ABSTRACT
This chapter deals with the modulation of lightwave sources by either direct or external modulation. For direct modulation, the generation of the lightwave within the cavity of the laser is manipulated by the injection or withdrawal of electrons, and hence it is called the stimulated emission process. On the other hand, in the case of external modulation, the laser is turned on at all times, and the generated optical continuous waves are then modulated, frequency, phase, or amplitude, through an optical modulator. The properties of modulated signals are described. The uses of these transmitters in optical communication transmission systems are given, especially those for long-haul transmission at a very high bit rate. MATLAB® and Simulink® models are also described.
