專業(yè)英語(yǔ)考試復(fù)習(xí)總結(jié)-資料下載頁(yè)
2025-04-16 12:51本頁(yè)面
【正文】 雜的，和外部調(diào)制器的成本比直接驅(qū)動(dòng)光源。然而它通常提供更高的性能。Fiberoptic receivers detect the optical signal emerging from the fiber and convert it into electronic photodetector(usually simply called a detector) generates an electric current or voltage from the light it in the receiver then amplify that signal and process it to decode the signal.光纖接收器檢測(cè)到從纖維的新興的光信號(hào)并將其轉(zhuǎn)換成電子形式。一個(gè)探測(cè)器（通常簡(jiǎn)稱檢測(cè)器）從光接收機(jī)產(chǎn)生的電流或電壓。在接收電子再放大，信號(hào)進(jìn)行解碼的信號(hào)How well the receiver does its job depends on its sensitivity,speed,and the strength of signal reaching ,in turn ,depends on performance of both the detector and circuits that process the electronic signal it respond to a relatively broad range of wavelengths ,but not to entire range of visible and infrared wavelengths that fiber systems can transmit.接收機(jī)的工作取決于它的靈敏度，速度如何，和信號(hào)到達(dá)它的力量。這，反過(guò)來(lái)，取決于兩個(gè)檢測(cè)器和電子信號(hào)處理電路產(chǎn)生的性能。探測(cè)器相對(duì)較寬的波長(zhǎng)范圍內(nèi)的響應(yīng)，但不可見和紅外波長(zhǎng)的光纖系統(tǒng)可以傳輸?shù)恼麄€(gè)范圍。課后題目。（lesson1） (1)模擬信息源產(chǎn)生的消息是一個(gè)連續(xù)集合，而數(shù)字信息源產(chǎn)生的則是消息的有限集合。An analog information source produces messages that are defined on a continuum, whilea digital information source produces a finite set of possible messages. (2)我國(guó)古代的烽火臺(tái)也是一個(gè)通信系統(tǒng) The beaconfire tower in ancient China was a munications system. (3)證明當(dāng)發(fā)出二進(jìn)制數(shù)1和0的概率相等時(shí)，熵（entropy）是最大的 Show that the entropy is a maximum when the probability of sending a binary 1 is equal to the probability of sending a binary 0 . (4) 信息容量是在給定時(shí)間內(nèi)，通信系統(tǒng)能傳送多少信息的量度Information capacity is a measure of how much information can be transferred through a munications system in a given period of time . (5) 帶寬越寬，傳送時(shí)間越長(zhǎng)，系統(tǒng)傳送的信息越多The wider the bandwidth and the longer the time of transmission, the more information can be conveyed through the system .3． Translate the following sentences into English. (lesson12)(1)波分復(fù)用發(fā)射器更加復(fù)雜，因?yàn)樗芏喙ぷ饔诓煌ㄩL(zhǎng)光源的，每一個(gè)光源都有它自己的電子部分。 A WDM transmitter is more plex because it contains many light sources operating at different wavelengths, each with its own associated electronics. (2)光源或外調(diào)制器確定了發(fā)射機(jī)的速度和功率 The light source or external modulator limits the raw speed and power of transmitter. (3) 因?yàn)榧す獠ㄩL(zhǎng)對(duì)溫度敏感，控制電路需要監(jiān)視溫度，如果有冷卻器的話，還要控制它們。 Because laser wavelength is temperaturesensitive, the control circuits also monitor temperature and control coolers when they are included. (4) 解復(fù)用器必須可靠地分離的光學(xué)通道，確保一個(gè)信道對(duì)鄰近信道的低泄漏。 Demultiplexers must reliably separate the optical channels, with low leakage of light from one optical channel into an adjacent channel. （5），但是這將引入波長(zhǎng)抖動(dòng)，這種抖動(dòng)在長(zhǎng)距離傳輸時(shí)引起色散。Although lasers can be directly modulated at data rates of , this induces a chirp in wavelength which can cause excessive dispersion in longdistance systems.
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