Dab tsi yog fiber ntau dispersion?
Kev sib txawv ntawm cov zauv sib txawv lossis ntau hom sib txawv ntawm cov teeb liab kho qhov muag (mem tes) kis tau rau hauv optical fiber ntau ntawm kev sib txawv, thiab cov teeb liab distortion (pulse broadening) yuav zam dhau kev tshwm sim tom qab mus txog ib qho deb. Qhov tshwm sim no hu ua dispersion lossis dispersion ntawm optical fiber. Cov paib hluav taws xob xa tawm hauv cov kab hluav taws xob muaj cov kab hluav taws xob pom qhov dav, uas yog hais, qhov teeb liab hluav taws xob muaj ntau yam sib txawv. Nyob rau tib lub sijhawm, hauv multimode fiber, lub teeb liab kho qhov muag yuav raug tsim los ntawm ntau hom, uas yog hais, txhua zaus zaus kuj tseem tuaj yeem ua ob peb hom kev sib xyaw.
Optical fiber dispersion hais txog lub teeb liab cuam tshuam los ntawm ntau qhov sib txawv thiab cov hom sib txawv nrog cov sib txawv ceev. Hauv qhov kev sib txuas lus optical fiber ntau, kev faib tawm kom dav dav rau cov mem tes kho qhov muag. Thaum cov kev tawg yog qhov teeb meem loj, cov pulses kho qhov muag yuav sib tshooj, ua rau cov cim kev cuam tshuam thiab nce tus nqi yuam kev. Yog li no, kev faib 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.
Thaum lub teeb tawm nyob rau hauv qhov kho qhov muag, vim nws cov zaus tsis yog ib qho zaus, hom kev ua haujlwm tsis yog ib hom ua haujlwm, yog li qhov kev faib tawm ceev me ntsis sib txawv, uas hu ua dispersion. Yog hais tias nthwv dej yoj tes tsho yog lub xaim digital, lub dav ntawm lub teeb liab demodulated yuav nthuav dav, uas yuav ua rau muaj qhov yuam kev me ntsis thiab txwv qhov kev txhim kho ntawm cov nqi sib kis. Thaum cov tes taws los piav waveform yog cov teeb liab analog, qib tom qab kuaj pom poob qis nrog qhov nce ntawm cov teeb liab zaus, uas qhia tau hais tias tsis hloov pauv tsis hloov thiab ua kom muaj kev cuam tshuam los ntawm cov khoom siv dav. Qhov kev xa ntawm CATV teeb liab hauv optical fiber network ua rau tsis muaj kev cuam tshuam ntawm CSO thiab CTB cov cim qhia. Cov xwm txheej no yog hu ua dispersion cov yam ntxwv ntawm optical fiber, thiab cov yam ntxwv dispersion ntawm tom kawg kuj hu ua bandwidth yam ntxwv (lossis cov yam ntxwv zaus).
Fiber dispersion qhia kev tshaj tawm lub xeev ntawm cov teeb liab tawm tswv yim hauv lub fiber, uas yog hais txog lub teeb liab cuam tshuam los ntawm ntau qhov sib txawv lossis cov hom sib txawv ntawm cov cim hluav taws xob tau tshaj tawm ntawm cov khoom sib txawv. Nws mas suav nrog intermodal dispersion, chromatic dispersion thiab hom polarization dispersion.
Intermodal dispersion
Intermodal dispersion yog ib hom kev teeb liab ntsiag to mechanism hauv multimode fibers thiab lwm yam yoj hluav taws. Hauv multimode fiber, lub teeb ci nkag mus rau hauv lub fiber ntawm qhov teeb meem sib txawv ntawm lub kaum ntse ntse txhais tau tias txoj hauv kev lossis hom. Vim txoj kev sib kis sib txawv ntawm txhua hom, kev sib kis ceev (pab pawg ceev) kuj tseem sib txawv, yog li lub sijhawm sib txawv ntawm cov teeb liab kis ntawm hom mus rau optical fiber davhlau ya nyob twg. Feem ntau, qee lub teeb duab hluav taws xob yuav hla ncaj qha ntawm cov tub ntxhais (hom axial), thaum lwm tus yuav tig rov qab thiab rov los nruab nrab ntawm tus caj dab / tub ntxhais ciaj ciam thiab kis raws zigzag waveguide, raws li qhia hauv cov kauj ruam index multimode fiber ntau hauv daim duab hauv qab no. Qhov tseeb yog tias thaum lub teeb tau refracted, intermodal dispersion / hom dispersion tshwm sim. Muaj qhov cuam tshuam zoo ntawm IMD thiab txoj kev sib kis. Qhov ntawd yog hais, qhov IMD tshwm sim los ntawm hom kev txiav txim siab dua (txoj hauv kev ntev dua thaum lub tshav ntuj nkag ntawm lub kaum sab xis loj dua) yog siab dua qhov uas tshwm sim los ntawm hom kev txiav txim qis dua (txoj hauv kev luv dua thaum lub tshav nkag ntawm lub zog me lub kaum ntse ntse).
Multimode fiber ntau tuaj yeem ua raws li 17 hom qauv ntawm lub teeb tawm mus rau tib lub sijhawm, thiab nws cov hom kev sib kis yog ntau dua li ntawm ib hom fiber ntau. Qhov no yog vim hais tias ib hom fiber ntau muaj ib qho kev faib tawm ib hom, uas yog, lub teeb tawm mus raws tus tub ntxhais (hom axial) yam tsis muaj qhov cuam tshuam txog qhov ciam ciam, yog li tsis muaj kev cuam tshuam kev sib kis.
Txawm li cas los xij, qhov xwm txheej yog qhov txawv yog tias qhov ntsuas kab zauv multimode fiber siv. Txawm hais tias lub teeb tseem tshaj tawm nyob rau ntau hom, vim tias qhov ntsuas tsis zoo ntawm cov tub ntxhais, qhov kev hloov lub teeb tsis yog ib txoj kab ncaj nraim tab sis kab nkhaus, thiab qhov kev tawm ntawm lub teeb kuj hloov. Yog li ntawd, kev sib txuam nrog hom kev faib tawm tuaj yeem txo tau ntau los ntawm kev xaiv qhov tsim nyog txhawm rau txhawm rau faib tawm.
Chromatic dispersion
Chromatic dispersion yog hais txog qhov tshwm sim ntawm qhov kho qhov muag pom los ntawm kev sib txawv ntawm cov pab pawg sib txawv ntawm cov sib txawv ntawm cov khoom sib xws hauv cov hluav taws xob, nrog rau cov khoom tawg thiab cov khoom tawg.
Cov khoom tawg yooj yim yog tshwm sim los ntawm wavelength dependence ntawm refractive index ntawm cov khoom siv tseem ceeb, thaum waveguide dispersion yog tshwm sim los ntawm kev xaiv ntawm hom kev tshaj tawm tsis tu ncua ntawm cov fiber ntau (cov xov hluav taws xob, refractive index sib txawv ntawm cov tub ntxhais thiab cladding) thiab cov teeb liab wavelength. Ntawm qee qhov zaus, cov khoom tawg thiab cov khoom tawg nthwv dej tuaj yeem tso tseg ib leeg kom tau txais lub yoj ze ntawm xoom chromatic dispersion.
Qhov tseeb, chromatic dispersion tsis ib txwm ua haujlwm tsis zoo. Lub teeb tawm zuj zus ntawm qhov nrawm sib txawv hauv cov txheej txheem sib txawv los yog cov khoom siv, ua rau muaj qhov dav los yog nrawm ntawm lub teeb pulses hauv cov fiber ntau, uas ua rau nws tuaj yeem kho qhov refractive index profile los ua cov fibers rau ntau lub hom phiaj. G. 652 fiber yog ua piv txwv.
Polarization hom dispersion
Hom kev sib faib hom (PMD) qhia txog cov polarization dependence ntawm lub teeb yoj tawm hauv cov hluav taws xob fiber ntau. Muaj ob hom polarization txiav txim sib tsub sib tshuam sib luag hauv qhov tseeb fiber ntau. Qhov tsim nyog, ob hom polarization yuav tsum muaj tib lub teeb hluav taws xob yoj kev tshaj tawm, tab sis feem ntau hais lus, muaj qhov sib txawv me me ntawm ntau hom polarization qauv. Qhov no yog vim muaj qhov hloov lossis cuam tshuam ntawm qhov kub thiab txias, siab thiab lwm yam hauv cov txheej txheem tshaj tawm, uas ua rau muaj kev sib kis ceev ntawm ob hom kev hloov pauv, uas ua rau kev ncua thiab hom polarization dispersion.
Yuav ua li cas kom them nyiaj rau kev faib tawm?
Txawm hais tias fiber ntau tawg tsis tau ua kom tsis muaj zog lub teeb liab, nws ua kom luv luv ntawm kev tshaj tawm ntawm cov teeb liab sab hauv lub fiber ntau thiab ua rau cov teeb liab tsis sib haum. Piv txwv li, 1 nanosecond optical pulse ntawm lub transmitter yuav raug dav rau 10 nanoseconds ntawm lub txais, uas ua rau lub teeb liab tsis tuaj yeem txais thiab txiav txim siab ib txwm. Yog li, nws yog qhov tseem ceeb heev rau txo fiber ntau cov kev faib tawm lossis them nyiaj rau kev faib tawm hauv DWDM thiab lwm qhov kev sib kis ntev. Cov hauv qab no yuav qhia peb qhov kev siv them rau kev faib ua kom tawg thiab cov hau kev.
Kev faib tawm fiber ntau
Los ntawm kev siv dispersion them fiber (DCF) thev naus laus zis, hluav taws xob tsis zoo dispersion yuav ntxiv rau cov khoom siv fiber ntau. Piv nrog rau fiber ntau them dispersion, tus nqi dispersion ntawm cov tshuaj fiber ntau heev thiab cov dispersion yog qhov zoo, uas ua rau lub teeb faib rau hom fiber ntau txo lossis txawm ploj. Los ntawm kev ntxiv ib qho kev tsis zoo ntawm kev them rov qab fiber ntau rau nws, tag nrho cov kev tawg ntawm tag nrho cov kab fiber ntau tuaj yeem kwv yees tau xoom, thiaj li ua tiav qhov siab ceev, lub peev xwm loj thiab kev sib txuas lus ntev. Muaj peb qho kev them nyiaj rau cov khoom siv dispersion fiber ntau, suav nrog kev them nyiaj ua ntej, kev them nyiaj tom qab thiab kev them nyiaj. Dispersion compensated fiber yog dav siv nyob rau hauv kev txhim kho ntawm 1310 nm fiber txuas, uas ua rau nws khiav ntawm 1550 nm.
Fiber Bragg grating
Fiber Bragg grating (FBG) yog ib hom khoom siv sib txuam uas muaj cov tshuaj fiber ntau, uas tuaj yeem hloov kho cov tub ntxhais qhov ntsuas siab tsis pub dhau qee qhov deb. Hauv 100 km kis kab ke, cov nyhuv tawg tau txo qis dua los ntawm kev siv cov cuab yeej no. Thaum lub nqaj hla dhau cov fiber Bragg grating, yoj yoj sib ntsib qhov kev sib hloov sib txawv yuav muaj kev cuam tshuam, thiab qhov seem ntawm lub wavelength yuav txuas mus dhau los ntawm cov fiber Bragg grating raws cov fiber. Siv cov fiber ntau Bragg grating rau dispersion them nyiaj tau zoo heev, vim hais tias fiber ntau Bragg grating tuaj yeem ua ke nrog lwm cov passive fiber ntau nrog poob zoo thiab cov nqi qis. Tsis tas li, fiber ntau Bragg grating siv tsis tau tsuas yog siv dispersion foob lim, tab sis kuj raws li sensor, wavelength stabilizer ntawm lub twj tso kua mis laser thiab nqaim band wavelength faib multiplexing ntxiv / rho lim.
Them nyiaj hauv hluav taws xob
Kev them nyiaj hauv hluav taws xob (EDC) yog ib txoj kev sib txawv ntawm kev them nyiaj rau hauv kev sib txuas lus kho qhov muag los ntawm kev siv hluav taws xob (los ntawm kev sib txig sib luag), uas yog, lim hauv cov kev sib txuas lus channel kom them cov teeb liab attenuation los ntawm kev sib kis nruab nrab. Kev them nyiaj taws hluav taws xob feem ntau tau lees paub los ntawm transverse lim, uas nws cov txiaj ntsig yog qhov hnyav ntawm cov lej ntawm cov khoom ncua qeeb. Nws tuaj yeem hloov kho qhov nyhav lim tau raws li cov yam ntxwv ntawm cov teeb liab tau txais, uas yog, yoog. Kev them nyiaj hauv tshuab hluav taws xob tuaj yeem siv tib hom kab ke fiber ntau thiab ntau hom fiber ntau. Ntxiv rau, nws tuaj yeem ua ke nrog lwm cov haujlwm rau 10Gbit / S receiver IC. Nws tuaj yeem txo qhov kev xa cov nqi ntawm ib hom fiber ntau qhov system, thiab tseem nce cov kev sib kis ntawm ntau hom fiber ntau qhov uas muaj tsawg tus nqi txais khoom poob.
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