Optical Vector Modulation Using Laser Direct Modulation and Electro-absorption Modulator

Implementing advanced optical modulation formats with coherent detection, enabling both amplitude and phase modulations of lightwave, is one of the methods to enhance the spectral efficiency in optical transmission. Modulation and demodulation of complex vector modulation of lightwave carrier in the same manner as that of the radio frequency carrier necessitates precise control over much higher lightwave frequencies. This chapter delves into methodologies for realizing optical vector modulation through dual modulation of a directly modulated laser and an electro-absorption modulator, serving as phase and amplitude modulators, respectively. Such modulation can be performed using either discrete or integrated devices. To achieve complex modulation by this method, it involves precise component characterization, the modulating signal generation, and signal processing at both transmitter and receiver. The compact nature of integrated laser and electro-absorption modulator components offers advantages for transmitting both baseband and analog radio frequency signals over short distances.