Optical characteristics of a light-focusing fiber guide and its applications

A lenslike glass fiber guide with a parabolic variation of refractive index has been developed. This optical guide named SELFOC® has the following characteristics: simultaneous transmission of laser beams modulated by wide-band signals through narrow space; optical image transmission; realization of a lens with tiny aperture or with extremely short focal length; and the possibility of being bent with a small radius of curvature without spoiling transmission characteristics. In the case of a typical fiber guide with length 1 meter and diameter 0.3 mm, transmission loss is about 0.2 dB and depolarization is about 20 dB at wavelength 0.63μ. The mode pattern of a laser beam after passing through the fiber guide is scarcely deformed. The fiber guide can be used as a transmission line or lens, in optical communication, optical data processing, and optical instruments.