Multimode optical fiber polymer-dispersed liquid crystal electric field sensor

Abstract

Modulation of light scattering by liquid crystal droplets dispersed in a polymer matrix by an electric field forms the basis of a compact electric field sensor. A thin layer of polymer dispersed liquid crystal is interspersed between two cleaved end faces of multimode fiber. In the absence of an electric field the droplets are randomly oriented. The anisotropy of the refractive index of the liquid crystal causes light to be scattered out of the acceptance angle of the receiving fiber. As the major axis of the indicatrix of the droplets aligns with the field, the anisotropy in refractive index is lowered. The fraction of the light which is scattered is therefore reduced. In this paper we report on the properties of an electric field sensor envisaged for application to overhead transmission lines and utility substations. We discuss linearity, hysteresis, and the effect of temperature on the sensor.