English-08課件

1、信息科學與電子工程專業(yè)英語信息科學與電子工程專業(yè)英語2信息科學與電子工程專業(yè)英語45678Nameaudioradiowavemm waveIROPT/UVx-rayGamma300km300m30cm3mm30m0.3m300.03(Hz)10310610910111013101510171020p3eV0.3meV30meV3eV300eV0.3MeV9101112 131415 161718192021222324252627282930 313233 3435信息科學與電子工程專業(yè)英語37383940414243 444546474849505152535455565758596061

2、6263Figure 8.1 A typical optical fiber consisting of a transparent material of refractive index n1 and surrounded by a cladding of a slightly lower refractive index n2. Most of the propagating energy is confined to the core region and the field decays exponentially in the cladding.Cladding (n2)Core

3、(n1)6465 6667 68697071Figure 8.2 A step-index multimode fiber in which the refractive index in the core is constant. Light rays impinging on the core-cladding interface at an angle greater than the critical angle are trapped inside the core of the waveguide. In such a fiber rays traveling at larger

4、angles to the axis have to traverse a larger path and hence take a longer time than those rays which propagate with lesser angles to the axis. This leads to a substantial amount of broadening in a pulse propagating through the fiber.xn(x)qCore: n1Cladding: n2(n1)z72Figure 8.3 A graded-index optical

5、fiber in which the refractive index in the core decreases continuously away from the axis. Figure 3(a) shows a typical variation of refractive index across the core of the optical fiber. Light rays in such a fiber are trapped by a continuous refraction towards the center of the core, which leads to

6、a periodic focusing of the rays, as illustrated in (b). In such a fiber, even though rays making larger angles with the axis traverse a longer path length, they do so in a region with a lower refractive index and hence at a higher speed of propagation: this leads to a smaller value of pulse dispersi

7、on in such fibers as compared to homogeneous core fibers.Core: n1xn(x)Cladding: n2(n1)z(a)(b)7374757677787980818283A1A Aa aalphaa:lf阿爾法角度；系數(shù)B2B Bb bbetabet貝塔磁通系數(shù)；角度；系數(shù)C22C Cc cchiphai西D4D Dd ddeltadelt德爾塔變動；密度；屈光度E5E Ee eepsilonepsilon伊普西龍對數(shù)之基數(shù)G3G Gg ggammaga:m伽馬電導系數(shù)（小寫）FF Ff fH7H Hh hetaeit艾塔磁滯系數(shù)；效

8、率（小寫）I9I Ii iiotaiot約塔微小，一點兒J21J Jj jphifai佛愛磁通；角K10K Kk kkappakap卡帕介質(zhì)常數(shù)L11L Ll llambdalambd蘭布達波長（小寫）；體積M12MMm mmumju繆磁導系數(shù)；微（千分之一）；放大因數(shù)（小寫）N13N Nn nnunju紐磁阻系數(shù)O15O Oo oomicronomikron奧密克戎P16P Pp ppipai派圓周率=圓周直徑=3.1416Q8Q Qq qthetit西塔溫度；相位角R17R Rr rrhorou肉電阻系數(shù)（小寫）S18S Ss ssigmasigma西格馬總和（大寫），表面密度；跨導（小寫）T19T Tt ttautau套時間常數(shù)U20U Uu uupsilonjupsilon宇普西龍位移VV Vv vW24W Ww womegaomiga歐米伽歐姆（大寫）；角速（小寫）；角X14X Xx xxiksi克西Y23Y Yy ypsipsai普西角速；介質(zhì)電通量（靜電力線）；角Z6Z Zz zzetazat截塔系數(shù)；方位角；阻抗；相對粘度；原子序數(shù)84SymbolPrefixExponentyyocto-10-24aatto-10-18阿ffemto-10-15飛，毫微微ppico-10-12皮，微微 Angstrom10-10meter埃埃 nnano-10-9納，毫微mmi