《通信与电子信息科技英语》课件unit 12

1、Fiber OpticNew words and phrases 1 fiber n.纤维 fiber optic(optical fiber)光纤(光纤电缆)2 innovation n.革新，技术革新，新方法3 immunity n.抗扰性，免除性，免疫(性)immune adj.免疫的;免受(伤害)的4 direct vt.引导，导引5 propagate v.传播6 refraction n.折射，折射度 refract vt.折射refractiveadj.折射的7 index n.指数，指标，索引 (pl.indices)refractive index（index of refraction）折射率8 external adj.外部的；n.外部,外面 external interference 外界干扰9 interception n.截取，窃听，监听10 abundant adj.丰富的,充裕的11 perceive v.察觉,感知Fiber Optic12 appreciation n.了解,懂得13 sine n.正弦14 incidence n.入射 angle

2、of incidence（incidence angle）入射角15 critical adj.临界的，决定性的，极限的 critical angle 临界角16 dielectric n.电介质,绝缘材料17 waveguide n.波导,波导管18 core n.（光纤）纤芯19 cladding n.包层20 sheath n.外皮，护层21 jacket n.护套，外壳22 govern v.支配，决定，起决定影响23 assembly n.装配,组合Fiber Optic24 radius n.半径(pl.radii)25 possess vt.有，具有，拥有26 knot n.结点，节27 diameter n.直径28 wavelength n.波长29 nanometer n.纳米，毫微米 30 perpendicular adj.垂直的，正交的 perpendicular to 与垂直，垂直于31 zigzag adj.之字形的，Z字形的32 opaque adj.不传导的,不透明的33 destructive adj.破坏(性)的destructivelyadv.破

3、坏地34 modal adj.n.模态(的)，形式(上的)35 bounce vi.反跳(弹);反射36 broaden vt.加宽，扩展Fiber Optic37 differentiate vt.区分,区别38 predefine n.预先确定（规定），预定义39 preclude vt.阻碍，妨碍40 outline vt.略述，概括地论述 41 uniform adj.均匀的，一致的42 mono (前缀)单，单一，一monomoden.单模43 dispersion n.色散 44 profile n.曲线，分布图refractive index profile 折射率分布45 devise vt.设计，发明46 chromatic adj.有色的，彩色的chromatic dispersion色散1 come of age 成年,到法定年龄,发达,充分发展2 freedom from 免除3 at the edge of 在的边缘4 Snells law 斯涅尔（折射）定律Fiber Optic5 multimode fiber 多模光纤6 single mode fibe

4、r(singlemode fiber)单模光纤7 clad fiber 包层光纤,涂层纤维8 parallel to 与平行,平行于9 light ray 光线10 light beam 光束11 back and forth 来来往往地,来回地12 modes of propagation（propagation mode）传播模，传播波型13 multimode propagation 多模传播14 optical receiver 光接收器 optical communication receiver 光通信接收机15 error rate 误码率Fiber Optic16 destructive interference 破坏性干扰，相消(性)干扰17 gradedindex fiber 渐变折射率光纤 gradedindex multimode fiber 渐变折射率多模光纤18 steppedindex fiber 阶跃折射率光纤19 intermodal dispersion 模间色散Fiber Optic Optical fiber transmission has c

5、ome of age as a major innovation in telecommunications.Such systems offer extremely high bandwidth,freedom from external interference,immunity from interception by external means,and cheap raw materials(silicon,the most abundant material on Earth).Fundamentals of Fiber Optic Systems Optical fibers guide light rays within the fiber material.They can do this because light rays bend or change direction when they pass from one medium to another.They bend because the speed of propagation of light in

6、each medium is different.This phenomenon is called refraction.One common example of refraction occurs when you stand at the edge of a pool and look at an object at the bottom of the pool.Unless you are directly over the object,it appears to befarther away than it really is.This effect occurs because the speed of the light rays from the object increases as the light rays pass from the water to the air.This causesthem to bend,changing the angle at which you Fiber Opticperceive the object.them to b

7、end,changing the angle at which you perceive the object.You can obtain an appreciation for the manner by which light flows by focusing upon Snells Law.Snells Law How optical fibers work can be explained by Snells Law,which states that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is equal to the ratio of the propagation velocities of the wave in the two respective media.This is equal to a constant that is the ratio of the refractive index of the second me

8、dium to that of the first.Written as an equation,Snells Law looks like this:sinA1/sinA2=V1/V2=K=n2/n1In this equation,A1 and A2 are the angles of incidence and refraction,respectively.V1 and V2 are the velocities of propagation of the wave in the two media.n1 and n2 are the indices of refraction of the two media.The parameters are demonstrated graphically in Fig.12.1.In each case,A1 is the angleof incidence,and A2 is the angle of refraction.The index of refraction(n1n2)of refraction of material

9、1,n1,is greater than the index of refraction of material 2,n2.This means that the velocity of Fiber Opticpropagation of light is greater in material 2 than in material 1.Fig.12.1(a)demonstrates how a light ray passing from material 1 to material 2 is refracted in material 2 when A1 is less than the critical angle.Fig.12.1(b)demonstrates the condition that exists when A1 is at the critical angle and the angle A2 is at 90dg.The light ray is directed along the boundary between the two materials.As

10、shown in Fig.12.1(c),any light rays that are incident at angles greater than A1 of Fig.121(.b)will be reflected back into material 1 with angle A2 equal to angle A1.The condition in Fig.12.1(c)is the one of particular interest for optical fibers.Exercises.Please translate the following words and phrases into Chinese.1.light beam2.propagation mode3.refractive index profile 4.chromatic dispersion 5.optical receiver 6.external interference 7.error rate8.dielectric 9.light ray10.clad fiber11.destruc

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