Optical fiber dispersion yog qhov nthuav dav ntawm lub teeb pulses thaum lawv taug kev los ntawm fiber ntau, tshwm sim los ntawm cov teeb liab sib txawv tuaj txog ntawm lub receiver ntawm lub sijhawm sib txawv me ntsis. Hauv kev sib txuas lus fiber ntau optic, qhov kev nthuav dav no txo cov teeb liab kom pom tseeb, txwv tsis pub cov ntaub ntawv tuaj yeem mus deb npaum li cas, thiab ua rau nws nyuaj rau cov neeg txais xov xwm qhia ib qho me ntsis los ntawm lwm qhov.
Tab sis to taub dispersion tsis yog hais txog physics xwb. Cov lus nug tiag tiag ntawm engineering yog: thaum twg dispersion dhau los ua qhov teeb meem koj xav tau los daws? Cov lus teb yog nyob ntawm hom fiber ntau, txuas ntev, cov ntaub ntawv tus nqi, kev khiav hauj lwm wavelength, thiab cov qauv qauv uas koj lub cev siv. Ib qho 100-meter multimode txuas hauv ib lub chaw khaws ntaub ntawv yuav tsis xav tau kev tswj xyuas kev tawg. Ib 200-kmtib - hom fiber ntautxuas nqa 100G tsheb yuav luag yeej yuav.
Dab tsi yog Optical Fiber Dispersion?
Optical fiber dispersion yog hais txog txoj kev uas tus mem tes kis tau tawm thaum nws nthuav tawm los ntawm cov tub ntxhais fiber ntau. Qhov kev sib kis tshwm sim vim hais tias ntau yam ntawm cov teeb liab kho qhov muag - seb qhov sib txawv wavelengths, txawv spatial hom, los yog txawv polarization xeev - tsis yog txhua txhua mus raws nraim tib yam ceev.
Qhov no tseem ceeb vim tias kev sib txuas lus kho qhov muag digital nyob ntawm qhov huv, zoo -siv pulses. Thaum pulses nthuav dav txaus los sib tshooj nrog lawv cov neeg nyob ze, tus txais tsis tuaj yeem paub qhov txawv ntawm tus kheej cov khoom ntseeg tau. Qhov tshwm sim no, hu ua inter-cim cuam tshuam (ISI), degrades me ntsis yuam kev tus nqi (BER) thiab txo cov kis tau tus mob. Raws li covITU-T G.652 kev pom zoo, uas txhais cov txheej txheem ib zaug - hom fiber ntau tsis, chromatic dispersion kev pab yog qhov tseem ceeb hauv kev tsim qauv rau siab - ntsis- cov ntawv thov.
Dispersion vs. Attenuation: Ib qho kev txawv txav tseem ceeb
Ib qho ntawm qhov yuam kev tshaj plaws hauv kev ntsuas kev sib txuas ntawm fiber ntau yog qhov tsis meej pem dispersion nrogattenuation. Lawv yog cov feem ntau txawv impairments:
Attenuationtxo optical zog. Nws yog qhov poob ntawm lub teeb liab lub zog dhau qhov deb, ntsuas hauv dB / km.Dispersiondistors teeb liab lub sij hawm. Lub teeb liab dispersed tseem tuaj yeem nqa lub zog txaus los kuaj pom, tab sis nws cov pulses tau smeared nyob rau lub sijhawm, ua rau cov ntaub ntawv nyeem tsis tau.
Ib qho kev sib txuas ntawm fiber ntau tuaj yeem dhau los ntawm kev siv nyiaj siv hluav taws xob kho qhov muag nrog cov paj zoo nkauj thiab tseem ua tsis tiav vim tias cov mem tes ntau dhau. Tias yog vim li cas cov kws paub txog kev paub txog kev ntsuas ob lub zog siv nyiaj txiag thiab cov nyiaj txiag tawg thaum tsim qhov txuas. Kev nkag siabinsertion poob thiab rov poobyog ib qho tseem ceeb, tab sis nws tsuas yog npog lub hwj chim ntawm qhov sib npaug.
Dab tsi ua rau Dispersion hauv Optical Fiber?
Dispersion tshwm sim thaum twg cov khoom sib txawv ntawm cov teeb liab kho qhov muag muaj qhov sib txawv ntawm kev nthuav tawm qeeb. Cov txheej txheem tshwj xeeb yog nyob ntawm tus qauv tsim fiber ntau thiab cov yam ntxwv ntawm lub teeb liab, tab sis lub hauv paus ua rau poob rau hauv peb pawg:
Txoj kev sib txawv ntawm hom.Nyob rau hauv multimode fiber, lub teeb mus raws ntau txoj kev spatial (hom) los ntawm cov tub ntxhais. Txhua hom ua raws li qhov sib txawv me ntsis, uas txhais tau hais tias lawv tuaj txog ntawm tus txais lub sijhawm sib txawv. Qhov no yog lub dominant dispersion mechanism nyob rau hauvmultimode fiber ntau systems.
Wavelength -nyob ntawm qhov nrawm.Txawm tias nqaim -linewidth laser qhov chaw emits lub teeb hla ib tug me me ntawm wavelengths. Vim hais tias cov iav refractive index sib txawv nrog wavelength - ib qho cuab yeej piav qhia los ntawm Sellmeier equation - txawv spectral Cheebtsam mus ntawm txawv speeds. Qhov no yog thawj qhov kev faib tawm hauv ib qho - hom fiber ntau ntawm kev khiav hauj lwm wavelengths.
Polarization- nyob ntawm ncua sij hawm.Tiag tiag optical fibers yeej tsis zoo kawg nkaus symmetrical. Kev ntxhov siab, khoov, thiab kev tsim khoom tsis zoo ua rau muaj kev cuam tshuam, uas txhais tau hais tias ob qho tib si orthogonal polarization xeev ntawm kev coj ua lub teeb pom kev sib txawv me ntsis thiab tuaj txog ntawm lub sijhawm sib txawv.
Main Hom Optical Fiber Dispersion
Modal Dispersion (Intermodal Dispersion)
Modal dispersion tshwm sim thaum ntau hom kev coj ua hauv ntau hom fiber ntau propagate nrog cov pab pawg sib txawv. Hauv kauj ruam -index multimode fiber ntau, qhov sib txawv ntawm txoj kab ntev ntawm qhov qis tshaj - xaj hom (mus ncig ze ntawm axis) thiab siab tshaj - hom kev txiav txim (thov tawm ntawm ciam teb cladding ntawm cov kaum sab xis) tuaj yeem yog qhov tseem ceeb. Rau ib kauj ruam -index fiber ntau nrog ib tug core refractive index ntawm 1.48 thiab tus lej aperture ntawm 0.3, intermodal ncua tuaj yeem tshaj 50 ns / km.
Qib -index multimode fiber ntau tau tsim tshwj xeeb los txo qhov teeb meem no. Los ntawm shaping lub refractive index profile kom siab dua - kev txiav txim hom mus sai dua nyob rau hauv lub cladding, graded -index designs txo modal dispersion los ntawm ib tug mus rau ob qhov kev txiav txim ntawm qhov ntau. Qhov no yog vim li cas niaj hnub cov ntaub ntawv chaw txuas txuas siv ntau dhauOM3, OM4, lossis OM5 qib -index multimode fiberes tsis yog kauj ruam -index designs.
Modal dispersion yog qhov tseem ceeb tshem tawm hauv ib qho - hom fiber ntau, uas tsuas yog txhawb LP01 hom tseem ceeb xwb. Qhov ntawd yog qhov laj thawj tseem ceeb ib zaug - hom fiber ntau yog siv rau ntev - nrug thiab siab dua - kis ceev.
Chromatic Dispersion
Chromatic dispersion feem ntau yog qhov tseem ceeb tshaj plaws dispersion hom nyob rau hauv ib qho - hom fiber ntau tshuab. Nws yog kev sib koom ua ke ntawm ob lub cev mechanisms:
Khoom siv dispersiontshwm sim vim qhov refractive index ntawm silica iav hloov nrog wavelength. Qhov kev sib raug zoo no yog tus cwj pwm zoo thiab txhais tau hais tias luv luv wavelengths feem ntau mus qeeb dua qhov ntev wavelengths nyob rau hauv ib txwm dispersion regime (hauv qab xoom-dispersion wavelength), thiab qhov opposite nyob rau hauv lub anomalous regime.
Waveguide dispersiontshwm sim vim hais tias cov fiber ntau geometry cuam tshuam li cas lub teeb yog confined. Qhov feem ntawm lub hwj chim kho qhov muag mus rau hauv lub hauv paus piv rau cov cladding nyob ntawm lub wavelength, uas qhia txog ib qho ntxiv wavelength- nyob ntawm cov nyhuv propagation. Cov kws tsim qauv tuaj yeem tsim cov qauv waveguide dispersion los ntawm fiber ntau tsim - qhov no yog li casdispersion-hloov thiab tsis yog-zero dispersion-hloov fibersua tiav lawv cov yam ntxwv hloov pauv dispersion.
Rau tus qauv ib zaug - hom fiber ntau (ITU-T G.652), xoom- dispersion wavelength ntog ze 1310 nm. Ntawm qhov siv 1550 nm kis tau tus mob qhov rai, chromatic dispersion coefficient yog kwv yees li +17 ps/(nm·km), raws li sau tseg hauvCorning SMF-28 fiber ntau specification. Tshaj li 100 km txuas, uas sib sau ua ke mus txog kwv yees li 1700 ps / nm - txaus los cuam tshuam lub teeb liab 10 Gbps yog tias tshuav tsis them nyiaj.
Polarization Hom Dispersion (PMD)
Polarization hom dispersion tshwm sim los ntawm cov pab pawg sib txawv ncua sij hawm (DGD) ntawm ob lub orthogonal polarization xeev ntawm lub hauv paus hom. Tsis zoo li chromatic dispersion, uas yog kev txiav txim siab thiab ruaj khov, PMD yog stochastic - nws txawv nrog lub sij hawm, qhov kub thiab txias, thiab mechanical stress ntawm fiber.
PMD tau teev tseg raws li kev txheeb cais. Rau cov fibers niaj hnub ua raws li ITU-T G.652.D, PMD txuas tus nqi tsim feem ntau qis dua 0.1 ps/√km. Qhov no yuav zoo li me me, tab sis ntawm 40 Gbps thiab siab dua, qhov twg lub sij hawm me ntsis poob mus rau 25 ps lossis tsawg dua, txawm tias PMD sib xyaw ua ke yuav cuam tshuam. Raws li kev lag luam tsim cov txheej txheem, qhov siab tshaj plaws ntawm DGD yog feem ntau txog 10% ntawm lub sijhawm me ntsis.
Rau cov tshuab khiav ntawm 10 Gbps dhau qhov kev ncua deb, PMD tsis tshua muaj qhov txwv nrog cov fiber ntau niaj hnub. Ntawm 40 Gbps thiab 100 Gbps, PMD- paub tsim qauv - suav nrog kev xaiv fiber ntau, txoj kev engineering, thiab receiver-sab sib npaug - dhau los ua ib feem ntawm kev coj ua.
Sib piv Dispersion Types at a Glance
| Hom Dispersion | Qhov Tseem Ceeb | Feem ntau cuam tshuam Fiber / System | Cov nyhuv tseem ceeb | Kev Txom Nyem Tseem Ceeb |
|---|---|---|---|---|
| Modal dispersion | Ntau hom nrog txoj kev sib txawv | Multimode fiber ntau (theem-index phem tshaj, qib-index zoo dua) | Pulse kis los ntawm intermodal ncua | Siv ib qho - hom fiber ntau; siv qib-index MMF; tswj kev tso tawm |
| Chromatic dispersion | Wavelength -dependent refractive index thiab waveguide effect | Tib - hom fiber ntau, tshwj xeeb tshaj yog ntev -haul thiabWDM systems | Pulse broading thiab inter{0}}cim cuam tshuam | DCF / DCM, fiber ntau Bragg grating, DSP / EDC, fiber ntau thiab wavelength xaiv |
| Khoom siv dispersion | Wavelength -nyob ntawm qhov ntsuas qhov ntsuas ntawm silica | Cheebtsam ntawm chromatic dispersion nyob rau hauv tag nrho cov silica fibers | Spectral Cheebtsam cais raws sijhawm | Fiber tsim, kev npaj wavelength |
| Waveguide dispersion | Fiber geometry thiab hom confinement | Engineered ib - hom fibers (DSF, NZ-DSF) | Hloov tag nrho chromatic dispersion profile | Fiber profile engineering, dispersion - hloov fiber ntau tsim |
| PMD | Birefringence los ntawm fiber ntau asymmetry thiab kev ntxhov siab | Siab -ceev ib leeg- hom tshuab (Ntau dua lossis sib npaug li 40 Gbps) | Random, lub sij hawm -pulse distortion | Tsawg-PMD fiber ntau, PMD them nyiaj, sib npaug DSP sib npaug |
Dab tsi Fiber Links feem ntau cuam tshuam los ntawm Dispersion?
Multimode Fiber Links: Modal Dispersion Dominates
Hauvmultimode fiber ntausystems - feem ntau yog siv rau luv luv - mus txog cov ntawv thov hauv cov chaw zov me nyuam, cov chaw lag luam LANs, thiab cov pob txha hauv tsev - modal dispersion yog thawj bandwidth limiter. Lub fiber ntau modal bandwidth, nyob rau hauv MHz·km, txiav txim siab npaum li cas deb thiab ceev npaum li cas koj yuav kis tau ua ntej mem tes sib tshooj yuav ua tsis tau.
Piv txwv li, OM3 fiber ntau muaj qhov ua tau zoo ntawm kev siv bandwidth ntawm 2000 MHz ·km ntawm 850 nm nrog laser - optimized launch, txhawb 10 Gbps txog li 300 meters. OM4 txuas qhov ntawd mus rau kwv yees li 400 meters. Chromatic dispersion kuj muaj nyob rau hauv multimode fiber ntau, tab sis cov teebmeem modal yog yuav luag ib txwm muaj kev cuam tshuam ntawm qhov kev ncua deb.
Tib -Mode Fiber Links: Chromatic Dispersion thiab PMD
Thaum modal dispersion raug tshem tawm los ntawm kev siv ib zaug - hom fiber ntau, chromatic dispersion yuav muaj kev txhawj xeeb ntxiv. Ntawm ib qho luv luv - hom kev sib txuas (ob peb mais), cov chromatic dispersion feem ntau yog nyob rau hauv qhov kev kam rau siab rau 10G thiab hauv qab no. Raws li qhov kev ncua deb nce mus rau kaum lossis ntau pua mais, tshwj xeeb tshaj yog ntawm cov ntaub ntawv tus nqi ntawm 10 Gbps thiab siab dua, kev tswj kev tawg yuav tsim nyog.
Hauv - ntev thiaboptical thauj network (OTN)systems, chromatic dispersion tebchaw tshaj txhua mais. A 400 km txuas ntawm G.652 fiber ntau ntawm 1550 nm accumulates roughly 6,800 ps / nm ntawm chromatic dispersion. Yog tias tsis muaj kev them nyiaj, qhov kev sib cais ntawd yuav ua rau txawm tias 2.5 Gbps teeb liab tsis tuaj yeem rov qab los.
PMD dhau los ua qhov cuam tshuam feem ntau ntawm 40 Gbps thiab siab dua, lossis ntawm cov nroj tsuag fiber ntau uas PMD coefficient yuav tshaj 0.5 ps / √km. Niaj hnub nimno fibers muaj ntau nruj PMD specifications, thiab coherent receivers nrog DSP tuaj yeem ua siab ntev PMD ntau dua li cov qauv ncaj qha - kuaj xyuas cov tshuab.
DWDM Systems: Txhua qhov cuam tshuam tsis zoo
Hauv ntom wavelength- faib multiplexing (DWDM) cov kab ke nqa 40, 80, lossis ntau txoj hauv kev hla C-band, kev tswj kev sib cais tsis yog xaiv tau. Txhua tus channel zaum ntawm qhov sib txawv wavelength thiab sib sau ua ke me ntsis sib txawv ntawm chromatic dispersion vim yog txoj kab nqes dispersion. Qhov no txhais tau hais tias ib -channel them nyiaj yuav xav tau, tsis yog ib qho kev kho ntau rau tag nrho pawg.
Tsis tas li ntawd, hauv DWDM systems, kev sib cuam tshuam ntawm chromatic dispersion thiab fiber ntau nonlinearities (tus kheej-phase modulation, cross-theem modulation, plaub-wave mixing) tsim teeb meem kev ua kom zoo dua. Cov neeg tsim qauv feem ntau txhob txwm ua kom muaj qhov seem seem me me ntawm ib ntu los txhawm rau tsis muaj kab sib txuas lus - uas yog vim li cas "zero dispersion txhua qhov chaw" tsis yog lub hom phiaj tsim.
Optical Fiber Dispersion Compensation Methods
Fiber xaiv thiab Wavelength Planning
Txoj hauv kev tseem ceeb tshaj plaws los tswj kev sib cais yog ua kom raug xaiv ua ntej cov khoom siv kho vajtse ntxiv. Qhov no suav nrog xaiv qhov tsim nyog fiber ntau thiab kev ua haujlwm wavelength rau daim ntawv thov.
Rau kev xa tawm tshiab, tus qauv G.652.D ib leeg- hom fiber ntau tseem yog qhov kev xaiv ntau tshaj plaws rau kev siv metro thiab ntev -chaw networks. Rau ultra-ntev-haul submarine lossis cov kev sib txuas hauv av, G.654.E qis-tsis muaj fiber ntau yuav raug teev tseg. Hauv cov tes hauj lwm qub uas G.653 dispersion{10}}hloov fiber ntau tau teeb tsa, qhov ze-zero dispersion ntawm 1550 nm yog qhov zoo rau ib leeg-channel systems tab sis tau dhau los ua kev lav phib xaub rau DWDM vim kev txhim kho plaub-yoj sib xyaw - ib zaj lus qhia uas txhawb nqa qhov tseem ceeb.
Kev npaj wavelength kuj tseem ceeb. Kev khiav haujlwm zero-dispersion wavelength txo qis chromatic dispersion tab sis tuaj yeem ua rau muaj kev cuam tshuam tsis zoo. Kev khiav hauj lwm ntxiv los ntawm xoom dispersion tso cai rau nonlinear tsuj tab sis yuav tsum tau them nyiaj. Tsis muaj ib qho "zoo tshaj" wavelength - txoj kev xaiv yog nyob ntawm qhov system architecture.
Dispersion Compensating Fiber (DCF) thiab Dispersion Compensating Modules (DCM)
Dispersion compensating fiber yog ib qho tshwj xeeb fiber engineered kom muaj qhov tsis zoo chromatic dispersion coefficient, feem ntau nyob rau hauv thaj tsam ntawm −80 txog −120 ps / (nm·km) ntawm 1550 nm. Los ntawm kev ntxig qhov ntev ntawm DCF rau hauv qhov txuas, qhov sib xyaw ua kom zoo ntawm qhov sib txuas ntawm fiber ntau tuaj yeem raug offset. Hauv daim ntawv ntim, qhov no yog hu ua dispersion compensating module (DCM).
Raws li kev siv tswv yim: txhawm rau txhawm rau 80 km ntawm tus qauv G.652 fiber ntau (uas suav txog kwv yees li +1, 360 ps / nm ntawm dispersion ntawm 1550 nm), kwv yees li 14 km ntawm DCF nrog qhov sib txawv ntawm −95 ps / (nm·km) yog xav tau, raws li tau sau tseg hauvScienceDirect encyclopedia nkag ntawm DCF.
DCF yog qhov ua tau zoo thiab zoo- pov thawj, tab sis nws qhia txog kev lag luam tawm - tawm. Cov fiber ntau ntxiv ntxiv qhov poob (feem ntau yog 0.5–0.7 dB / km rau DCF, piv rau 0.2 dB / km rau kev sib kis fiber ntau), uas tej zaum yuav xav tau kev nthuav dav ntxiv thiab txo qis cov teeb liab kho qhov muag - rau - suab nrov piv. DCF kuj tseem muaj qhov chaw me me dua li cov qauv fiber ntau, uas ua rau nws muaj kev cuam tshuam ntau dua rau cov teebmeem uas tsis yog-linear. Cov kev lag luam no-offs raug soj ntsuam siv daim duab ntawm qhov tsim nyog (FOM), txhais tau tias yog qhov sib piv ntawm kev sib faib coefficient rau attenuation.
Chirped Fiber Bragg Gratings (FBG)
Lub chirped fiber ntau Bragg grating compensates dispersion los ntawm kev xav txog txawv wavelengths los ntawm txawv txoj hauj lwm raws grating, tsim ib tug wavelength - nyob ntawm ncua sij hawm. Qhov luv luv wavelengths tuaj yeem cuam tshuam ze rau pem hauv ntej ntawm grating thaum lub wavelengths ntev dua mus tob dua ua ntej yuav cuam tshuam, lossis rov ua dua. Qhov tshwm sim yog ib pawg tswj tau ncua uas tuaj yeem cuam tshuam chromatic dispersion.
Piv nrog rau DCF, FBG-raws li cov nyiaj them poob haujlwm yog compact, muaj qhov poob qis dua, thiab qhia txog qhov tsis zoo ntawm qhov tsis sib xws, raws li tau piav qhia hauvRP Photonics encyclopedia ntawm kev them nyiaj dispersion. Txawm li cas los xij, lawv tuaj yeem raug kev txom nyem los ntawm pab pawg qeeb ripple - me me lub sij hawm hloov pauv hauv cov yam ntxwv qeeb - uas tuaj yeem ua rau muaj teeb meem cuam tshuam. Kev tsim khoom niaj hnub no tau txo qhov teeb meem no ntau, tab sis nws tseem yog ib qho kev txiav txim siab rau kev ua haujlwm siab -.
Electronic Dispersion Compensation (EDC) thiab Digital Signal Processing (DSP)
Tsis yog txhua qhov kev them nyiaj dispersion tshwm sim hauv qhov chaw kho qhov muag. Kev them nyiaj hluav taws xob dispersion thiab cov teeb liab ua tiav ntawm lub receiver tuaj yeem sib npaug ntau qhov kev cuam tshuam los ntawm fiber ntau dispersion.
Nyob rau hauv niaj hnub coherent optical systems - 100G, 200G, 400G, thiab dhau ntawm - DSP-raws li kev them nyiaj yog ib feem tseem ceeb ntawm cov receiver architecture. Coherent receivers rov qab ob qho tib si lub amplitude thiab theem ntawm lub teeb liab kho qhov muag, uas muab lub DSP cav txaus cov ntaub ntawv rau digitally thim rov qab chromatic dispersion, PMD, thiab lwm yam linear impairments. Qhov no yog ib qho laj thawj uas vim li cas kev sib koom ua ke 100G tshuab feem ntau tuaj yeem ua haujlwm ntau dua txhiab mais ntawm G.652 fiber ntau yam tsis muaj kev cuam tshuam cov khoom siv kho qhov muag inline.
Rau qhov ncaj qha - kuaj pom cov tshuab ntawm 10G, kev sib npaug hauv hluav taws xob (pub- kev sib npaug rau pem hauv ntej, qhov siab tshaj plaws- kev kwv yees ua ntu zus) tuaj yeem ncua kev sib cais- txwv mus txog, tab sis nrog kev txhim kho me ntsis ntau dua li DSP coherent. Thaum txhim kho cov kev sib txuas qub, kev xaiv ntawm kev ntxiv cov nyiaj kho qhov muag (DCM) thiab hloov kho mus rau acoherent transceivernrog tsim -hauv DSP nyob ntawm tus nqi, kev xav tau kev loj hlob ntawm cov tsheb thauj mus los, thiab cov khoom siv hluav taws xob uas twb muaj lawm.
Vim li cas "Zero Dispersion" Tsis Yog Lub Hom Phiaj
Cov kws tsim kho tshiab rau fiber ntau optics qee zaum xav tias qhov txuas zoo tshaj plaws yuav muaj xoom net dispersion txhua qhov chaw. Hauv kev xyaum, qhov ntawd feem ntau tsis yog lub hom phiaj tsim zoo tshaj plaws. Muaj ob qho laj thawj:
Ua ntej, nyob rau hauv WDM systems, kev khiav hauj lwm zero dispersion txhim khu tej yam uas tsis yog-linear impairments - tshwj xeeb tshaj yog plaub-wave mixing - uas yuav ua rau crosstalk ntawm raws. Kev tswj hwm qhov nruab nrab ntawm kev sib cais hauv zos hauv txhua qhov kev sib tw ua rau cov teebmeem no. Tag nrho cov khoom tawg ua ke yog tom qab ntawd them nyiaj rau qhov kawg ntawm qhov txuas lossis ntawm qhov chaw them nyiaj raws sijhawm.
Qhov thib ob, overcorrecting dispersion tuaj yeem qhia nws cov teeb meem. Yog tias qhov nyiaj them tsis raug raws li qhov tseeb ntawm qhov sib txawv ntawm qhov sib txawv (sau cov kev hloov pauv ntawm qhov kub thiab txias, fiber ntau aging, thiab wavelength -dependent dispersion slope), qhov seem tsis sib haum tuaj yeem ua rau kev ua haujlwm tsis zoo. Qhov no yog vim li cas kev lag luam siv lo lus "kev tswj xyuas dispersion" es tsis yog "dispersion tshem tawm." Lub hom phiaj yog kom khaws cov net dispersion nyob rau hauv lub qhov rais uas tau txais, tsis txhob yuam kom nws mus raws nraim xoom ntawm txhua lub ntsiab lus.
Yuav txiav txim siab li cas yog tias koj qhov txuas xav tau Dispersion Compensation
Tsis yog kev kho cov nyiaj dispersion raws li qhov yuav tsum tau ua, ua haujlwm los ntawm cov lus nug kuaj mob no:
Koj hom fiber ntau yog dab tsi?Yog koj sivmultimode fiber ntau, modal dispersion yog koj qhov kev txhawj xeeb tseem ceeb, thiab koj hais nws los ntawm kev xaiv qib fiber ntau thiab tso tawm cov xwm txheej - tsis yog los ntawm DCMs lossis FBGs. Yog tias koj nyob ntawm ib qho - hom fiber ntau, txuas mus rau cov lus nug tom ntej.
Dab tsi yog qhov txuas nrug thiab cov ntaub ntawv tus nqi?Raws li cov lus qhia ntxhib, chromatic dispersion ua qhov tseem ceeb rau 10 Gbps NRZ cov cim ntawm kwv yees li 60-80 km ntawm G.652 fiber ntau ntawm 1550 nm. Ntawm 2.5 Gbps, qhov kam rau ua txuas mus rau ntau pua mais. Ntawm 40 Gbps, qhov kev txwv tsis pub xa mus rau kwv yees li 4-6 km yam tsis tau them nyiaj. Siab dua - cov qauv kev txiav txim siab (siv hauv 100G + coherent systems) muaj lawv tus kheej cov yam ntxwv ntawm kev ua siab ntev.
Qhov no puas yog qhov txuas qub txeeg qub teg lossis kev tsim kho tshiab?Ntawm cov nroj tsuag fiber ntau, ntxiv DCMs ntawm qhov chaw amplifier yog ib qho kev qhia thiab ua pov thawj. Rau kev xa tawm tshiab, xaiv hom fiber ntau thiab kev npaj rau kev sib txuas lus transceivers nrog DSP tej zaum yuav raug nqi ntau dua - zoo dua li kev tsim kho qhov muag los ntawm qhov pib.
Dab tsi yog receiver technology koj siv?Tus neeg txais kev sib txuas nrog DSP tuaj yeem them nyiaj ntau txhiab ps / nm ntawm chromatic dispersion digitally. Ib tug ncaj qha - ntes tau txais muaj qhov kam rau siab qis dua. Covtransceiver modulespecification yog ib qho tseem ceeb input rau cov nyiaj txiag dispersion xam.
Puas yog PMD yog qhov tseem ceeb?Tshawb xyuas koj cov nroj tsuag fiber ntau PMD tus yam ntxwv. Nyob rau niaj hnub G.652.D fiber ntau, PMD tsis zoo li yuav muaj kev txhawj xeeb hauv qab 40 Gbps. Ntawm cov laus fiber ntau uas tsis paub txog PMD keeb kwm, kev sim ua ntej xa mus yog qhov pom zoo.
Tswvyim Scenarios: Siv Dispersion Paub Txog Kev Sib Txuas Tiag
Scenario 1: Enterprise Data Center Multimode Txuas
Lub tsev kawm ntawv cov ntaub ntawv chaw txuas ob lub tsev sib nrug 150 meters siv OM4 multimode fiber ntau ntawm 10 Gbps (850 nm). Ntawm qhov kev ncua deb, modal bandwidth zoo nyob rau hauv OM4 specification (4700 MHz ·km zoo modal bandwidth). Chromatic dispersion ntawm 850 nm yog tam sim no tab sis negligible ntawm qhov ntev. Tsis xav tau kev them nyiaj dispersion tshwj xeeb. Thawj qhov kev xav txog kev tsim qauv yog ua kom zoocable installationzoo thiab connector huv si kompoob poobhauv pob nyiaj siv.
Scenario 2: Metro Ib Leeg-Mode Link ntawm 10 Gbps
Tus neeg tsav tsheb hauv nroog loj khiav 10G DWDM tshaj 120 km ntawm G.652.D fiber ntau ntawm 1550 nm. Accumulated chromatic dispersion yog kwv yees li 2,040 ps / nm. Qhov no dhau ntawm qhov kev ua siab ntev ntev rau 10G NRZ ncaj qha- kuaj pom tus txais (kwv yees li 1,000–1,200 ps / nm). Tus neeg teb xov tooj xa DCM ntawm nruab nrab - qhov chaw amplifier kom nqa cov khoom tawg mus rau hauv kev ua siab ntev. PMD ntawm cov fiber ntau niaj hnub no yog qis dua 0.1 ps / √km thiab tsis xav tau kev kho mob sib cais ntawm 10 Gbps.
Scenario 3: Ntev -Haul Coherent 100G Thauj
Qhov ntev -kev txuas ntawm 800 km siv G.652.D fiber ntau nrog EDFA amplification txhua 80 km, nqa 100G DP-QPSK tsheb. Tag nrho cov chromatic dispersion ntau tshaj 13,000 ps / nm. Txawm li cas los xij, tus neeg txais kev sib koom ua ke DSP tau them nyiaj chromatic dispersion digitally, tshem tawm qhov xav tau rau hauv DCMs. Lub vev xaib amplifier tsim tsom rau kev tswj cov suab nrov thiab OSNR optimization es tsis yog kho qhov muag dispersion them nyiaj. PMD kam rau ntawm tus neeg txais kev sib koom ua ke feem ntau yog 20-30 ps ntawm DGD, uas zoo tshaj qhov cov nroj tsuag fiber ntau tsim. Cov txiaj ntsig tau zoo yog qhov yooj yim dua, qis dua - tus nqi amplifier saw piv rau cov keeb kwm 10G ncaj qha - kev tshawb pom qhov system hla tib txoj kev.
Feem ntau yuam kev thaum ntsuas Fiber Dispersion
Tsis meej pem dispersion nrog attenuation.Raws li tau hais los saum no, cov no yog cov kev puas tsuaj sib txawv. Ib qho txuas uas dhau nws cov peev nyiaj siv hluav taws xob kho qhov muag kuj tseem yuav ua tsis tiav los ntawm kev tawg ntau dhau. Ib txwm suav ob qho kev siv nyiaj txiag.
Kho txhua hom dispersion li interchangeable.Modal dispersion nyob rau hauv multimode fiber ntau, chromatic dispersion nyob rau hauv ib tug - hom fiber ntau, thiab PMD yog tshwm sim los ntawm txawv mechanisms, muaj feem xyuam rau ntau hom kab ke, thiab yuav tsum tau sib txawv mitigation tswv yim. Kev siv DCM ntawm qhov sib txuas sib txuas, lossis sim kho cov teeb meem kev teeb tsa bandwidth nrog tus txais kev sib txuas, yuav yog kev siv thev naus laus zis tsis raug.
Piv txwv tias yuav tsum tau them nyiaj tas li.Ntaufiber optic thaj qaumkev sib txuas thiab luv - mus txog qhov txuas ua haujlwm tau zoo nyob rau hauv lawv txoj kev kam rau siab tawg. Ntxiv cov nyiaj them tsis tsim nyog kho vajtse ua rau tus nqi nce ntxiv, qhov poob qis, thiab qhov system complexity. Ib txwm pib los ntawm qhov txuas pob nyiaj siv, tsis yog los ntawm qhov kev xav tsis zoo.
Tsis quav ntsej qhov dispersion nqes hav.Hauv DWDM systems, chromatic dispersion coefficient sib txawv ntawm lub wavelength band. Lub DCM uas zoo kawg nkaus them nyiaj rau qhov chaw nruab nrab tuaj yeem tawm ntawm ntug kev nrog qhov cuam tshuam loj heev. Txoj kab nqes-match them nyiaj modules lossis ib -channel tunable compensators tej zaum yuav xav tau rau broadband systems.
Saib xyuas cov ntaub ntawv cog qoob fiber ntau.Kev paub tseeb ntawm kev teeb tsa fiber ntau, qhov ntev, thiab ntsuas qhov sib txawv yog qhov tseem ceeb rau kev tsim cov nyiaj them. Piv txwv tias muaj txiaj ntsig zoo thaum muaj cov ntaub ntawv cog qoob loo tiag tiag yog ib qho ntawm cov qauv tsim cov khoom pov tseg lossis, phem dua, nyob rau hauv - cov nyiaj them poob haujlwm.
Cov lus nug nquag
Dab tsi yog optical fiber dispersion hauv cov ntsiab lus yooj yim?
Nws yog kev sib kis ntawm lub teeb pulses thaum lawv taug kev los ntawm fiber ntau, tshwm sim los ntawm ntau qhov chaw ntawm lub teeb liab tuaj txog ntawm lub sijhawm sib txawv. Qhov tshwm sim yog qhov muag plooj pulses uas txo tus neeg txais lub peev xwm rov qab tau cov ntaub ntawv xa mus.
Dab tsi yog qhov tseem ceeb ntawm optical fiber dispersion?
Peb pawg tseem ceeb yog modal dispersion (tseem ceeb nyob rau hauv multimode fiber), chromatic dispersion (tseem ceeb nyob rau hauv ib qho - hom fiber ntau), thiab polarization hom dispersion (tseem ceeb ntawm tus nqi siab hauv ib qho -mode systems). Chromatic dispersion yog ntxiv ntawm cov khoom dispersion thiab waveguide dispersion.
Hom kev sib cais twg tseem ceeb tshaj plaws hauv ib qho - hom fiber ntau?
Chromatic dispersion yog qhov kev txhawj xeeb tseem ceeb rau feem ntau ib leeg - hom fiber ntau txuas. PMD dhau los ua qhov tseem ceeb ntawm 40 Gbps thiab siab dua, tshwj xeeb tshaj yog cov laus fiber ntau nrog PMD coefficients siab dua. Modal dispersion tsis tshwm sim nyob rau hauv ib qho - hom fiber ntau vim tsuas yog ib hom propagates.
Yuav ua li cas yog chromatic dispersion compensated?
Peb txoj hauv kev tseem ceeb yog: kev them nyiaj kho qhov muag siv DCF / DCM lossis fiber ntau Bragg gratings; hluav taws xob them nyiaj siv DSP ntawm tus txais (tshwj xeeb tshaj yog nyob rau hauv coherent systems); thiab kev tiv thaiv los ntawm kev xaiv hom fiber ntau thiab kev npaj wavelength. Hauv cov tes hauj lwm niaj hnub no, DSP-raws li kev them nyiaj sib koom ua keoptical transceiversyog nce mus rau hauv lub neej ntawd mus kom ze rau siab - ceev txuas.
Puas yog txhua qhov txuas fiber ntau xav tau kev them nyiaj dispersion?
Tsis yog. Cov kev sib txuas luv luv thiab qis dua - cov tshuab ceev feem ntau ua haujlwm tau zoo nyob rau hauv lawv qhov kev ua siab ntev dispersion yam tsis muaj kev them nyiaj tshwj xeeb. Qhov kev xav tau nyob ntawm qhov sib xyaw ua ke ntawm fiber ntau hom, nrug, cov ntaub ntawv tus nqi, wavelength, thiab receiver rhiab heev. Kev suav nyiaj txuas kom raug yuav tsum ua ntej txhua qhov kev txiav txim siab them nyiaj.
Dab tsi ua rau dispersion hauv optical fiber?
Dispersion yog tshwm sim los ntawm qhov sib txawv ntawm kev nthuav tawm ceev ntawm cov khoom ntawm cov teeb liab optical. Nyob rau hauv multimode fiber ntau, txawv spatial hom taug kev sib txawv. Hauv ib hom - hom fiber ntau, qhov sib txawv wavelengths mus ntawm qhov sib txawv ntawm qhov sib txawv vim yog cov khoom siv thiab waveguide zog ntawm fiber ntau. Birefringence hauv fiber ntau ua rau ob lub xeev polarization muaj kev ncua sijhawm sib txawv.
Puas yog xoom dispersion ib txwm yog lub hom phiaj zoo tshaj plaws?
Tsis nyob rau hauv kev xyaum. Hauv WDM systems, ib qho me me ntawm kev sib cais hauv zos hauv txhua qhov fiber ntau pab txo qis kev tsis zoo xws li plaub-yoj sib xyaw. Lub hom phiaj ntawm engineering yog los tswj cov net dispersion nyob rau hauv lub qhov rais txais tau, tsis txhob tshem tawm nws ntawm txhua qhov chaw hauv qhov txuas.
Xaus
Optical fiber dispersion yog ib qho tseem ceeb ntawm kev sib kis tsis zoo nyob rau hauv fiber ntau optic tes hauj lwm, nrog rau attenuation thiab nonlinear los. Kev nkag siab txog hom kev faib tawm twg cuam tshuam rau koj qhov system tshwj xeeb - modal, chromatic, lossis PMD - yog thawj kauj ruam mus rau kev tswj hwm zoo. Cov kauj ruam tom ntej yog txuam nrog txoj kev txo qis rau qhov txuas: kev xaiv fiber ntau, kev them nyiaj kho qhov muag, kev them nyiaj hluav taws xob, lossis tsuas yog lees paub tias tsis tas yuav them nyiaj.
Rau cov engineers ua haujlwm nrogtib - hom fiber ntaunyob rau hauv metro thiab ntev -haul networks, chromatic dispersion kev tswj tseem yog ib qho tseem ceeb tsim kev qhuab qhia. Rau cov uas sivmultimode fiber ntaunyob rau hauv luv luv - mus txog daim ntawv thov, nkag siab txog modal bandwidth txwv yog qhov tseem ceeb sib npaug. Thiab raws li kev sib koom ua ke DSP txuas ntxiv mus, ciam teb ntawm "dispersion- txwv" thiab "DSP- tswj tau" txuas ntxiv mus - ua rau nws tseem ceeb dua puas tau mus cuag kev tawg ua ib qho system- theem engineering teeb meem es tsis yog ib qho - cov khoom kho.
