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CNG TTQ

Cu 1: cc giai on pht trin, u nhc im, ng dng v xu th pht trin ca hthng TTQ

Cc giai on pht trin

- Th h th nht: s dng si quang a mode, hot ng bc sng 850 nm, c ly vikm- Th h th 2 (1980s): s dng si quang n mode, h ti bc sng = 1300nm- Th h th 3 (1900s): s dng si quang n mode,hot ng ti bc sng =150nm- Th h th 4 (t 1995): s dng k thut ghp knh theo bc sng (WDM), khuch i

quang tng dung lng v c ly truyn dn- Th h th 5: vi vic gii quyt tn sc ca si quang cng vi ng dng khuch i

quang trn din rng, h thng TTQ Solitons.

u im:

- Di thng ln khnng truyn thng tin rt ln (c th ti hng chc Tbits/s)- Suy hao thp (0.20.3 dB/km)- Si quang ko bnh hng c nhiu in t.- Khnng nng cp tc d dng.- Trng lng nh, kch thc nh- Tnh bo mt, linh hot cao.

Nhc im:

- Vn bin i inquang.- Hn ni, o th si quang i hi thit b chuyn dng, t tin- Vn an ton lao ng- Tn hiu nh sng trong si quang b suy hao v bin dng, hn ch c ly truyn dn v

tc ti a ca tuyn.

ng dng:

- trong vin thng: - mng ng trc quc giang trung k

ng cp th bin lin quc qua (quc t).- ng dng trong dch v tng hp: mng my tnh, LAN, WLAN

truyn hnh cp

cable TV

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Optical Fiber Sensors

Xu hng pht trin: trong tng li h thng truyn dn VN spt theo xu hng chung cath gii l cp quang ha. Cp quang sc trin khai ti a thay th cc h thng viba hincn li (ch yu nhng ni cha trin khai c cp quang do iu kin a hnh).

Trong tng lai gn, cp quang sc trin khai rng ri hn trong mng truy nhp cung cp

cc dch v yu cu tc cao nh truyn s liu v hnh nh bn cnh dch v thoi truynthng

Tng cng dung lng v tc bit truyn trn mt tuyn si quang s dng cc cng nghnh WDM, OTDM,...

Nng cao nhy ca my thu quang in lm vic tc bit cao nhcng ngh khuch iquang.

Pht trin cng ngh mch t hp quang in v quang tch phn.

Hon thin v a vo s dng trong thc t k thut h thng TTQ phi tuyn Soliton.

Xy dng cc mng thng tin ton quang.

Cu 2: v v trnh by chc nng ca cc thnh phn trong h thng TTQ.

- B pht quang: Ngun quang (Light Source):

Bin i tn hiu in sang tn hiu quang LED (light emitting diode) LASER (light by stimulated emission of radiation)

Mch iu khin: Mch in t iu khin qu trnh bin i in quang

- Phn truyn dn quang: gm cc si quang, cc b ni, b chia/ghp, cc trm lptrong si quang chnh l mi trng truyn dn tn hiu quang.

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- B thu quang: B tch sng quang (photodiode):

Bin i tn hiu quang thnh tn hiu in PIN Diode thc APD Photodiode

Khuch i: khuch i tn hiu in b li nhng suy hao do ng truyn. Phc hi tn hiu: nhn bit cc gi tr 0,1 ca chui bit tn hiu phc hi li nh

tn hiu ban u.- Trm lp: khi truyn dn vi c ly xa, tn hiu quang c th b suy gim nhiu, khng

m bo b thu khi phc li tn hiu ban u, cn phi t thm cc trm lp quang(Repeater hoc Regenerator) khuch i tn hiu, b li suy hao. Khuch i quangin (hnh v) Khuch i quangquang: EDFA

- Cc phn ttch cc: B pht quang hay ngun quang

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B tch quang (thu quang) B khuch i quang B chuyn i bc sng

Cc phn t tch cc hot ng phi c ngun nui, nhcc ngun ny m phn ttch cc c th bin i tn hiu cn x l.

- Cc phn tthng: Si quang Coupler quang B lc quang B cch ly quang B b tn sc

Phn t thng hot ng khng cn ngun kch thch, n chn thun bin itn hiu trong min quang m khng c s chuyn i sang min in.

Cu 3: cu trc vo phn loi si quang

- Cu trc: cu trc hnh tr, dn nh sng theo hng song song vi trc ca n.Gm 3 lp: li, v phn x, v bo v

Li si: c chit sut n1ng knh d=2a. C tc dng truyn lan nh sng theohng song song vi trc ca n.V si: c chit sut n2

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- Suy hao tn hiu:Khi nim: suy hao tn hiu l s suy gim cng sut tn hiu trong qu trnh

truyn dn trong si quang.

Suy hao (suy hao ton trnh) ca si:

H s suy hao (hay suy hao trn mi km si): ()

Cc nguyn nhn gy suy hao: Suy hao do ghp vi linh kin pht quang Suy hao do tn x Reyleigh Suy hao do hn ni Suy hao do hp th Suy hao tn x do cu trc khng ng nht Suy hao vi cong Suy hao bc x do b b cong Suy hao do ghp vi linh kin thu quang

- Tn sc:Khi nim: tn sc l hin tng gin xung nh sng theo thi gian khi truyn tn

hiu trn si quang gy nn mo tn hiu.Nguyn nhn gy ra tn sc:

Tn sc mode (modal dispersion)tn sc gia cc mode

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Tn sc th (chromatic dispersion)tn sc trong mode Tn sc cht liu (material dispersion) Tn sc dn sng (waveguide dispersion)

- Cc hiu ng phi tuyn: hiu ng quang c gi l phi tuyn nu cc tham s ca nph thuc vo cng nh sng.Phn loi:

Th nht: xut hin khi sng nh sng b tn xtrong mi trng truyn dndo qu trnh tng tc ca cc sng nh sng vi cc photon ca silicat: hiung tn x Brillouin v Raman

Th2: c trng bi s ph thuc ca chit sut vo cng sut ca tn hiuquang: FWM, SPM,XPM. Cn gi l hiu ng Kerr.

Cu 5: so snh si n mode v a mode

Si a mode:-Truyn ng thi nhiu mode sng

-u im:+ C ng knh li ln d ghp cng sut quang vo si, d kt ni vi nhng si

tng t+ nh sng ghp vo si dng nhiu ngun led r tin, d ch to, thi gian sng lu

hn Laser diode-Nhc im: C tn sc modeMMF thch hp nht vi khong cch truyn dnngn.

Si n mode:-Ch yu cu mt mode duy nht yu cu ng knh li nh, yu cu cu toconnector, k thut ghp ni kht khe hn.-Cho cht lng thng tin tt hn do:

+ m bo c chnh xc ca xung nh sng khi truyn+ Khng c hin tng tn sc mode+ Suy hao cp thp hn si a mode

SMF thch hp cho khong cch truyn dn lnCu 6: Cc loi cp quang n mode mi

Nguyn tc to si quang mi: iu chnh cc tham sc bn trong cu trc loi si nmode dch tn sc ti thiu vng nm sang vng 1310= = 1550 nm

Si SMF hay si G652, si DSF hay si G653, si CSF hay si G654, si NZ-DSF hay siG655

Si SMF l cp n mode c D=0 v suy hao 0,4 dB/km trong vng .1310nm=

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SMF c thit k ti u cho cc h thng n knh trong vng 1310nm nhng cng c=

thc s dng cvng 1550nm vi 0,2 dB/km v D Tuy nhin si SMF khng ph hp vi h thng WDM tc cao, c ly truyn dn ln

Ch to si quang n mode mi : DSF v NZ-DSF

DSF l si quang n mode dch tn sc c to ra bng cch thay i s phn b khc x lmcho cc im tn sc bng khng dch t ca s1310=nm sang 1550nm=

Si DSF c suy hao nh v tn sc D=0 ti 1550nm= hiu qu cho cc h thng hot ngvng 1550nm v h= thng c EDFA, c bit hiu qucho ht n knh

Cp ny ch thch hp cho truyn dn quang bnh thng, v khi truyn tc cao th lmtng hiu ng FWM t s dng

C tn sc nh 0,1ps/km.nm

Dmin

Dmax

6ps/km.nm trong vng 1530nm -1565nm nhng

khng bng 0 ti vng ca s 1550nm.

Ti u ha chng li cc hiu ng phi tuyn ( nht l FWM) gm 2 loi:

+ +NZ-DSF c im tn sc bng khng nm vng bc sng nhhn 1500nm

+ -NZ-DSF c im tn sc bng khng nm vng bc sng ln hn 1600nm

Cu 7: qu trnh pht x nh sng

- C ch pht x nh sngMt in ttrng thi nng lng E1 hp th mt ngun nng lng (dng in, nh sng,...) s nhy ln mc nng lng cao hn (E2). Trong qu trnh trv trng thi ban u ns gii phng ra mt nng lng nh sng di dng sng in tng bng nng lng mn hp th.

- Nng lng nh sng pht x EPXc x bi CT:

Trong : h l hng s Planck (=6,625*10-34

J.s)F l tn s nh sng pht ra- Bc sng ca nh sng pht ra c x theo:

Vi c l vn tc nh sng trong khng gian t do ( bng 3*108 m/s)

- Pht x t pht v pht x kch thch

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cc nguyn t mc nng lng E2 thng c xu hng quay v mc E1 v pht raphoton. Pht x tpht: photon pht ra c hng ngu nhin v khng ng pha vi nhau

nh sng pht xtrong trng hp ny gi l nh sng ko kt hp. Pht xkch thch: khi c photon p vo nguyn ttrng thi kch thch pht

ra photon tn hiu nh sng ti. nh sng pht xtrong trng hp ny gi l nh

sng kt hp.- Nguyn l pht x nh sng ca tip gip pn

Trong k thut TTQ, ngi ta thng s dng cc ngun pht x nh sng l ccphn t bn dn da trn cu trc tip gip pn.

Tip gip pn v qu trnh pht xnh sng khi c in p ngoi tc ng (phn ccthun).

- Qu trnh bin i in quang da trn 3 hin tng:

Cu 8: cu trc, nguyn l hot ng v c tnh pht x ca LED v LD

cu trc c bn ca led l s dng tip gip bn dn pn.

C 2 loi:

Cu trc tip gip pn thun nht : nguyn l pht quang ca led ging nh nguyn l phtquangca tip gip pn- hiu sut thp.

Cu trc d th kp : c 2 lp bn dn p v n mi bn ca vng tch cc chn khng chocc in t di chuyn v vng p v l trng di chuyn vvng n, in tch tp trung chyu vng tch cc v lm cho mt in tch vng hot tnh tng ln rt cao. Chngti hp vi nhau v pht ra nh sng trong vng hot tnh vi cng sut ln.

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-

Nguyn l hot ng ca led:

- c tuyn pht x nh sng ca LEDKhi dng iu khin LED l nhng chui xung c tc bit thp, tc l LED hotng khu vc tn s thp, th nh hng ca in dung tip gip ca cc lp P-Ntrong LED, in dung ca ti v cc hiu ng k sinh (in dung gia LED vi vc th b qua trng qu trnh bin i in- quang ca LED. Khi , cng sut nh

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sng ca LED bc x ra ch l hm s ca cng dng in iu khin ctuyn bin i in quang tnh ca LED.

Khi dng iu khin LED l chui xung c tc bit ln v do LED hkhu vctn scao. Khi LED h tn scao, th in dung tip gip ca cc lp P-N trongLED, in dung ca ti v cc hiu ng k sinh ( in dung gia LED vi v) ngvai tr quan trng trong qt bin i inquang ca LED. Khi , qu trnh bin i

in- quang ca LED ko tun theo c tuyn tnh ca n na, cos ngha l trongtrng hp ny c tuyn tnh ko cn ng na. Qu trnh bin i inquang caLED trong trng hp ny s ph thuc vo tn s. chnh l qu trnh bin ngca LED.

- Cu trc LD (light amplication by stimulate emission of radiation diode) S dng tip gip bn dn pn kt hp vi khoang cng hng nh sng. S dng cu trc d th kp. Cu trc ca LD c khoang cng hng nh sng:

Mc ch ca khoang cng hng nh sng: To nh sng LASER (a/s kt hp di k bc x kch thch) La chn tt ( trng thi sng nh sng)

Nguyn tc cu trc: Ch khuch i cc sng nh sng chy theo phng dc ca khoang

cng hng.

Cc sng nh sng ko chy theo phng dc ca khoang cng hngs b hp th.

iu kin cng hng nh sng: sng nh sng chy theo phng dc cakhoang cng hng, k cng hng /s ca LD l:L= k*/2

Trong : Vi k l 1 s nguyn L l chiu di hp cng hng l bc sng nh sng trong vt liu

- i vi laser bn dn, cu trc bung cng hng c sd nhiu nht l bung cng hngkiu FarbyPerot.- Nguyn l pht x nh sng ca LD Qu trnh o ln mt v pht x tpht trong LD tng tnh trong LED Hin tng hp th photon v pht x kch thch:

Khi /s pht ra trong qu trnh trv trng thi E1 vi nng lng E2-E1 tiptc kch thch 1 in tkhc ang trng thi kch thch.

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in t ny hp thnng lt /s ti v trong qu trnh trv trng thi E1n s gii phng ra 1 nng lng /s di dng sng in t vi ln lnhn nhiu ln E2-E1

Qu trnh pht x kch thch hay pht xcng bc v /s c gii phng ra l /s pht xkch thch.

Khi dng bm nhhn gi trngng, /s ca bc x kch thch pht ra trong vng tch ccs b hp th ht trong vng ny, nn /s pht ra ca LD khi l /s pht x t pht rt yutng tnh /s ca LED.

Khi ta nng dng thin p ln vt gi trngng, khi vng tch cc trthnh mt khuchi bx kch thc. Nn khi bx kch thch truyn dc nhiu ln gia 2 gng trong vng ny ckhuch i ln rt ln v t c k cng hng trong hp. Lc ny /s kch thch do LDL

pht ra c cng rt mnh, vt tri s tiu hao do hp th trong hp cng hng. V /sca LD trong trng hp ny l /s kt hp.

Cu 9: so snh LED v LD

LED LDnh sng khng c tnh kt hp (incoherent) nh sng c tnh kt hp (coherent)

- Tnh n sc cao ( b rn ph hp)- hi t chm sng cao

Cng sut: vi chc W Cng sut 110W rng ph: 20100nmdng cho MMF rng ph: 0,1 4nm dng cho SMF

v MMF

Tc iu ch: 100200 Mbps Tc iu ch: 10Gbpsng dng ng truyn c ly ngn, tc thp

ng dng ng truyn c ly di, tc cao

Mch iu khin n gin Mch iu khin phc tp v c nhiu nhitv cn mch n nh

Gi thnh r Gi thnh cao

Cu 10: nguyn l c bn ca b tch sng quang.

- Qu trnh hp th xy ra ch yu trong vng him (vng c t cc in tch t do)- Vng him c to ra t nhinhphiu sut thp- Mun tng hiu sut bin i quang- in ( hiu sut lng t):

Tng rng ca vng him bng cch tng in p phn cc ko hiu qu t gia 2 lp bn dn p n 1 lp bn dn c rng ln c tch cht tng tnh

vng him diode thu quang PIN

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Cu 11: nguyn l c bn ca b tch sng quangCu to diod thu quang PIN : gia 2 lp bn dn c pha tp cao p+ v n+l 1 vng bn dnc pha tp thp, cn gi l lp t dn I.

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Cu to diod APD : gm 4 lp I , P+,P, N+.

Lp p in trsut cao lm nn. ( P+)

Ni in trng thp lp I ni to ra cp e-h t do

vng in trng cao gia P v N+. ni cc ht mang in c gia tc v nhn ln.

in p phn cc ngc t vo APD ln ti hang trm vn.

Nguyn l hot ng :

- Khi khng c /s chiu vo APD khng c dng in- Khi c photon ti c nng lng E= hv/Eg chiu vo APD, trong lp I sinh ra cc cp

in t v l trng ban u gi l s cp.- 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 ( phn t th cp), gi ls ion ha do va chm.

- Cc phn t th cp ny n lt mnh li to ra s ion ha do va chm tm na, gy nnhiu ng quang thc v lm cho dng in chy trong APD c khuch i ln nhiu lnso vi photodiode PIN. Lp P c gi l lp nhn thc ca photodiode

Cu 12 : u im ca h thng coherent

- nhy my thu cao hn nhiu so vi h thng IM-DD( c10dB -20 dB)-

Tng khong cch trm lp- Tng khnng chn la tn s knh v tn dng rng bng tn ca si quang.- Tc bit v dung lng ca h thng t c rt cao- Cu hnh v cng ngh thit b rt phc tp, i hi k thut cao.- Gi thnh ca thit b v ht cao s dng trong thc t cn b hn ch, trong tng lai

s pht trin rng ri.

Cu 13: so snh h h thng IM-DD v cohenver.

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IM-DD CONHENVERCu trc thit bn gin. Cu hnh cng ngh phc tp.Khng i hi cng ngh qu cao vqu phc tp.

i hi k thut cao.

Gi thnh thit b khng cao Gi thnh thit b v h thng cao. nhy my thu khng cao. nhy my thu cao.Tc dung lng bit t c mc nht nh.

Tc bt v dung lng t c rtcao.