Measurements of Dielectric Tapered Waveguides in the Optical Region.

Optical experiments investigating the propagation of light in tapered dielectric cylinders of circular cross-section are described. The core of the waveguide is made of lossy glass; the cladding consists of a low-index fluid. A simplified theory of the propagation of light on a dielectric taper is given. The result shows a relation between the light attenuation and the taper radii r//e and r//a (r//a for the narrow end, r//e for the large one) for a narrowing-down taper. In the other direction the light attenuation depends on the taper angle. As a typical application of the theory the variations of the radius of multi-mode fibers are discussed.