Optical Modulator

Optical modulators are used in optical communication systems to convert electrical signals representing Data or voice into modulated optical signals.

An optical Modulator may be used for generating the required optical power, color and the like in the passing Light by changing optical parameters such as the Transmission factor, refractive index, Reflection factor, degree of deflection and coherency of light in the optical System according to the modulating signal. Optical modulators are typically based on direct or external modulation. With direct modulation, the optical Source is turned on and off at intervals. With external modulation, the optical source is operated continuously and its output light is modulated using an optical external modulator. As the external optical modulator, there are an electro-optical modulator, a magneto-optical modulator, an acousto-optic modulator, an electric field Absorption type modulator and the like. Semiconductor-based optical modulators have been developed using many different technologies and are used for modulating light for optical communications. One such semiconductor-based optical modulator is referred to as an electro-absorption modulator. The electroabsorption optical modulator (EA modulator) is an optical modulator that utilizes the electroabsorption effect that the optical Absorption Coefficient of a substance varies depending on the electric field applied to it. The EA modulator is generally classified into a type using an absorption Waveguide Layer having a quantum well structure and a type using a bulk Semiconductor layer rather than a waveguide layer. A Mach-Zehnder type optical modulator with a branching Interference type Optical Waveguide structure is known as one of optical waveguide devices using such electro-optical crystal. Variable optical attenuators (VOA) are used to permit dynamic control of Optical Power levels throughout a communications, Telecommunications or other transmission network. As traffic in networks increase, VOAs may be used to dynamically lower the optical power levels depending on the length of the Network route SO that appropriate power levels are received at the end receivers. The performance of optical modulators may be affected by numerous factors, such as a change in the environmental temperature.

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