English-08课件

1、信息科学与电子工程专业英语信息科学与电子工程专业英语2信息科学与电子工程专业英语45678Nameaudioradiowavemm waveIROPT/UVx-rayGamma300km300m30cm3mm30m0.3m300.03(Hz)10310610910111013101510171020p3eV0.3meV30meV3eV300eV0.3MeV9101112 131415 161718192021222324252627282930 313233 3435信息科学与电子工程专业英语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阿尔法角度；系数B2B Bb bbetabet贝塔磁通系数；角度；系数C22C Cc cchiphai西D4D Dd ddeltadelt德尔塔变动；密度；屈光度E5E Ee eepsilonepsilon伊普西龙对数之基数G3G Gg ggammaga:m伽马电导系数（小写）FF Ff fH7H Hh hetaeit艾塔磁滞系数；效

8、率（小写）I9I Ii iiotaiot约塔微小，一点儿J21J Jj jphifai佛爱磁通；角K10K Kk kkappakap卡帕介质常数L11L Ll llambdalambd兰布达波长（小写）；体积M12MMm mmumju缪磁导系数；微（千分之一）；放大因数（小写）N13N Nn nnunju纽磁阻系数O15O Oo oomicronomikron奥密克戎P16P Pp ppipai派圆周率=圆周直径=3.1416Q8Q Qq qthetit西塔温度；相位角R17R Rr rrhorou肉电阻系数（小写）S18S Ss ssigmasigma西格马总和（大写），表面密度；跨导（小写）T19T Tt ttautau套时间常数U20U Uu uupsilonjupsilon宇普西龙位移VV Vv vW24W Ww womegaomiga欧米伽欧姆（大写）；角速（小写）；角X14X Xx xxiksi克西Y23Y Yy ypsipsai普西角速；介质电通量（静电力线）；角Z6Z Zz zzetazat截塔系数；方位角；阻抗；相对粘度；原子序数84SymbolPrefixExponentyyocto-10-24aatto-10-18阿ffemto-10-15飞，毫微微ppico-10-12皮，微微 Angstrom10-10meter埃埃 nnano-10-9纳，毫微mmi