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n tt nghip nh tuyn v gn bc sng trong mng quang WDM

Sinh vin thc hin:Trn Ngc Quang Lp D2002 VT 1

MC LCMC LC............................................................................................................. 1THUT NGVIT TT..................................................................................... 4

LI NI U ...................................................................................................... 7Chng I................................................................................................................ 9GII THIU CHUNG V CNG NGH WDM................................................9

1.1S pht trin ca cng ngh WDM ......................................................... 91.2K thut WDM.......................................................................................... 10

1.2.1 Nguyn l cbn ca ghp bc sng quang WDM ........................ 101.2.2 Cu trc h thng WDM.................................................................... 111.2.3 Cc phn t cbn ca h thng WDM............................................ 12

1.2.3.1 Si quang.....................................................................................12a. Si quang G.652.............................................................................. 12b. Si quang G.653.............................................................................. 13c. Si quang G.654. .............................................................................13 d. Si quang G.655.............................................................................. 14e. Si quang c tit din hiu dng ln............................................... 14

1.2.3.2 Phn pht ..................................................................................... 141.2.3.3 Phn thu.......................................................................................17

a.Nguyn l lm vic chung ca PIN v APD .................................... 18b. PIN-Photodiode............................................................................... 19c. Diode quang thc APD....................................................................20

1.2.3.4 Trm lp ...................................................................................... 26

1.2.3.5 B tn sc .................................................................................... 261.2.3.6 Khuch i quang OA (EDFA) ................................................ 271.2.3.7 B lc quang ............................................................................... 281.2.3.8 B xen r quang OADM ............................................................. 30

a. Cu trc ca b ghp tch quang OADM...................................... 321.2.3.9 B ni cho quang OXC ............................................................. 37

a. Phn tch v so snh kt cu OXC.................................................. 37b. Kt cu OXC da trn chuyn mch khng gian............................38c. Kt cu OXC da vo chuyn mch chia bc sng......................40

1.2.3.10 Chuyn mch khng gian..........................................................42

a. Cc chuyn mch cbn ................................................................ 421.3 Cu trc mng WDM ............................................................................... 46

1.3.1 Cu trc mng ring............................................................................. 461.3.2 Cu trc mng Mesh .......................................................................... 471.3.3 Cu trc hnh sao n......................................................................... 471.3.4 Cu trc hnh sao kp ......................................................................... 48

1.4 Cc kin trc mng li in hnh ..............................................................481.4.1 Kin trc ring OMS-SP hai lp..........................................................49

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1.4.2 Kin trc Mesh - Ring hai lp............................................................ 501.4.3 Kin trc Ring - Mesh hai lp........................................................... 50

1.5 Cc tham sc trng ca mng quang ................................................... 511.5.1 c trng ring ca mng quang ....................................................... 511.5.2 Cc tham s lin quan n topo mng ............................................... 52

1.5.3 Cc tham s lin quan ti nhng gii hn vt l ............................... 531.5.4 Cc tham s lin quan n nhu cu lu lng mng.........................541.5.5 Nhng tham s lin quan n kin trc ............................................. 551.5.6 Cc tham s lin quan n s gim st .............................................. 56

Chng II ............................................................................................................ 57TNG QUAN VNH TUYN V GN BC SNG TRONG MNG

QUANG WDM .............................................................................................. 572.1 Gii thiu chung........................................................................................ 57

2.1.1 Gii php WCA trong nh tuyn v gn bc sng......................... 592.2 Topo vt l ................................................................................................62

2.3 nh tuyn v gn bc sng tnh ............................................................ 622.4 nh tuyn v gn bc sng vi b chuyn i bc sng....................652.5 nh tuyn v gn bc sng ng........................................................... 66

Chng III ........................................................................................................... 69CC PHNG PHP NH TUYN V GN BC SNG TRONG

M NG QUANG WDM................................................................................. 693.1 Phng php nh tuyn ...........................................................................69

3.1.1 Phng php nh tuyn trong mng MESH..................................... 693.1.1.1 nh tuyn cnh......................................................................693.1.1.2 nh tuyn lun phin cnh .................................................... 70

3.1.1.3 nh tuyn thch nghi.................................................................. 713.1.1.4 nh tuyn bo v ....................................................................... 723.1.1.5 Cc hm trng thch nghi cho thut ton nh tuyn.................72

3.1.2 Phng php nh tuyn trong mng cu trc RING WDM............. 763.1.2.1 nh tuyn trong mng Ring n................................................ 77

3.1.2.1.1 Cc phng php nh tuyn ti u.....................................773.1.2.1.2 Cc phng php nh tuyn Heuristic................................ 78

a. Cc phng php Heuristic khng thch nghi ............................78b. Cc phng php Heuristic thch nghi....................................... 81

3.1.2.2 nh tuyn trong mng a Ring.................................................. 81

3.2 Phng php gn bc sng ....................................................................833.2.1 Phng php gn bc sng tnh.......................................................833.3.1.1 Thut ton gn bc sng t bc ln nht (LF Largest First

Algorithm)...................................................................................................... 843.2.1.2 Phng php gn bc sng trong mng Ring........................... 86

a. Phng php t mu th............................................................ 86b. Phng php Heuristic ................................................................... 88

3.2.2 Phng php gn bc sng ng..................................................... 89

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3.2.2.1 Gn bc sng ngu nhin.............................................................. 893.2.2.2 Gn bc sng theo ph hp nht .................................................. 893.2.2.3 Gn bc sng theo chiu di lung quang di nht (LF Longest

First) ............................................................................................................... 903.3.2.4 Gn bc sng da trn bc sng s dng t nht (LU- Least

Used) .............................................................................................................. 903.3.2.5 Gn bc sng theo s bc sng s dng nhiu nht (MU- MostUsed) .............................................................................................................. 91

3.3.2.6 Thut ton gn bc sng theo tch s nh nht (MP- min-Product) .......................................................................................................... 93

3.3.2.7 Gn bc sng a trn ti t nht (LL-Least Loaded) ..............94PH LC96THUT TON DIJKSTRA ............................................................................. 966KT LUN ......................................................................................................... 99TI LIU THAM KHO.................................................................................100

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THUT NGVIT TT

Vit tt Ting Anh Ting VitADM

AGANAOTF

APDAWGM

ATM

ADPAW

CDCADEMUXDSFDXCDLEDWDM

FBGEDFA

FDMFFWF

GMPLS

GWIPISDNLANLCLCPLCGLF

LEC

LL

LSP

Add/drop multiplexer

Auxiliary GraphAcces NodeAcousto OpticTurnable FilterAvalanche PhotodiodeArrayed - WavelengthGrating MultiplexerAsynchronous Transfer Mode

Avalanche Photo DiodeAvailable Wavelength

CoreDistinct Channel AssignmentDemultiplexerDispersion Shifted FiberDigital Cross ConnectDynamic Lightpath EstablishmentDifferential WavelengthDivision MultiplexerFibre GratingErbium doped fiber amplifer

Frequency Division MultiplexingFirst Fit Wavelength First

Generalized Multiple ProtocolLabel SwithchingGatewayInternet ProtocolIntegrated service digital networkLocal Area NetworkLogical ConnectionLeast Congested PathLogical Connection GraphLargest First

Least Converter First

Least Loaded

Label Swithched Path

B ghp knh xen k

Dng mt th phNt truy nhpB lc thanh quangc iu chnhit quang thcB ghp knh li quangdn sng kiu dnPhng thc truyn khngng bit quang thcBc sng kh dng

ng trcGn knh ring bitB gii ghp knhSi dch tn sc

Ni cho sThit lp lung quangGhp knh chia bcsng vi saiLi si quangKhuch i si quangtrn erbium

Ghp knh phn chia tn sThut ton gn bc sngtheo th t bc sngChuyn mch nhn agiao thc tng qutCngGiao thc internetMng s lin kt dch vMng cc bKt ni logicnh tuyn ng nghn t nhtHng kt ni logc biu Thut ton gn bc sngt bc ln nhtChuyn i bc sngtheo th t cao nhtThut ton gn bcsng da trn ti t nhtLung chuyn mch nhn

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LSR

LU

M

MESHMPLS

NP-

NZ-DSF

OADMOCO/E/O

OchOLAOXCOTDM

RWASDHSGCSONETSNCPSTM

SWRSOS

TAW

TDM

ThrTSIWADMWC

WDMWGR

WPWRWRSOSCDFK

Label Swithching Router

Least Used

Max-Sum

MeshMulti Protocol Label SwithchingSubset of class NP

problem complete

Non-Zero Dispersion Shifted Fiber

Optical add/drop multiplexerOptical CirculatorOptical/Electrical/ Optical

Optical ChannelOptical Line AmplifierOptical Cross ConnectOptical Time Division Multiplex

Routing and Wavelength AssignmenSynchronous Digital HierarchySequential Graph ColoringSynchronous Optical NetworkSub-Network Connection ProtectionSynchronous Transport Module

Static Wavelength RoutingSpace Optical Switch

Total wavelength and AvailablewavelengthTime Division Multiplexing

Thr - Protecting ThresholdTime Slot InterchangerWavelength Add- Drop MultiplexerWavelegth Converter

Wavelength Division MultiplexWaveguide Grating Router

Wavelength PathWavelength RouterWavelength Router SwitchOptical Supervision ChanelDispersion Shifted Fiber

B nh tuyn chuynmch nhnGn bc sng da trn

bc sng s dng t nhtThut ton gn bc sng datrn tng dung lng ln nhtDng liChuyn mch nhn a giao thcTp hp con ca lp cc biton NP m n c xem lkh giiSi quang dch chuyn tn sckhc khngB ghp knh xen/r quangBu vng quangQuang/ in/ Quang

Knh quangKhuch i ng quangNi cho quangGhp knh quang phn chiathi giannh tuyn v gn bc sngPhn cp sng bT mu th tun tMng quang ng bBo v kt ni mng conModun truyn ti ng b

Bnh tuyn bc sng tnhChuyn mch quang khnggianTng bc sng ca cc

bc sng kh dngGhp knh phn chia theothi gian

Ngng bo vTrao i khe thi gianB nhp tch bc sngB chuyn i bc sng

Ghp knh chia bc sngB nh tuyn li quangdn sngng bc sngBnh tuyn bc sngKho nh tuyn bc sngKnh gim st quangSi dch tn sc

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DFFSMFDCFCBFGOAOADMOXCOMS-DP

OMS-SP

OMSRWASLE

WCARCLRCARsvWRN

Dispersion Flattened FiberSingle Mode FiberDispersion Compensating FiberChirper Bargg Fiber GratingOptical AmplifierOptical Add Drop MultiplexerOptical Cross ConnectOptical Multiplexer SectionDedicated ProtectionOptical Multiplexer SectionShared ProtectionOptical Multiplexer SectionRouting and Wavelength AssignmenStatic Lightpath Establishment

Wavelength conveter AwaveRelative Capacity LossRouting and Channel AssignmentWavelength ReservationWavelength Router Network

Si tn sc phngSi n modeSi b tn scCch t BarggKhuch i quangB xen tch quangKt ni cho quangBo v dng ring mc onghp knh quangBo v dng chung mc onghp knh quangon ghp knh quangnh tuyn gn bc sngThit lp lung quang tnh

B chuyn i bc sngTn tht dung lng tng inh tuyn v gn knhGn bc sng t trcMng nh tuyn bc sng

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LI NI U

Trong h thng truyn ti, vi sra i ca cng ngh mng quang WDM

c bit l cng ngh DWDMc coi nhl mt cng ngh ti u thay thchocng ngh TDM truyn thng. Vi sra i ca cng ngh WDM cho php ccnh thit kmng la chn c phng n ti u nht tng dung lngng truyn vi chi ph thp nht. Cho n nay hu ht cc h thng thng tinquangng trc c dung lng cao u sdng cng ngh WDM. Ban u tnhng tuyn WDMim im n nay xut hin cc mng vi nhiu cutrc phc t p. Tuy nhin, do hin nay s lng bc sng s dng trong hthng WDM l rt hn ch, vn t ra l phi lm thno c thsdngngun ti nguyn ny mt cch hiu qu nht. Gii quytc vn ny tc l

nng cao nng lc ca mng vi sti a ti trn mt bc sng cho trc, ychnh l vai tr ca vic nh truyn cc bc sng trong mng. Vic nhtruyn tt scho php sdng ti u cc bc sng khi xy dng mt mng miv lm gim chi ph cho thit b. Do , vai tr ca vic nh tuyn v gn bcsng trong mng quang WDM l rt quan trng. Vic sdng cng ngh ghpknh theo bc sng WDM cho php nng cao ng kbng thng m vn duytr hin trng hotng ca mng, n cngc chng minh l mt giiphp hiu qu vmt chi ph cho cc mngng di.

V l ti nh tuyn v gn bc sng trong mng quang WDM snghin cu vn ny mt cch c thhn trong ni dung ca n ny. n ny bao gm c 3 chng vi ni dungc tm tt c thnhsau :

Chng I: Gii thiu chung vh thng ghp knh theo bc sng, cck thut c bn, nguyn k hot ng ca cc phn t c bn ca h thngquang WDM. Gii thiu tng quan cu trc h thng, cc phn tmng WDM,cc kin trc ca mng li in hnh, cc tham sc trng ca mng nhtpomng, gii hn vt l, nhu cu lu lng....

Chng II: Gii thiu mt cch tng quan v nh tuyn v gn bc sng trong mng quang WDM. Cc gii php trongnh truyn v gn bcsng, nh tuyn gn bc sng tnh, nh truyn gn bc sng vi b chuyni bc sng.nh tuyn gn bc sngng.

Chng III: a ra mt sphng php nh tuyn v gn bc sngtrong mng quang WDM Bao gm : Cc phng php nh tuyn trong mng

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MESH, nh tuyn trong mng cu trc RING WDM. Gn bc sng tnh, gnbc sngng.

Mc d c nhiu cgng song do thi gian v trnh c hn nn nny khng th trnh khi nhng thiu st. Rt mong nhn c nhng kin

ng gp ca cc thy c gio v cc bn.Nhn y em xin gi li cm n chn thnh ti thy gio Ths. Cao Hng

Sn to mi iu kin v tn tnh hng dn, gip em trong qu trnh thchin n.

Em cng xin chn thnh cm n cc thy c gio trong khoa Vin thng I gip em trong thi gian qua.

Xin gi li cm n chn thnh ti gia nh, bn b ngi thn- nhngngi lun cvng vin gip kp thi em trong sut thi gian qua.

H Ni, ngy 20 thng 10 nm 2006Sinh vin thc hin

Trn Ngc Quang

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Chng IGII THIU CHUNG V CNG NGH WDM

1.1Spht trin ca cng ngh WDMCng ngh mng quang tr thnh nhn t quan trng trong s pht trin

ca mng vin thng. Yu cu bng tn s dng ln l h qu tt yu ca nhucu truyn thng d liu ngy nay. Trong hai thp k qua, cng ngh truyn tiquang WDM c s pht trin vt bc. S pht trin ny c c l nhcngngh ch to linh kin quang. Nhng thnh tu ca cng ngh ny gp phnto nn h thng WDM dung lng ln nh ngy nay.

Theo thi gian, xut pht t nhng nhu cu thc t, cc h thng WDM ngycng trnn phc tp. mt gc no, s phc tp trong h thng WDM ltrong nhng chc nng ca thit b. Nhc chc nng ny m cu hnh h thngWDM chuyn tn gin nh cu hnh im- im sang cu hnh phc tp nhRing v Mesh. Cc h thng WDM u tin xut hin t cui nhng nm 1980s dng hai knh bc sng trong cc vng 1310nm v 1550nm v thng cgi l h thng WDM bng rng.

u nhng nm 1990 xut hin cc h thng WDM th h hai s dng ccphn t WDM thng, c gi l h thng WDM bng hp t 2 n 8 knh.Cc knh ny nm trong ca s 1550nm v vi khong cch knh 400GHz. n

gia nhng nm 1990 c h thng WDM mt cao (DWDM) s dng t 16n 40 knh vi khong cch knh t 100 n 200 GHz. Cc h thng ny tch hp cc chc nng xen r v qun l mng.

Cc h thng WDM ban u s dng vi khong cch knh ln. Vic lp th thng WDM chi phi bi nhng l do kinh t. Vic nng cp thit bu cui khai thc cc nng lc ca WDM c chi phi thp hn vic lp t cp siquang mi. S xut hin b khuch i quang EDFA chuyn hu ht cc hthng WDM sang ca s 1530 nm n 1565nm. Cc h thng WDM mi lp t

gn y s dng cc knh quang c khong cch gia cc knh hp t 25GHz n 50 GHz.

Nhu cu v bng tn mng ang tng gn 100%/mt nm s tip tc gia tngt nht l trong vi chc nm tip theo. Vic gim gi thnh ca cc nh cung cpv trn ht l ng dng ph cp ca Internet i hi bng tn ln sc tip tcy mnh.

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Cc gii php thc ti vi cc vn gii hn nh hng ca tn scmode phn cc, hiu ng phi tuyn, s lm tng c s lng knh v tc btca h thng WDM. S lng cc knh tng i hi yu cu kht khe hn ivi n nh ca laser, chnh xc ca b lc v vn lin quan n qun

l tn sc, hiu ng phi tuyn...Mng tin dn ti m hnh ton quang, do s xut hin cc h thng thit

b quang mi c kh nng thc hin cc chc nng m cc thit bin tangm nhn. Vic loi b cc yu cu khi phc v ti to lu lng qua thit bin t lm gim ng k tnh phc tp phn cng ca mng, nhng s lm tngcc hiu ng quang khc. Mc d trn kha cnh no cc k thut WDM mt cao st ti gii hn ca n. S truyn dn ca vi trm knh trn mt siquang cng c kim chng. Nh c s pht trin ca cng ngh WDM,trong tng lai khng xa s xut hin cc dch v thng tin quang gi thnh thptc cao.

1.2K thut WDM1.2.1 Nguyn l cbn ca ghp bc sng quang WDM

Nguyn l ghp knh theo bc sng c th minh ho nhhnh 1.1. Gis c cc ngun quang lm vic cc bc sng khc nhau 1, 2, 3, j,.n. Cc tn hiu quang vi cc bc sng khc nhau c ghp li pha pht

nhb ghp knh; b ghp bc sng phi m bo c suy hao nh v tn hiusau khi ghp sc truyn dc theo si n pha thu. B tch knh quang pha thu s tch cc lung tn hiu vi cc bc sng ring r.

Hnh 1.1 M t tuyn thng tin quang c ghp bc sng.

C hai phng n thit lp h thng WDM nh hnh 1.2 . Phng ntruyn dn ghp bc sng quang theo mt hng nh trong hnh 1.2(a), l kthp cc tn hiu c bc sng khc nhau vo si quang ti mt u v thc hin

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tch chng chuyn ti cc b tch sng quang u kia. Phng n truyndn ghp bc sng quang theo hai hng nh trong hnh 1.2(b) th khng quynh pht mt u v thu mt u; iu ny c ngha l c th pht thng tintheo mt hng ti bc sng 1 v cng ng thi truyn thng tin theo hng

ngc li ti bc sng 2.

Hnh 1.2H thng ghp bc sng (a) theo mt hng

(b) theo hai hng

Nh vy trn cng mt si c th truyn ng thi nhiu bc sngquang. Mi bc sng quang c gi l mt knh quang, mi knh quang smang lu lng t cc lp trn nh SDH, ATM . Nh vy s dng cng nghWDM dung lng truyn dn c nng cao m khng cn lp t thm cp.Khi kt hp cc thut ton nh tuyn thng minh, s phn b hp l ti nguyncc bc sng s nng cao dung lng ti a ca mng WDM.

1.2.2 Cu trc h thng WDMGhp knh theo bc sng l k thut s dng cc knh bc sng quang

truyn ti lung d liu khc qua si quang trn mng vin thng. Trongtrng hp mt tuyn WDM im- im, mt tp cc knh quang c kt hpli trong b ghp knh WDM, c truyn qua mt tuyn si quang v ctch ra qua b gii ghp knh WDM.

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Trong hnh 1.3 ch ra mt cu trc h thng chung WDM. Trong v d nyc bn knh quang ti cc bc sng 1, 2, 3 v 4c ghp vi nhau qua bghp knh theo bc sng. B khuch i ng quang (OLA) khuch i cctn hiu quang. B xen tch quang (OADM) tch bc sng 1 v xen mt khnh

quang ti bc sng 5.

Hnh 1.3 Cu trc h thng WDM cbn

Ti u thu, b gii ghp knh WDM tch bn knh quang ti cc bcsng 2, 3, 4 v 5. Do vy c mt knh t node 1 n node 2 bng 1, ba knht node 1 n node 3 bng 2, 3 v 4, mt knh t node 2 sang node 3 bng 5.

L do chnh ca vic s dng WDM l cho php truyn ti dung lng rtcao v cung cp kh nng mm do trong nh tuyn v bo v, thun li cho

quy hoch v thit k mng.

1.2.3 Cc phn tcbn ca h thng WDM

1.2.3.1 Si quang

Cc mng quang u s dng mi trng truyn dn l cc si quang. Siquang c c tnh l suy hao v tn sc thp v l mi trng phi dn. Si quangn mode chun cng nh si dch tn sc, hoc si tn sc phng c ITU-T chun ho.

a.Si quang G.652.y l loi si quang n mode c s dng ph bin trn mng li vin

thng nhiu nc hin nay, n c th lm vic 2 ca s truyn dn 1310 nm v

1550 nm. Khi lm vic ca s 1310 nm, G.652 c tn sc nh nht (xp x 0

ps/nm.km) v suy hao tng i ln. Ngc li, khi lm vic ca s 1550 nm,

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G.652 c suy hao truyn dn nh nht v h s tn sc tng i ln (xp x 20

ps/nm.km).

b.Si quang G.653.Mun xy dng cc tuyn thng tin quang tc cao, c ly di th cn phi

s dng mt loi si c c suy hao v tn sc ti u ti mt bc sng. Hin nay,bng cch thay i mt ct chit sut c th ch to c si tn sc dch

chuyn, tc l si c tn sc v suy hao ti u cng mt bc sng. Loi si

ny gi l si DSF hay si G.653.

Hnh 1.4 m t ng cong tn sc ca si G.653.

H s suy hao ca si DSF thng nh hn 0,50 dB/km ca s 1300 nm v

nh hn 0,3 dB/km ca s 1550 nm. H s tn sc vng bc sng 1550 nm

khong 20 ps/nm.km, cn vng bc sng 1300 nm nh hn 3,5 ps/nm.km.

Bc sng ct thng nh hn 1270 nm.

Xt v mt k thut, si G.653 cho php xy dng cc h thng thng tin

quang vi suy hao ch bng khong mt na suy hao ca h thng lm vic

bc sng 1300 nm. Nh vy, c ly trm lp ca h thng si tn sc dch

chuyn s di gp i h thng s dng si G.652 bc sng 1300 nm. Cn i

vi cc tuyn hot ng bc sng 1550 nm th do si G.653 c h s tn sc

rt nh nn nu ch xt v tn sc th gn nh khng c s gii hn v tc truyn tn hiu trong cc h thng ny. Nh vy do gim s trm lp trn tuyn

m gi thnh cao ca si G.653 phn no c dung ho.

c.Si quang G.654.G.654 l si quang n mode ti hn thay i v tr bc sng ct. Loi si

ny c c im: suy hao bc sng 1550 nm gim nhng tn sc vn tng

-20

0

-10

1020

30

-30

Tn sc

vt liu

Tn sc tngca si G.652

Tn sc tngca si G.653

Tn sc dn sng

1000 16001400 1800 Bc sng[nm]

Tn sc[ps/nm.km]

Hnh 1.4 Tn sc ca si G653

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i ln; im tn sc bng khng vn bc sng 1310 nm; G.654 ch yu c

s dng cc tuyn cp quang bin.

d.Si quang G.655.S dng si quang no thch hp nht cho h thng WDM lun l vn

c nhiu nh khoa hc quan tm. Do tnh cht u vit ca si quang G.653(DSF) bc sng 1550 nm m n tr thnh si quang c ch nht. Nhng

nghin cu k ngi ta pht hin ra rng khi dng G.653 trong h thng WDM

th khu vc bc sng c tn sc bng khng s b nh hng nghim trng bi

hiu ng phi tuyn. y l nhc im chnh ca DSF. T xut hin mt loi

si quang mi - si quang dch chuyn tn sc khc khng (NZ-DSF), cn gi l

si quang n mode G.655. im tn sc bng khng ca n khng nm 1550

nm m dch ti 1570nm hoc gn 1510 - 1520 nm. Gi tr tn sc trong phm vi

1548 - 1565 nm l 1 4 ps/nm.km m bo tn sc khng bng 0, trong

khi vn duy tr c tn sc tng i nh.

e.Si quang c tit din hiu dng ln.Loi si ny thch hp cho ng dng trong h thng WDM c dung lng v

c ly truyn dn ln. Tit din hiu dng l 72 m2, im tn sc bng khng l1510 nm, cho cng sut tng i ln.

1.2.3.2 Phn pht

Phn pht quan trng nht l laser diode. Yu cu ngun quang trong hthng WDM l phi c rng ph hp, n nh tn s. Tuy nhin laser diodec khoang cng hng Fabry Perot c nhiu u im hn so vi LED nhngcha tht s l cc ngun n mode. Vn cn cc mode khc ngoi mode cbntrong ngun ny. Trong h thng WDM nht l h thng ghp bc sng c mt cao DWDM cn c nhng lasern mode to ra mt mode dc chnh, cn licc mode bn cn c loi b. Lasern mode c nhiu loi, in hnh l laserhi tip phn tn (DFB )v laser phn x Bragg phn tn (DBR).

Diode laser hi tip phn tn(DFB)

Laser DFB gm c mt lp cch t nhiu x c cu trc chu kt cnhlp hot tnh to ra nh sng sut chiu di khoang cng hng vi mc chnn cc mode bn trong v chn lc tn s nhhnh 1.5.

Sng quang lan truyn song song vi cch t, do cch t c cu trc honton theo chu k to hin tng giao thoa gia hai sng ghp lan truyn ngc

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nhau. hin tng giao thoa ny xy ra th sau mt chu k cch t pha thayi 2m, trong m l s nguyn c gi l bc ca nhiu x Bragg tc l:

2m = 2B

n

2 ( 1.1)

Trong : n trit xut hiu dng ca mode, l chu k cch t, h s 2 sut hintrong biu thc v nh sng phn x hai ln cng pha vi sng ti. Nhngiu kin trn khng tho mn th nh sng tn x cch t s trit tiu nhau, ktqu l ch c c bc sng tho mn l B. Khi m = 1 th Bc gi l bcsng bc mt v B = 2n.

Hnh 1.5 Cu trc diode laser hi tip phn tn

Diode Laser phn x Bargg phn tn (DBR)

Laser phn x Bargg phn tn (DBR) s dng nguyn l phn x Bargg ch to ra mt mode dc. Khc nhau gia DBR v DEB l trong DBR cc ccht chiu di ngn ng vai tr b phn x chn lc tn s. C cu trc cch tnm hai bn vng hot tnh c tc dng nh hai gng phn x vi cc bcsng tho mn iu kin phn x nhhnh 1.6. Nh vy c nhiu mode trongvng hot tnh nhng ch c mt bc sng c phn x trli v c khuchi.

Hnh 1.6 Cu trc laser phn x phn tn Bargg DBR

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Hai loi laser ny c dng in ngng khong 20 mA, rng ph rthp v nh hn c0,5nm, do cc tuyn c ly xa yu cu tc cao thng sdng hai loi ny.

Diode Laser iu chnh bc sng

B pht quang n mode c th iu chnh c bc sng l linh kinquang then cht ca h thng WDM v mng chuyn mch quang. Ch tiu tnh

nng ca n l iu chnh tc v iu chnh phm vi bc sng. Mc d ang

cn nghin cu trong phng th nghim nhng vi s tin b khng ngng ca

cng ngh bn dn, b pht quang bn dn c th iu chnh c bc sng

cht lng cao s sm c s dng trong tng lai.

Nh ta bit, bc sng u ra b pht quang kk (bc sng trong khngkh) quan h vi bc sng trong mi trng cht bn dn bd theo cng thc:

kk = bd n (1.2)T cng thc (1.2): khi thay i n (chit sut ca vt liu bn dn) th kk sthay i, tc l c th thay i v iu khin c bc sng u ra ca b pht

quang trong phm vi nht nh. Di y s gii thiu cu to v nguyn l hot

ng ca mt s b pht quang bin i bc sng tin tin.

- B pht quang c th iu chnh ngoi khoang Cu toThc hin m trn mt ct pha sau ca khoang cng hng mt mng tng

thu (AR), sau ngoi a vo b lc c th iu chnh to thnh b pht

quang c th iu chnh ngoi khoang. Hnh 1.7m t cu to b pht quang

ny.

Nguyn l hot ng

Cc tia sng i qua mng tng thu, qua thu knh bin thnh chm tia sng

song song p vo cch t. y cch t s ng vai tr gng phn x kim b

lc bng hp. Nu ta quay cch t th c th iu chnh th bc sng quang u

ra. Cn nu ta iu chnh cch t theo chiu dc th c th tinh chnh c bc

sng quang u ra.

u im, nhc im

u im chnh ca loi pht quang ny l rng ph pht cc hp v c th

iu chnh bc sng trong phm vi rng. Cn nhc im chnh l tc iu

chnh thp, th tch tng i ln, n nh v c khng cao.

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- B pht quang DFB 2 ccB pht quang DFB 2 cc c cu to khc vi b pht quang DFB bnh

thng ch n c 2 in cc iu khin cng sut ra v iu khin bc

sng pht x.Hnh 1.8 m t cu to ca b pht quang loi ny.

Tn hiu in c chia thnh 2 thnh phn: dng vo cc th nht l dng

Ia t nh thin trn ngng, c tc dng chuyn tn hiu in u vo thnh tn

hiu quang; dng vo th hai l dng Ib nh hn tr s ngng, c tc dng thay

i chit sut iu chnh bc sng u ra b pht quang.

1.2.3.3 Phn thuB thu quang ca h thng WDM cng tng t nh b thu quang h

thng n knh. Chng thc cht l cc photodiode (PD), thc hin chc nng c

bn l bin i tn hiu quang thu c thnh tn hiu in. B thu quang phi

m bo yu cu v tc ln, nhy thu cao v bc sng hot ng thch

u ra quang

Mng AR

LDCch t

Hnh 1.7B pht quang c iu chnh ngoi khoang

Thu knh

iu chnh th(50 - 240 nm)

iu chnhnh (Ghz)

Tng ch Chn bc sng

5,25 cm

u ra quang

Mng AR

Cch t

Tn hiu in

Hnh 1.8B pht quang DFB 2 cc iu chnh bc sng

Tng ch iu chnhIa Ib

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hp. Hai loi photodiode c s dng rng ri trong b thu quang l photodiode

PIN v photodiode thc APD.

a.Nguyn l lm vic chung ca PIN v APDNguyn l lm vic chung ca PIN-photodiode v APD da trn nguyn l

bc x nh sng ca lp tip gip P-N, c ch ra hnh 1.9.C hai loi photodiode u hot ng da vo tip gip p-n phn cc ngc.

Khi nh sng c bc sng trong khng gian t do b hn bc sng ct:

c (m) =( )

( )eVEmeV.1,24

g

(1.3)

chiu vo Photodiode th bn dn hp th cc photon. cng thc (1.3), E g l

rng di cm ca tip gip p-n.

Khi mt photon c hp th trong vng ngho, n s kch thch mt in t

trong di ho tr nhy ln di dn v li trong di ho tr mt l trng. Nh

vy mi photon c hp th s to ra mt cp in t-l trng. in p phn

cc ngc to ra mt in trng mnh trong vng ngho hnh 1.9 (b). Di tc

dng ca in trng mnh, in t v l trng b qut rt nhanh ra khi vng

ngho. L trng t vng ngho i vo lp p, in t t vng ngho i vo lp n

to thnh dng khuych tn v chng tr thnh cc ht ti in a s trong cc

vng ny. Khi in t i ti in cc bn phi hnh 1.9 (a), di tc dng cangun phn cc ngc buc n phi i qua mch ngoi to thnh dng tch

quang. Cc in t qua mch ngoi v i ti in cc bn tri i vo vng p, ti

hp vi l trng vng ny.

Trong k thut thng tin quang, ngi ta thng s dng cc phn t bin i

quan-in: PIN-Photodiode v Diode quang thc APD.

p n

V

nh sng ti

EngoiETX

a)

x

E

b)

Hnh 1.9Diode tch quang p-n

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Di y ta s trnh by nguyn l bin i quang-in, cu to v tnh cht

ca cc phn t ny.

b. PIN-Photodiode

Cu to

Nguyn tc bin i quang-in ca PIN-Photodiode da vo nguyn l bini quang-in ca lp tip gip p-n c phn cc ngc. Cu trc c bn v

phn b in trng ca PIN-Photodiode c ch ra hnh 1.10.

Cu to ca PIN-Photodiode bao gm:

- Mt tip gip gm 2 bn dn tt l P+ v N+ lm nn, gia c mt lp mng

bn dn yu loi N hay mt lp t dn I (Intrisic).

- Trn b mt ca lp bn dn P+ l mt in cc vng ( gia cho nh sng

thm nhp vo min I).

- Trn lp bn dn P+ ph mt lp chng phn x.- in p phn cc ngc cho diode.

Hnh 1.10 Cu to ca PIN-Photodiode (a) v s phn bin trng (b)

Nguyn l hot ng:

Khi cc photon i vo lp P+ c mc nng lng ln hn rng ca di cm,

s sinh ra trong min P+, I, N+ ca PIN-Photodiode cc cp in t v l trng

(ch yu lp I).

P+ N+I

in ccin cc vng

Lp chng phn x

nh sng ti

(a)

(b)

E

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Cc in t v l trng trong min I va c sinh ra b in trng mnh

ht v hai pha (in t v pha N+ v c in p dng, l trng v min P+ v c

in p m).

Mt khc, cc in t mi sinh ra trong min P+ khuch tn sang min I

nh gradien mt ti tip gip P

+

I, ri chy v pha N

+

v c in p d

ng vl trng mi sinh ra trong min N+ khuch tn sang min I nh gradien mt

ti tip gip N+I, ri chy v pha v min P+ v c in p m.

Tt c cc phn t ny sinh ra mch ngoi ca PIN-Photodiode mt dng

in v trn ti mt in p.

C mt s in t v l trng khng tham gia vo qu trnh to ra dng

in ngoi, v chng c sinh ra min P+ v N+ cch xa cc lp tip gip P+I

v N+I khng c khuch tn vo min I (do khong cch xa hn di

khuch tn ca ng t thiu s), nn chng li ti hp vi nhau ngay trong cc

min P+ v N+.

Trong trng hp l tng, mi photon chiu vo PIN-Photodiode s sinh

ra mt cp in t v l trng v gi tr trung bnh ca dng in ra t l vi cng

sut chiu vo. Nhng thc t khng phi nh vy, v mt phn nh sng b tn

tht do phn x b mt.

Kh nng thm nhp ca nh sng vo cc lp bn dn thay i theo bc

sng. V vy, lp P+ khng c qu dy. Min I cng dy th hiu sut lng t

cng ln, v xc sut to ra cc cp in t v l trng tng ln theo dy ca

min ny v do cc photon c nhiu kh nng tip xc vi cc nguyn t hn.Tuy nhin, trong truyn dn s di ca xung nh sng a vo phi ln

hn thi gian tri Td cn thit cc phn t mang in chy qua vng tri c

rng d ca min I. Do , d khng c ln qu v nh th tc bit s b gim

i.

Khi bc sng nh sng tng th kh nng i qua bn dn cng tng ln,

nh sng c th i qua bn dn m khng to ra cc cp in t v l trng. Do

, vi cc vt liu phi c mt bc sng ti hn.

c. Diode quang thc APD

Cu to

Cu trc c bn ca APD c ch ra hnh 1.11(a).

Cu to ca APD c bn ging nh PIN-Photodiode. Ngoi ra trong APD

cn c mt lp bn dn yu P c xen gia lp I v lp N+. Bn tri lp I b gii

hn bi lp P+, cn bn phi lp I b gii hn bi tip gip PN +.

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in p phn cc ngc t vo APD rt ln, ti hng trm vn.

in trng thay i theo cc lp c ch ra bi hnh 1.11(b). Trong vng

I, in trng tng chm, nhng trong tip gip PN+ in trng tng rt nhanh.

Lp tip gip PN+ l min thc, y xy ra qu trnh nhn in t.

Nguyn l hot ng:Do APD c t mt in p phn cc ngc rt ln, ti hng trm vn,

cho nn cng in trng min in tch khng gian tng ln rt cao. Do

, khi cc in t trong min I di chuyn n min thc PN+ chng c tng

tc, va chm vo cc nguyn t gii phng ra cc cp in t v l trng mi, gi

l s ion ho do va chm. Cc phn t th cp ny n lt mnh li to ra s s

ion ho do va chm thm na, gy ln hiu ng quang thc v lm cho dng in

tng ln ng k.

Thng qua hiu ng quang thc ny m vi cng mt s lng photon ti,

APD gii phng ra cc in t nhiu hn rt nhiu ln so vi PIN-Photodiode.

Hnh 1.11 Cu to ca APD(a)v s phn bin trng theo cc lp (b)

Dng ra ca cc photodiode

Dng ra ca PIN - Photodiode

PIN- Photodiode l photodiode khng c hiu ng quang thc, do dng

ra ca n chnh l dng photo, tc l:

iT-PIN = iP= HTPT (1.4)

Trong :

aP

PP+ N+I

in ccin ccvn

Lp chng phnx

nh sng ti

b

E

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hc

eHT

= (1.5)

gi l h s bin i quang - in ca photodiode.

PT: l cng sut nh sng chiu vo photodiode

S cp n t - L trng sinh ra=

S photon hp th

l hiu sut lng t ho ca APD/PIN Photodiode.

: bc sng ca nh sng.

e: n tch ca in t (e = 1,602.10-19 As).

h: hng s Plank (h = 6,62.10-34 Ws2).

c: vn tc nh sng (c = 3.108 m/s).

Dng ra ca APD

i vi APD, do c hiu ng quang khc m dng ra ca APD c tngln M ln, tc l:

iT-APD = MiP= MHTPT , (1.7)

Trong :

1

1n

D

P

T

U

Ui

iM

==(1.8)

l h s khuych i ca APD,

U : n p t vo APD.

UD: in p nh thng ca APD

n: nhn cc gi tr t 1,5 6, tu thuc vo vt liu v cu trc ca APD.

Nhiu ca cc b thu quangTheo bn cht gy nn nhiu c: nhiu lng t tnh hiu, nhiu dng

in ti, nhiu dng r, nhiu nhit v nhiu do hiu ng quang thc (trong

APD). + Nhiu dng ti

Nhiu dng ti l do dng in ti ca photodiode sinh ra. Dng in tigm rt nhiu xung khng c quy lut. Ngi ta ch xc nh c tr hoc dng can, ph bin ca chng bng phng mi tn s. Theo [6], cng sut nhiu dngin ti pNTtheo cng thc :

(1.6)

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eTNT BIMMFep2)(2= (1.9)

Trong , IT l ga tr trung bnh ca dng in ti, gi tr trung bnh nyph thuc cht liu bn dn, din tch b mt tip xc P-N v nhit v B e lbng tn hiu dng hay cn gi l bng tn in ca photodiode.

+ Nhiu dng r

Nhiu dng r l do dng in r ca photodiode to ra. Dng in r l docc tia sng pha trong v nh sng bn cnh to ra. Trn thc t ngi ta ch xcnh c gi tr trung bnh ca dng in r. Theo [6], cng sut nhiu dng rpr theo cng thc :

erNr BIMMFep2)(2= (1.10)

Trong , Ir l gi tr trung bnh ca dng in r.

+ Nhiu nhit

Nhiu nhit ca Photodiode l nhiu xut hin trong in tr lp chn, intr ti, do chuyn ng nhit ca cc in t trong in tr to ra.

Theo [7], cng sut nhiu nhit pNN ca photodiode c xc nh theo cngthc :

eTCNN BGGTkp )(4 += (1.11)

Trong : GC =

C

R

1l in dn ca in tr lp chn RC,

GT=TR

1l in dn ca in tr ti RT,

k: hng s Bolzomal,

T: Nhit tuyt i.

+ Nhiu do hiu ng quang thc

i vi APD, nhiu do hiu ng quang thc sinh ra ph thuc vo h skhuych i v t l vi t s gia h s ion ho l trng v h s ion ho in ttrong vng khuych i quang thc.

Nhiu do hiu ng quang thc c c trng qua h s tp m F(M) vn c xc nh gn ng theo cng thc:

++=M

MkM

MF i1

21

2)( (1.12)

Trong :

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M l h s khuych i ca APD,

p

nki

=

(1.13)

n l h s ion ho in t trong vng quang thc,p l h s ion ho l trng trong vng quang thc.

Trong thc t, ngi ta c th s dng gn ng F(M) bi:

F(M) = MX (1.14)

Trong , gi tr c trng ca x = 0,3 0,5 i vi Si APD, x = 0,7 i

vi InGaAsP-APD v x=1 i vi Ge-APD

+ Nhiu lng t tn hiu

Nhiu lng t tn hiu sinh ra trong qu trnh gii phng ra cc cp in

t - l trng do cc photon chiu vo photodiode.Cc tp m dng ti, tp m dng r v tp m nhit tp m l nhng tp

m khng ph thuc tn hiu ca APD v PIN-Photodiode. Cn tp m lng t

tn hiu l tp m ph thuc tn hiu, cn phi c xem xt tn hiu truyn dn

tng t hay s, tn hiu truyn dn bin i nhanh hay chm.

Theo [6], cng sut nhiu lng t ca photodiode c xc nh theo

cng thc:

eTTNL BPHMMFep2)(2= (1.15)

Trong :

TP :Gi tr trung bnh ca cng sut nh sng n photodiode

e:in tch ca in t

Be:bng tn in ca photodiode

F(M): h s tp m ph thm ca APD

M:h s khuych i ca APD

HT: h s bin i quang in ca photodiode

+ Nhiu tng ca photodiodeTrong thc t, cc ngun nhiu ch ra m hnh ton hc ca photodiode

l khng tng quan nhau. Do , cng sut nhiu tng ca photodiode c tnh

theo cng thc:

NNNrNTNLN ppppp +++= (1.16)

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Thay cc cng thc (1.9)-(1.12) v (1.15) vo (1.16), ta nhn c cng

sut nhiu tng ca APD theo cng thc:

[ ]eTCrTTTAPDN BGGkTeIIPHMMeFp )(42)()(2

2 ++++= (1.17)

Thay cng thc (1.14) vo cng thc (1.17) v thc hin bin i ton hc,ta nhn c cng sut nhiu tng ca APD di dng:

[ ] eTCrTTTxAPDN BGGkTeIIPHeMp )(42)(2 2 ++++= + (1.18)

T cng thc (1.18) v thay M = 1 ta nhn c cng sut nhiu tng caPIN-Photodiode theo cc cng thc:

[ ] eTCrTTTPINN BGGkTeIIPHep )(42)(2 ++++= (1.19)

T s tn hiu trn nhiu (SNR)T cng thc (1.7), (1.18), ta nhn c t s tn hiu/nhiu ca APD nh

sau:

eTCrTTT

x

TTAPD

BGGkTeIIPHeM

PMHSNR

++++

=+ )(42)(2 2

222

(1.20)

T cng thc (1.4), (1.19), ta nhn c t s tn hiu/nhiu ca PIN-photodiode nh sau:

eTCrTTT

TTPIN

BGGkTIIPHe

PHSNR

++++

=)(4)(2

22

(1.21)

T s li bit (BER)BER l t s gia s bit b li v s bit c pht i (xc sut sai lm bit). L

thuyt chng minh BER l mt hm ca SNR v c biu din theo cng

thc sau:

=

21

2

1 SNRerfBER (1.22)

Trong , erfc(x) l hm li.

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1.2.3.4 Trm lp

Trm lp l b chuyn i tn s quang in cbn bao gm mt b thuquang v b pht quang. B thu quang chuyn i tn hiu quang u vo thnhtn hiu in v c khuch i, sa dng xung, nh thi li. Tn hiu ny sau

c chuyn thnh tn hiu quang nhlaser pht. Hu ht cc nh sn xut hthng WDM tin tng vo b lp transponder nh l giao din u vo ca hthng WDM. Ngy nay n c ch to vi tc bit ti gn 10 Gbit/s. nhy u vo bin i trong khong -5 dBm n -20 dBm tu theo tit b ca cc

nh sn xut khc nhau. Cc transponder c th hot ng bc sng 1,3 m

cng nh 1,5 m v cng sut ngun ra c0 dBm.

Cc trm lp m khng ti to li tn hiu u vo s lm vic vi bt kloi tc tn hiu s no v tn hiu lp trn c lp v dng tn hiu (SDH,

ATM) v tc bt ( 155Mb/s, 622Mb/s, 2,5Gb/s, 10Gb/s).

1.2.3.5 B tn sc

Bn cnh suy hao ca si l mt hiu ng tn sc m gii hn chnh cakhong cch cc trm lp trong tuyn thng tin quang. Tr nhm l mt hiu ngchnh gy ra bi tn sc. Trong truyn dn quang hiu ng tn sc tng tuyntnh vi di v rng ph ngun quang v l nguyn nhn lm mo xung vnhiu gia cc k t.

Si b tn scSi b tn sc (DCF- Dispersion Sompensating Fiber) l loi si c bit

m nh sng vng bc sng 1,5 m c h s tn sc khng m vi khong 80

ps/(nm.km). Do 1 km si DCF c th b tn sc cho 5 km si SMF, khi h stn sc ca si SMF l 17 ps/(nm.km).

H s tn sc ca si DCF cng thay i theo tn s nh si SMF, do khng th c kh nng b tn sc tt nu di tn s m rng. Suy hao ca siDCF c tr gi c0,6 dBm/km v ln hn si SMF.

Cch tBrarg

S dng cch t Bragg (BFG) l mt la chn khc b tn sc. Thit bny cho suy hao th p. Tuy nhin n hot ng mode phn x v do cndng Circulator quang hoc coupler quang tch tn hiu u vo v u ra.Hin ti di bng tn b tn sc mi ch vi trm GHz vi mt BFG (hp hn sovi DCF). Bng thng c th rng hn nu s dng cc t di hoc cch t thay

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th. Nhng vic phi thay thm Circulator quang hoc coupler quang l mt trngi.

1.2.3.6 Khuch i quang OA (EDFA)

Khuch i quang si pha Erbium l cha kho xy dng nn h thngWDM. H thng ny c c tnh: tnh tng ch cao, bng tn rng, tp m thp.c tnh tng ch khng c quan h vi phn cc, trong sut vi tc s vkhun dng. y l cc c tnh rt c li trong thng tin quang ni chung vWDM ni ring. Tng ch c tnh ton nh l t s cng sut ra trn cng sutvo b khuch i. Gi tr ny xc nh trc tip suy hao ti a cho php giahai b EDFA lin tip. N ph thuc vo s knh v di ca tuyn. Trong cctuyn thc t gi tr ny bin i t di 20 dB n 30dB. Cng sut u ra ca

b khuch i khi u vo cng sut cao. Hin nay c thng mi ha ccb khuch i EDFA vi di u vo t 13 17 dB cho u ra cng sut ti 30dBm.Hnh 1.12 m t cu to ca khuch i quang si EDFA.

Hnh 1.12 Cu to ca khuch i quang si EDFA

Cch hot ng ca EDFA c minh ha trn hnh 1.13. Khi mt intmt trng thi cbn (E1) c kch thch t mt ngun bc x c bcsng ph hp, n s hp th nng lng v s chuyn ti mc cao hn (E2). Tmc ny n s phn r trc tip xung trng thi cbn theo cch bc x. Ty, in t t pht c th pht x xung mc(E1) nhhnh 1.13 (a) hoc (E4)1.13 (b). Nu thi gian sng ca ca mc (E3) di cc in tc ngunbm kch thch th c th xy ra nghch o tch ly. y l iu kin c mcin t siu bn E3 nhiu hn mc ti (E1 v E4). Mt photon c nng lngtng ng vi s chnh lch nng lng gia mc E3 v E1 (i vi ba mc),hoc gia E3 v E4 (i vi bn mc) khi n va trm trn mi trng gy ra bc

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x kch thch ca cc photon. Khi iu kin khng kch thch hu ht cc in

ttrng thi cbn E1. Si pha Erbium (Er3+) cho bc x 1,55 v 2,7 m . Khi

cc photon tn hiu quang i vo si Erbium va chm vi cc in tang trng thi kch thch s lm cc in t ny chuyn xung mc in t thp hn

ng thi bc x mt photon c pha cng vi pha ca tn hiu. Do vy tn hiukhi i qua si EDF s c tng ch l c ch hot ng ca khuch quangEDFA.

Hnh 1.13 (a) cchba phat x , (b) cchbn pht x

1.2.3.7 B lc quang

Trong k thut WDM c nhiu loi b lc quang c s dng, nhng ph

bin nht l b lc mng mng in mi (TFF). TFF lm vic theo nguyn tc

phn x tn hiu mt di ph no v cho phn di ph cn li i qua. B lc

ny thuc loi b lc bc sng c nh. Cu trc ca n gm mt khoang cng

hng bng in mi trong sut, hai u khoang c cc gng phn x c cu

to t nhiu lp mng mng in mi c chit sut cao (TiO2 c n = 2,2) v chit

sut thp (MgF2 c n = 1,35 hoc SiO2 c n = 1,46) xen k nhau. Mi lp c b

dy ne = 0/4 (i vi b lc bc 0) hoc ne = 30/4 (i vi b lc bc 1), vi 0

l bc sng trung tm.Hnh 1.14 m t cu to b lc mng mng in mi.Cc b lc ny hot ng da trn nguyn tc ca bung cng hng

Fabry-Perot. y l b lc cng hng c tnh chn lc bc sng. Sng nh

sng no c th to ra trong khoang cng hng mt sng ng (chiu di

khoang cng hng bng bi s nguyn ln na bc sng) th s lt qua c

b lc v c cng sut cc i ti u ra.

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Trn c s ngi ta ch to b lc mng mng nhiu khoang cng

hng vi cc c tnh ph khc nhau. B lc ny c th gm hai hoc nhiu

khoang tch bit nhau bi cc lp mng mng in mi phn x. nh hng ca

nhiu khoang n c tnh cng hng ca b lc c th hin trong hnh 1.15.S khoang cng nhiu th nh hm truyn t cng phng v sn cng dc. C

hai c tnh ny ca b lc u rt cn thit.

Tu theo c tnh ph ca b lc, ngi ta phn b lc thnh hai h: Blc thng di v b lc bng thng.

B lc thng di, bao gm b lc thng thp (SWPF) v b lc thng cao(LWPF). Trong , SWPF s dng cu trc b lc bc 0 cn LWPF s dng cutrc b lc bc 1. B lc thng di c c trng bi bc sng ct c. Cc blc ny c s dng rng ri trong cc thit b hai knh ghp (hoc tch) haibc sng hon ton phn cch nh 850 nm v 1310nm hoc 1310nm v1550nm. Cc thit b ny c s dng kh hiu qu cho c cc ngun quang cph rng (v d: LED).Hnh 1.16(a) v 1.16(b) tng ng l p ng ph ca blc thng thp v thng cao.

1.0040/

0

-10

-20

-30

-40

H s truyndn b lc

[dB]

Hnh 1.15H struyn dn cc b lc mng mng

1.00210.0980.096

Chit sut thp

Chit sut cao

in mi

trong sut

Gng phn x Gng phn x

Hnh 1.14 Cu trc b lc mng mngin

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B lc bng thng (BPF). B lc ny c to ra t nhiu b lc cng hng,c c trng bi bc sng trung tm 0 v rng bng thng ca b lc.B lc ny s dng tt cho cc thit b WDM, rt ph hp vi cc ngun pht cph hp.Hnh 1.16(c) l p ng ph ca b lc bng thng.

tch c nhiu bc sng ngi ta s dng nhiu b lc ni vi nhautheo cu trc tng nh hnh 1.17.

1.2.3.8 B xen rquang OADM

Thit b ODAM thc hin chc nng thm vo v tch ra mt knh tnhiu t tn hiu WDM m khng gy ra nhiu vi nhng knh khc trong si.Theo thi gian cc chc nng xen/r knh quang ca OADM dn hon thinhn. C hai giai on chnh trong cu trc OADM, giai on th nht c trngtrong cu trc l c cc b chuyn i quang - in; giai on sau cc OADM cnng lc cao hn nhkhng phi chuyn i quang in.

Thit b OADM thh thnht

0

T 2200 +

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Trong thit b th h th nht tt c cc knh trn tn hiu WDM ti uc tch xung v a cho qua cc b bin i quang- in nh trn hnh 1.18.Cc knh xen vo tch ra c a n cng xen/r kt ni vi cc b bin iO/E/O cnh, cc knh chuyn qua cng a qua b bin i O/E/O cnh

trc khi ra ti cng vo ra ca phn t tch/ghp (MUX/DEMUX). Cu hnhny c quy nh bi nh sn xut, khng th thay i bc sng xen/r cngnh bc sng chuyn qua thit b.

Hnh 1.18 Thit b OADM thh thnht

Thit b OADM thh hai

Trong thit b th h ny, s dng nhng linh kin quang xen vo hoc

tch ra bc sng mong mun. Cc linh kin quang hin ang c ng dng ch to OADM l cch t dn sng quang (AWG), circulator kt hp vi cch tBragg si (FBG) hoc s dng tng giao thoa k March Zehnder. Hnh 1.19m t mt OADM s dng Circulator v cch t Bargg si.

Hnh 1.19 Thit b OADM da trn circulator v FBG.

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Trn hnh m t thit b OADM s dng cch t Bragg v circulator cho chcnng xen/r knh. Hot ng ca thit b ny nh sau.

1. Tn hiu i vo t tri c nh tuyn qua circulator ti FBG.

2. Cc bc sng khng b tch sc chuyn qua FBG ti circulator tiptheo.

3.Nhng bc sng cu cn tch b phn x bi FBG hng ti cng tchca circulator.

4. Cc bc sng xen vo c a vo cng xen. Bc sng ny di chuynquanh Circulatorn FBG v b phn x trli. Ti y n c trn vidng tn hiu chuyn qua thnh tn hiu ghp knh.

OADM loi ny c suy hao th p, khong 3 dBm i vi tn hiu ghp

knh. Loi OADM ny ph hp cho nhng ng dng trong mng ni ht.Ngoi loi OADM trn cn c cc loi khc nh dng giao thoa k March

Zehnder. Trong trng hp ny ngi ta cn s dng mt lot cc b ghp(coupler) cy trn nn planar to ra mt b giao thoa k March Zehnder.

Hin nay pht trin thit b OADM c cc tnh nng nh tuyn bcsng ngy cng linh hot. Ngi ta phn ra lm hai loi OADM.

Loi xen/ r bc sng cnh: Thc hin xen r cc bc sng cnhno . Cu hnh loi ny khng thay i trong qu trnh hot ng.

Loi xen/r bc sng thay i: y l loi c th thay i cu hnh. Chcnng xen/r bc sng c thm bo vic thm hoc tch mt s knh(bc sng) ti cng xen/r ca thit b. iu ny cho php nh khai thcc th thay i cu hnh mng theo nhng yu cu lu lng trn mng

bng cch cu hnh li (nh tuyn bc sng) thit b OADM ti cc nodexen/r.

a. Cu trc ca b ghp tch quang OADM

Cu trc ca OADM bao gm tch knh, phn t lc c iu khin tchxen v phn t ghp knh. Trong phn t tch knh khng c ngha l tt cknh bc sng trn si n u phi tch knh, thng im nt OADMdng b tch knh tch ra bc sng cn thit ( a ), ng thi ghp bc sng

( a ) qua b ghp knh ln si quang truyn dn i. Khi dng cc phng n

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khc nhau tch knh v ghp knh th n to ra cc kt cu OADM khcnhau.

Hin nay c nhiu phng n OADM, nhng v tng qut chia lm hailoi :

Kt cu trng lp Kt cu khng trng lp

Kt cu trng l p ch yu dng linh kin khng ngun l b ghp tchknh v b lc cnh, im nt tch ghp mt v nhiu bc sng cnh, tcl nh tuyn ca im nt c xc nh, loi ny thiu linh hot, nhng tin cy cao v khng c tr.

Kt cu khng trng lp dng kho quang, b lc c iu khin c thiu tit bc sng ng ng thoi tch nhp ca im nt OADM. Kt cu

ny phc tp, c tr nhng c th phn phi ti nguyn bc sng ca mng hpl.

Cc phng n cbn ca OADM c mt s hnh thc sau :

B tch sng, phn t chuyn mch khng gian v b ghp sng

Phn t phi ghp, phn t lc sng v b tch sng

Da vo b lc c iu chnh thanh quang (AOTF).

Da vo bnh tuyn li quang bc sng (WGM)

B tch sng, phn tchuyn mch khng gian v b ghp sngTrong phng n ny b tch knh c th l loi dng cc b lc mng

mng hoc loi cch t dy ng dn sng (AWG). Phn t chuyn mch khnggian s dng kho quang hoc ma trn kho quang, b ghp bc sng c th lb ghp knh hoc b phi ghp nh hnh 1.20.

Hnh 1.20 OADM da vo b tch knh v kho quang

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Do mc xuyn nhiu ca ton b OADM l do b tch knh quytnh. Hin nay b tch knh c th lm cho cch li t ti 0,8nm/25dB trln, do tho mn yu cu ca h thng.

Hnh 1.21 OADM da vo b ghp knh v ma trn kho

Phn tphi ghp, phn tlc sng v b ghp sng

Kt cu OADM loi ny n gin, nhng linh kin s dng d tm. Trongkt cu ny phn t phi ghp thng l (Coupler) hoc b quay vng quang(Optical Circulator) phn t lc sng c li quang (FBG), cc b lc nhloi F-P b ghp sng l b ghp ph thng hoc b ghp knh. Tnh nng caphng n ny ph thuc ch yu vo b lc. Linh kin hin nay c cch lica li si quang cao hn 20dB/ 0,8nm, tnh nng cch li ca khoang F-P tthn c tht 40dB/ 0,8nm.Hnh 1.22 l mt v d c th.

Hnh 1.22 OADM da trn li si quang v kho

Phng n trong hnh 1.22 l kt cu OADM dng ph bin hin nay,tn hiu u vo WDM i qua kho nh tuyn, a vo li quang. Li quangca mi ng chun ng vi mt bc sng, bc sng b li quang phn x

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si qua b quay vng tch ra, i vo mang ti ch, nhng tn hiu WDMkhc qua li quang v b quay vng ghp sng vi tn hiu bc sng caim nt ti ch, tip tc truyn dn ln pha trc.

Hnh 1.23 OADM dng b lc khoang F-P

Phng n trong hnh 1.23 l kt cu OADM dng b lc khoang F-P.Tn hiu vo WDM sau khi i qua b lc khoang F-P, bc sng cn thit ctch ra i vo nt ni ht, cc bc sng khc b phn x ri tip tc truyn dntrn ng trc. Cc dch v tim nt ti chn ng trc s s sng bcsng ghp vo ging bc sng tch ra. Trong phng n ny c u im nibt l b lc khoang F-P c thiu chnh lin tc, nn c th cn c vo nhucu nhp tch ra cc bc sng bt k nhng n li khng n nh v nhit.

OADM da trn AOTFB lc c iu chnh thanh quang (AOTF) c c tnh tt, nhng phm vi

iu chnh rng, tc iu chnh nhanh v cch li cao.., nhng n nhy cmvi hiu ng phn cc y chnh l mt hn ch ln

Hnh 1.24 OADM da vo AOTF

Kt cu hnh 1.24 tn hiu bc sng quang nhp vo thng gc vi hng phn cc ca tn hiu quang cng bc sng vi tn hiu WDM vo, sau khi

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chng i vo AOTF, tn hiu a vo WDM qua b tch chm phn cc (PBS)chia thnh mode TM v mode TE ri i vo phn t chuyn i mode (thng ltinh th LiNbO3) do on sng m thanh chn tn s fiu khin, tin hnh iu

chnh chn tn s f tng ng vi cc bc sng cn tch ra. Nu bc sng 1

iu chnh chn tn s tng ng khi tn hiu WDM i qua phn t mode thmode TE v mode TM ca bc sng quang 1 pht sinh chuyn i, mode TE

bin thnh mode TM v mode TM bin thnh mode TE. Qua mt 1 PBS pha

sau ri tu dy tch ra a v sti, nhng bc sng khc ca WDM khng pht sinh bin i mode, t u ra a ra si quang v bc sng nh p vothng qua phn t chuyn i mode cng tu ra a ra si quang. Hin naytc ca OADM da vo AOTF c tht n c p microgiy, bc sng1550nm c thiu chnh bng tn nh tuyn ln nht t 25nm, cch li giasng gn nhau t 35dB/ 0,8nm. Mc r bc sng i qua nh hn -30dB.

Kt cu hnh 1.25 l bin thn gin ca phng n ny, bc sng ng thoi nh p tch l cnh, khng iu chnh c. cch li i vibc sng ln cn (1550nm) l trn 22 dB/ 0,8nm, mc r tn hiu bc sng iqua nh hn -30dB.

Hnh 1.25 OADM da vo PBS v FBG

OADM a trn bnh tuyn li quang bc sng (WGR)

WGR l bnh tuyn bc sng hnh li quang, c hai chiu, mt chiu

vo l tch knh, mt chiu vo l ghp knh.Kt cu hnh 1.26 ly WGR NxN, th t bc sng tch knh ra c

u ra c quan h vi u vo. Tn hiu WDM gi s c N bc sng tng ngvi WGR, th t sp xp t u dy vo ra l 1~N, bc sng tch knh ca

u dy ra 1~N l 1 N . Khi i vo u th 2 , bc sng tch knh c

u dy ra 1~N l N , 1 N , do u vo WGR dng kho quang chn

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u vo khc nhau cho tn hiu WDM, t quyt nh bc sng tch ra thc hin iu chnh OADM. Tn hiu ghp vo v i qua tin vo WGR B dngphng thc ghp knh hp bc sng thnh tn hiu WDM, qua kho chn in u ra si quang.

Hnh 1.26 OADM da vo WGR

1.2.3.9 B ni cho quang OXC

OXC c hai chc nng chnh :

Chc nng ni cho ca knh quang

Chc nng ghp tch ng ti ch

Chc nng ny c th lm cho knh quang no tch ra vo mng aphng hay sau khi trc tip a vo DXC ca l p SDH thng qua bin iquang, do quang in trong DXC s x l. ng thi cho php knh quang a

phng nhp vo v ghp knh truyn n u ra ca ng kt ni. Khi nhgi kt cu ca OXC cn xt n cc ch tiu sau:

- Trgip knh bc sng hay knh bc sng o

- c tnh nghn

- Tnh modun ca kt ni

- Tnh modun ca bc sng

- Kh nng pht qung b

- Gi thnh

a. Phn tch v so snh kt cu OXC

Hai loi chuyn mch thng dng trong moun chuyn mch quangOXC

Chuyn mch chia thi gian

Chuyn mch chia bc sng

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Linh kin thc hin chuyn mch chia thi gian l cc loi kho quang,chng hon thnh chc nng chuyn mch tu vo n u ra trong min thigian. Linh kin thc hin chuyn mch bc sng l cc b chuyn i bcsng, chng c th chuyn i tn hiu t bc sng ny sang bc sng khc,

thc hin chuyn mch trn min bc sng. Ngoi ra trong moun chuynmch cn s dng rng ri b chn bc sng (nh cc loi lc quang c thiu chnh v b tch knh). N hon thnh trn tn hiu WDM mt hoc nhiutn hiu bc sng i qua v lc i nhng tn hiu c bc sng khc. Cc thp khc nhau ca linh kin c th to thnh cc kt cu OXC khc nhau. Tutheo chc nng nh tuyn do linh kin no thc hin l chnh m c th chialm hai loi ln :

- OXC da trn chuyn mch chia khng gian

- OXC da trn chuyn mch chia bc sng

Hin nay c rt nhiu loi kt cu OXC, hn na do tnh thay i lnnhau ca linh kin chung cn c th bin ho thnh nhiu loi kt cu khc.

b. Kt cu OXC da trn chuyn mch khng gian

Da vo ma trn kho quang khng gian v b ghp / tch knh chiabc sng ca kt cu OXC

C hai kt cu OXC hnh 1.27da vo ma trn kho quang v b ghptch knh chia bc sng. Chng dng b tch knh tch tn hiu WDM v

khng gian, sau s dng ma trn kho quang chuyn mch khng gian. Saukhi hon thnh chuyn mch khng gian cc tn hiu bc sng c ghp knhln ng kt ni ra, kt cu loi ny khng c kh nng pht qung b.

Theo hnh 1.27gi thit im nt c Nfng kt ni vo ra. Mi ngkt ni ghp knh cng mt nhm M bc sng, dung lng chuyn mch cama trn kho quang khng gian l NxN ( N > N r ). Mi ma trn kho quang cN- Nfu dy dng cho chc nng lung i /n ti ch v ni vi DXC

Kt cu (a) c tnh moun bc sng nhng khng c tnh moun ng

kt ni. Cn kt ni (b) khng c tnh mun bc sng v ng kt ni nhngn h trknh bc sng o.

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Hnh 1.27Kt cu OXC da trn ma trn kho quang v b tch/ghp knh chia

bc sng

Kt cu OXC da trn ma trn kho khng gian v b lc c iu chnh

C hai kt cu chung s dng b phi ghp v b lc c iu chnh hon thnh chc nng phn tch v mt khng gian tn hiu WDM a vo. Quama trn kho quang khng gian v b bin i bc sng v b phi ghp knh

ghp hai sng li.

Hnh 1.28 (a) Kt cu OXC c ma trn kho khng gian v b lc c iu chnh

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Hnh 1.28 (b) Kt cu OXC c ma trn kho khng gian v b lc c iu chnh

c. Kt cu OXC da vo chuyn mch chia bc sng

Kt cu OXC chuyn mch bc sng nhiu cp da vo b ghp cch tng n sng AWGM (Arayed Waveguide Grating Multiplexer).

Mt cu trc AWGM do ng Wen De Zhang xut nm 1996 nhhnh1.29. Kt cu ny li dng c tnh ca b ghp knh AWGM, kt ni cc cpca b bin i bc sng nhiu cp khc nhau, thc hin chuyn mch knhquang hon ton trn min bc sng. Mt b ghp knh AWGM c thngthi thc hin chc nng ghp knh chia bc sng v tch knh, ghp nhiubc sng c bi s nguyn trong khong ph t do n u ra. Trong hnh vb bin i bc sng 1x1 do mt b tch knh, M b bin i bc sng vmt b phi ghp to thnh, hon thnh bin i M bc sng u vo thnhmt bc sng no trong R bc sng ni b.

Khi R [(2M-1)/N]*N th kt cu ny c th thc hin u ni cho knh

o thnh nhiu kiu tuyt i khng nghn, ([x] biu th ln hn hoc bng snguyn nh nht ca x).

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Hnh 1.29Kt cu OXC da vo 3 cp bin i bc sng ca b ghp knh

AWGMKt cu ny c tnh mun bc sng, khng c tnh mun ng kt

ni v khng c kh nng pht qung b.

Kt cu OXC hon da trn chuyn mch bc sng

Nm 1996 R. Sabella v E. Lannene sut mt kiu kt cu tr gipknh bc sng o nhhnh 1.30. Trong kt cu ny c tn hiu WDM trongng kt ni vo u tin n c b bin i bc sng chuyn ho thnhMN bc sng ni b khc nhau. Sau a n MN ng nhnh thng qua

mt b phi ghp ln, qua b lc c iu chnh chn ra mt bc sng cn thit,b bin i bc sng chuyn thnh bc sng bn ngoi cn thit ghp knhcng vi bc sng khc a ln ng kt ni ra.

Hnh 1.30Kt cu OXC hon ton da vo chuyn mch bc sng.

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1.2.3.10 Chuyn mch khng gian

Cc ma trn chuyn mch khng gian c s dng trong cc thit bOADM v OXC. Cc thit b ny da vo hot ng c hc bao gm motor,in t tnh hoc p in lm lch cc vi gng cho chuyn mch cc tn hiu

quang. Do yu cu chuyn ng chc ca phn t chuyn mch thi gian tc di kh rng t 30ms n 500ms. Thit b dn sng to tc dng ca nhitnng hoc hiu ng quang- in l c thi gian chuyn mch tng i nhanh,

bng 1.1 bao gm cc c tnh ca cc ma trn chuyn mch khc nhau.

Cng ngh Chc Nhit C-quang

S kch thch Motor Mirror Electro-

static

Polyme Thermal

Kch c 64x64

100x100

8x8

64x64

16x16 8x8

27x27

8x8 8x8

Suy hao xen 2 2 4 8 8 8

Thi gian chuynmch (ms)

500 30 40 2 2 < 2

S cch ly ccknh (dB)

60 60 60 50 40 30

Bng 1.1 Tnh cht ca thit b ma trn chuyn mch quang

a. Cc chuyn mch cbn

Chuyn mch quang phn chia theo khng gian

Kho quang khng gian (SOS Space Optical Switch) l kho c bnnht trong chuyn mch quang. N c th trc tip to thnh phn t chuynmch thi gian v phn t chuyn mch bc sng. Kho quang khng gian cth chia lm hai loi: si quang v loi khng gian.

Loi kho quang cbn l loi si quang, u vo v u ra c hai siquang, c th hnh thnh hai trng thi kt ni l kt ni song song v kt nicho nhau.

Kho quang 2x2 trong hnh 1.31 (a) v (b) l loi kho quang kiu ngdn sng, nhiu khin bn ngoi thay i chit sut ca si chn u ra.Tin hnh iu khin hiu sut khc x do in p bn ngoi a vo hnh thnh

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in trng (kho quang kiu in quang), hoc thng qua si t nng (khoquang kiu nhit quang). Loi kho quang ny khi chuyn mch tn hiu, ngoitn hao ca bn thn n chuyn mch, tt c cng sut tn hiu n si quangu ra s lng ph i mt na nng lng, t dn n tn hao ph, m s

ng chuyn mch cng nhiu th tn hao cng ln. Dng b khuch i quanglm kho quang kiu giao din c th gii quyt vn ny. Nhng khi qunhiu kho khng gian ni vi nhau thnh b chuyn mch ln, th b khuchi quang gy ra hin tng bc x v lm bng thng hp li. Loi kho hnh1.31 (c) c kh nng truyn qung b, iu ny rt c li khi cung cp dch vqung b. Ngoi ra c loi kho quang ckh thng dng, c u im l tnhao nh, cch ly cao lm vic n nh tin cy nhng tc kho tng ichm

Giao din quang

a) Kho quang 2 x 2 b) Kho quang 1 x 2 c) Kho quang

kt ni song song kt ni cho khng gian

Hnh 1.31Phong n thc hin kho quang khng gian

Chuyn mch quang phn chia theo thi gian

Chuyn mch quang chia thi gian l phn phi thi gian ti u ra chocc tn hiu vo khc nhau. Th d phn phi thi gian tj ti u ra cho tn hiuvo ti thi gian tj. Ginh tn hiu quang ghp knh thi gian mi khung ghpT khe thi gian, rng cc khe bng nhau v cng trn mt knh.

Chuyn mch quang chia thi gian phi c b chuyn mch khe thi gianTSI (Time Slot Interchanger) chuyn mch bt k mt khe thi gian ti uvo n mt khe thi gian ti u ra.

Chuyn mch khe thi gian cn phi c b tr quang. B kch quang cth dng lm b tr quang nhng ch tr theo v tr m li mc phi vn v tc v dung lng chuyn mch. Dy tr si quang rt thch h p gy tr cachuyn mch thi gian. N ly rng ca khe thi gian lm n v, tn hiuquang cn tr bao nhiu khe thi gian th n i qua by nhiu n v chiu di

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si quang. Cho nn b chuyn mch khe thi gian hin nay do kho quangkhng gian v nhm si dy tr to thnh nhhnh 1.32.

(a) (b)

(c) (d)

Hnh 1.32 Bn loi chuyn mch khe thi gianChuyn mch quang phn chia theo bc sng.

Ghp knh bc sng dy c l xu th trong thng tin quang. N lidng bng thng rng ca si quang, trong ca s bc sng 1550nm c tn haothp ghp knh nhiu tn hiu quang v nng dung lng thng tin si quang

ln rt cao. Chuyn mch bc sng trong thng tin quang l bc sng i bt

k trong tn hiu ghp bc sng c bin i thnh bc sng j khc.

Chuyn mch bc sng quang cn b bin i bc sng (Wavelegth

Converter ) b tch bc sng chia ct knh tn hiu v khng gian, tin hnhchuyn i bc sng i vi mi mt knh, ri ghp li v a ra nh trn hnh1.33.

Hin nay c ba phng php chuyn i bc sng :

S dng b bin i bc sng O/E/O chuyn i tn hiu quang thnh tnhiu in, ri dng tn hiu in iu ch Laser, iu chnh bc sng ra

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ca Laser chuyn i bc sng, phng n ny c th sa xung,khuch i nhng mt tnh trong sut ca min quang.

Li dng c tnh bo ho v hp th ca b khuch i bn dn, li dnghiu ng iu ch tng ch xen k nhau ca b khuch i bn dn hoc

hiu ng iu ch pha xen k nhau thc hin bin i bc sng.Li dng hiu ng trn tn bn bc sng trong b khuch i quang bn

dn v cc u im tc cao, bng tn rng v tnh trong sut tt trong minquang.

B chuyn i bc sngHnh 1.33 Chuyn mch quang phn chia theobc sng

Chuyn mch quang phc hp.

Chuyn mch quang phc h p l s kt h p cc phng thc chuynmch khng, thi gian, bc sng.

Trn hnh 1.34 l cu trc ca hai loi chuyn mch quang kt cu kiuTST v STS, hnh 1.35 l cu trc ca chuyn mch quang khng gian ghp

bc sng.

a) Kt cu TST b) Kt cu STSHnh 1.34Hai loi phn tchuyn mch khng gian v thi gian

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Hnh 1.35 Modun chuyn mch quang khng gian ghp knh bc sng

1.3 Cu trc mng WDM

Khi ra i h thng WDM chn gin l cu trc im- im. Hin nay

cc mng WDM c cu trc mng phc tp hn rt nhiu. N bao gm cc mngcon c kt ni trc tip vi nhau. C hai loi cc trc mng con nh sau: Cutrc Ring, v cu trc Mesh, cu trc hnh sao n cu trc hnh sao kp.

1.3.1 Cu trc mng ring

Mt node ch lin kt vt l trc tip vi hai node lin k to thnh vngring khp kn. V kt ni logic, mt node c th c kt ni n tt c cc nodebng cch nh tuyn qua cc node trung gian. Kt ni ny thun li cho vicbo v vi hiu nng cao, gi thnh thp v s dng cc phn t mng hiu qu.

Mi node ring c cc b ghp knh xen/r quang OADM r /xen cc bcsng.Hnh 1.36miu t kt ni ring 5 node.

Hnh 1.36 Mt cu trc ring 5 node

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1.3.2 Cu trc mng Mesh

Mt node c th kt ni vt l n tt c cc node khc hoc l c kt nin mt node bt k. N cung cp nhiu kh nng nh tuyn. Lu lng trncp trong mng Mesh c th mrng, v dung lng yu cu trn tuyn c th

d dng d bo c. Cu trc ny c tin cy cao, nhng kt cu phc tp,vic iu khin v qun l i hi phc tp hn. N thng c s dng trongcc mng trc yu cu tin cy cao. Hnh 1.37 m t mt mng Mesh c cutrc 6 node.

Hnh 1.37 Cu trc dng Mesh.

1.3.3 Cu trc hnh sao n

T node trung tm tn hiu c truyn thng n cc node khc nh trnhnh 1.38. Cu trc ny n gin, cho php truyn c dung lng knh ln,

thit b mng khng phc tp, thun li cho khai thc v bo dng. Tuy nhincu trc ny c nhc im l s dng nhiu si quang do khng tn dngc hiu qu bng tn. Mt nhc im gia node trung tm phi c kh nngdung lng cao, m khi node ny c s c th h thng khng lm vic c.

Hnh 1.38 Cu trc hnh sao n.

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1.3.4 Cu trc hnh sao kp

i vi cu trc hnh sao kp, ngoi node trung tm cn c cc thit bu xa. T node trung tm ti cc thit bu xa, cng nh t cc thit bu xati node con u c cu trc hnh sao, nh vy to thnh cu trc hnh sao kp

nh trn hnh 1.39. Cu trc kp cho php s dng hiu qu v mi nhnh c thc nhiu node con. Tuy nhin cu trc ny c nhc im l do c s dng thitbu xa nn chi ph lp t cao hn, cu hnh phc tp hn s lm gim tincy, kh pht trin cho cc dch v bng rng. Cng ging nhc im chungca cu trc hnh sao, cu hnh ny i hi nng lc qun l ca node trung tmphi mnh, c th lu thot thng tin gia cc node trung tm ti cc node con,v gia cc node con vi nhau.

Hnh 1.39 Cu trc hnh sao kp

1.4 Cc kin trc mng li in hnh

Cc mng phn cp s to iu kin d dng trong nh tuyn v qun l. Vthc nghim mng li c chia ra cc cp t quan im nh tuyn lu lng.Kin trc ny c th chuyn i mt cch t nhin sang min topo lin kt nithch h p, kt qu c cc topo mng phc h p. Trong phn sau chng tanghin cu nhng loi kin trc quang phn cp m bao gm nhng kin trccon cbn sau

Cc Ring OMS-SP

Mesh quang da trn OXC

Nhng l do cho s la chn nhng kin trc ring ny l:

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- OMS-OP l mt kin trc hon ton quang rt tin li, cnh tuyn vbo vu thc hin bng quang. Do mong mun rng OMS-OP rings mang n nhng vn c bit m phi tnh n trong quy hochmng quang.

- Mesh quang da trn OXC c nhn nhn l mt kin trc quang tintin, n a ra nh tuyn quang v s phc hi c th gp phn lm ngin ha s phc tp ca thit bin trong nhng mng Mesh dung lngcao.

Nhng cu hnh mng phn cp c la chn nhn nhn l c kh nngtt trong vic chia nh cc mng thc t vi kh nng qun l tt hn. Trong qutrnh pht trin t mng c sang mng mi da trn nn tng nhng cu hnhmng quang mi, nhng cu hnh ny c mong i l hu ch trong nhiumng khc nhau v s c kh nng trin khai nhiu giai on khc nhau.

Cc nghin cu gii hn chkin trc hai lp bi v nhng kin trc nyc thc quan tm l mt gii php hin thc cho nhng mng li. Nhng cctrc mng quang phc hp bao gm nhng mng vng ny s c hiu nng phthuc vo nhng kiu bo v v chin lc nh tuyn li c p dng chonhng mng con ring bit. Ch nhng kin trc lin kt ni nhng node kp lc la chn v nhng mng li ln dung lng cao vic tch ra cc phngphp nh tuyn l yu cu cn thit.

1.4.1 Kin trc ring OMS-SP hai lp

Hnh 1.40 Kin trc OMS-OP hai lp

Thun li chnh ca cu trc ny l kh nng kt ni quang gia cc ring.Trong cc hub tnh mm do ca OCH quang ph thuc vo kh nng kt nicho ca cc OADM. Cc OADM th h 1 ch xen/tch cnh. Trong trnghp ny bin i bc sng c th cn thit cho cc lin kt ni.

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1.4.2 Kin trc Mesh - Ring hai lp

Cu trc ny l cu trc ha hn trong tng lai nh trn hnh 1.41. Lulng trong cc ring dung lng thp c la chn v truyn ti bi lp trn cdung lng rt cao, nh trong mng SDH truyn thng. Trong trng hp mng

ln, cc OXC c th phi s dng bin i bc sng thit lp c s tuynln hn. Cn nghin cu su hn pht trin cch bo v v phc hi h choloi cu trc ny. Cng nh cu trc mng SDH, cch bo v lin kt ni ccmng quang con (PSNCP) (1 + 1 bo v tuyn) l mt c cho yu cu ny.

Hnh 1.41 Kin trc hai lp Optical Mesh-Optical Ring

1.4.3 Kin trc Ring - Mesh hai lp

Trong mt s trng hp cu trc ny c th l mt gii php ph hp. l trng hp mt mng Ring quang dung lng rt cao cn thit phi lin ktcc mng con cu trc Mesh lp thp nh trn hnh 1.42. Cch bo v phchi tng t nh c trc Mesh Ring.

Hnh 1.42 Kin trc hai lp Optical Ring-Optical Mesh

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Nh vy ghp knh theo bc sng l mt cng ngh cha kha cho gii php tng dung lng truyn dn. Cng ngh ny cho php tng dung lngtruyn dn ca si quang ln rt nhiu ln m khng cn ci t thm tuyn mi.Cng ngh WDM ang c s pht trin nhanh chng, v ngy cng hon thin.

Cc d n hin i ho mng quang nc ta u tha nhn WDM l mt trongnhng cng ngh ct li cho mng truyn ti th h sau.

1.5 Cc tham sc trng ca mng quang

Vic quy hoch nh cmng, trong c nh tuyn khng th khngtnh n cc tham sc trng ca mng, c nhng vn cng ngh hin ticha vt qua, c nhng rng buc v vt l, rng buc v topo i vi vic pdng vo mng quang. Hay nh vic la chn kin trc hai lp hay ba lp. Mc

ch ca phn ny l a ra tho lun cc tham s khc nhau tnh ton chophp nh tuyn trong tng lai v nh cmng quang. Sau y l cc tham sc trng ca mng quang trong cc gii hn yu cu trong nh tuyn niring v quy hoch thit k mng ni chung.

1.5.1 c trng ring ca mng quang

1. Dung lng cao : Mng li phi s dng vi nhiu ng dng v dch vc d tnh trong tng lai, vi rng bng tn khc nhau. Do mngphi c dung lng ln v c kh nng kim sot tn hiu ca knh quang.

2. Strong sut : Vi chc nng quang hc v gim bt s phc tp cathit b, tn hiu phi hon ton trong sut trong min quang. C mt vidch v c th xc nh nh l khun dng tn hiu, tc bit, modetruyn ti dch v. S trong sut thng khng tn ti, trong khi cc rngbuc vt l lun lun gy ra gii hn ca s trong sut.

3. Tnh linh hot: Tham chiu ti kh nng ca mng iu tit thay itrong nhng mu lu lng. iu ny c th d dng trong mng quangkhi tnh ht ca tn hiu c kim sot.

4. Tnh kt ni c: l kh nng thit lp kt ni mt cch c lp vitrng thi thc trng ca mng. Kh nng kt ni y c ngha l bt kkt ni no gia hai node bt k ca mng c th thit lp bt k mithi im. Trong mng quang l cc bc sng c th dng c, khaOXC hoc gii hn s bc sng ca OADM l gii hn chnh ca s hnch kh nng kt ni quang ton in.

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5. Tnh pht trin: L kh nng cung cp dung lng hoc chc nng camng bng cch thm thit b mi ng nht. Trong mng quang vic tngdn cc bc sng c th s dng c m khng thay i ton b thit bWDM l mt th hin tnh pht trin.

1.5.2 Cc tham s lin quan n topo mng

Snh ngha ca mng thit k nhng quy tc cho mng quang WDM, gitr ca nhng thut gii ti u v topo mng v cc cng c quy hoch mngphi c s dng nhng m phng s. Tuy nhin, s minh ha ca cc kt quchung c tht c trong vi trng hp, m cung cp cc quy tc thit kn gin c th s dng cho cc nguyn tc quy hoch mng. Mt s tham smng quan trng l:

S cc node (N), mt node l ngun ca lu lng (knh quang) hoc lnode trung gian thun ty.

kt ni node (D), c nh ngha nh l s trung bnh ca cc nodetrc tip (khng qua bt k transit no) c kt ni ti mt node qua mthoc nhiu si.

di tuyn (LF) c chun ha cho khong cch node.

S si trn mt tuyn (F)

Dng hnh th ca mng.

Mt mng.

T nhng tham s ny, n c chng minh bi sc lng gn ng W,s bc sng c yu cu ph hp vi nhu cu lu lng (T l s knh trnkt ni) c tnh bi cng thc sau.

W FDFL

TN

N

.

212

1 2/3

(1.23)

Tuy nhin, nhng tham s ny cha thy hon ton cho vic m t mtmng, t topo c tnh cn c ch .

Mt mng c dnh ngha bi cng thc : d =1N

D

Tham s ny phn nh su ca li trong mng, a ra node mng cnhtrong mng, nhng gi tr cc i t c vi mng Mesh y (d = 1) v

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ring ( d =1

2

n). Hnh 1.43 m t nhiu trng thi khc nhau ca cc topo mng

vi mt tuyn cho.

Full Mesh Mesh Ring Mesh

D = 4, N = 5 D = 3, N = 6 D = 2, N = 6 D= 2,5, N = 8

d = 1 d = 0.6 d = 0,4 d = 0.357

Hnh 1.43 Cc th d vcc mu mt khc nhau

1.5.3 Cc tham s lin quan ti nhng gii hn vt lCht lng ca tn hiu qua mng p t nhng quy tc k thut cho quy

hoch mng. Trong mt mng hon ton quang, d liu cn truyn nguyn l tnhiu quang trn tt c cc tuyn trn lp quang. Tuy nhin, mi tuyn khng thn gin nh tuyn WDM im im, bi v cc tn hiu trn cc tuyn khcnhau c thi qua mt s thit b khc, s cc bc sng c trng cho tn hiutrn cc si c th khc nhau vi cc tuyn khc nhau. Nhng gii hn vt ldn n gim cht lng ca tn hiu qua xuyn m, mo tn hiu v nhiu tch

ly. Thit k ca cc kt ni cho v nh ngha kin trc ca cc node c thbo m node thc hin cc chc nng cn thit. Tuy nhin c mt vn lbao nhin node c thc xp tng dc theo tuyn quang trong khi phi gicht lng tn hiu mc chp nhn c. V s ti to tn hiu phi thc hinc, do vy gii hn ca di tuyn quang cn c quan tm v n c giihn nht nh. Mt s vn lin quan n gii hn s bc sng trn mi si vvn xuyn m v gii hn bng tn khuch i. Kh khn c th khc phcbng cch ti s dng bc sng. Nhng iu ny li lm kh khn cho vicphn phi bc sng v vn nh tuyn. Nhng tham s sau y cn quan tmn lin quan n cht lng ca tn hiu.

Gi tr trung bnh v ln nht ca di on ni trong mng

S node quang ln nht m c thi qua m khng cn ti to

di tuyn quang ln nht m khng cn ti to

S ln bin i bc sng trn tuyn

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S bc sng, knh quang c s dng trn ni si

Gim cp BER v bng thng ca h thng

S tch hp cc knh quang ring (mc cng sut pht quang, n nhbc sng )

Thi gian cu hnh li (nh truyn li v chuyn mch thi gian)

1.5.4 Cc tham s lin quan n nhu cu lu lng mng

Ma trn nhu cu l rt quan trng trong qu trnh quy hoch, bi v n cth lm nh hng n s la chn cu hnh, phng n chun b v nh truyn,c trng truyn ti ca lp V nguyn tc, ma trn nhu cu cho lp quangphi c biu din qua cc bc sng , nhng thng n c biu din bin v thng thng ca lp client (SDH, ATM..) m iu cho php quyhoch thit k lp quang, mt mc t do cao hn trong thit k lp quang.

Phn phi lu lng

Phn phi lu lng trong cc node quang l mt c im quan trng camng. Nhng cch phn phi khc nhau c th dn nh quy hoch hng vkin trc mng quang khc nhau v cho php v cho php s dng nhngphng php gii thut khc nhau trong qu trnh quy hoch.

Cu trc khung ca knh quang

Thit k ca cc mng truyn ti hin ti l da trn lu lng tnh, cci tng cn c tnh ton ti u. Thng thng, cc u vo cho cMbit/s.Cu trc khung hoc dung lng knh, nh ngha s tng ng gia ma trnnhu cu trong lp quang v cc ma trn bc sng. S la chn cu trc khungc th hin bng la chn cng ngh. Hu ht cc h thng a bc sng hinc s dng cu trc khung STM-16, nhng nghin cu ch ra c th s dngn STM-64 cho php trn nhiu cu trc khung ca knh quang trn cng mtsi.

Dung lng trn mi on ni

Cc gii hn vt l dn n gii hn ca s knh quang trn si. Ngunpht i vi mi bc sng phi ln cung cp tn hiu trn tp m ti uthu. Tuy nhin n khng th tng mi cng sut ca ngun quang c v bkhuch i quang c th bo ha v c hiu ng phi tuyn nh trng hp trnbn bc sng s lm gim hiu nng truyn dn tn hiu. Do c s cn bng

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dung lng trn mi on ni, khong cch b khuch i v s tng khuch itrn ton tuyn.

Dbo nhu cu p ng

Ty thuc vo cc yu cu dch v mng, nhiu loi nhu cu lu lng

khc nhau c mang trn tng quang: Tn hiu video, data, thu knh ringTc bit cho mi loi ny c th khc nhau. Qu trnh quy hoch bao gm dbo v p ng cho nhng cho nhng loi tn hiu ny vo lp quang. S chunb c th da vo phn phi nhu cu quang, nhng yu cu ca chng. Vi mcch , vic chun b tt nht c th tnh n tc ng ca lp quang, nhm ccnhu cu lu lng lp client nh SDH, thnh cc lung quang nh tuyn saocho ti u nht v vic s sng ti nguyn, trnh lu lng trn mt tuyn niqu cao trong khi lu lng trn tuyn khc li qu th p, lng ph ti nguyn.Hnh sau miu t qu trnh nhm cc lu lng lp SDH thnh lu lng giacc node quang.

1.5.5 Nhng tham s lin quan n kin trc

Mng mt cp v mng c kin trc

Mng c thc cu trc theo hai cch: Phng (mt c p) v mng ckin trc. Mng mt c p khng c s bt buc no v nh tuyn lu lngtrong khi mt mng c kin trc l c, v nguyn tc vic giao tip gia hai node

ng kin trc s qua mt hoc nhiu node c p cao hn. Thng thng lulng trn mng vin thng ln thng c chia thnh kin trc nhiu lp xpchng. Thng thng l 2 hoc 3 lp, trong mt vi trng hp c bit kintrc mng c thit k l 4 lp. Thun li chnh ca kin trc phn cp l quytc nh tuyn v qun l d dng. Trong tng lai gn, mng hon ton quangkin trc hai lp s l ph bin cho cc ng dng mng li.

S mng con trong mi phn cp

C hai mng mt cp v mng c kin trc c th chia ra nhiu mng con.

Ni chung mng con c xc nh bi s kt ni cc node v sc lp ca ntrong cch gim st. Thng thng trong mng c cu trc lin kt ni ca ccmng con trong cng mt mng c cho php cho qua mt cp cao hn k trn.S mng con trong mt cp l khng gii hn, v ch ph thuc vo kch cmng thc.

Nhng loi mng con

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Mt mng con c th c nhiu kiu phn chia, nhng thng mt vi topocbn, nh Ring hoc Mesh con. Nhng ng c vin cho cc mng con l mngWDM quang dng Ring v Mesh quang.

S node trung gian trn mi mng con

Tr khi s phn phi nhu cu khng cn nhiu qua hn mt mng con,mi mng con phi c t nht mt mode c bit ni m truyn lu lng ira. Nhng node ny (thng c gi l node trung tm) c nhng chc nngc bit cho lin kt ni gia nhng mng con khc nhau.

1.5.6 Cc tham s lin quan n sgim st

Cch bo v hoc phc hi c p dng chung trn mng lm tngyu cu gim st chng li li xy ra. Cch phc hi thng thm vo nhng

rng buc mi n hot ng quy hoch mng nh thi gian phc hi, dica cc tuyn, ti nguyn d phng, snh tuyn

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Chng II

TNG QUAN VNH TUYN V GN BC SNGTRONG MNG QUANG WDM

2.1 Gii thiu chungCng ngh truyn dn WDM i vo giai on ng dng v thng mi

ho theo xu hng ngy cng hon thin ca cng ngh. Trong lnh vc thngtin quang, vn quan trng l li dng c mng quang hin c v tng lais xy dng to thnh mng WDM tc cao, dung lng ln a dch v.Trong khi thc hin mng vn then cht quyt nh hiu sut s dng tinguyn mng l quy hoch hp l ti nguyn bc sng v n lin quan trc tipti vn nh tuyn v gn bc sng trong mng.

Vn tm cc tuyn v gn bc sng cho lung quang c gi l biton nh tuyn v gn bc sng (RWA- Routing and WavelengthAssignment). Cc yu cu kt ni c hai dng: dng tnh v dng ng.

K thut WDM trong cc mng quang c pht trin nhanh chng, n p ng cc yu cu v bng tn ca ngi s dng mng. Trong mng nhtuyn cc nt truy nhp thng tin vi nhau qua cc knh ton quang, cc knhny c xem nh cc lung quang.

Mt lung quang c s dng h trmt kt ni trong mng nh tuyn

bc sng WDM v n c th lin kt cc si quang. Trong trng hp khngs dng b chuyn i bc sng, mt lung quang chim cng bc sng trntt c cc lin kt si m n i qua. c tnh ny gi l iu kin rng buc bcsng lin tc.Hnh 2.1 minh ho mt mng nh tuyn bc sng ni cc lungquang c thit l p gia cc c p nt truy nh p trn cc bc sng khcnhau. Trong bi ton RWA, vi lu lng tnh th ton b tp cc kt ni cbit trc v khi phi thit lp lung quang cho cc kt ni ny trong khi ccti nguyn mng phi ti thiu ho s bc sng hoc s cc si trong mng.Vi la chn nh vy, c th thit lp nhiu kt ni cho s cc bc sng cnh a ra. Bi ton RWA cho lu lng tnh gi l bi ton thit l p lungquang tnh (SLE Static Lightpath Establishment). Trong trng hp lu lngng, mt lung quang c thit l p cho mi yu cu kt ni n v lungquang c gii phng sau mt thi gian qui nh. i tng trong trng hplu lng ng l thit lp lung quang v gn bc sng theo cch ti thiutng s kt ni b nghn hoc ti a s cc kt ni c thit lp trong mng ti

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bt c thi im no. Bi ton ny gi l bi ton thit l p lung quang ng(DLE- Dynamic Lightpath Establishment).

Bi ton SLE c thc gii nh l qui hoch tuyn tnh nguyn, n l bi ton NP-y . gii bi ton d dng hn, bi ton SLE c th chia

thnh 2 bi ton nh (1) nh tuyn, (2)gn bc sng mi bi ton ny giitheo nhng cch khc nhau. Mt s thut ton trong a ra cc thut ton gnng gii bi ton SLE cho cc mng ln v cc thut ton t mu thc dng gn cc bc sng ti cc lung quang mt khi cc lung quangc nh tuyn ng. Vic gii cc bi ton thit lp lung quang ng l khhn, cc phng php heuristic thng c dng. Phng php heuristic thchin cho c hai bi ton nh tuyn v gn bc sng.

Hnh 2.1 Mng chuyn mch knh quang vi cc kt ni lung quang

Vi bi ton nh tuyn c 3 cch tip cn. nh tuyn cnh, nh tuynthay th cnh v nh tuyn thch nghi. Trong s cc cch tip cn ny nhtuyn cnh l n gin nht nhng nh tuyn thch nghi mang li c tnh ttnht. nh tuyn thay th em li s tho hi p gia s phc t p v c tnhmng.

Vi bi ton gn bc sng bao gm bi ton gn bc sng tnh (t mu th tun t,...) v bi ton gn bc sng ng (bao gm mt s cc phngphp heuristic in hnh)

i vi mng thng tin quang, RWA l vn rt quang trng. Gii phpnhn bit b chuyn i bc sng WC l mt trong nhng cng c quan trngc s dng trong nh tuyn v gn bc sng.

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2.1.1 Gii php WCA trong nh tuyn v gn bc sng

Mt sgi thit

Gii php WCA xy dng trn mt s gi thit sau y:

Gi thit rng tc n ca cc yu cu kt ni tun theo lut phn b

Poisson v thi gian chim ging truyn tun theo lut phn b hms m.

Mi node mng c mt s hu hn cc b chuyn i bc sng v schuyn i l hon ton sng (bt k mt u vo c th no n bt kmt u ra c th no).

Vic nh tuyn gn bc sng c thc hin phn tn (nh tuyn gnbc sng ti mi nt mt cch c lp)

M hnh hthng

M hnh ha mng WDM bng th G (N,L), trong N l tp cc nt(node) v L l tp cc tuyn (link).

Thit lp cc tham s lin quan bao gm: Tng s bc sng s dng tint v trn tuyn, tng s b chuyn i bc sng, s bc sng cho php tint, s bc sng cho php ti u vo ca nt, s lng lung nhnh cho phpca mt cnh trn lung nhnh t ngun n ch khng cn n b chuyn ibc sng v s lng lung nhnh trn mi cnh t ngun n ch cn phi sdng b chuyn i bc sng.

Gii php tng th

- Chuyn th nhm mc ch nh tuyn.

- Xc nh ng i ngn nht.

- Chuyn th nhm mc ch gn bc sng.

- Thc hin gii

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