Novel optical fiber refractometric transducer employing hemispherical detection element

Abstract

We present the results of a theoretical numerical analysis of a novel fiber optic refractometric transducer. It consists of a hemispherical glass detection element and a pair of the multimode optical fibers attached symmetrically to the element's flat equatorial plane. The internal reflection of light from the element's spherical surface is sensitive to the refractive index of the surrounding medium. We exploit several internal reflections in series and the focusing of the beam by the element's spherical surface to achieve enhanced sensitivity to the refractive index of the surrounding medium and reduced intrinsic optical loss in the transducer. We present the data on the effect of transducer's parameters on its transmission function. We show that the transducer can operate in a relatively wide range of the refractive index of the surrounding medium (we show this for the interval n = 1.0 to n = 1.45). We also present experimental data confirming our theoretical results.