The measurement of the relative density of homogeneous fluids by means of an optical technique

A transducer that uses an intensity-modulated optical method to measure the relative density of homogeneous fluids is described. An optical fiber is used in a special way as a refractometer, measuring index of refraction, which has a direct relationship with relative density. The method relies on the optical power loss exhibited by a fiber bent beyond a critical radius. For such a fiber the critical angle of reflection is a function of the refractive index of the surrounding medium. The latter will therefore determine the amount of leakage, which can be measured and related to the value of relative density