通信考试内容总结.docVIP

本次考试试题共由四部分组成，分别是填空（40分），英译汉（10分）名词解释（15分），简答题（35分） 其中填空和英译汉针对基本知识的考查，占试卷50％，所以希望同学们好好复习基础知识，按往年的考试情况，填空题做不好的一般很难及格。 基础知识每章都有涉及，举例来说，填空主要考查例如：光纤的组成、光缆的组成、激光发光的条件、光纤通信的大气窗口、掺铒光纤放大器模块的形式、典型点到点光纤通信系统组成结构等等。共40空，每空1分。 英译汉只有10题，都是课堂上常说的专业词汇，因此，希望同学们把专业词汇尽可能多的掌握。 名词解释： (1) NA：numerical aperture（数值孔径）NA=sin θa= NA characterizes the fiber’s ability to gather light from a source. (2) MFD：The measure of the distribution of the beam’s intensity is mode-field diameter(MFD).MFD is the cross-sectional dimension 2w0, where the beam’s intensity drops to 1/e2=0.135 of its peak value. (3) refractive index：The characteristic that describe the property that different media resist light propagation with different strengths is called the refractive index.n=c/v (4) cutoff wavelength：截止波长 ≤2.405 V=2.405-------λc is cutoff wavelength This is the shortest wavelength at which a fiber can support single mode operation, only refers to SM fiber. (5) modes：The fact is that light can propagate inside an optical fiber only as a set of separate beams, or rays, that is a set of beams traveling at distinct propagating angles, α,ranging from 0 to the critical value, αc ,these different beams are called modes. (6) microbending loss：微弯损耗The microbending loss is also caused by failure to achieve the condition of total internal reflection. Microbending is loss caused by microdeformations of the fiber axis,which is really an imaginary line , (in reality, this line is determined by core-cladding geometry) microdeformation of the core-cladding boundary. (7) scattering：the reason to cause scattering is the slight variation of the refractive index. (8) BER： Bit-error rate－误码率 BER is the ratio of the number of erroneous bits to the total number of bits transmitted, that is :ER=number of erroneous bits/numbers of total bits. BER=P(0)P(1/0)+P(1)P(0/1) (9) NEP：Noise-equivalent Power (噪声等效功率）NEP is the RMS of the optical power that produ