According to the particular optical-field parameter being modulated, optical modulation can be categorized into different modulation schemes: phase modulation, frequency modulation, polarization modulation, amplitude modulation, spatial modulation, and diffraction modulation. Optical fiber telecommunication relies on modulation – the process of encoding information onto light waves – to transmit digital data efficiently. Light itself is a single waveform and cannot directly carry complex information. Therefore, certain characteristics of light (such as brightness and vibration state) need to be adjusted. Optical modulation allows one to control an optical wave or to encode information on a carrier optical wave. Wave propagation is guided by optical fibres.
[PDF Version]