theo mt thi gian mu, mu ny l gi tr ca b m

cc b ca ONU tng ng. Tc truyn d liu E-PON c th t ti 1Gbit/s.

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. 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

AON and PON


ni duy nht gia OLT v b chia, nu kt ni ny mt ton b ONT khng c cung cp

dch v.

G-PON l giao thc FSAN TDMA PON th 2 c nh ngha trong chui khuyn ngh

G.984 ca ITU-T. G-PON c xy dng trn tri nghim ca B-PON v E-PON. 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 G-

PON (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 t mo u 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.

c tnh B-

PON G-PON E-PON

T chc chun ha FSAN v ITU-T

SG15

(G.983 series)

FSANv ITU-T SG15

(G.984 series)

IEEE 802.3

(802.3ah)

Tc d liu

155.52 Mbit/s hng

ln. 155.52 hoc

622.08

Mbit/s hng xung

Ln ti 2.488 Gbit/s c 2

hng

1 Gbit/s c 2 hng

T l chia 1:64 1:64 1:64 **

AON and PON


M ng truyn Scrambled NRZ Scrambled NRZ 8B/10B S lng si quang 1 hoc 2 1 hoc 2 1

Bc sng

1310nm c 2 hng

hoc 1490nm xung

&

1310nm c 2 hng hoc

1490nm xung &

1310nm ln

1490nm xung &

1310nm ln C ly ti a OLT- 20 km (10 20) km (10 20) km Chuyn mch bo C h tr C h tr Khng h tr

Khun dng d

ATM

GEM v/hoc ATM

Khng (s dng trc

tip cc khung

H tr TDM

Qua ATM

Trc tip (qua GEM

hoc

ATM) hoc CES

CES

H tr thoi Qua ATM Qua TDM hoc VoIP VoIP

QoS C (DBA) C (DBA) C (u tin 802.1Q) Sa li hng ti

trc

Khng

RS(255, 239)

RS(255, 239) M ha bo mt AES 128 AES - 128, 192, 256 Khng

OAM

PLOAM v ATM

GTC v ATM/GEM

OAM

802.3ah Ethernet

OAM

2.3.3 WDM-PON

WDM-PON l mng quang th ng s dng phng thc a ghp knh phn chia theo

bc sng thay v theo thi gian nh trong phng thc TDMA. OLT s dng mt bc

sng ring r thng tin vi mi ONT theo dng im-im. Mi mt ONU c mt b lc

quang la chn bc sng tng thch vi n, OLT cng c mt b lc cho mi ONU.

Nhiu phng thc khc c tm hiu to ra cc bc sng ONU nh l:

- S dng cc khi quang c th lp t ti ch la chn cc bc sng ONU

- Dng cc laser iu chnh c.

- Ct ph tn hiu.

- Cc phng thc th ng m theo OLT cung cp tn hiu sng mang ti cc ONU.

AON and PON


- S dng tn hiu hng xung iu chnh bc sng u ra ca laser ONU.

Cu trc ca WDM-PON c m t nh trong Hnh 1.3

. Trong WDM-PON c th c s dng cho nhiu ng dng khc nhau nh l FTTH,

cc ng dng VDSL v cc im truy nhp v tuyn t xa. Cc b thu WDM-PON s dng

k thut lc quang mng ng dn sng AWG (Array Waveguide Grating). Mt AWG c th

c t mi trng trong nh hoc ngoi tri.

Hnh 1.3-Cu trc ca WDM-PON

u im chnh ca WDM-PON l n kh nng cung cp cc dch v d liu theo cc cu

trc khc nhau (DS1/E1/DS3, 10/100/1000 Base Ethernet) ty theo yu cu v bng

thng ca khch hng. Tuy nhin, nhc im chnh ca WDM-PON l chi ph kh ln cho

cc linh kin quang sn xut b lc nhng bc sng khc nhau. WDM-PON cng

c trin khai kt hp vi cc giao thc TDMA PON ci thin bng thng truyn tin.

2.3.4 CDMA-PON

Cng ngh a truy nhp phn chia theo m CDMA cng c th trin khai trong cc ng

dng PON. Cng ging nh WDM-PON, CMDA-PON cho php mi ONU s dng khun

dng v tc d liu khc nhau tng ng vi cc nhu cu ca khch hng. CDMA-PON

cng c th kt hp vi WDM tng dung lng bng thng.

AON and PON


CDMA-PON truyn ti cc tn hiu khch hng vi nhiu ph tn truyn dn tri trn cng

mt knh thng tin. Cc k hiu t cc tn hiu khc nhau c m ha v nhn dng thng

qua b gii m. Phn ln cng ngh ng dng trong CDMA- PON tun theo phng thc

tri ph chui trc tip. Trong phng thc ny mi k hiu 0, 1 (tng ng vi mi tn

hiu) c m ha thnh chui k t di hn v c tc cao hn.

Mi ONU s dng tr s chui khc nhau cho k t ca n. khi phc li d liu, OLT

chia nh tn hiu quang thu c sau gi ti cc b lc nhiu x tch ly tn hiu ca

mi OUN.

u im chnh ca CDMA-PON l cho php truyn ti lu lng cao v c tnh nng bo

mt ni tri so cc chun PON khc. Tuy nhin, mt tr ngi ln trong CDMA-

PON l cc b khuch i quang i hi phi c thit k sao cho m bo tng ng vi

t s tn hiu/tp m. Vi h thng CDMA-PON khng c b khuch i quang th ty

thuc vo tn hao b sung trong cc b chia, b xoay vng, cc b lc m h s t chia

ONU/OLT ch l 1:2 hoc 1:8. Trong khi vi b khuych i quang h s ny c th t

1:32 hoc cao hn. Bn cnh cc b thu tn hiu trong CDMA-PON l kh phc tp v

gi thnh tng i cao. Chnh v nhng nhc im ny nn hin ti CDMA-PON cha

c pht trin rng ri.

2.3.5 GEPON Trong thng 6 nm 2004, cng ngh Ethernet c khuyn ngh dng cho

mng truy cp v c tn l IEEE 802.3ah. N c coi l mt h thng mng truy

nhp quang tc cao. Do y l h thng mng PON c ti u cho cng ngh

Ethernet nn c tn thng gi l EPON. Ngoi ra n cn c thm tin t G l vit tt

ca Gigabit nn cn gi l GEPON.

Cng ngh GPON cung cp nhiu loi hnh dch v trn mt khung n. H tr

nhiu giao din u ra cho tng loi hnh dch v vi u cui khc nhau. C kh

nng h tr tivi theo yu cu cht lng cao. Cc dch v bao gm:

- Internet tc cao

- Dch v thoi PSTN, VoIP

AON and PON


- Dch v truyn hnh qung b, IPTV

- Dch v knh thu ring

Mt h thng GEPON vi t l chia l 32 c th cung cp mt bng thng i

xng l >30 Mbps cho mi khch hng. Bng thng ny l cung cp cc dch v

yu cu bng thng ln nh cc ng dng video cng nh cc ng dng thoi v data.

Thm ch vi ng thi 3 lung video n nt cao vi dung lng mi lung l 6-7

Mbps (tng cng l 18-21Mbps) th vn cn dung lng cho VoIP v truy cp

Internet. Dung lng dnh ring cho VoIP thng thng ch khong 64k trn mt

knh thoi trong khi truy nhp in Internet tc cao thng gii hn cc mc

512kbps, 1Mbps, 2Mbps, 4Mbps. Bng thng tng cng cho c 3 dch v ch khong

25Mbps, do GEPON l mt cng ngh mng truy cp l tng cho vic h tr a

dch v hin c cng nh cc dch v ca tng lai.

Hin ti, chun GEPON cng ang c pht trin c th h tr bng thng

ti a ln ti 10GB v t l chia s trn mt si quang l 1:64.

GEPON c cc c im chnh sau y:

- PON topology

- Tc truyn ti a 1,25Gbps trn mt ng quang v tc ti tng user

c th thay i ty theo t l chia (>30Mbps/1 user khi c t l chia l 1:32)

- Tn hiu c gi v nhn bng cc khung Ethernet

AON and PON


Hnh 1.4. M hnh cng ngh GEPON

Trong h thng PON, mc ch ca vic chia s ng quang cng nh thit b

ti phng my trung tm l v l do kinh t. Thm vo , vic gi v nhn cc tn

hiu bng khung Ethernet, lm cho h thng mng tr nn n gin v gi thnh thp.

Cng sut v dng sng ca tn hiu quang c iu ch lp vt l. C 2

chun c bn l 1000 BASE-PX10 dng truyn vi khong cch ti a 10km v

1000 BASE-PX20 dng truyn vi khong cch ti a 20km. Bc sng truyn

trn si quang c quy nh da trn khuyn ngh ITU-T G.983.3 l 1490nm v

1310nm, v ta c th cung cp thm dch v truyn hnh qung b trn bc sng

1550nm. S lng u chia ti a khng c quy nh trong IEEE 802.3ah v n ph

thuc vo suy hao ca tn hiu quang trn thc t v thng thng s lng u chia

l 32. GEPON cung cp 2 octet (16 bit) cho thnh phn nh danh lin kt logic

(LLID) v 15 bit dnh cho mi mt a ch MAC (Media Access Control). V vy c

th c hn 30.000 b ONU c s dng trong mt mng PON.

c im chnh ca GEPON l d liu c truyn nhn bng cc khung

Ethernet c kch thc thay i ti 1518 octets. Vi d liu downstream, OLT s

broadcast khung Ethernet n tt c cc ONU trong mt mng PON. Tuy nhin phn

LLID bao gm thng tin a ch nh ch c ONU c nh a ch mi tip nhn

AON and PON


khung d liu c a ch MAC ca n, cc ONU s loi b nhng khung m khng

nh a ch tng ng vi chng. Ngoi ra vic truyn d liu upstream da trn

cng ngh a truy cp phn chia theo thi gian (TDMA) trnh xung t d liu

gia cc ONU. OLT phn phi mt ca s truyn dn c gi l cng ng vi mt

ONU. Khi mt ONU nhn c mt khung cng, n s truyn cc khung d liu vi

tc 1 Gbps trong sut khe thi gian c ng k bi cng. Giao thc iu khin

a im (MPCP) qun l cc cng c cp cho mi ONU, cng c yu cu t

ONU v c dng pht hin v ng k cc ONU vi mng PON.

Thm vo , do mi ONU ch c th nhn tn hiu c a ch ng vi a ch

duy nht ca n nn mt thnh phn nh danh s c gi km u khung

Ethernet.

Hnh 1.5. Cu trc OLT v ONU

3. KT LUN

Cng ngh PON ra i m ra mt tim nng ln cho trin khai cc dch v bng rng v

thay th dn cc h thng mng truy nhp cp ng bng thng hp v cht lng thp. Cc

mng PON s dng h thng thng tin quang c bng thng rng t l li bt thp ( BER:

AON and PON


10-10 10-12) Tuy nhin, n cng c nhc im l gi thnh xy dng tng i cao v

khng trin khai c ti nhng a hnh phc tp. C nhiu chun PON khc nhau, do vy

trong thc t ty vo yu cu thc t m mt nh khai thc cn la chn gii php cho ph

hp.

4. CHNH KIN V CNG NGH AON V PON

4.1 NGUYN VN DNG : V CNG NGH GPON

Vic s dng cng ngh PON (passive optical network mng quang th ng) trong

mng bng rng c nh pht trin ph bin trong vi nm gn y, mc chi ph thp hn

so vi s dng ng cp quang ring cho tng h gia nh. Cng ngh ny ch s dng mt

ng cp quang chia s cho mt s h gia nh vi kh nng ngang nhau.

Cc h thng hin nay c tc ti v khong 2,5Gbps, trong khi GPON (Gigabit

Passive Optical Network) c tc ln n 10Gbps, tng gp 4 ln. Ngoi ra, theo Verizon

Communications, GPON cng h tr ti ln mc tc 10Gbps, cao hn 8 ln so vi cc

mng hin ti. Tc tng nn h tr cho nhiu ngi hn, bng thng cao hn

4.2 NGUYN TH THU H : V CNG NGH AON V PON

Bng so snh 2 cng ngh AON v PON Cng ngh AON PON

Bng thng trn mi thu bao 100Mbps 1Gbps 2,5Gbps/1,25Gbps nu khng dng splitter, trin khai theo m

AON and PON


hnh im - im, tuy nhin thng chia thnh 1:32 (78Mbps) hay 1:64 (39Mbps).

Tng bng thng tm thi cho thu bao (cn sao lu d phng my ch chng hn).

n gin Phc tp

S thu bao b nh hng khi c li t Nhiu

Thi gian xc nh li Nhanh Chm hn

Kh nng b nghe ln Rt thp Cao

tin cy ca ng cp n thu bao

Cao, do ty m hnh khch hang c th c kt ni theo dual homing (c 2 ng truyn khc nhau), vng trn (ring) hay 2 kt ni.

Thp, khng c 2 phng n kt ni trn mt PON

Chi ph trin khai Cao do mi thu bao l mt si quang ring

Thp v si quang t OLT s c chia s cho nhiu thu bao qua b chia th ng (passive splitter).

Chi ph vn hnh

Cao do cc thit b nh Access Node cn cp ngun v kch thc cng ln, yu cu khng gian. Khng gian cho cp cng cn nhiu.

Thp do cc OLT kch thc nh v passive splitter khng cn ngun. Phc v khong 8000 thu bao ch cn khng gian ca mt t rack.

Chi ph nng cp

Thp, do c tnh im n im nn vic nng cp bng thng n gin, chng hn ch cn thay thit b u cui (CPE).

Cao do mt ton b thu bao trong mt dy PON (t OLT qua splitter n ngi dng) phi c nng cp.

tl mang tt quang (1) (1)

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