electro absorptions modulator (EA)
For E/O converters, external modulation of laser light has some advantages over direct modulation, which affect chromatic dispersion and thus possible transmission rates.
In external modulation, a modulation unit is connected downstream of the laser, which can be an integral part of the laser component. One such component is the electro- absorption modulator, which is made of similar material to the laser diode. The electro-absorption modulator is controlled by electric current and, depending on the polarity of the applied voltage, allows the laser light to pass or blocks it when the polarity is reversed. The level of light emitted by the laser remains constant; the output level of the modulator, on the other hand, changes in rhythm with the change in polarity.