THUYT TRNH QUANG IN T

KHO STLINH KIN CA H THNG THNG TIN QUANG

GVHD: Thy gio Hong Ph An Ph trng khoa in - in t SVTH: 1. V Vn Ti 4. Nguyn Th Kiu 2. Nguyn Duy Thn 5. Ng Tin Hun 3. Nguyn VnTrung

Cc vn c bn H thng truyn dn quang Khi nim v k thut ghp knh phn chia theo bc sng -WDMB lc quang mng mngNguyn l ghp knh theo bc sng quang (WDM) B ghp/tch tn hiu (Coupler)B isolator/circulatorB lc quangB ghp/tch knh bc sngB chuyn mch quang B chuyn i bc sng

H thng truyn dn quang S khi ca cc h thng thng tin

H thng truyn dn quangNhim v v chc nng c bn ca cc khiNgun tn hiu: l cc dng thng tin thng thng nh ting ni, hnh nh, s liu, vn bn...Mch in t : c nhim v x l ngun thng tin to ra cc tn hiu in di dng analog hoc digitalKhi E/O: l mch bin i in - quang c nhim v iu bin tn hiu in thnh cng bc x nh sng pht i (bin i tn hiu in thnh tn hiu quang).Si quang c nhim v truyn dn tn hiu quang t ni pht n ni thuKhi O/E : mch bin i quang - in cn gi l b thu quang c nhim v tip nhn nh sng t si quang a n v bin i tr li thnh tn hiu in nh tn hiu in pht iTi tin : Trong h thng in th ti tin l cc sng in t cao tn, trong h thng quang ti tin l nh sng v cng l sng in t song c tn s rt cao ( 1014 1015 Hz) do vy ti tin quang rt thun li cho ti cc tn hiu bng rng

Trm lp quang in (optoelectronic repeater)Cu trc ca mt trm lp quang in (optoelectronic repeater)

Trm lp quang in (optoelectronic repeater)Trong qu trnh truyn thng tin suy hao ca si quang l nguyn nhn gii hn c ly truyn ca cc h thng thng tin quang. i vi cc h thng truyn dn quang c ly di, gii hn v suy hao c khc phc bng cch s dng cc trm lp quang in (optoelectronic repeater)Qu trnh khuch i tn hiu quang c thc hin qua nhiu bc. u tin, tn hiu quang s c bin i thnh dng in bi cc b thu quang (optical receiver) s dng linh kin tch sng quang nh PIN hay APDDng quang in thu c s c ti to li dng xung, nh thi v khuch i bi cc mch phc hi tn hiu v mch khuch i. Sau , tn hiu in s c bin i thnh tn hiu quang thng qua cc ngun quang trong b pht quang (optical transmitter) v c truyn i trong si quang.

Trm lp quang in (optoelectronic repeater)u im ca h thng truyn dn quang+ Si quang nh, nh hn dy kim loi, d un cong, tn t vt liu.+ Si quang ch to t thu tinh thch anh khng b nh hng ca nc, axit, kim nn khng b n mn. ng thi, si l cht in mi nn cch in hon ton, tn hiu truyn trong si quang khng b nh hng ca nhiu bn ngoi ti v cng khng gy nhiu ra mi trng xung quanh.+ m bo b mt thng tin, khng s b nghe trm.+ Kh nng truyn c rt nhiu knh trong mt si quang c ng knh rt nh. Tiu hao nh v khng ph thuc tn s nn cho php truyn dn bng rng v tc truyn ln hn nhiu so vi si kim loi.+ Gi thnh rt r.

Khi nim v k thut ghp knh phn chia theo bc sng -WDMKhi nim v k thut thng tin quang WDM B lc quang lin quan n k thut ghp knh phn chia theo bc sng -WDM. V mi mt ngun sng n sc c rng ph hp, nn trong truyn dn n ch s dng mt phn rt nh bng truyn dn ca mt si quang. Ghp knh phn chia theo bc sng s to ra rt nhiu knh ph s dng ng thi.Mt cch l tng, s tng t bin dung lng thng tin ca mt si quang c th t c bng vic truyn dn ng thi cc tn hiu quang trn cng mt si quang t nhiu ngun nh sng khc nhau c cc bc sng nh bc x t cch nhau mt cch chnh xc. Bi mi ngun sng hot ng ti mt bc sng nh khc nhau, tnh ton vn ca cc tin tc c lp t mi ngun c duy tr vic chuyn i tun t sang tn hiu in u thu. y l c s ca ghp knh phn chia theo bc sng (WDM).

Khi nim v k thut ghp knh phn chia theo bc sng -WDM

Hnh 6.3. Mt ngun quang n s dng mt phn rt nh bng truyn dn ca ph c sn ca si quang ghp knh phn chia theo bc sng (WDM) to ra rt nhiu knh ph s dng ng thi.

Khi nim v k thut ghp knh phn chia theo bc sng -WDM

Hnh 6.4. H thng WDM n hng kt hp N tn hiu c lp truyn trn 1 si quang n.Trong hnh trn, linh kin WDM n hng c s dng kt hp cc bc sng mang tn hiu khc nhau trn mt si quang n ti mt u v tch chng vo b tch quang thch hp ti u kia.

Khi nim v k thut ghp knh phn chia theo bc sng -WDM

Hnh 6.5. H thng WDM hai hng, trong , hai bc sng hoc nhiu hn c truyn ng thi trong cc hng ngc nhau trn cng mt si quang.S ny gm vic gi tin tc trong mt hng ti mt bc sng 1 v ng thi trong hng ngc li ti bc sng 2.

Khi nim v k thut ghp knh phn chia theo bc sng -WDMB lc quang bng cc linh kin tn sc (hay b ghp knh tn sc cnh)

Hnh 6.6. S biu din mt phn t WDM tn sc cnh cho 3 bc sng. Nhiu bc sng c th kt hp hoc phn chia vi loi linh kin ny.Khi linh kin s dng nh mt b phn knh, nh sng t si quang i ra c chun trc bng thu knh L1 (gi l thu knh chun trc) v i qua phn t tn sc cnh v n c phn chia thnh cc knh c bc sng i vo cc chm tia c nh hng khng gian khc nhau. Thu knh L2 (thu knh hi t) s hi t cc tia u ra vo cc si quang thu thch hp hoc cc b tch quang thch hp.

B lc quang mng mng

Hnh 6.7. B lc mng mng nhiu lp phn x s dng cho WDM. Linh kin ny trong sut ti bc sng 2 v phn x ti bc sng 1. B lc phn x gm mt tm knh phng, bn trn n nhiu lp mng mng cht cch in khc nhau c lng ng tu theo tnh chn lc ca bc sng. Cc b lc ny c th s dng ni tip thnh chui phn chia thm cc knh bc sng. S phc tp cng tng theo s lng cc b lc ni tip v s tng tn hao tn hiu cng xy ra vi vic tng thm cc b ghp knh ni tip. Nhn chung ch nn hn ch hot ng n 2 hoc 3 b lc (c ngha l hot ng 3 hoc 4 knh).

B lc quang mng mngB lc c th iu chnh bc sng (a wavelengthtunable-filter)

Hnh 6.8. V d v b lc iu chnh bc sng. Mt tm thch anh di ng thay i di tuyn ng i qua tinh th thay i ph ra hnh sin.

B lc quang mng mngTrong phng php ny, cc tn hiu tin tc khc nhau c gi vo cc knh tn s ring ca rng bng B. Bng vic s dng mt b lc vi di thng c rng B m n c th iu chnh trn khong tn s ca cc knh ny, ngi ta c th chn c knh theo yu cu. y, mt phn t a cp lng chit sut cu to t hai ng dn sng bng thch anh (a birefringent multiple - order element) c t gia hai b tch tia phn cc (polarizing beam splitters). S bin i hnh sin ca ph ra c th c thay i bng cch thay i di ng truyn L i qua tinh th. iu ny t c bng cch di chuyn mt trong cc tm thch anh ln trn hoc xung di. S thay i chiu di theo cp bc chu k quay phn cc s xc nh v tr ca knh.V tuyn quang l thun nghch, linh kin ny c th c s dng nh l b ghp knh v hoc nh l b phn knh u c.

Nguyn l ghp knh theo bc sng quang (WDM)nh ngha Ghp knh theo bc sng WDM (Wavelength Devision Multiplexing) l cng ngh trong mt si quang ng thi truyn dn nhiu bc sng tn hiu quang. u pht, nhiu tn hiu quang c bc sng khc nhau c t hp li (ghp knh) truyn i trn mt si quang. u thu, tn hiu t hp c phn gii ra (tch knh), khi phc li tn hiu gc ri a vo cc u cui khc nhau.b) S chc nng m bo vic truyn nhn nhiu bc sng trn mt si quang, h thng WDM phi thc hin cc chc nng sau:

Nguyn l ghp knh theo bc sng quang (WDM)Ghp/tch tn hiu

Hnh 6.10. S chc nng h thng WDM

Nguyn l ghp knh theo bc sng quang (WDM)Ghp tn hiu WDM l s kt hp mt s ngun sng khc nhau thnh mt lung tn hiu nh sng tng hp truyn dn qua si quang. Tch tn hiu WDM l s phn chia lung nh sng tng hp thnh cc tn hiu nh sng ring r ti mi cng u ra b tch. Hin ti c cc b tch/ghp tn hiu WDM nh: b lc mng mng in mi, cch t Bragg si, cch t nhiu x, linh kin quang t hp AWG, b lc Fabry-Perot... Khi dng b tch/ghp WDM, ta phi xt cc tham s nh: khong cch gia cc knh, rng bng tn ca cc knh bc sng, bc sng trung tm ca knh, mc xuyn m gia cc knh, tnh ng u ca knh, suy hao xen, suy hao phn x, xuyn m u gn u xa...

Nguyn l ghp knh theo bc sng quang (WDM) Truyn dn tn hiuQu trnh truyn dn tn hiu trong si quang chu s nh hng ca nhiu yu t: suy hao si quang, tn sc, cc hiu ng phi tuyn, vn lin quan n khuch i tn hiu ... Mi vn k trn u ph thuc rt nhiu vo yu t si quang (loi si quang, cht lng si...) Khuch i tn hiuC ba ch khuch i: khuch i cng sut, khuch i ng v tin khuch i. Thu tn hiu Thu tn hiu trong cc h thng WDM cng s dng cc b tch sng quang nh trong h thng thng tin quang thng thng: PIN, APD.

Nguyn l ghp knh theo bc sng quang (WDM)Phn loi h thng WDM

Nguyn l ghp knh theo bc sng quang (WDM)u nhc im ca 2 h thng trnH thng WDM v c bn chia lm hai loi: h thng n hng v song hng. H thng n hng ch truyn theo mt chiu trn si quang. Do vy, truyn thng tin gia hai im cn hai si quang. H thng WDM song hng, ngc li, truyn hai chiu trn mt si quang nn ch cn 1 si quang c th trao i thng tin gia 2 im.Xt v dung lng, h thng n hng c kh nng cung cp dung lng cao gp i so vi h thng song hng. Ngc li, s si quang cn dng gp i so vi h thng song hng.Khi s c t cp xy ra, h thng song hng khng cn n c ch chuyn mch bo v t ng APS (Automatic Protection-Switching) v c hai u ca lin kt u c kh nng nhn bit s c mt cch tc thi.

Nguyn l ghp knh theo bc sng quang (WDM)Cc linh kin trong kin trong h thng WDMCc linh kin c s dng trong cc mng quang hin i bao gm cc b ghp/tch (couplers)b pht laser (lasers)b tch quang (photodetectors)b khuch i quang (optical amplifiers)b chuyn mch quang (optical switches)b lc (filters) b ghp/tch knh (multiplexers).

B ghp/tch tn hiu (Coupler) nh ngha B ghp/tch tn hiu (Coupler) l thit b quang dng kt hp cc tn hiu truyn n t cc si quang khc nhau. Nu coupler ch cho php nh sng truyn qua n theo mt chiu, ta gi l coupler c hng (directional coupler). Nu n cho php nh sng i theo 2 chiu, ta gi l coupler song hng (bidirectional coupler).

Hnh 6.13. Cu to coupler FBT 2 x 2 Hnh 6.14. Coupler hnh sao vi 8 ng vo v 8 ng ra

B ghp/tch tn hiu (Coupler)Nguyn l hot ng Khi hai si quang c t cnh nhau, nh sng s c ghp t si ny sang si kia v ngc li. l do qu trnh truyn mt nh sng trn si quang qua vng ghp s khc so vi truyn trn si quang n. Khi , ton b nh sng thuc mt si quang s c ghp hon ton sang si quang ghp vi n, phn nh sng ny li tip tc c ghp ngc tr li sang si quang ban u theo mt chu k tun hon khp kn. Kt qu ta c cng trng in t u ra ca b ghp ng dng - B coupler vi t s ghp 1 c dng trch mt phn nh tn hiu quang, phc v cho mc ch gim st. - Coupler cn l b phn c bn to nn cc thnh phn quang khc, chng hn nh: cc b chuyn mch tnh, cc b iu ch, b giao thoa.. - Thc hin ghp/tch bc sng trn si quang. Coupler 2 x 2 ghp 50:50 phn b cng sut nh sng t mt u vo ra lm 2 phn bng nhau 2 ng ra. Coupler ny cn c gi l coupler 3 dB, ng dng ph bin nht.

B isolator/circulator Isolator l thit b khng thun ngc (nonreciprocal). N ch truyn nh sng qua n theo mt chiu v ngn khng cho truyn theo chiu ngc li. N c dng ti u ra ca cc thit b quang (b khuch i, ngun pht laser) ngn qu trnh phn x ngc tr li cc thit b , gy nhiu v h hi thit b. Hai tham s chnh ca Isolator l suy hao xen v cch ly.Circulator cng thc hin chc nng tng t nh b Isolator nhng n thng c nhiu cng, thng l 3 hoc 4 ca. Chnh v s tng ng gia hai loi thit b, ta s ch trnh by hot ng ca b Isolator m thi.

B isolator/circulator S khi ca b isolator/circulator

Hnh 6.15. (a) S khi ca b Circulator 3 ca. (b) S khi ca b Circulator 4 ca. (c) S khi ca b Isolator.

B isolator/circulator Nguyn l hot ng

Hnh 6.16. (a) Cu to b Isolator khi nh sng vo phn cc dc.(b) Cu to b Isolator khi nh sng vo phn cc bt k.

B isolator/circulator Nguyn l hot ng nh sng truyn trong si quang vi trng thi phn cc bt k c a n b tch/ghp trng thi phn cc SWP (Spatial Walk-off Polarizer), tch thnh hai dng tn hiu phn cc dc v ngang theo hai ng c lp nhau. Tip theo, n b quay pha Faraday, quay pha 45o theo chiu kim ng h. Mt phng /2 (Half-wave plate) thc hin quay pha 45o theo chiu kim ng h i vi tn hiu truyn t tri sang phi, quay pha 45o theo chiu ngc kim ng h theo chiu truyn ngc li. Cui cng, tn hiu hai nhnh c kt hp li nh b SWP th hai. Nu theo chiu ngc li, hai b SWP s kh ln nhau. nh sng truyn qua b SWP th hai, qua b quay pha Faraday s khng th kt hp li c ti b SWP th nht nh minh ho trn Hnh 6.16.

B isolator/circulator ng dngB Isolator v Circulator c nhng ng dng sau:B Isolator thng ng trc u ra b khuch i quang hoc ngun pht laser ngn nh sng phn x ngc tr li thit b gy nhiu v c th lm h thit b.B Circulator c dng nh mt b phn ch to phn t xen rt quang OADM.

B lc quang Tng quan

Hnh 6.17. S khi ca b lc. (a) B lc c nh bc sng k. (b) B lc c th iu chnh bc sng c tronkhongng .nh ngha B lc l thit b ch cho php mt knh bc sng i qua, kho i vi tt c cc knh bc sng khc. Nguyn l c bn nht ca b lc l s giao thoa gia cc tn hiu, bc sng hot ng ca b lc s c cng pha nhiu ln khi i qua n, cc knh bc sng khc, ngc li, s b trit tiu v pha

B lc quang Thng s c bn

Hnh 6.18. (a) Cc thng s c trng ca b lc. (b) gn sng ca b lc.

B lc quangCc thng s c trng ca b lc rng bng thng (Pass Bandwidth): l rng ca hm truyn t ti mc suy hao xen cch nh 0.5 dB. Trong mt s trng hp, ngi ta cn c th xt bng thng i qua 1 dB, 3 dB. c tnh ny rt quan trng v laser trong trng hp khng l tng ch pht tn hiu c bc sng dao ng nht nh so vi bc sng trung tm c qui nh theo chun ITU-T. rng bng chn (Stop Bandwidth): l rng ca hm truyn t ti mc suy hao xen cch nh 20 dB. Di chn ca b lc phi cng nh cng tt trnh hin tng xuyn nhiu gia cc knh. cch ly (Isolation): ch cng sut ca mt knh bc sng xuyn nhiu sang cc knh bc sng ln cn. gn sng (Ripple): l chnh lch nh-nh trong phm vi mt knh bc sng.H s s dng bng thng BUF (Bandwidth-utilization Factor): l t s ca rng knh truyn LW (Linewidth) ca nh sng c truyn i so vi nh sng phn x ti mt mc suy hao xc nh.

B ghp/tch knh bc sng B ghp/tch knh bc sng, cng vi b kt ni cho quang, l thit b quan trng nht cu thnh nn h thng WDM.nh ngha Nguyn l hot ng ca b MUX/DEMUX cng tng t nh b Coupler. Tuy nhin, b Coupler/Splitter thc hin ghp tch tn hiu c cng bc sng, cn b MUX/DEMUX thc hin ghp tch tn hiu cc bc sng khc nhau. S khi b MUX/DEMUX cho trong hnh 6.22. (a) v (b).

B ghp/tch knh bc sng

Hnh 6.22. B tch/ghp knh bc sng quang. S khi b ghp knh bc sng (MUX). S khi b tch knh bc sng (DEMUX). Cc thng s c trng ca b MUX/DEMUX.

B ghp/tch knh bc sng c tnh b tch/ghp knh bc sng B MUX/DEMUX thng c m t theo nhng thng s sau:Suy hao xen (Insertion Loss): m t phn coupler.S lng knh x l: l s lng knh bc sng u vo v u ra ca b ghp/tch knh. Thng s ny c trng cho dung lng ca thit b.Bc sng trung tm: Cc bc sng trung tm phi tun theo chun ca ITU-T m bo vn tng thch.Bng thng: l rng ph (linewidth) ca knh bc sng trn thc t. Bng thng thng c tnh l rng ca hm truyn t cng sut cc mc cch nh 1dB, 3dB, 20dB.Gi tr ln nht suy hao xen: c tnh l khong cch nh nht gia nh ca hm truyn t cng sut ca mt knh bc sng no so vi mc IL=0 (dB) (minh ho trn 6.22. (c)). chnh lch suy hao xen vo gia cc knh: c tnh l hiu ca gi tr ln nht v nh nht suy hao xen vo gia cc knh bc sng.

B ghp/tch knh bc sngGhp tng: Ghp tng to b ghp knh dung lng caoGhp tng ni tip n knh (Serial) Trong phng php ny thc hin ghp n tng, mi tng ch thc hin ghp/tch mt knh bc sng. Mt v d tiu biu l b DEMUX 8 knh bc sng, ch to t cc phn t c bn l b lc TFMFGhp mt tng (Single-Stage) Tt c cc bc sng u c tch ng thi trong mt tng duy nht. V d cho cu trc ny l b lc AWG.Ghp tng theo tng bng sng (Multistage Banding): Phng php ny thc hin vi n/m tng, mi tng thc hin ghp/tch m knh bc sng thuc cng mt bng sngGhp tng an xen chn l:Tng u lm nhim v ghp/tch cc knh bc sng chn, a n tng hai. Tip theo, tng hai c th thc hin chc nng tng t nh tng mt hoc thc hin ghp/tch ring ra thnh cc knh ring l

B ghp/tch knh bc sng

Hnh 6.23. Ghp tng tng dung lng ghp/tch cc knh bc sng. (a) Ghp tng theo tng bng sng. (b) Ghp tng an xen chn l.

B chuyn mch quang Cc b chuyn mch n (Single Switch)

Hnh 6.24. Cc loi cu hnh chuyn mch quang: (a) chuyn mch On/Off (1x1); (b) chuyn mch chuyn tip (1x2) (khng nghn); (d) chuyn mch 2x2 c nghn.

B chuyn mch quangNguyn l hot ng ca cc chuyn mch nNguyn l hot ng ca cc chuyn mch n in hnh thng da trn: in-quang, quang c hc, nhit quang. Hnh 6.25 trnh by mt s nguyn l hot ng ca b chuyn mch.Nu chuyn mch thin p ca mt b khuch i quang bn dn (SOA- Semiconductor Optical Amplifier) sang hai trng thi on/off th to ra c mt chuyn mch in-quang (hnh 6.25. (a)) v mt SOA ch khuch i nh sng khi n c phn cc v hp th nh sng khi n khng c phn cc. Hnh 6.25(b) trnh by mt v d khc ca chuyn mch EO, trong t s ghp ca b ghp ng dn sng ph thuc vo in p p vo. Thay i t s ghp bng cch dng LiNbO3 ch to lp trn cng ca b ghp v LiNbO3 l loi nhin liu c ch s khc x thay i theo gi tr ca in p p vo.

B chuyn mch quangNguyn l hot ng ca cc chuyn mch nChuyn mch quang c hc hot ng da trn chuyn ng c hc ca cc linh kin quang. V d, di chuyn lng knh trong hnh 6.25(c) theo chiu dc s cho php chuyn mch mt tn hiu quang t si 2 sang si 3. Ta cng c th t c kt qu tng t khi t nh ln tr mt gng hnh cu (hnh 6.25(d)). Cc thu knh GRIN (graded-index) s lm cho vic chuyn tip nh sng ghp t/vo si quang c d dng hn. Hnh 6.25(e) trnh by v d v chuyn mch quang. Mt cp si quang ng vo chuyn t v tr ny sang v tr khc thc hin vic chuyn mch tn hiu quang.

B chuyn mch quang

Hnh 6.25. Nguyn l hot ng ca cc b chuyn mch quang: (a) chuyn mch on/off dng SOA;(b) b ghp ng dn sng ch to t LiNBO3; (c) chuyn mch dng lng knh chuyn ng; (d) chuyn mch dng gng hnh cu; (e) chuyn mch bng cch di chuyn si quang; (f) chuyn mch ng dng hiu ng FTIR; (g) chuyn mch quang-nhit s dng b giao thoa Mach-Zehnder

B chuyn mch quang Mt s tham s chnh quy nh c tnh ca cc b chuyn mch:T s tt m (extinction ratio): th hin c tnh ca b chuyn mch on/off. y l t s gia nng lng nh sng khi chuyn mch trng thi on v nng lng nh sng khi chuyn mch trng thi off. Gi tr ny cng cao cng tt, thng nm trong khong t 45 n 50 dB.Suy hao xen (insertion loss): l n v o cng sut suy hao do b chuyn mch gy ra thng c gi tr khong 0.5 dB.Nhiu xuyn m (crosstalk): t s gia cng sut ng ra c to ra bi ng vo mong mun v cng sut ng ra c to ra bi ng vo khng mong mun. Gi tr ny cng cao cng tt, thng khong 80 dB.Thi gian chuyn mch (switching time): l tham s rt quan trng. Khi s dng cc b lc hiu chnh c, thi gian chuyn mch yu cu ph thuc vo cc ng dng ca chuyn mch. Cc b chuyn mch n quang-c hc v quang-nhit c thi gian chuyn mch nm trong khong t 2 n 20 ms, trong khi cc b chuyn mch n quang-in c thi gian chuyn mch c ns.

B chuyn i bc sng B chuyn i bc sng l thit b chuyn i tn hiu c bc sng ny u vo ra thnh tn hiu c bc sng khc u ra.C bn phng php ch to b chuyn i bc sng: phng php quang-in, phng php ca quang, phng php giao thoa v phng php trn bc sng. Phng php trn bc sng l phng php ton quang, hot ng hon ton khng da vo tn hiu inB chuyn i khi c trang b trong cc cu hnh nt mng WDM gip s dng ti nguyn bc sng hiu qu hn, linh ng hn

B chuyn i bc sng To bng phng php quang-in

Hnh 6.26. Cc loi chuyn i bc sng quang in: (a) 1R; (b) 2R; (c) 3RTn hiu u vo trc ht c chuyn sang dng tn hiu in, ti to li v sau c mt b pht laser pht bc sng khc

B chuyn i bc sng Ch to bng phng php ca quang

Hnh 6.27. B chuyn i bc sng ch to theo phng php ca quang.Cc thit b ch to theo phng php ny thng thuc dng u vo thay i-u ra c nh, hoc u vo thay i-u ra thay i tu theo tn hiu d l c nh hoc c th iu chnh bc sng

B chuyn i bc sngCh to bng phng php giao thoa

Hnh 6.28. Bin i bc sng bng iu ch xuyn phas dng b khuch i quang bn dn c gn b lc Mach-Zender bn trongK thut chnh ca phng php ny chnh l iu ch cho pha. Khi cng sng mang trong b khuch i thay i cng vi tn hiu u vo, n lm thay i chit sut ca mi trng li, dn n thay i pha ca tn hiu d

B chuyn i bc sngCh to bng phng php trn bc sng Hnh 6.29. Chuyn i bc sng bng cch trn bn bc sng trong b khuch i quangPhng php ch to ny da trn hin tng trn bn bc sng, trong nu c ba bc sng f1, f2, f3 cng truyn trong si quang th theo hin tng phi tuyn tnh s xut hin sng nh hng do hiu ng phi tuyn tnh c tnh l: f1+f2-f3. ng dng cho b chuyn i bc sng khi f1 = f2 v sau cho qua b khuch i SOA. Gi s sng vo k hiu l fs v sng d l fp, b khuch i SOA c cu hnh sao cho mt trong hai bc sng sinh do hin tng FWM 2fp-fs v 2fs-fp nm trong bng thng hot ng ca tn hiu, khi ta thc hin c chc nng chuyn i bc sng.

LI KT Mot lan na em xin chan thanh cam n s hng dan cua thay giao Hoang Phu An va s giup cua cac ban sinh vien lp DHDT5LTTB a giup nhom chung em hoan thanh bai thuyet trnh nay. Nhom chung em rat mong nhan c s ong gop phan hoi t pha thay va cac ban e bai thuyet trnh hoan thien hn. Chuc thay giao doi dao sc khoe e tiep tuc nang chung em tren con ng hoc tap! Chuc cac ban trong lp thanh cong vi bai thuyet trnh cua nhom mnh!Nhom chung em xin chan thanh cam n!