Optical Networks - _Chapter 5 Transmission System Engineering_56

Optical Networks - _Chapter 5 Transmission System Engineering_56

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5 chapter Transmission System Engineering O ur goal in this chapter is to understand how to design the physical layer of an optical network. To this end, we will discuss the various impairments that we must deal with, how to allocate margins for each of these impairments, how to reduce the effect of these impairments, and finally all the trade-offs that are involved between the different design parameters. 5.1 System Model Figure 5.1 shows a block diagram of the various components of a unidirectional WDM link. The transmitter consists of a set of DFB lasers, with or without external modulators, one for each wavelength. The signals at the different wavelengths are combined into a single fiber by means of an optical multiplexer. An optical power amplifier may be used to increase the transmission power. After some distance along
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Unformatted text preview: the ber, the signal is amplied by an optical in-line amplier. Depending on the distance, bit rate, and type of ber used, the signal may also be passed through a dispersion-compensating module, usually at each amplier stage. At the receiving end, the signal may be amplied by an optical preamplier before it is passed through a demultiplexer. Each wavelength is then received by a separate photodetector. Throughout this chapter, we will be focusing on digital systems, although it is possible to transmit analog signals over ber as well. The physical layer of the system must ensure that bits are transmitted from the source to their destination reliably. The measures of quality are the bit error rate (BER) and the additional power budget 289...
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This note was uploaded on 01/15/2011 for the course ECE 6543 taught by Professor Boussert during the Spring '09 term at Georgia Institute of Technology.

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