Raws li cov qauv sib txawv ntawm cov zauv refractive index, multimode fibers tuaj yeem muab faib ua cov kauj ruam-hom multimode fibers thiab maj mam-hom multimode fibers. Vim tias lawv cov ntsiab lus sib txawv ua haujlwm, muaj kev sib txawv hauv lawv cov ntawv thov.
Ua haujlwm cov ntsiab cai thiab thov cov kauj ruam hom multimode fiber
Muaj qhov kev sib cais ntawm qhov khoo zoo rau hauv qib theem fiber. Txij li lub refractive index nyob rau hauv cladding yog tsawg, uas yog hais, qhov tseem ceeb refractive index yog siab dua qhov ntawm cladding, yog li ntawd qhov refractive index ntawm qhov ciaj ciam ntawm cov tub ntxhais thiab cladding poob qis heev, yog li tsim cov kauj ruam. Rau kauj ruam hom multimode fiber ntau, lub teeb propagates raws txoj kab hluav taws xob axis raws li lub ntsiab cai ntawm tag nrho cov kev xav. Ntawm lawv, cov kab sib kis mus rau hauv cov hluav taws xob fiber ntau nrog cov xwm txheej sib txawv cov sib txawv. Txawm hais tias qhov teeb meem sib kis mus rau ntawm tib lub nrawm ntawm lub tswv yim kawg, nws siv sijhawm sib txawv kom ncav cuag cov zis kawg, ua rau lub sijhawm tawg, uas ua rau muaj qhov cuam tshuam loj ntawm cov mem tes, uas yog qhov thiaj li hu ua inter-mode dispersion. Cov.
Vim tias kev sib txuas xov tooj digital siv lub teeb pulses kom teeb liab raws optical fiber, modal dispersion ua rau cov pulses loj dua thiab kis tau thaum lawv taug kev nrog lub fiber. Qhov ntau hom fiber ntau mus ncig cov pulses ntau nws yuav tsum taug kev. Qhov no kuj zoo heev txwv txoj kev bandwidth ntawm kauj ruam - hom multimode fiber. Ntxiv mus, sib cuam tshuam kev sib cais hom tsis tsim nyog rau kev sib txuas lus fiber ntau. Rau cov kho qhov muag digital fiber, thaum kev tawg yog qhov hnyav, nws yuav ua rau sib tshooj ntawm cov pulses, uas yuav ua rau ISI thiab nce BER. Yog li no, kev tawg tawm ntawm cov hluav taws xob optical fiber tsis tsuas yog cuam tshuam kev xa cov peev xwm ntawm cov hluav taws xob fiber ntau, tab sis kuj txwv cov relay kev deb ntawm kev sib txuas lus fiber ntau. Vim tias cov kev txwv no, kauj ruam fiber ntau hom feem ntau siv ntawm tus nqi pheej yig hauv kev sib txuas lus dhau ntawm luv nrug (tsis pub dhau ob peb kis lus mev) thiab ntawm qhov nrawm (qis dua 8Mb / s).
Ua haujlwm cov ntsiab cai thiab daim ntawv thov ntawm tapered multimode fiber
Qhov ntsuas txhim kho ntawm cov kab xev fiber ntau sib txawv tsis tu ncua raws li qee txoj cai thiab tsis yog ib qho tsis sib xws. Qhov ntsuas kev txhim kho ntawm cov kab xev fiber ntau yog qhov loj tshaj plaws ntawm lub tshuab fiber ntau thiab qhov tsawg tshaj plaws ze rau qhov ciam ciam av. Hauv lwm lo lus, qhov ntsuas kev txhim kho ntawm daim kab xev fiber ntau poob qis nrog qhov nce ntawm qhov tseem ceeb vojvoog. Hauv kev muaj fiber ntau, qhov hloov pauv ntawm qhov ntsuas qhov hloov ua rau muaj qhov cuam tshuam, tab sis tsis yog tag nrho qhov kev cuam tshuam, thiab thaum lub teeb xa mus rau qhov chaw muaj ciam (nrog rau qhov tsawg kawg nkaus refractive index), lub fiber yuav refracted rov qab mus rau lub fiber axis.
Rau cov kab xev fiber ntau, lub teeb mus rau pem hauv ntej hauv daim ntawv ntawm sinusoidal oscillation. Ib yam li cov kauj ruam hom multimode fiber ntau, qhov sib txawv lub teeb tawm mus raws txoj kev sib txawv hauv cov graded multimode fiber. Ntawm lawv, lub teeb tawm ntawm qhov sib txawv yog txawv, vim hais tias lub teeb tus nqi yuav hloov nrog lub refractive index ntawm lub fiber fiber. Qhov kev taws teeb deb tshaj yog los ntawm lub tshuab fiber ntau, qhov ceev dua yuav tau. Hauv lwm lo lus, qhov me me qhov ntsuas refractive, qhov ntau dua qhov kev faib tawm. Nyob rau tib lub sijhawm, tapered multimode fiber muaj qhov ua kom pom tus kheej, thiab cov duab sib dhos ntawm qhov sib txawv cov ces kaum yuav tsom rau tib lub sijhawm, thiab lub sijhawm qeeb ntawm cov duab hluav taws xob yog kwv yees sib npaug. Vim tias qhov no, qhov kev sib txuam-kev cuam tshuam tau txo ntau heev, yog li cov kab xev ntawm tapered multimode fiber ntau dua li cov kauj ruam multimode fiber. Raws li qhov tshwm sim, feem ntau multimode fibers niaj hnub no yog tapered. Piv nrog cov kauj ruam multimode fibers, tapering multimode fibers feem ntau siv hauv kev sib txuas lus nruab nrog nruab nrab nrug (10 ~ 20 tabs) thiab tus nqi sib kis tau zoo (34 ~ 140Mb / s), uas ua rau tus nqi ntau dua.
