vidhyalakshmi

 An Optical Modulator is used for modulating optical signal by changing the properties of light Depending on the properties of light changed,there are Intensity modulators,Phase modulators and polarization modulators. There are two types of modulation techniques for optical signals. They are  direct Modulation and External modulation Direct Modulation  Fig 1* The Message signal is Superimposed on the bias current which modulates the laser beam It causes issues like Frequency chirping,Pulse spreading and Loss of Information External Modulation Fig 2* The laser beam is modulated by an external optical modulator It is used in High end systems It is most complex and expensive  The below figure shows the classification of Optical Modulators Fig 3* Refractive Modulator-by varying refractive index of the modulating Material Absorptive Modulator-by varying absorption coefficient of the material *Figure courtesy:Google Images