Chuyen de Thong Tin Quang (Chi Tiet) - Nhom 10 L11CQVT7

7/30/2019 Chuyen de Thong Tin Quang (Chi Tiet) - Nhom 10 L11CQVT7

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HC VIN CNG NGH BU CHNH VIN THNG

KHOA IN T VIN THNG

GVHD : Ths. Hong Vn VSVTH : Nhm 10 - L11CQVT07 B

L Vn Ngha

Nguyn Ngc QunhNguyn Khc Xun TngPhm Th Yn

TI: CCH T BRAGG SI QUANG V NG DNG

H NI 3/2013


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Chuyn thng tin quang Mc lc

MC LC

MC LC.....................................................................................................................iiDANH SCH HNH V.............................................................................................vi

THUT NG VIT TT........................................................................................viiiLI NI U..............................................................................................................1CHNG I: C IM CU TRC V TNH CHT CA FBG.....................3

1. 1 Cu to chung..............................................................................................................31.2 Nguyn l. ...................................................................................................................31. 3 iu kin kt hp pha..................................................................................................51. 4 Cc phng trnh ghp mode.......................................................................................61. 5 L thuyt m hnh ho FBG........................................................................................71. 6 Cu trc v tnh cht ca cc dng cch t..................................................................9

1. 6. 1 Cch t Bragg u (Uniform FBG).....................................................................9

1. 6. 1. 1 Cu trc.......................................................................................................91.6. 1. 2 M t ton hc............................................................................................101. 6. 1. 3 Thi gian tr v tn sc..............................................................................12

1.6.2. Cch t Bragg quang chu k thay i CFBG......................................................121. 6. 2. 1 Cu trc.....................................................................................................121. 6. 2. 2 M t ton hc ca CFBG.........................................................................13

1. 6. 3 Cch t iu bin chit sut ..............................................................................161. 6. 3. 1 Nguyn l.................................................................................................161. 6. 3. 2 M t ton hc ca AFBG.........................................................................16

CHNG 2: CC NG DNG CA FBG............................................................20

2. 1 ng dng ca cch t Bragg quang trong b tn sc ................................................202. 1. 1 Gii thiu...........................................................................................................202. 1. 2 Hin tng tn sc trong si cp quang.............................................................202. 1. 3 B tn sc bng quang si cch t Bragg chu k bin i tuyn tnh................22

1. 2 ng dng ca FBG trong b tch ghp knh (xen-r) OADM..................................241. 2. 1 Tng quan v WDM..........................................................................................242.2.2. K thut tch ghp knh quang............................................................................252. 2. 3 Cc cu hnh OADM ........................................................................................26

2. 2. 3. 1 OADM da trn FBG v coupler 3 dB......................................................262. 2. 3. 2 OADM da trn FBG v cu hnh giao thoa March-Zehnder...................272. 2. 3. 3 Cu hnh OADM s dng FBG v Circulator...........................................282. 2. 3. 4 OADM da trn cch t t gia Coupler.................................................292. 2. 3. 5 Cc tham s ca cc cu hnh OADM.......................................................30

2. 3 ng dng ca FBG trong cn bng khuych i ca thit b K quang si EDFA.. .322. 3. 1 Tng quan v EDFA..........................................................................................32

2. 3. 1. 1 Cu to v nguyn l hot ng ca EDFA:..............................................322. 3. 1. 2 Tng cn bng cho khuych i EDFA................................................34

2. 3. 2 ng dng ca FBG trong b cn bng khuych i EDFA...............................35

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2. 4 Mt s ng dng khc ca FBG.................................................................................382. 4. 1 ng dng trong cm bin..................................................................................382. 4. 2 ng dng trong cng ngh Laser ......................................................................39

KT LUN.................................................................................................................40TI LIU THAM KHO.........................................................................................41

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Chuyn thng tin quang Danh mc hnh v

DANH SCH HNH V

MC LC.....................................................................................................................iiDANH SCH HNH V.............................................................................................viTHUT NG VIT TT........................................................................................viii

LI NI U..............................................................................................................1CHNG I: C IM CU TRC V TNH CHT CA FBG.....................3

1. 1 Cu to chung..............................................................................................................3Hnh 1. 1 Cu to v chit sut ca FBG............................................................................... 3

1.2 Nguyn l. ...................................................................................................................3Hnh 1. 2: M t c tnh ca FBG........................................................................................ 4

Hnh 1. 3: Ph phn x ca cch t Bragg dng cch t u, =0. 53559nm gi tr

L=0,53559cm, neff=1,447, n=0,0009,.................................................................................. 5

1. 3 iu kin kt hp pha..................................................................................................51. 4 Cc phng trnh ghp mode.......................................................................................61. 5 L thuyt m hnh ho FBG........................................................................................7

Hnh 1. 4 : iu kin u v s tnh ton p ng ca cch t i vi nh sng ti.............9

1. 6 Cu trc v tnh cht ca cc dng cch t..................................................................91. 6. 1 Cch t Bragg u (Uniform FBG).....................................................................9

1. 6. 1. 1 Cu trc.......................................................................................................9Hnh 1. 5: Cch t Bragg chu k u UFBG.........................................................................10

1.6. 1. 2 M t ton hc............................................................................................10

Hnh 1. 6: S nguyn l ca ma trn truyn t dnh cho UFBG v non - UFBG..........111. 6. 1. 3 Thi gian tr v tn sc..............................................................................12

1.6.2. Cch t Bragg quang chu k thay i CFBG......................................................121. 6. 2. 1 Cu trc.....................................................................................................12

Hnh 1. 7: M hnh cch t Bragg chu k thay i CFBG....................................................13

1. 6. 2. 2 M t ton hc ca CFBG.........................................................................13Hnh 1.9: a) Ph phn x ca 2 cch t c gi tr Chirp dD/dz =-1(nm/cm)(ng mu

nt lin), dD/dz =-2(nm/cm)(ng mu xanh lc nt t) v dD/dz =-4(nm/cm)(ng

mu xanh lam nt chm) vi cc gi tr L= 0,1cm, neff=1,447, n=0,0004, D=1550(nm) b) thi gian tr theo bc sng ca CFBG...............................................................................16

1. 6. 3 Cch t iu bin chit sut ..............................................................................161. 6. 3. 1 Nguyn l.................................................................................................161. 6. 3. 2 M t ton hc ca AFBG.........................................................................16

Hnh 1.10: th biu din s thay i ch s khc x iu bin chit sut si quang AFBG.

ng nt lin mu l phng trnh 1.48. ng nt t mu xanh lc l phng trnh vi


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1.50. ng nt chm mu xanh lc l phng trnh 1.51 v ng nt gch chm mu

hng l phng trnh 1.52, K=5 vi cc gi tr L= 0,1cm, neff=1,447, n=0,0002...........18

Hnh 1.10: S phn b ph phn x ca 4 AFBG vi c tnh Gauss phng trnh 1.48 (nt

lin mu ). c tnh Raised cosine phng trnh 1.50 (nt t mu xanh lc). c tnh

Sinc phng trnh 1.51 ( nt chm mu xanh lc). c tnh Kaiser phng trnh 1.52 (nt

gch chm mu hng), K=5 vi cc gi tr L= 0,1cm, neff=1,447, , D=1550(nm)

n=0,0002.............................................................................................................................19

CHNG 2: CC NG DNG CA FBG............................................................202. 1 ng dng ca cch t Bragg quang trong b tn sc ................................................20

2. 1. 1 Gii thiu...........................................................................................................202. 1. 2 Hin tng tn sc trong si cp quang.............................................................20

Hnh 2.1 S thay i ca vn tc nhm theo bc sng trong quang si n mode thng

thng...................................................................................................................................21

Hnh 2.2 Hu qu ca tn sc i vi tc truyn ca mng a) xung ti u pht .b) xung

thu c ti u thu v thit b thu khng th phn bit c hai xung k tip...................22

2. 1. 3 B tn sc bng quang si cch t Bragg chu k bin i tuyn tnh................22Hnh 2.3 Nguyn l b tn sc ca quang si cch t Bagg chu k bin i........................23

Hnh 2. 4. M hnh c bn ca thit b b tn sc dng cch t Bagg chu k thay i tuyn

tnh........................................................................................................................................23

1. 2 ng dng ca FBG trong b tch ghp knh (xen-r) OADM..................................241. 2. 1 Tng quan v WDM..........................................................................................24

Hnh 2.5: S h thng WDM n hng thng tin 2 chiu..............................................24

Hnh 2.6: S h thng WDM n hng thng tin 2 chiu..............................................25

2.2.2. K thut tch ghp knh quang............................................................................25Hnh 2. 7: M hnh c bn ca OADM................................................................................. 26

2. 2. 3 Cc cu hnh OADM ........................................................................................262. 2. 3. 1 OADM da trn FBG v coupler 3 dB......................................................26

Hnh 2. 8 : M hnh OADM da trn FBG v coupler 3 dB.................................................272. 2. 3. 2 OADM da trn FBG v cu hnh giao thoa March-Zehnder...................27

Hnh 2. 9: OADM da trn cu hnh giao thoa Mach-Zehnder............................................28

2. 2. 3. 3 Cu hnh OADM s dng FBG v Circulator...........................................28Hnh 2. 10: OADM da trn FBG v Circulator..................................................................29

2. 2. 3. 4 OADM da trn cch t t gia Coupler.................................................29Hnh 2. 11: Cu hnh OADM dng cch t nm gia Coupler.............................................30

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2. 2. 3. 5 Cc tham s ca cc cu hnh OADM.......................................................30Hnh 2. 12: M hnh cch ly knh OADM.........................................................................30

Hnh 2. 13: Suy hao xen trong OADM..................................................................................31

Hnh 2. 14: M hnh v tham s ca phn x ngc trong OADM......................................32

2. 3 ng dng ca FBG trong cn bng khuych i ca thit b K quang si EDFA.. .322. 3. 1 Tng quan v EDFA..........................................................................................32

2. 3. 1. 1 Cu to v nguyn l hot ng ca EDFA:..............................................32Hnh 2.15 Qa trnh khuch i tn hiu xy ra trong EDFA vi hai bc sng bm 980nm

v 1480 nm...........................................................................................................................33

Hnh 2.16: Cu trc tng qut ca mt b khuch i EDFA..............................................34

2. 3. 1. 2 Tng cn bng cho khuych i EDFA................................................34Hnh 2. 17: Cu hnh b lc t ngoi EDFA......................................................................35

Hnh 2. 18: Cu hnh b lc t gia EDFA........................................................................352. 3. 2 ng dng ca FBG trong b cn bng khuych i EDFA...............................35

Hnh 2. 19: EDFA khng s dng v c s dng FBG.........................................................35

2. 4 Mt s ng dng khc ca FBG.................................................................................382. 4. 1 ng dng trong cm bin..................................................................................38

Hnh 2. 20 M hnh h thng cm bin s dng FBG v nguyn l hot ng.....................39

2. 4. 2 ng dng trong cng ngh Laser ......................................................................39KT LUN.................................................................................................................40TI LIU THAM KHO.........................................................................................41

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Chuyn thng tin quang Thut ng vit tt

THUT NG VIT TT

Thut ng Ting Anh Ting VitA

ADM Add / Drop Multiplexing B tch ghp (xen,r) knhAFBG Apodization Fibre Bragg Grating Cch t iu bin chit sutASE Amplified Spontaneous Emission Pht x t pht c khuch iAWG Arrayed Waveguide Gratings Cch t ng dn sng

CCFBG Chirped Fibre Bragg Grating Bragg si quang chu k bin i

DDWDM Dense Wavelength Division

MultiplexGhp knh theo bc sng mt cao

DEMUX Demultiplexing B tch knhE

EDF Erbium Doped Fiber Si quang pha ErbiumEDFA Erbium Doped Fibre Amplifier B khuych i quang si pha tp Er

FI

I-TUT International TelecommunicationUnion - TelecommunicationStandardization Sector

Tiu chun ha vin thng quc t

FBG Fibre Bragg Grating Cch t Bragg si quangFWHM Full Width at Half Maximum rng ton phn ti na ln nht

MMUX Multiplexing B ghp knh

LLCFBG Linear Chirped Fiber Bragg Grating Cch t Bragg si quang chu k thay i

tuyn tnhO

OADM Optical Add / Drop Mutiplexing B tch ghp knh quangOCDMA Optical Code Divission Multiplex

Accessa truy nhp phn chia theo m trn siquang

OFA Optical Fibre Amplifier B khuych i quang siOTDM Optical Time Division Multiplex Ghp knh quang phn chia theo thi gian

RREG Regenerator Trm lpRZ Return to Zero Tr v khng

TTDM Time Division Multiplex Ghp knh phn chia theo thi gian

U

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Chuyn thng tin quang Thut ng vit tt

UFBG Uniform Chirped Fibre Bragg Grating Cch t Bragg si quang chu k u

UV Ultra Violet Tia cc tmW

WDM Wavelength Division Multiplex Ghp knh phn chia theo bc sngWGR Wavelength Gratings Router B nh tuyn cch t bc sng

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Chuyn thng tin quang Li ni u

LI NI U

Ngy nay, vi s pht trin mnh m ca khoa hc x hi, ngnh cng nghip vinthng cng , ang v lun ng vai tr v cng quan trng trong mi mt ca x hi.

Cng ngh thng tin quang ra i v pht trin v song hnh vi n l s pht trin caMng truyn dn quang vi vic p ng p ng c cc nhu cu ca ngi s dng dchv vin thng v bng thng ln, cht lng tn hiu m bo v nhanh chng tr thnhmng ng trc tc ln vi nhiu cng ngh mi ra i phc v cho mng nh WDMhay EDFA

Do , nhim v ca ngnh khoa hc Vin thng l phi nghin cu, a ra cc giiphp, cc thit b mi ra i nhm tng tc v cht lng truyn dn cho mng cng nhkhc phc cc nhc im c hu ca mng quang nh l tn sc, suy hao, khuych icng sut l rt cp thit.

M hnh cch t Bragg quang c a ra v chng minh cc tnh cht ca n ln u

tin vo nm 1978 bi Hilletal. V k t n nay, Bragg cch t FBG v ang tr nnrt ph bin vi t cch l mt thit b quang n gin, linh hot v c v s cc ng dngtrong cc thit b v h thng quang. Vi s pht trin ca mnh, FBG c lin quan trc tipv cht ch vi s pht trin ca si quang, n c kh nng s dng trong vic xy dng ccb lc dng tch ghp knh trong h thng truyn ti d liu a knh. Ni bt nht trongnhng ng dng ny l FBG c dng cho h thng DWDM. FBG l c s cho cc thit bla chn th ng cho cc bc sng n, ghp bc sng v chn bc sng bng hp. Nlm vic tt trong iu kin cc yu t v nhit v sc cng c m bo bi v cc iukin ny c th nh hng n tin cy ca FBG.

Nh cc tnh cht m FBG c th mang li nn Nhm 10 chn ti Cch t

Bragg si quang v ng dng lm ni dung nghin cu trong chuyn ca mnh.Ni dung Chuyn gm 2 chng:Chng 1:c im cu trc v tnh cht ca FBGChng ny cung cp ci nhn

tng th v cu to nguyn l v cc c tnh ca cc loi FBG in hnh.Chng 2: Cc ng dng ca cch t Bragg si quang trnh by v cc ng dng

ph bin v tch cc nht ca FBG trong h thng thng tin quang tin tin. Cng trongchng ny nhm cng cp ti mt s ng dng khc ca FBG s dng cho lnh vckhc.

Mc d rt c gng nhng do kin thc ca nhm cn hn ch, vn ting anhchuyn ngnh li hn hp v thi gian tm hiu kh t, ni dung chuyn li tng i rngv mi m nn kh trnh khi nhiu thiu st. Rt mong nhn c mi kin ng gp cabn b v thy c gip cho chuyn c hon thin hn.

Cui cng, Nhm xin chn thnh gi li cm n ti thy Hong Vn V tn tnhgip , ch bo hon thnh chuyn ny.

H Ni, ngy thng 03 nm 2013

Nhm thc hin

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Chuyn thng tin quang Li ni u

Nhm 10

2


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Chuyn thng tin quang Chng I: c im cu trc tnh cht ca FGB

CHNG I: C IM CU TRC V TNH CHT CA FBG1. 1 Cu to chung

Cch t Bragg trong si quang l linh kin quang in t c lm bng si nhyquang, trong phn li si quang c chit sut thay i theo mt chu k nht nh dc theo

chiu di ca si quang, s thay i chit sut ny tha mn iu kin Bragg:

Hnh 1. 1 Cu to v chit sut ca FBGCch t Bragg quang thc cht l s xo trn cu trc ch s chit sut theo dng chu k

dc theo hng truyn sng ca si quang v c m t trong hnh 1.1

Ch s chit sut ca FBG c tnh theo phng trnh sau :

Trong l ch s chit sut trung bnh ca li si quang v l ch s

iu ch v l chu k ca FBG

1.2 Nguyn l.Mt lng nh nh sng c phn x ti mi im ni ch s chit sut ca FBG thay

i. S phn x hon ton trong FBG xy ra ti cc bc sng ring khi xut hin modeghp mnh nht. y gi l iu kin Bragg c m t trong phng trnh (1.2), bc sng

m ti c s phn x hon ton c gi l bc sng Bragg B. Ch c nhng bc sngtho mn iu kin Bragg l chu nh hng ca cch t v phn x mt cch mnh m. FBGtrong sut i vi cc bc sng nm ngoi vng bc sng Bragg.

Bc sng Bragg c tnh nh sau:

3

truynti

B

phn x

Khong cchf

Chiu di Bragg

Chitsu

t


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Trong neff l ch s khc x nh hng v l chu k ca FBG. y chnh l iukin xy ra phn x Bragg. T phng trnh (1. 2) chng ta c th thy rng bc sngBragg hon ton ph thuc vo ch s phn x v chu k ca cch t.

Cc cch t di vi ch s khc x thay i khng ng k c nh phn x rt nhn v

bng tn phn x rt nh nh m t trong hnh (1.2):

Hnh 1. 2: M t c tnh ca FBGi vi cch t Bragg u, cc tham s ch s khc x nh hng neff v chu k cch t

l c nh. Dng ph phn x ca loi cch t ny c m t trong hnh (1. 3):

4

Phnng

lng

Phnng

lng

Phn

ng

lng

Hng phn x

Hng ra

Hng ti

B

phnx

(p.u)

Bc

sng(m)


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Hnh 1. 3: Ph phn x ca cch t Bragg dng cch t u, =0. 53559nm gi trL=0,53559cm, neff=1,447, n=0,0009,

1. 3 iu kin kt hp phaFBG cho php truyn nng lng gia cc mode trong mt si quang. iu ny c th

t c bng vic thay i pha ca mt mode sao cho n kt hp c vi pha ca mtmode khc. Cc FBG thng c lm trn si quang trn sau khi bc i lp v acrylat cngha l si quang c xem nh c cu trc 3 lp vi cc chit sut khc nhau, trong lptrong cng l lp li c chit sut l n1, tip n l lp v c chit sut l n2 v ngoi cng lkhng kh vi n3 = 1. Vi si quang n mode vi cc tham s nh trn thi mode trung tmc hng s truyn t CO cho bi:

V cc mode ngoi c ch ra bi cu trc v - khng kh c hng s truyn nh sau:

Kt qu, cc mode pht x c th hng s truyn trong gii hn:

tm hiu s bin i ch s chit sut theo chu k dc theo chiu di si quang, vickt hp u tin c thc hin gia mode c bn v mode chm (mode v) xut hin khi:

Trong trng hp ghp cn mode gia hai mode ny, 2 1 = v phng trnh c

vit li:

Trong cc biu thc (1. 6) v 1. 7) l chu k ca s thay i ch s iu ch v 1

v 2 tng ng l hng s truyn ca mode c bn v mode c ghp i cng vi n.

Cch t thc hin ghp mode chm c xem nh l m b phn x hay l cch t Bragg.c trng ca cc thit b ny da trn c s ghp mode gia mode c bn ti v i.

i vi cc cch t chu k ln (c 1 v 2 u ln). iu kin kt hp cho ghp

hng ti cha mode c bn v mode truyn ca v cho bi phng trnh 1.6

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1. 4 Cc phng trnh ghp modeNguyn l ghp cp mode c s dng thnh cng m t cc thuc tnh ph ca

cc cch t Bragg. S bin i ch s phn x theo chu k dc theo chiu di ca siquang c m t nh sau:

Cc hm v l cc hm bin i chm hn so vi chu k cch t ; n0 l

chit sut ca li, l hiu s chit sut li - v. Tham s l pha ca ch s iu

ch; n c s dng miu t s dch chuyn pha hay l chirp cch t. Dc theo cch t

sng ti 1 v sng phn x 2 lin quan vi nhau bi phng trnh mode:

Ni bin ca vng 1 v 2 quan h vi bin ca trng in t, ta c:

a(z) l ch s ghp mode, cho bi:

V l ch s mt iu hng ca bc sng phn x t FBG:

c nh ngha:

Trong trng hp cch t Bragg c nhiu gi tr n dc theo chiu di cch t, ccphn tch ph c th t c bng cch gii quyt cc phng trnh ghp mode khc nhau.Trng hp cc cch t ng dng cng c gii quyt tng t. H s phn x

v ti im bt u ca cch t l (t-v):

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Mt vi ng dng quan trng t kt qu ny: l c th chng minh h s phn x

Rmax xut hin khi quan st iu kin phn x ti = 0:

Tip theo bng tn zero c xem l im zero th 2 trong tnh ton phn x:

Vi cch t c , cng thc c n gin ho nh sau:

Phng trnh (1. 16) cung cp thng tin v vic gy ra hiu ng ch s thay i ngin bng cch tnh ton ph bng tn ca cch t. Tng t cho cch t cng loi, vic thayi ch s cng sut cng c th dng phng trnh (1. 14) tnh ton, vi Rmax ti =Bragg

hiu mt cch y v cc thuc tnh ca cch t Bragg quang, khi nim trnhm hay tr thi gian phi c tnh ton. Vi cch t loi ny thi gian tr c th c

quyt nh bi pha ca h s phn x cho trn. Nu v thi gian tr

cho nh sng phn x ngc tr li t cch t cho bi:

V di hiu qu Leff m nh sng ti cc bc sng ring s i qua trong cch t

trc khi quay ngc tr li c tnh bng . Trong cc cch t loi ny thi

gian tr nh nht xut hin ti =Bragg. i vi cc bc sng gn cnh cc bng tn cacch t c tn sc ln nht vi thi gian t bin ng ln ti cc bc sng. V vy,

chnh lch thi gian t rng ln l c tnh ca dng ny, n ph thuc vo bc sng trckhi ra khi cch t.

1. 5 L thuyt m hnh ho FBGTrong hu ht cc cch t si quang, cc ch s thay i trn nhng khong tng i

u nhau theo b ngang ca li si, v hu nh khng c mt mode nh sng no truyn bn ngoi li. Chng ta gi nh rng s khng c mode v v b qua dng mode ny, nhvy th c tnh trng in t ca cch t c th c n gin ho v ch cn s chng

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mode gia mode hng i v hng v ca cc mode trong li. Trng in dc theo li casi c th c biu din theo phng trnh sau:

Trong A+(z) vA-(z) l cc bin bin i chm ca sng nh sng hng i v v

dc theo li si.E(x, y, z) c th c thay th bng phng trnh ghp mode. Phng trnhghp mode c th n gin ho bng vic gim s mode xung cn hai mode v c m tnh sau:

Trong R(z) = A+(z)e [i( /2)]v S(z) = A-(z)e [-i( + /2)],R(z) l mode hng ti v S(z)

l mode ca hng phn x ngc tr li, c hai l cc hm th hin cc mode bao thay ichm. l mt h s t ghp mode chung DC hay cn gi l s mt iu hng ni. k(z)l h s ghp mode AC hay cn c gi l mnh ghp mode bn trong ca cch t.Cc phng trnh ghp mode (1.20) c s dng trong vic tnh ton ph p ng phn xca FBG. H s ghp mode k(z) v ch s iu hng ni (z) l hai tham s rt quan trngca phng trnh ghp mode. Chng l cc tham s c bn trong vic tnh ton ph p ngphn x ca FBG.

H s t ghp mode c tnh nh sau:

Trong l m t ca kh nng chirp c th ca chu k cch t v l pha ca FBG. H

s mt iu hng c tnh nh sau:

Trong D = 2neff l bc sng thit k cho s phn x Bragg khi khong cch ccht rt nh neff 0.

Trong l s thay i ch s khc x c bn. H s ghp k(z) c th c tnh theo

phng trnh sau:

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Trong g(z) l hm ca iu bin chit sut v v l vn c th quan st c. H s ghpk(z) tng ng vi su iu ch ch s khc x:

Khng c tn hiu vo nu nh sng ti (pha phi ca FBG) c S(L/2) = 0 v s c tnhiu ti nu phn bn phi ca FBG tho mn R(-L/2) = 1. Da vo hai iu kin bin ny,iu kin ban u ca FBG c th c vit theo cc phng trnh (1. 20). H s phn x vtruyn nh sng ca FBG do c th nhn c t cc iu kin u v phng trnh ghpmode:

Pha tri :

Pha phi:

ln ca h s phn x c tnh nh sau:

H s phn x nng lng r (h s phn x) c tnh theo cng thc:

Hnh 1. 4 : iu kin u v s tnh ton p ng ca cch t i vi nh sng ti

1. 6 Cu trc v tnh cht ca cc dng cch t

1. 6. 1 Cch t Bragg u (Uniform FBG)

1. 6. 1. 1 Cu trc

9

nh sng ti

S(+L/2)

nh sng phn x Chiu di cch t L

nh sng pht

Pha tri: R(-L/2) =1

Pha phi: S(+L/2) = 0+L/2-L/2 0

R(+L/2)R(-L/2)

S(-L/2)


20/51


Cch t Bragg quang chu k u UFBG l dng cch t n gin nht trong h ccFBGs. N c ch to bng li si quang v dng phng php t nh hng gy ra bigiao thoa UV t cm ng. Trong cch t dng ny chu k cch t khng i v chit sutca cch t dc theo phng truyn sng bin i mt cch tun hon.

Hnh 1. 5: Cch t Bragg chu k u UFBG

1.6. 1. 2 M t ton hcCc h s kt hp pha v h s ghp mode ca UFBG l hng s. Cc phng trnh (1.

20) s dng trong trng hp tng qut c thay th bng cc h s l hng s. Chng tac mt s phng php s dng phn tch tnh ton trong cc phng trnh (1. 20). Ccphng php dng phn tch ca phng trnh ghp mode c th tm c da trn ccphng trnh iu kin bin (1. 25) v (1. 26).

Nu x dch d / dz l 0, h s mt iu hng ni tng ng vi h s mt iuhng . Phng trnh gii quyt s lin h gia s phn x v s cho php truyn nh sngc biu din bi:

Trong B c m t nh sau:

Ph phn x v ph truyn dn c m t theo cng thc sau:

N tho mn nh lut bo ton nng lng vi r() + t() =1. Pha ca nh sng phnx i vi nh sng ti c th tnh ton da trn cc phng trnh (1. 29) v (1. 30) nh sau:

10

truynti

B

phn x

Chit sut thay i

V

LiFBG

Ngun sng


21/51


Ti bc sng Bragg, = 0, cch t c nh phn x ln nht rmaxv c xc nhbng phng trnh:

Hin nhin t phng trnh ny h s phn x ca FBG l gn ti 1 khi iu ch ch schit sut v di cch t c tng chnh xc.

Bng thng c tnh bi r(D +/2) = r(D)/2 v phng trnh (1. 33). Cng cmt s phng php khc c dng tnh ton i lng ny.

- Ma trn truyn t ca UFBG:

Ma trn truyn t ca FBG c dng u tin bi Yamada s dng phn tch qutrnh truyn tn hiu quang. Phng php ny cng c s dng phn tch cc vn lin quan n FBGs.

C th gii quyt phng trnh ghp mode (1. 20) bng ma trn truyn t cho c haidng UFBG v non UFBG. Hnh 1. 6 l cu trc l thuyt c bn v s dng ma trntruyn t gii quyt cc vn cho UFBG.

Hnh 1. 6: S nguyn l ca ma trn truyn t dnh cho UFBG v non - UFBG

Trong trng hp ny, ma trn truyn t 2 2 hon ton ging nhau i vi mi chu k cacch t. Ma trn truyn t tng t c bng cch nhn cc ma trn con ca mi chu k.

- Ma trn truyn t ca non UFBG:

Phng php ma trn truyn t cng c dng phn tch cc tnh cht ca cccch t non UFBG. Mt cch t non UFBG c th c chia thnh nhiu phn nh dctheo si quang v mi phn c coi nh mt cch t UFBG. nh sng ti truyn quaphn cch t UFBG th i c m t bi ma trn truyn t Fi.

11

R(+L/2)

S(+L/2)L

R(+L/2)

S(+L/2)L

1

R(-L/2)

S(-L/2)

1 2 M

R(-L/2)

S(-L/2)

2

F1

F2

FM


22/51


Theo cu trc ca FBG, Fi c dng:

Trong kc m t bi phng trnh (1.24) v c m t bi cc phng trnh (1.21)v B bi phng trnh (1.22) v (1. 23).

Ma trn truyn t tng c tnh nh sau:

1. 6. 1. 3 Thi gian tr v tn sc

Thi gian tr nhm v tn sc ca cch t c th tnh ton da trn cc thng s v phaca nh sng ti v nh sng phn x, nh sng truyn qua.

Thi gian tr p i vi nh sng phn x t cch t c tnh nh cng thc 1.18 theo :

Tn sc dp (ps/nm) c tnh theo phng php sau:

Kt qu tng cng ca thi gian tr v tn sc ca cch t c th so snh vi cc thams ca h thng ti u ho. N cho php chng ta tnh ton cc tham s c thit b chocc ng dng ph hp.

1.6.2. Cch t Bragg quang chu k thay i CFBG

1. 6. 2. 1 Cu trc

12

truynti

B

phn x

V

Li

Ngun bng rng

1

2

1>

2


23/51


Hnh 1. 7: M hnh cch t Bragg chu k thay i CFBG

Theo iu kin kt hp pha, chu k ca cch t nh hng ti ph phn x ca FBG.Bng cch thay i tham s ny theo mt trnh t nht nh chng ta c cch t BraggCFBG, dng cch t ny c m t trong hnh 1. 7. LCFBG c ch to bng li si

quang v hin ti cc chirp t ti khong 0. 4 nm ti bc sng 1549 nm.ng dng ni bt ca CFBG lin quan ti vic b tn sc v c th hin trong hnh

1. 7, chng ta thy rng c nhiu bc sng c cch t phn x tr li dc theo chiu dica cch t. Cc bc sng di c phn x khi n i vo cch t vi khong cch ngn,cn ngc li cc bc sng ngn b phn x ti cc cch t xa hn. iu ny c ngha lcc bc sng ngn s i trong cch t vi qung ng di hn v do vy thi gian tr can cng ln hn so vi cc bc sng di. y l c s ca b tn sc. Chng ta s xem xtvn ny c th hn trong cc chng sau.

1. 6. 2. 2 M t ton hc ca CFBGCFBG c th m hnh ho da trn phng trnh ghp mode. Ch s chit sut ca

CFBG c th biu din nh sau:

Trong l chu k ca cch t v ()biu din pha tc thi ca cch t CFBG. Cnhiu phng php dng gii phng trnh ny, trong c hai phng php chnh l sdng ma trn truyn t v phng php tch phn trc tip.

Phng php tch phn trc tip:

Chu k ca CFBG thay i dc theo chiu ca trc z, bi vy bc sng phn x B cacc im khc nhau dc theo cch t l khc nhau. S thay i chit sut ca cch t cngc nh hng ging nh s thay i ca chu k cch t. iu ny c ngha l chu k quangvn c thay i mc d chu k cch t l c nh.

Biu thc pha trong phng trnh (1. 21) i vi cch t chu k tuyn tnh nh sau:

Trong dD/dz l tc thay i pha ca cc bc sng ti cc v tr trong cch t.Thay phng trnh ny v phng trnh (1. 21) vo phng trnh ghp mode ta thu cphng trnh c tnh ca CFBG.

i vi cch t quang Bragg chu k bin i tuyn tnh, nh vy th dD/dz l hng s.i vi mt s ng dng, CFBG c th c m t theo tham s chirp F cho bi:

13


24/51


Trong F l s thay i ca chu k cch t v FWHM l full width at half maximum ca GP (grating profile).

T phng trnh (1. 42) v (1. 42) phng trnh pha (1. 21) i vi cch t LCFBG cdng nh sau:

Phng php ma trn truyn t:

Trong phn trc chng ta phn tch dng ma trn truyn t ca cch t non uniform FBG, ma trn c dng :

Thay phng trnh (1.42) hoc (1.44) vo ma trn ny ta c ma trn truyn t ca CFBG.

14


25/51


Hnh 1.8: a) Ph phn x ca 2 cch t c gi tr Chirp dD/dz =-1(nm/cm)(ng mu nt lin) v dD/dz =1(nm/cm)(ng mu xanh lc nt t) vi cc gi tr L= 0,1cm,

neff=1,447, n=0,0004, D=1550(nm) b)thi gian tr theo bc sng ca CFBG

15

phn

x(p.u)

Bc

sng

(m)

phnx(p.u)

Bc

sng

(m)


26/51


Hnh 1.9: a) Ph phn x ca 2 cch t c gi tr Chirp dD/dz =-1(nm/cm)(ng mu nt lin),dD/dz =-2(nm/cm)(ng mu xanh lc nt t) v dD/dz =-4(nm/cm)(ng muxanh lam nt chm) vi cc gi tr L= 0,1cm, neff=1,447, n=0,0004, D=1550(nm)

b)thi gian tr theo bcsng ca CFBG

1. 6. 3 Cch t iu bin chit sut

1. 6. 3. 1 Nguyn lTrong AFBG, cc ch s thay i ca h s chit sut l hng s. Ph phn x ca mt

cch t Bragg di hn ch c ch to theo phng php AFBG c cc nh sn bnti cc bc sng k nhau. N rt quan trng cho vic gim thiu v cng c th loi trvic phn x ca cc nh sn bn ny.

Hnh 1.3 cho chng ta thy ph ca UFBG, cc cch t ny c cc nh sn bn ln.Tnh nng ca UFBG phi c ci tin c th s dng cho cc ng dng trong cc hthng vin thng. Mt phng php thc hin iu ny l s dng iu bin chit sut.iu bin chit sut c th thc hin bng vic chiu x tia UV theo ng vin gim chs chit sut chch khi ch s chit sut trung tm theo c hai hng ca cch t.

AFBG c th m hnh ho da trn phng trnh ghp mode. Chng ta s xem xt haiphng php chnh l tch phn trc tip v phng php ma trn truyn t.

1. 6. 3. 2 M t ton hc ca AFBGPhng php tch phn trc tip:

Hiu qu ca iu bin chit sut trong cc m hnh FBG c th biu din da trn hmph thuc to hng z ca ch s chit sut l g(z). Ch s chit sut ca AFBG c thhin trong phng trnh sau:

16

phnx

(p.u)

B

c

sn

g(m)


27/51


Trong n l su ca iu ch v g(z) l hm iu ch (cn c gi l hm iubin chit sut). Ni chung dng ca g(z) thng c dng hm Gausse. i vi UFBG gi tr

ca g(z) l 1. H s ghp ca AFBG c cho bi phng trnh (1.24):Nu nh chng ta thay phng trnh ny vo trong phng trnh ghp mode (1. 19) v

(1. 20), gii phng trnh thu c ta c th tnh ton c ph ca dng cch t AFBG ny.

Phng php ma trn truyn t:

Nu chng ta thay th phng trnh (3. 24) vo ma trn truyn t (3. 39), p ng phca cch t AFBG c tnh ton bng cch gii quyt cc phng trnh ny.

Cc hm iu bin chit sut:

i vi UFBG:1. c tnh Gaussian:

Trong FWHM = 0, 4L. Phng trnh ny cn c dng khc nh sau:

2. c tnh Raised cosine:

Trong FWHM = L.

3. c tnh sinc:

4. c tnh Kaiser :

Trong k l tham s ca s Kaiser vI0 l hm Bessel th 0.

17


28/51


Hnh 1.10: th biu din s thay i ch s khc x iu bin chit sut si quang AFBG.ng nt lin mu l phng trnh 1.48. ng nt t mu xanh lc l

phng trnh 1.50. ng nt chm mu xanh lc l phng trnh 1.51 v ngnt gch chm mu hng l phng trnh 1.52, K=5vi cc gi tr L= 0,1cm,

neff=1,447,n=0,0002

18

C

hskhcx

(

p.u)

V

tr

(mm)

phn

x

(

p.u)

Bcsng(m)


29/51


Hnh 1.10: S phn b ph phn x ca 4 AFBG vi c tnh Gauss phng trnh 1.48 (ntlin mu ). c tnh Raised cosine phng trnh 1.50 (nt t mu xanh lc).

c tnh Sinc phng trnh 1.51 ( nt chm mu xanh lc). c tnh Kaiserphng trnh 1.52 (nt gch chm mu hng), K=5 vi cc gi tr L= 0,1cm,

neff=1,447, , D=1550(nm) n=0,0002

Nh vy chng ta c th thy trn c tnh ph ca AFBG cc nh sn bn cgim thiu so vi cc dng cch t UFBG. Chnh iu ny l u im ni tri ca AFBGtrong vic thc hin chng nhiu do nh sn bn gy ra trong cc ng dng.

19


30/51

Chuyn thng tin quang Chng II: Cc ng dng ca cch t Bragg si quang

CHNG 2: CC NG DNG CA FBG

2. 1 ng dng ca cch t Bragg quang trong b tn sc

2. 1. 1 Gii thiu

Tn sc trong quang si n mode l mt trong nhng hin tng vt l nh hngnghim trng n cht lng ca mng thng tin quang tc cao dng bc sng nh sngvng ca s 1550nm. N lm tng t l li bit, gii hn tc hoc khong cch truyn camng. xy dng hoc nng cp nhng mng thng tin quang (OTDM, DWDM,OCDMA) kch thc ln (vi nghn km), tc cao (vi chc Gbit/s) th mt vn quan trng phi gii quyt l gim ti thiu tn sc trong si cp quang.

Mt s gii php khc phc hin tng tn sc ang c p dng hin nay trn thgii l s dng cc cp quang thng tin c tn sc ti thiu (DSF) hoc cp quang c khnng b tn sc (DCF). Tuy nhin cc phng php ny c mt nhc im l chi ph ln

do gi thnh cp quang c bit ny t hn nhiu so vi cp quang thng tin thng thng.Ngoi ra phi tnh n chi ph thay th ton b cc cp quang thng thng lp ttrc hoc lp t thm nhng on cp quang b tn sc kh di (c vi km cp quangb tn sc b cho vi chc km cp quang thng). Hin nay c mt hng nghin cumi s dng cc quang si c li l cc cch t Bragg b tn sc. u im caphng php ny l thit b c kch thc nh gn, ch to n gin, v hot ng rt chiu qu. Phng php b tn sc trong quang si n mode dng quang si cch tBragg chu k thay i tuyn tnh (linear chirped Fiber Bragg Grating).

2. 1. 2 Hin tng tn sc trong si cp quangHin tng mt xung nh sng b gin rng ra v mt thi gian sau mt qung ngtruyn nht nh trong si cp quang c gi l hin tng tn sc trong si cp quang. Cba ngun gy nn hin tng tn sc l:

- Tn sc vt liu

- Tn sc dn sng

- Tr nhm

i vi cc bc sng trong phm vi 1550nm th tn sc vt liu l nguyn nhn chnh

gy nn hin tng tn sc. Tn sc vt liu sinh ra l do trong mt si cp quang, vn tcnh sng cng nh chit xut ca quang si l mt hm s ca bc sng nh sng tn hiu.Hnh v 2.1 biu din s thay i ca vn tc nhm ca mt xung nh sng i vi cc bcsng khc nhau trong mt si cp quang thng tin n mode thng thng.

20


31/51


Hnh 2.1 S thay i ca vn tc nhm theo bc sng trong quang si n mode thngthng

Trn hnh v 2.1, chng ta nhn thy ti cc bc sng vng ca s 1550nm, vn tcnhm t l nghch vi bc sng ca nh sng. Nh chng ta bit, trn thc t khng thc mt ngun sng n sc tuyt i, mi ngun sng u c mt rng ph nht nh.Gi s mt xung nh sng c bc sng trung tm ti 1550nm, rng ph 0 truyn qua

mt si cp quang n mode. Cc thnh phn bc sng di hn ca xung s chuyn chmhn cc thnh phn bc sng ngn hn. Nh vy, sau mt qung ng truyn di, rng xung s b ko gin ra ti mc hai xung k tip nhau s b chn ln nhau (hnh 2.2).

21

1,2 1,3 1,4 1,5 1,62,0485

2,0487

2,0489

2,0491

2,0493

2,0495

Bc sng (m)

Vs(

x108m/s)

Binxung

Binxung

Thi gian Thi giana) b)


32/51


Hnh 2.2 Hu qu ca tn sc i vi tc truyn ca mng a) xung ti u pht .b) xungthu c ti u thu v thit b thu khng th phn bit c hai xung k tip

Hu qu l thit b u thu s khng th phn bit c 2 xung ring bit. thit bthu c tn hiu xung, ngi ta phi gim tc truyn hoc rt ngn khong cch giabn pht v bn thu.

2. 1. 3 B tn sc bng quang si cch t Bragg chu k bin i tuyn tnhQuang si cch t Bragg chu k bin i tuyn tnh l mt si quang n mode c mt

on li c ghi nhng cch t c chu k thay i mt cch tuyn tnh dc theo chiu dica quang si.

0 l chu k im bt u ca on cch t, 1 l s thay i tuyn tnh dc theo

chiu di ca on cch t.

Ti v tr z trn on cch t Bragg, mt sng nh sng s b phn x ngc li nubc sng ca n tho mn cng thc:

B(z) l bc sng Bragg ti v tr z tng ng vi chu k cch t (z).

c tnh ca quang si cch t Bragg chu k bin i l ti nhng v tr tng ng vi

chu k di hn s phn x nhng nh sng c bc sng di hn.Gi s xung tn hiu i vo u c chu k di hn ca on cch t nh hnh v 2.3.

Khi , nhng bc sng di hn s b phn x gn phn u ca on cch t hn. Nicch khc, nhng bc sng ngn hn s phi i mt qung ng xa hn trong on ccht trc khi chng c phn x ngc li. Kt qu l mt khong thi gian tr d s cto ra gia thnh phn bc sng ngn so vi thnh phn bc sng di.

Trong c l hiu s gia bc sng b phn x u on cch t (thnh phn bcsng di nht) so vi bc sng b phn x cui on cch t (thnh phn ngn nht).

22


33/51


Hnh 2.3 Nguyn l b tn sc ca quang si cch t Bagg chu k bin iy l hin tng ngc vi hin tng tn sc v l nguyn l ca thit b b tn sc

trong mng thng tin quang dng cch t Bragg chu k thay i tuyn tnh.

Hnh v 2.4 l mt m hnh c bn ca thit b b tn sc dng cch t Bragg chu kthay i tuyn tnh.

Hnh 2. 4. M hnh c bn ca thit b b tn sc dng cch t Bagg chu k thay i tuyntnh

Trn hnh v circulator l thit b ghp ni quang ch cho nh sng i ln lt cc cng1, 2, 3 theo chiu kim ng h. Mt xung b gin rng sau khi c khuch i s i qua

mt circulator ti on cch t Bragg c chu k bin i nh hnh v. Ti on cch t,thnh phn bc sng ngn ti trc do tn sc s phi i thm qung ng na trc khic phn x ngc li ti thit b u thu. Trong khi , thnh phn bc sng di hn,n chm hn do b tn sc, s c phn x ngay khi ti cch t Bragg. Kt qu l xung tnhiu sau khi i qua thit b b c co li. Tnh ton hp l cc s liu v di oncch t Bragg, hm thay i ca chu k cc cch t L(z), ngi ta c th thu c xung nhsng c rng nh u pht.

23

truynti

B

phn x

V

Li

Chiu gim ca chu k cch t

Ngun bng rng

1

2

1>

2

Bc sng di

Bc sng ngn

TxTx RxRx

u vo

Circulator

EDFA

FBG

Xung m rng Xung sau khi b


34/51


Ngi ta chng minh rng mt on cch t Bragg di 5, 7cm c th b cho 100kmquang si truyn thng c tn sc 17ps/nm km dng bc sng 1550nm, rng ph0,2nm.

1. 2 ng dng ca FBG trong b tch ghp knh (xen-r) OADM

1. 2. 1 Tng quan v WDMGhp knh theo bc sng l cng ngh c bn to nn mng quang. K thut ny

s dng si quang mang nhiu knh quang c lp ring r. Mi mt bc sng biu thcho mt knh quang trong si.

Ghp knh theo bc sng WDM (Wavelength Division Multiplexing) l cng nghNhiu bc sng tn hiu khc nhau c t hp li (ghp knh) v truyn i ng thi trnmt si quang. u thu tn hiu c t hp c phn gii ra (tch knh), khi phcli tn hiu gc vo cc u cui khc nhau

Qua qu trnh pht trin cng ngh khi nim WDM c thay bng khi nimDWDM. V nguyn l khng c s khc bit no ln gia hai cng ngh trn, DWDM nin khong cch gn gia cc knh v ch ra mt cch nh tnh s lng knh ring r (mt knh) trong h thng. Nhng knh quang trong h thng DWDM thng nm trong cas mt bc sng ch yu l 1550 nm.

H thng WDM hon ton tng t nh h thng TDM truyn thng. Cu to ca nbao gm cc b pht v thu hai pha cng vi cc b lp v xen r gia. Tuy nhin nkhc ch WDM truyn dn ng thi cc knh quang qua si. Chng ta c th xem WDMnh l mt h thng nhiu TDM dng chung ng truyn l si quang. Ngi ta chia h

thng WDM thnh hai dng da trn s lng si nm gia pht v thu :

H thng ghp bc sng mt hng:

H thng ghp bc sng n hng s dng mi si quang cho tng hng truyn dn:

Hnh 2.5: S h thng WDM n hng thng tin 2 chiu H thng ghp bc sng hai hng:

24

MUX/DE

MUX

MUX/DE

MUX

MUX/DE

MUX

MUX/DE

MUX

1,

2,

3,,

n

1,

2,

3,,

n

1

N

1

N

Tx/Rx1

Tx/RxN

Tx/Rx1

Tx/RxN

REG

REG

REG

REG

OADM

OADM


35/51


Hnh 2.6: S h thng WDM n hng thng tin 2 chiuNguyn l hot ng chung ca h thng WDM ny nh sau :

Mi tn hiu cn truyn i u pht c iu ch vi mi bc sng khc nhau (cth l iu pha, iu tn hay iu bin), sau tt c cc tn hiu sau iu ch ny c avo mt b ghp knh MUX, tn hiu ra khi b ghp knh l tn hiu quang t hp ca

nhiu bc sng dng iu ch 1, 2 N. Tn hiu ny c khuych i sau avo si quang truyn ti b thu. i vi mng truyn dn quang khong cch ln ngita cn dng thm cc trm lp v cc b tch ghp knh quang t trn ng truyn nhmti to tn hiu, tch ghp lung nng cao cht lng truyn dn.

Cu hnh mng thc t ca mng WDM quang bao gm cc cu hnh im - im, cuhnh Ring v cu hnh Meshed.

2.2.2. K thut tch ghp knh quangH thng ghp knh phn chia theo bc sng WDM l mt trong nhng gii php

quan trng nht ca cc h thng truyn dn quang tc cao. S pht trin ca cc tuyntruyn dn quang im- im vi bc sng n ln thnh h thng truyn dn quang ghpknh theo bc sng a ra nhu cu v cc b tch ghp knh theo bc sng OADMdng tch ghp v nh tuyn cc knh bc sng khc nhau. Cc thit b ny c th cs dng ti nhiu im khc nhau trn mng dc theo cc tuyn truyn dn quang v c chcnng ghp/tch cc knh quang vi cc bc sng c la chn, vi chc nng ny mm do linh hot ca h thng c ci thin r rt. N tr thnh mt phn rt quantrng ca cc ng dng WDM, chng hn nh cc khu vc khc nhau c th cng kt nitrn mt tuyn quang bng vic tch/ghp knh t mt ng truyn quang. Thm vo ,

s mm do trong tc d liu ca cc knh WDM ring bit cho php cung cp tc tutheo nhu cu. M hnh ca b tch ghp knh c m t trong hnh sau :

25

MUX/DE

MUX

MUX/DE

MUX

MUX/DE

MUX

MUX/DE

MUX

1,

2,

3,,

i

i+1,

i+2,,

i+n

1

N

1

N

Tx/Rx1

Tx/RxN

Tx/Rx1

Tx/RxN

REG

REG

REG

REG

OADM

OADM

i+1

i+N

i+1

i+N


36/51


Hnh 2. 7: M hnh c bn ca OADMC hai dng OADM chnh c s dng trong cc mng quang WDM, l fixed

OADM c dng tch hoc ghp cc tn hiu d liu trn cc knh WDM ring bit cnh v OADM c th iu chnh v vy n c kh nng la chn nh tuyn c cc bcsng khc nhau trong mng quang. Chc nng chnh ca dng thit b OADM th hai ny lcung cp nh tuyn li mt cch mm do cho cc lung quang, nh tuyn vng cho cc

kt ni hng, do vy n lm cho gim ti thiu vic phi ngt dch v v cng nh kh nngthch ng hay nng cp mng quang vi cc k thut WDM khc nhau.

Cc cu hnh gii thiu trc y dng thc hin tch hay ghp knh quang sdng c hai cng ngh Planar v cng ngh si. Cc thit b Planar cung cp cc t hp giiphp vi kh nng tch v ghp nhiu knh s dng duy nht ch mt mch quang tch hps dng k thut dy cch t dn sng AWG (arrayed waveguide gratings) hoc k thut nhtuyn cch t dn sng WGR (waveguide grating router). Mt hn ch chnh ca thit bPlanar l suy hao xen cao, c th ln ti 7 dB v tnh ph thuc phn cc. Mt khc cc thit

b ton quang l cng l cc gii php rt hp dn bi v tnh suy hao xen thp, tnh nhyphn cc (ph thuc vo si v cu hnh) v d dng s dng cho vic ghp gia cc thit bu vo v u ra ca mng quang bng vic s dng cc ghp ni n gin.

Mt dng ring ca cc OADM ton quang l da trn cch t Bragg t gia cccoupler quang. Cu hnh ny c chng minh l ph hp cho vic thc hin tch ghpknh, bao gm cc cch t Bragg v cc dng coupler nh l coupler na chu k, coupler cchu k.

2. 2. 3 Cc cu hnh OADM

2. 2. 3. 1 OADM da trn FBG v coupler 3 dBCu hnh m bo tnh n nh v thc hin tt chc nng tch ghp knh c a ra

da trn thit b 4 cng PW (planar waveguide) c m t trong hnh 2.8 N bao gm ccthit b : b chia 3 dB v cch t mt trong cc cng ra output ca coupler lm nhim vchn bc sng.

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Hnh 2. 8 : M hnh OADM da trn FBG v coupler 3 dBNguyn l hot ng ca m hnh thit b ny nh sau: nh sng a vo cng 1 v

c chia lm 2, ti cng ra FBG s phn x cc nh sng c bc sng G v quay tr licng Dropped 4 v c ly ra ngoi. Cng ra cn li ca Coupler c ngm chm vo

trong cht lu c ch s chit sut ph hp lm cho nh sng khng phn x tr li. Tnhiu c chn s xut hin ti c cng 1 v 4 (cng In v Drop). Mt thit b Isolatort ti cng 1 ca Coupler bo v tn hiu vo ca h thng khng b nh hng bi cctn hiu phn x. Tn hiu tch yu hn 6 dB so vi tn hiu gc a vo. Trong truyn dn,mt Coupler 3 dB th hai s chia tn hiu khng c cch t phn x. Chc nng thm vony c thc hin bng cch a mt tn hiu vo cng 3, bc sng ca tn hiu la chnsao cho n b phn x bi cch t ( G) v v vy n c ghp vo tn hiu quang cng 2theo nguyn l hot ng ca Coupler. Mt thit b Isolator cng c s dng v t ticng 3 cch ly tn hiu a vo v tn hiu truyn dn t cng vo a ti. Khi s dnghai Isolator ti cng vo v cng ghp thm , cu hnh khng giao thoa cho php thc hinkh nng tch ghp rt tt. Trong cu hnh ny khng c gii hn hay iu kin no v di, v tr hay apodisation ca cch t. Cch t lc bc sng c th c thit k s dngphng php inverse scattering. Nhc im ca cu hnh ny l vic h tr mt dung lngcho tt c cc knh thp nht 6 dB. Tuy nhin khi so snh n vi cc thit b da trn c sPW (planar waveguide) c mt tn hiu tng t nhng li c s linh hot hn trong vicch to v iu chnh bc sng la chn ca cch t.

2. 2. 3. 2 OADM da trn FBG v cu hnh giao thoa March-Zehnder

Mt phng php khc phc vic mt tn hiu ca cu hnh trn yu cu thm mtcch t ging ht nh cch t u tin v tt c cc cng ca Coupler u s dng, v vycu hnh ny cn gi l cu hnh giao thoa Mach Zehnder. C hai dng thit b ch to theocng ngh planar hay cng ngh ton quang s dng cho cu hnh ny u c m t vthc nghim.

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Hnh 2. 9: OADM da trn cu hnh giao thoa Mach-ZehnderV mt l thuyt thit b ny l i xng v c th mang li nhng kt qu kh quan

trong chng mt tn hiu, s phn x ngc v chng xuyn m.

Nguyn l ca cu hnh ny c miu t trong hnh v trn: Mt Coupler 3 dB chianh sng a vo t cng 1 v nh sng c bc sng G c phn x bi hai cch t FBG

ging nhau. Cc tn hiu phn x ny c a tr li vo Coupler v c ly ra ti cngDrop. Tn hiu phn hi ngc tr li cng 1 c trit tiu hon ton nh s dng Couplerph hp (b chia 50%). Cc bc sng pht c lm nhiu trong Coupler 3 dB th hai vth chng n cng ra m khng c phn d no phn x tr li cng Add, tnh nng nycng do Coupler quyt nh. Cu hnh ny da trn c s chia v nhiu ca nh sng v vth kh nhy trong vic thay i di truyn tn hiu, c im ca cc cch t ging nhau,tnh cht ca b Coupler 3 dB. V vy n nh ca mi trng, ca cc Coupler gingnhau, ca cc FBG quyt nh vic thit b thc hin cc tnh nng ca n c m bo haykhng. S n nh v kh nng chu nh hng ca thit b ny trong h thng WDM thc t

c phn tch bi Erdogan: cu hnh ny nu s dng cc thit b theo cng ngh Planarc di truyn dn ngn hn v vy d n nh hn. Nhng mt khc cc thit b da trnsi li kp trnh c yu cu v lung UV s dng trong cu hnh giao thoa Mach Zehnder.

2. 2. 3. 3 Cu hnh OADM s dng FBG v CirculatorCu hnh ny tng t nh cc cu hnh 4 cng ni trn, nhng trong cc

Coupler c thay th bng cc Circulator quang. V l thuyt, cu hnh ny s dng ccthit b khng giao thoa l l tng. Cc tnh cht ph theo nguyn l ph thuc vo hot

ng v tnh cht ca FBG v c th c thit k nh mt b lc trc giao l tng sdng k thut scattering ngc, s mt tn hiu v xuyn m ch yu ph thuc vo hotng ca cc Circulator quang.

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Hnh 2. 10: OADM da trn FBG v CirculatorNguyn l hot ng ca OADM dng ny nh sau : nh sng c a vo cng In 1

v c nh hng ti FBG c bc sng phn x l G, nh sng c bc sng ny ccch t phn x tr li Circulator v c tch ra cng Drop 4, cc phn nh sng cn lis chuyn qua cch t v a ti Circulator 2. Circulator 2, mt tn hiu khc c bcsng G c a vo cng Add 3, tn hiu ny c cch t phn x tr li v i ra cngOut 2.

Nhc im chnh ca cu hnh OADM dng ny l Circulator tng i t vcng knh. Tuy nhin, cng vi s pht trin ca cc cng ngh Circulator gi r v mt mttn hiu khng ln, cu hnh ny l mt gii php rt tt cho thit b OADM bi v tnh nnh ca n.

2. 2. 3. 4 OADM da trn cch t t gia Coupler

Tnh n nh ca OADM da trn cu hnh ca giao thoa Mach-Zehnder gii thiutrong 2. 2. 3. 2 cng c th c ci thin nh s dng nhiu gia cc mode ca Couplerquang. Vic to ra mt cch t gia mt coupler na vng (100%) c chng minhtrong c hai dng cu hnh thit b Planar v thit b ton quang.

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Hnh 2. 11: Cu hnh OADM dng cch t nm gia CouplerThit b ny rt nh gn, tuy vy v nguyn l ch c s i xng hon ton khi ch to

cch t c dng nh mt b phn x im. iu ny ch c kh nng thc hin khi s dngcc cch t rt ngn hoc cc coupler rt di. Hnh trn cho thy cu hnh dng ny : nhsng c a vo cng 1 v c truyn ti trung tm ca coupler. Mt cch t c t

ti trung tm ca coupler ni s khc pha gia cc mode eigen l /4, ni nh sng cchia mt cch u nhau gia hai cc phn dn sng ca coupler. Knh c bc sng Gdc phn x tr li do cch t v phn tn hiu cn li truyn qua coupler n cng ra 2.Trong qu trnh phn x, cc eigenmode phn x trong coupler t n khc pha tngcng l /2 v v th knh c bc sng G c tch ra ti cng 4. V nguyn l, n nhca thit b giao thoa c ci thin vi cu hnh Mach-Zehnder bi v s phn x im vnhiu t c thng qua vic truyn cc eigenmode ca coupler. Tuy nhin cc gii hn cai vi di cch t v di cc coupler ch to i hi phi c cc tnh ton ph hp.

2. 2. 3. 5 Cc tham s ca cc cu hnh OADMHot ng ca cc OADM c m t bng cch s dng cc k hiu scattering S ij cho

mi cp cng. K hiu u tin i l k hiu cng ch (cng ra) v k hiu j l k hiu cngvo. Mt vi tham s ca c th m t bng cch s dng cc k hiu Scattering nh l : suyhao xen, s phn cc ph thuc mt tn hiu PDL (polarisation depent loss), cch ly knh,phn x ngc .

Cch ly v xuyn m:

Hai tham s chnh lin quan ti s cch ly cc knh trong b tch ghp knh OADM l

tham s cch ly ca cc knh v xuyn m gia cc knh trong h thng WDM.

Hnh 2. 12: M hnh cch ly knh OADMNu nng lng ca tn hiu quang cng vo 1 l P1 v nng lng ca tn hiu c

tch t cng 4 l P4 v nng lng cn li ca tn hiu sau tch l P2 th h s cch ly ctnh bng -10 log (P1/P2).

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Xuyn m l do cc tn hiu khng mong mun truyn t cc knh ln cn ti mt knh no trong b lc, n c tn l xuyn m lin knh. Dng xuyn m ny c th xut hin trongcc cu hnh OADM giao thoa v l kt qu ca vic t l phn chia nng lng nh sngtrong coupler 3 dB khng chnh xc. Tuy vy dng xuyn m ny khng nh hng nhiun hot ng ca h thng WDM.

Suy hao xen:

Suy hao xen lm nng lng ca cc tn hiu quang ca cc knh yu i, m hnh ca chngc m t trong hnh sau, trong c hai tn hiu ca knh tch v phn tn hiu cn lisau tch u b yu i :

H s suy hao xenLinstng ng vi hiu sut truyn nh sng t mt cng i ti mtcng j v nh hng ca n ln tt c cc knh l nh nhau v c tnh theo cng thc:

Trong Pi v Pj l nng lng ca tn hiu quang ti cc cng ra ca OADM v gi skhng xut hin xuyn m hay PDL.

Hnh 2. 13: Suy hao xen trong OADM Phn x ngc:

M hnh v cc tham s nh hng n qu trnh phn x ngc c m t trong hnh2.14. Nu OADM la chn bc sng da trn cch t Bragg vi bc sng phn x l Gv khi cc knh (cc tn hiu quang c bc sng khc nhau) c a vo cng 1 hoc 3cc tn hiu c bc sng G c la chn s c phn x v a n cng 4 hoc 2 theoth t . Tuy nhin cng c mt b phn ca nh sng b phn x ngc tr li cng banu, ta xem phn phn x ngc tr li ny c nng lng l P 1 v P3. Nh vy h s phn

x ngc Sii c tnh bng 10log(Pi / Pi). Cc nh hng ca vic phn x ngc ny cth trnh c bng vic s dng cc b cch ly Isolator ti c hai cng ny (cng In 1 vcng Add 3). Cng c mt phng php khc dng trnh hin tng ny l dng b cnbng OADM ph hp.

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Hnh 2. 14: M hnh v tham s ca phn x ngc trong OADM

2. 3 ng dng ca FBG trong cn bng khuych i ca thit b K quang si EDFA

2. 3. 1 Tng quan v EDFA

2. 3. 1. 1 Cu to v nguyn l hot ng ca EDFA:Thit b EDFA l mt dng ca thit b khuych i quang si OFA (Optical Fibre

Amplifier). Cu to ca n bao gm mt si quang c pha tp thm nguyn t t himErbium. Si quang sau khi c pha tp s thay i cu trc phn t v trong bn thn siquang xut hin cc mc nng lng m ti Electron c tp trung ti trong nhngiu kin ph hp. Cc mc nng lng c m t c th trong s sau :

EDFA bao gm mt on ngn si cp quang v phn li ca n c pha tp khong 0,1%Erbium. Nguyn l hot ng ca n nh sau:

Khi s dng ngun bm laser 980nm, cc ion Er+3 vng nn s hp th nng lngt cc photon (EPhoton= 1,27 eV) v chuyn nn trng thi nng lng cao hn vng bm(4I11/2). (1)

Ti vng bm (4I11/2), cc ion Er3+ phn r khng bc x rt nhanh (khong 1s) vchuyn xung vng gi bn (4I13/2). (2)

Khi s dng ngun bm laser 1480nm, cc ion Er3+ vng nn s hp th nng lngt cc photon (EPhonton= 0.841 eV) v chuyn sang trng thi nng lng cao hn nh vnggi bn (3).

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Hnh 2.15 Qa trnh khuch i tn hiu xy ra trong EDFA vi hai bc sng bm 980nmv 1480 nm

Cc ion Er3+ nm nh vng gi bn lun c khuynh hng chuyn vng c mcnng lng thp (y vng gi bn) (4).

Sau khong thi gian sng (khong 10ms), nu khng nhn c bt c kch thch nobi cc photon c nng lng thch hp (pht x kch thch) cc ion Er3+ s chuyn sang

trng thi nng lng thp vng nn v pht x ra photon (pht x t pht) (5).Khi cho tn hiu nh sang i vo b EDFA, s xy ra ng thi hai hin tng sau: b hpth bi cc Er3+

Cc phonton tn hiu b hp th bi cc Er3+ vng nn (6). Tn hiu nh sng b suyhao

Cc phonton tn hiu kch thch cc ion Er3+ vng gi bn (7). Hin tng pht xkch thch xy ra. Khi , cc ion Er3+ b kch thch s chuyn trng thi nng lng t mcnng lng cao vng gi bn xung mc nng lng thp vng nn v pht x ra photon

mi c cng hng truyn, cng phn cc, cng pha v cng bc sng. Tn hiu nh sngc khuch i. Cc h thng EDFA trong thc t c m t trong 2.16

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Hnh 2.16:Cu trc tng qut ca mt b khuch i EDFA2. 3. 1. 2 Tng cn bng cho khuych i EDFA

Khuch i EDFA c bit ph hp vi cc h thng truyn dn quang WDM bi nlm vic ti bc sng 1550 nm vi h s khuych i cao, cng sut ra ln v nhiu thp.Tuy nhin i vi cc ng dng trong h thng truyn dn quang WDM, EDFA cng cnhng hn ch l do cu trc mc nng lng, EDFA c h s khuych i khng unhau i vi cc bc sng khc nhau ca h thng WDM, iu ny dn n cc h thngWDM s dng khuych i EDFA c cht lng ca cc knh tn hiu khng u nhau nhhng n cht lng truyn dn, do vy s cn bng ph khuych i ca mt b khuychi rt cn thit cho vic cn bng nng lng gia cc knh nhm trnh li cc tn hiuc truyn qua h thng truyn dn quang. c mt s phng php s dng cho cc bcn bng EDFA (cc b cn bng ny c th l cn bng trong hoc cn bng ngoi). Cc

phng php cn bng trong to ra s thay i ca cc thuc tnh ph hp th ca si v phnh sng truyn qua si bng cch s dng cc k thut co doping i vi cc ion. Ccphng php da trn c s cc thit b lc c thit k vi ph lc ph thuc vo phkhuych i ca EDFA. Cc dng b lc ny hin c m t v thc nghim. Cc dngthit b ny c th c phn chia lm hai loi: l thit b ch ng vi kh nng cu hnhli do n c kh nng thay i c tnh ph tu thuc vo cc hiu ng bo ho, dngthit b th ng c c tnh ph hon ton c nh khng c kh nng thay i.

Cc dng thit b ch ng bao gm: cc b lc acousto- optic tunable, Strain- tuneables dng FBG, micro mechanical v b lc quang tch hp s dng cng ngh planar. Cc

dng thit b th ng bao gm cc dng : cc thit b LPG, FBG, v cc b lc s dng sikch thch pha Samarium.

Tt c cc thit b trn u c cc thuc tnh l kh nng cn bng khuych i vgim suy hao xen. Cu hnh ca EDFA s dng b lc nh sau :

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Hnh 2. 17: Cu hnh b lc t ngoi EDFA

Hnh 2. 18: Cu hnh b lc t gia EDFAVic la chn cu hnh cng nh loi thit b dng cn bng khuych i cho h thng

EDFA ph thuc vo nhiu yu t nh yu cu ca h thng WDM ang s dng, yu cuv cc thuc tnh k thut nh l suy hao, xuyn m . Tuy vy, trong cc h thng thc thin nay cc thit b cn bng dng FBG hin ang rt pht trin v c nhiu ng dng rng

ri v t ra rt ph hp vi cc h thng WDM bi tin cy cao v chi ph sn xut r.2. 3. 2 ng dng ca FBG trong b cn bng khuych i EDFA

Hnh 2. 19: EDFA khng s dng v c s dng FBGHnh (2. 19) m t cu hnh EDFA c s dng b cn bng v khng s dng b cn

bng khuych i. Trong cu hnh s dng b cn bng khuych i, cch t Bragg c t

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ngay trc si quang pha Erbium nhm mc ch phn x gn nh ton b nhiu khuychi t pht ASE quay tr li si EDF nhm gim bo ho gy nn bi tn hiu, do vy lm tng di bin thin cng sut u vo. Xt ring tng cu hnh v so snh h s khuychi ca chng, ta thy :

i vi trng hp khng s dng FBG:Theo nh ngha, h s khuych i ca b khuych i l t s cng sut gia u ra

v u vo :

i vi EDFA cng sut u ra ngoi tn hiu cn thm phn cng sut ASE, do

cng sut ra l tng cng sut ca tn hiu c khuych i v tng

cng sut ASE trung bnh trn c hai hng thun ngc :

Nh vy h s khuych i ca EDFA c tnh nh sau :

y l cng sut ca tn hiu vo. nh hng ca gia tng cng sut tn hiu

vo i vi h s khuych i ca EDFA c c t bi ng cong (. Trong ch nng lng tn hiu vo nh, ng cong ny l tuyn

tnh nhng trong ch tn hiu vo ln ng cong ny l phi tuyn v xy ra hin tngbo ho khuych i. Theo quy nh, bo ho xy ra khi khuych i ca EDFA gimxung 3 dB di gi tr cha bo ho Gmax, hay ni cch khc h s khuych i ca EDFAgim xung mt na. Quan h ny nh sau:

Hoc:

Hai tham s Gmax v hoc tng ng vi mi cng sut bm s quyt

nh di rng thay i cng sut tn hiu u vo ca EDFA trong gii hn:

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i vi trng hp EDFA s dng FBG:

Trong trng hp s dng FBG, thnh phn cng sut nhiu ASE hng ngc

s b FBG ngn chn v phn x ngc tr li si EDF. Khi cng sut nhiu ASE phn xbi FBG ngc tr li si EDF xc nh nh sau:

Trong RFBG( ) l phn x ca FBG. Sau khi thnh phn ASE phn x ngc tr

li t FBG n li tr thnh truyn cng hng vi nh sng tn hiu, khi cng

sut u vo v u ra c xc nh nh sau:

v l cng sut tn hiu u vo v u ra khi s dng FBG. T phng

trnh (11), (12), (13) suy ra h s khuych i trong trng hp s dng FBG nh sau:

Phng trnh cho thy tn hiu u vo EDFA c thm thnh phn nhiu ASE b phnx ngc tr li bi FBG, do vy h s khuych i s b gim xung.

cn bng khuych i ca EDFA, bin php n gin v hiu qu l da trn c ss dng FBG u vo si EDF phn x (ti trn 99%) thnh phn nhiu ASE tr li siEDF (hnh 2.19). T cc biu thc ton hc xc nh v cn bng h s khuych i ca

EDFA l cng sut nhiu ASE hng ngc .

H s khuych i i vi cng sut tn hiu u vo ph thuc vo c tnh khuychi tnh hiu ca EDFA. Trong ch khuych i tn hiu nh (hay khuych i cha boho), h s khuyc i G thay i tuyn tnh vi cng sut tn hiu u vo hu nh t thayi trong mt phm vi xc nh. Trong ch khuych i tn hiu ln (hay khuych i bo

ho), h s khuych i G thay i phi tuyn vi cng sut tn hiu u vo

H s khuych i ca EDFA cao nht trong trng hp khng s dng FBG v gimxung trong trng hp s dng FBG. S suy gim h s khuych i ca EDFA khi sdng FBG so vi khi khng s dng FBG l do: trong cu hnh s dng FBG phn xnhiu ASE ngc tr li si EDF, nh phn tch trn, nhiu ASE b phn x ngc trli si EDF bi FBG tr thnh cng chiu vi hng truyn tn hiu, cho nn tc ng lm

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suy gim cng sut tn hiu u vo v gim bo ho khuych i gy nn bi tn hiu ckhuych i; theo phng trnh (7), (11), (14), thnh phn cng sut nhiu ASE hng

ngc phn x ngc tr li si EDF bi FBG v tham gia vo hng truyn tn

hiu nh mt tn hiu u vo ca EDFA, v vy h s khuych i ca EDFA khi s dng

FBG do c thm thnh phn cng sut thp hn so vi khng s dngFBG.

2. 4 Mt s ng dng khc ca FBG

2. 4. 1 ng dng trong cm binCch t Bragg quang l mt trong nhng s pht trin th v nht trong lnh vc nghin

cu cc h thng cm bin si quang trong nhng nm gn y. Cc dng FBG nh FBGthng thng, FBG chu k bin i tuyn tnh, FBG dch pha u c th s dng trongcc h thng cm bin.

Cc dng cm bin c th ng dng cch t Bragg quang l nhit v sc cng.iu ny c ngha l chng ta c th dng FBG gim st trng thi v nhit hoc sccng ca mi trng hay gim st c hai yu t ny cng lc. Cch t quang bc sng kps dng nhn bit cc nh hng ca nhit v sc cng c tm ra ti phng thnghim M. G. Xu et al.

Hn na, FBG cho thy cc p ng bc sng rt tt i vi nhit v sc cng mchng ta c th s dng iu chnh mt cch chnh xc cc bc sng trong cc phn tchuyn i tn hiu cm bin.

FBG c kh nng phn x cao vi bc sng hp ti bc sng Bragg ca n G, thngthng hiu sut phn x ca FBG c th ln hn 75%. Vi hiu sut phn x ny s c nng lng cho photodiode thc hin tch sng. c im ring ny ca cm bin FBG viG duy nht gip cho n khng ph thuc nhiu vo cng quang trong h thng.

Nguyn l hot ng v m hnh ca cc h thng cm bin s dng FBG c m ttrong hnh (2.20). Trong h thng ny, FBG c t di cc tc ng trc tip ca mitrng cn gim st, di tc ng ca cc yu t mi trng nh nhit , p sut hay sccng FBG s thay i cc c tnh ca n v lm cho G thay i, b tch sng v x l khipht hin ra s thay i ny s iu khin v pht ra tn hiu cnh bo.

Nh ni trn, FBG c th p ng i vi nhiu yu t nh hng ca mi trngnn rt d dng ghp nhiu loi cm bin vo trong cng mt si quang. Khi cn m rngcc chc nng ca h thng, chng ta c th thm vo trong h thng cm bin c nhiusensor phc v cho cc chc nng c m rng.

So vi cc dng sensor khc, sensor FBG c rt nhiu u im: kch thc nh gn,khng chu cc tc ng ca trng in t, khng dn in, c cm bin v ghp knh th

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ng (mng cm bin). C rt nhiu ng dng i vi dng thit b cm bin ny, ngoi ccdng trn n cn c th dng trong gim st cu trc bn trong cng trnh xy dng nhnh ca, cu cng hay p nc

Hnh 2. 20 M hnh h thng cm bin s dng FBG v nguyn l hot ng

2. 4. 2 ng dng trong cng ngh LaserFBG c mt s ng dng quan trng trong dng thit b quang ny. FBG c th s dng nhmt thit b phn x c khong bc sng phn x rt nh ph hp cho vic cung cp ccdng xung ngn hay laser n sc, n cng c th s dng cho cc b lc ca h thng thngtin quang WDM.

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Bin

Bin

Tc ng

Bc sng lc qua FBGBc sng ti

Mi trng

CouplerFBG

Bin

Tch sng& x l

Ngun bngrng

Ngun bngrng

Bc sng phn x

Bin

Bc sng phn x


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Chuyn thng tin quangKt lun

KT LUN

Qua mt thi gian tm hiu nghin cu v tng hp v cch t Bragg si quang,nhm thu c mt s kt qu nh sau:

Nm bt c tng quan v cc tnh cht quang ca cch t Bragg si quang (FBG).

Tm hiu cc ng dng ca cc dng cch t trong cc h thng thc t nh cm

bin, laser v ni bt l ng dng trong h thng truyn dn quang

Trong tng lai, cch t Bragg si quang s cn c nhiu ng dng quan trng cnc nghin cu s dng ht tim nng. iu i hi phi c nhng nghin cu suv ton din hn na v kh nng ca dng thit b ny.

Trong chuyn ny chc chn khng th trnh khi nhiu thiu st. Cc thnh vintrong Nhm mong c s ch bo v gp ca cc thy c v cc bn hon thin hn

na bn chuyn .

Mt ln na, xin chn thnh cm n s hng dn tn tnh ca thy Hong Vn V gip Nhm hon thnh chuyn ny.

Nhm thc hin

Nhm 10

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Chuyn thng tin quang Ti liu thamkho

TI LIU THAM KHO

[1] Phng Vn Vn, Trn Hng Qun, Nguyn Cnh Tun, Phm Hng K, NguynHoi Nam,H thng thng tin si quang, Nxb Khoa hc v k thut, 2002

[2] Cao Phn, Cao Hng Sn, C s k thut thng tin quang, Hc vin Cng ngh Buchnh Vin thng, 2000

[3] NgTh Thu Trang, Cao Hng Sn, Nguyn Thnh Nam, K thut thng tin siquang, Hc vin Cng ngh Bu chnh Vin thng, 2010

[4] L Quc Cng, Vn Vit Em, Phm Quc Hp ,K thut thng quang 2, Hcvin Cng ngh Bu chnh Vin thng, 2009

[5] V Vn San,H thng thng tin quang 2 tp, Nxb Bu in, 2008

[6] V Vn San,K Thut Thng tin quang, Nxb Khoa hc k thut, 1997

[7] ThS. Vn Vit Em, K thut thng tin quang 2, Hc vin Cng ngh Bu chnhVin thng, 2007.

[9] Nguyn Th Thu Nga, Nguyn Thnh Nam,Cao Hng Sn , Bi ging MngTruyn Ti Quang, Hc vin Cng ngh Bu chnh Vin thng, 2010

[10] Hong Vn V,Mng thng tin quang th h sau, Nxb Bu in, 2008

[11]L Thanh Thy, Slide Bi ging thng tin quang nng cao, 2010

[12]Hong Trng Giang, n tt nghip Cch t Bragg si quang, Hc vin CngNgh Bu Chnh Vin Thng, 2005

[13]Nguyn Mnh Tng, n tt nghip Nghin cu ch to cm bin quang si sdng cch t Bragg, i hc Cng ngh - i hc Quc gia H Ni, 2011

[14]H Huy Thnh,Phng php b tn sc trong mng thng tin quang tc caodng quang si cch t Bragg chu k thay i tuyn tnh, Tp ch Cng ngh thng tin &Truyn thng, Th Ba, 25/05/2004

[15]Jianfeng Zhao,An Object-Oriented Simulation Program for Fibre BraggGratings, Rand Afrikaans University Johannesburg Republic of South Africa

Chuyen de Thong Tin Quang (Chi Tiet) - Nhom 10 L11CQVT7

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