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1/Nhc ca h thng thng tin quang.

-kh u ni, i hi k thut cao

- cn c cc ng dy , cp ngun cho tip pht.

- Cn cc phng thc chnh li mi (cp)

2/Vai tr v chc nng ca con tr trong h thng SDH.

K thut con tr dc s dng ng b ha. Con tr ny dc s dng ch th s thay i mi quan hkhi VC dc ng chnh theo tn hiu TU v AU hoc khi VC ch th a ch xut pht trong mt khung TUhoc AU v im xut pht ca n b thay i.

+Cc loi con tr, phm vi, ng dng ca n.

C 2 loi pointer:

AU pointer gm: AU-4PTR,AU-31PTR, AU-32PTR.

AU-4PTR v AU-3PTR xut hin trn v tr ca AU PRT

TU Pointer gm: TU-31PTR,TU-32PTR, TU 1X/TU-2X PTR

TU -3PTR dc b tr trn nh ca hng u tin trong phm vi khung TU-3

+Cho v d v hot ng ca con tr AU-4MP.

AU-4 =VC-4 + AU PTR c cu trc (9x261) bytes + 9byte PTR. AU PTR c chc nng ghi li miquan h phase gia khung truyn dn v cc VC tng ng. AU-PTR dc gn khng c nh vo 9 byteu tin ca hng th 4 trong khung STM-1 c chc nng nh u cc AU.

3/Trnh by 1 gii php trong vic nng cao tc truyn trong TTQ.

H thng cp quang xuyn bin hin hay s dng cng ngh ghp knh theo bc sng c cc b khuchi quang si EDFA mc chui. Trong tng lai gn, nhu cu thng tin lin lc tng cao th s knh cng

tng, dung lng ngy cng ln cho t s tn hiu quang trn nhiu (OSNR) gim xung, cht lng tnhiu khng t yu cu. Gii php hiu qu cho vn ny l t thm cc b khuch i Raman, tothnh b ghp khuch i ghp lai HFA trn ng truyn. L do l v khng phi b hoc lp thm ccEDFA m ch cn t thm cc b Raman vo v tr thch hp trong cc trm lp c sn. B khuch iRaman dc t trc b khuch i EDFA, ng vai tr nh 1 b khuch i nhiu thp. N khng yucu mc tn hiu vo cao nn gim c hiu ng phi tuyn. ng thi tn hiu vo b EDFA cng khnggim xung mc qu thp do c khuch i Raman nng mc cng sut tn hiu vo ca EDFA, lmcho OSNR cui tuyn dc ci thin.

4/Hy gii thch s trang 10 (ti liu SDH ca thy?).

-Cc d liu dc ghp vo container theo nguyn l ghp bit hoc byte, a vo n v nh nht trongkhung truyn dn l container. Vi tc truyn dn khc nhau (C-11 1,544 ; C-12 2,048;C-2 6.312; C-3

34,368; C-4 139.264 Mb/s). ty theo kch thc ca lung data u vo m gn container C tng ng.

- sau container C s dc kt hp vi POH to thnh khung hon chnh (VC) truyn n u thu. POHs mang thng tin b tr, gim st v bo tr ng truyn ng thi thng bo v tr m container s dctruyn n. POH dc gn vo u khung v VC cng ty loi tng ng vi kch thc ca C.

-Trc khi chuyn n STM-1 dc pht i cc cp VC cp thp s c ghp vo mt VC cp cao hn.TU=VC + Pointer. Pointer to ra mi lin kt gia phase ca cc VC, c ghp theo vo VC ti mt vtr c nh trong VC v thng bo s bt u vo VC . Tng ng vi VC, TU cng c nhiu bc.

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-sau khi x l pointer cc TU s c ghp thnh cc nhm khi nhnh lung TUG. TUG-2 =3.TU-12=4.Tu-1=1.TU2.. cc TU sp xp theo nguyn l xen tng byte to thnh TUG. Lu l ta c th ghp7 TUG-2 dc TUG-3. Cc TUG2,TUG3 sau s dc ghp vo to thnh VC-3, VC-4. Ring C-3, C-4l cc lung ln nn ko cn ghp TU cng nh TUG m ch cn POH l c th to thnh VC-3,VC-4.

- T VC-3,VC-4 ta thm gi tr con tr thnh n v qun l AU. Gi tr con tr AU ghi li mi quanh phase gia khung truyn dn v cc VC tng ng. AU c th cu thnh t: 1xVC-4 hoc 1xVC-3.

- Sau cc AU dc sp xp theo nguyn l xen byte to thnh AUG. AUG dc to thnh t 1xAU-4 hoc3xAU-3. AUG c cu trc khung ging nh cu trc khung STM-1 khi cha c khung mo u SOH.SOH cha cc thng tin qun l truyn dn.

- Khung truyn dn STM-N c to ra bng cch ghp NxAUG. Khung lc ny s dc gn thm mo uon SOH. Khi ghp NxAUG thnh STM-N th phn ti tin payload s gm VC-4 to thnh. Vicghp knh s thc hin thoe nguyn l byte xen byte NxVC-4. Sau khi thc hin byte xen cc AU Pointers dc sp xp vo hng th 4 ca khung. STM-N c th c th t dc bng cch ghp N cp STM-1 theophng thc ghp tng byte to thnh cc cp.

5/ Ngha ca khu s trong TTQ. Tnh khu s ca si quang chit sut v l n1, chit sut si ln2.

Khu s ca si quang c nh ngha: NA= sin max

Vi max: gc m s phn x ton phn s xy ra trong li ch i vi nhng tia sng c gc ti u siquang nh hn max

Thng s NA c ngha rt quang trong thng tin quang. Cho bit iu kin a nh sng vo siquang. y l thng s c bn nh hng n hiu sut ghp nh sng ca ngun quang vo siquang.

Tnh khu s:

Chng minh:

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Ta c: n0.sin max = n1.sin (90-c) vi n0=1

sin (90-c) = cos c =

li c: n1.sin = n2.sin 90 => sin c= n2/n1

Sin max= n1.

6/ xut h thng TTQ c nhiu u im nht. Gii thch.

Trong thc t si quang l phng tin truyn dn thng tin hiu qu v kinh t nht dang c hin nay.V:

Trc ht, v c bng thng ln nn n c th truyn 1 khi lng thng tin ln nh cc tn hiu mthanh, d liu v cc tin hiu hn hp thng qua 1 h thng c c ly n 100 GHz/km. Tng ng, bngcch s dng si quang, mt khi lng ln cc tn hiu m thanh v hnh nh c th dc truyn n nhnga im cch xa hng 100km m khng cn n cc b ti to.

Th hai, si quang nh nh v khng c xuyn m. Do vy, chng c th c lp t d dng cc thnhph, tu thy, my bay v cc ta nh cao tng khng cn phi lp thm cc ng ng v cng cp.

Th ba, v si quang dc ch to t cc cht in mi phi dn nn chng khng chu nh hng bi cannhiu ca sng in t v ca xung in t. V vy chng c th s dng truyn dn m khng cting n. iu c ngha l n c th lp t cng vi cp in lc.v.v.

Th t, do nguyn liu ch yu sn xut si quang l ct v cht do l nhng th r hn ng nhiu nn n kinh t hn cp ng trc nhiu. Gi thnh ca si quang s gim nhanh mt khi cng ngh midc a ra. Ngoi ra, do c trng l c tn tht thp gi thnh lp t ban u cng nh gi thnh bodng v sa cha thp bi v chng cn t cc b ti to hn.

Ngoi nhng u im nu trn, si quang c an ton, bo mt cao, tui th di v c kh nng khng mi trng ln. N cng d bo dng, sa cha v c tin cy cao. Hn na, n khng b r rtn hiu v d ko di khi cn v c th ch to vi gi thnh thp.