![]() The optical source which pro- vides the electrical–optical conversion may be either a semiconductor laser or light-emitting diode (LED). In this case the information source pro- vides an electrical signal to a transmitter comprising an electrical stage which drives an optical source to give modulation of the light wave carrier. ![]() This is often achieved by modulating a carrier, which, as mentioned pre- viously, may be an electromagnetic wave.įor optical fiber communications the system shown in Figure 1.1(a) may be considered in slightly greater detail, as given in Figure 1.1(b). sound), to a transmitter comprising electrical and electronic components which converts the signal into a suitable form for propagation over the transmission medium. In electrical communications the information source provides an electrical signal, usually derived from a message signal which is not electrical (e.g. 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. A block schematic of a general communication system is shown in Figure 1.2(a), the function of which is to convey the signal from the information source over the transmission medium to the destination. However, ‘communication’ may also be achieved using an electromagnetic carrier which is selected from the optical range of frequencies.Īn optical fiber communication system is similar in basic concept to any type of communication system. Sophisticated techniques have been developed for this process using electromagnetic carrier waves operating at radio frequencies as well as microwave and millimeter wave frequencies. ![]() This modulated carrier is then trans- mitted to the required destination where it is received and the original information signal is obtained by demodulation. ![]() 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. When the information is to be conveyed over any distance a communication system is usually required. Communication may be broadly defined as the transfer of information from one point to another. ![]()
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