Basic Principles ntawm Optical Fibers thiab Cables

Kev sib kis ntawm fiber ntau yog ua raws li lub hauv paus ntsiab lus ntawm tag nrho cov kev xav sab hauv, uas tshwm sim thaum lub teeb ntsib qhov sib cuam tshuam ntawm ob qhov kev tshaj tawm sib txawv. Nyob rau hauv ib kauj ruam -index optical fiber- qhov twg n1 sawv cev rau lub refractive index ntawm cov tub ntxhais nruab nrab thiab n2 sawv cev rau lub refractive index ntawm cladding nruab nrab, nrog n1 > n2- tag nrho cov sab hauv xav tau tshwm sim thaum lub teeb nkag mus rau hauv lub tub ntxhais ntaus lub core-cladding interface ntawm lub kaum sab xis ntawm qhov tshwm sim ntau dua li qhov tseem ceeb ntawm lub kaum sab xis (θ). Nyob rau hauv cov xwm txheej no, tsis muaj lub teeb lub zog khiav tawm ntawm lub hauv paus, thiab qhov teeb meem tshwm sim tuaj yeem nthuav tawm rau pem hauv ntej los ntawm kev sib cuam tshuam los ntawm suav tsis txheeb tag nrho cov kev xav sab hauv.

Txawm li cas los xij, thaum kho qhov muag fiber ntau yog khoov, qhov ib txwm mus rau qhov sib cuam tshuam hloov kev taw qhia, ua rau cov kaum me me ntawm qhov xwm txheej. Yog li ntawd, lub kaum sab xis ntawm qhov tshwm sim rau ib feem ntawm lub teeb rays poob qis dua θc, tiv thaiv lawv los ntawm kev xav txog tag nrho sab hauv. Txawm li cas los xij, cov rays uas muaj qhov pib loj dua ntawm qhov xwm txheej tseem tuaj yeem ua rau tag nrho sab hauv xav txog; Yog li, lub teeb xa mus txuas ntxiv txawm tias thaum lub fiber yog khoov, txawm tias qhov kev khoov no ua rau lub zog poob. Feem ntau, thaum lub vojvoog dabtsi yog khoov tshaj 50 mus rau 100 millimeters, qhov tshwm sim poob yog negligible. Conversely, feeb khoov tuaj yeem ua rau hnyav "microbending poob."

Electromagnetic yoj txoj kev xav tau nquag ua haujlwm los tshawb xyuas cov txheej txheem ntawm kev sib kis ntawm fiber ntau, tshwj xeeb los ntawm kev daws cov yoj sib npaug raws li thaj tsam ntawm qhov nruab nrab ntawm fiber ntau waveguide. Lub teeb propagating nyob rau hauv ib qho optical fiber ntau muaj ntau "hom", txhua tus sawv cev rau ib qho kev faib tawm ntawm electromagnetic teb thiab sib xws rau ib qho teeb pom kev zoo raws li tau piav qhia hauv geometric optics. Cov kev qhia tshwj xeeb uas muaj nyob rau hauv ib qho kev kho qhov muag fiber ntau nyob ntawm cov fiber ntau zaus (V-number).
Hauv cov ntsiab lus no, NA qhia txog Numerical Aperture, ib qho kev ntsuas cuam tshuam txog qhov ntsuas qhov ntsuas ntawm qhov tseem ceeb thiab cladding xov xwm; *a* sawv cev rau lub vojvoog ntawm cov tub ntxhais fiber ntau; thiab λ sawv cev rau lub wavelength ntawm lub teeb kis. Thaum kho qhov muag fiber ntau yog khoov, hom coupling tshwm sim; ib feem ntawm lub zog hloov ntawm cov qauv coj mus rau hauv cov qauv hluav taws xob, yog li khiav ntawm lub hauv paus thiab poob.
Cov yam ntxwv ua tau zoo: Cov yam ntxwv tseem ceeb ntawm cov khoom siv kho qhov muag muaj xws li attenuation, bandwidth, thiab lwm yam.