Light modulator, demodulator and method of communication employing the same

摘要

A light modulator for generating a beam of phase modulated light including a source of polarized light, at least one and preferably two liquid crystal cells having a thin layer of nematic liquid crystals of positive dielectric anisotropy through which the polarized light is directed to produce a beam of light having a phase shift corresponding to a modulating electrical signal which is applied to each of the liquid crystal cells. The liquid crystal cells in addition have a continuing electrical bias applied across the layers in order to achieve the rapid response times necessary to achieve modulation of the polarized light. Demodulation of the polarized light occurs by splitting the modulated light beam into its quadrature components and developing an electrical signal corresponding to the phase difference between the two quadrature components. A communication system involving its modulators and demodulators delivers communication through light as a transmission medium.