光纤通信业论文外文翻译.docVIP

东华理工大学长江学院 毕业设计 外 文 翻 译 学生姓名： 学 号： 专 业： 信息工程 系 别： 信息工程 指导教师： 职称： 讲师 二0一三年六月 五 日 Original Optical Fiber Communications The General System Communication may be broadly de?ned as the transfer of information from one point to another. When the information is to be conveyed over any distance a communication system is usually required. Within a communication system the information transfer is frequently achieved by superimposing or modulating the information onto an electromagnetic wave which acts as a carrier for the information signal. This modulated carrier is then transmitted to the required destination where it is received and the original information signal is obtained by demodulation. Sophisticated techniques have been developed for this process by using electromagnetic carrier waves operating at radio frequencies as well as microwave and millimeter wave frequencies. However, ‘communication’ may also be achieved by using an electromagnetic carrier which is selected from the optical range of frequencies. An optical fiber communication system is similar in basic concept to any type of communication system.The communication system therefore consists of a transmitter or modulator linked to the information source, the transmission medium,and a receiver or demodulator at the destination point. In electrical communications the information source provides an electrical signal, usually derived from a message signal which is not electrical (e.g. sound), to a transmitter comprising electrical and electronic components which converts the signal into a suitable form for propagation over the trans-mission medium. This is often achieved by modulating a carrier, which, as mentioned previously, may be an electromagnetic wave. The transmission medium can consist of a pair of wires, a coaxial cable or a radio link through free space down wh