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Fibre optic communication systems P8

Multichannel Systems In principle, the capacity of optical communication systems can exceed 10 Tb/s because of a large frequency associated with the optical carrier. In practice, however, the bit rate was limited to 10 Gb/s or less until 1995 because of the limitations imposed by the dispersive and nonlinear effects and by the speed of electronic components. Since then, transmission of multiple optical channels over the same fiber has provided a simple way for extending the system capacity to beyond 1 Tb/s. Channel multiplexing can be done in the time or the frequency domain through time-division multiplexing (TDM) and frequency-division multiplexing. | Fiber-Optic Communications Systems Third Edition. Govind P. Agrawal Copyright 2002 John Wiley Sons Inc. ISBNs 0-471-21571-6 Hardback 0-471-22114-7 Electronic Chapter 8 Multichannel Systems In principle the capacity of optical communication systems can exceed 10 Tb s because of a large frequency associated with the optical carrier. In practice however the bit rate was limited to 10 Gb s or less until 1995 because of the limitations imposed by the dispersive and nonlinear effects and by the speed of electronic components. Since then transmission of multiple optical channels over the same fiber has provided a simple way for extending the system capacity to beyond 1 Tb s. Channel multiplexing can be done in the time or the frequency domain through time-division multiplexing TDM and frequency-division multiplexing FDM respectively. The TDM and FDM techniques can also be used in the electrical domain see Section 1.2.2 . To make the distinction explicit it is common to refer to the two optical-domain techniques as optical TDM OTDM and wavelength-division multiplexing WDM respectively. The development of such multichannel systems attracted considerable attention during the 1990s. In fact WDM lightwave systems were available commercially by 1996. This chapter is organized as follows. Sections 8.1-8.3 are devoted to WDM lightwave systems by considering in different sections the architectural aspects of such systems the optical components needed for their implementation and the performance issues such as interchannel crosstalk. In Section 8.4 we focus on the basic concepts behind OTDM systems and issues related to their practical implementation. Subcarrier multiplexing a scheme in which FDM is implemented in the microwave domain is discussed in Section 8.5. The technique of code-division multiplexing is the focus of Section 8.6. 8.1 WDM Lightwave Systems WDM corresponds to the scheme in which multiple optical carriers at different wavelengths are modulated by using .