Fiber-optical waveguides with a high numerical aperture

Optical fibers consisting of a glass and a polymer were fabricated. They had a numerical aperture of 0.37 when the core was made of quartz glass and 0.5–0.56 when it was made of multicomponent glasses. A study was made of the optical and physicomechanical properties of various polymer claddings. The results led to a recommendation for the use of a silicone composition characterized by a high transparency in the visible part of the spectrum. Fibers with losses of 20 dB/km and a breaking strength in excess of 400 kg/mm${}^2$ were obtained.