Published online by Cambridge University Press: 05 March 2013
Wireless and fiber-optic communication systems
Communication systems transfer information between two points (point-to-point) or from one point to multiple points (point-to-multi-point) located at a distance from each other. The distance may be anywhere from a few centimeters in personal area networks (PAN), to a few thousand kilometers in long-haul optical fiber communication systems. The information can be conveyed using carrier frequencies and energies occupying the audio, microwave, mm-wave, optical, and infrared portions of the electromagnetic spectrum. In this book, we refer to the range spanning GHz to hundreds of GHz as high-frequency. Although optical frequencies do not fall into this category, the baseband information content of most current fiber-optic systems covers the frequency spectrum from DC to tens of GHz. This makes the circuit topologies and design methodologies discussed in this book applicable to the electronic portion of fiber-optic systems.
Wireless versus fiber systems
Figure 2.1 illustrates the block diagrams of typical wireless and fiber-optic communication systems. They both consist of a transmitter and a receiver, a synchronization block, and a transmission medium. The information signal modulates a high-frequency (GHz to hundreds of GHz) or optical (hundreds of THz) carrier which is transmitted through the air, or through an optical fiber, to the receiver. The receiver amplifies the modulated carrier and extracts (demodulates) the information from the carrier. In both cases, an increasing portion of the system is occupied by analog-to-digital converters (ADC), digital to analog converters (DAC), and digital signal processors (DSP), operating with clock frequencies extending well into the GHz domain.
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