Analogous to the modulation ofcarrier frequencies used in wireless radio technology and wireline transmission technology, light is modulated with the modulation signal in optical transmission technology. In principle, the light can be varied in amplitude, phase and polarization.
As far as light modulation of amplitude is concerned, it is called intensity mod ulation( IM) or analog intensity modulation( AIM). Here, the intensity of the light beam is changed in rhythm with the modulation signal, making the light beam brighter or darker. Another light modulation works with phase shifting and interference. This technique is implemented with Mach-Zehnder modulators. However, light can also be bent by modulation.
Light modulation is used in optical transmission technology via optical fibers, but also in infrared LANs and in Visible Light Communication( VLC), a wireless technology in which visible light is modulated. Furthermore, the process of light modulation is also used in fiber optic microphones for the conversion of sound pressure.