Characterization of single and double fiber-coupled diffusing spheres

A fiber-optic sensor, consisting of an optical fiber with and without a 1.59-mm-diameter spherical ceramic tip, inserted into a 19-mm-diameter Spectralon sphere has been characterized. This sensor is evaluated as a large-area omnidirectional sensor. An optical transport measurement system that rotates the sphere about two axes has been designed. The system measured the UV transport efficiency at 351 nm of light impinging on the sphere with an f-6 cone angle. When a bare fiber was placed at the center of the target sphere, the detection sensitivity was biased in the forward direction. The peak of the sensitivity of the inverse integrating sphere shifted from front to back as the bare fiber was withdrawn from the sphere and the numerical aperture of the fiber viewed more of the scattering volume. The response function with respect to the angle of incidence of the dual sphere was much more uniform than that obtained with a bare fiber in the center of the sphere.